Forestry Commission

The ARCHIVE Forestry Authority Forestry Commission

Bulletin 111

Forest Nursery Practice Edited by J R Aldhous and WL Mason

FORESTRY COMMISSION BULLETIN 111

Forest Nursery Practice

Edited by J. R. Aldhous and W. L. Mason

LONDON: HMSO © Crown copyright 1994 Applications for reproduction should be made to HMSO. First edition Crown copyright 1972.

ISBN 0 11 710323 3 FDC 232.32 : (410)

KEYWORDS: Seed Forest Nurseries Forestry Propagation

Enquiries relating to this publication should be addressed to: The Research Publications Officer, The Forestry Authority, Research Division, Alice Holt Lodge, Wrecclesham, Famham, Surrey GU10 4LH.

Front cover: Precision sowing into prepared beds at Wykeham Nursery using a Summit precision sower. (39375) Contents

Page Preface vii Summary ix Resume ix Zusammenfassung ix

List of contributors X L Nursery policy and planning 1 1.1 Whether to start a nursery 2 1.2 Planning production 3 1.3 Records 4 1.4 Sale of plants 5 1.5 Quality of plants 6 1.6 Names and ages of plants 10 2. Selection, layout and formation of a nursery for the production of bare-root plants 13 2.1 Physical limits for nursery sites 13 2.2 Site selection 14 2.3 Layout of nursery 17 2.4 Breaking-in a new nursery 20 2.5 Costs of formation 23 2.6 Site requirements for nurseries producing other types of forest planting stock 23 2.7 First crops in new nurseries 23 3. Forest nursery soils 25 3.1 Physical characteristics 25 3.2 Soil pH 29 3.3 Soil analysis 32 4. Plant nutrition 37 4.1 Foundations 37 4.2 Use of fertilisers 41 4.3 Nutrient deficiencies and remedial fertilisers 50 4.4 Soil organic matter 58 5. Seed 66 5.1 Choice of seed origin 66 5.2 Seed identity numbers 68 5.3 Procurement of seed 70 5.4 Collection and extraction of seed 71 5.5 Seed storage 71 5.6 Seed testing 72 5.7 Seed dormancy 79 6. Production of bare-root seedlings and transplants Seedbed production 84 6.1 Preparation of the ground for sowing 84 6.2 Preparation of seed for sowing 87 6.3 Sowing 88 6.4 Subsequent care 96 Transplant production 97 6.5 Transplanting 97 6.6 Plants for transplanting 98 6.7 Technique and methods of lining out 100 6.8 Tending 102 7. Mycorrhizas, actinorhizas and rhizobia 104 7.1 Mycorrhizas 104 7.2 Non-leguminous nitrogen fixers 107 7.3 Legumes and their nitrogen fixers 109 8. Production of undercut stock 112 8.1 Potential of undercutting 112 8.2 Sowing for undercut production 114 8.3 Recommended undercutting regimes 116 8.4 Use of undercutting with other systems 119 8.5 Implications for nursery management 120 9. Container production of tree seedlings 122 9.1 Container systems 122 9.2 Nursery facilities 123 9.3 Growing media 125 9.4 Liquid feeds 128 9.5 Seedling production 129 10. Vegetative propagation 135 10.1 Propagation of broadleaves 136 10.2 Propagation of conifers 139 10.3 Overview and future developments 146 1L Irrigation 148 11.1 Energy and water demand 148 11.2 Soil water 150 11.3 Water tension in plants 154 11.4 Planning for irrigation 155 11.5 Irrigation equipment 160 11.6 How much water to apply and how often 162 iv 12. Nursery weed control 167 12.1 Weed control over the whole nursery 167 12.2 Chemical control of weeds in nursery stock in open ground 168 12.3 Recommended herbicides 170 12.4 Mechanical control of weeds 178 12.5 Spraying equipment 178 13. Protection against climatic damage, fungal diseases, insects and animal pests 181 13.1 Climatic damage 181 13.2 Protection against fungal diseases 183 13.3 Control of insects 188 13.4 Protection of seedbeds against birds 195 13.5 Protection of seedbeds against mice 196 13.6 Damage by other animals 196 14. Lifting, storage, handling and despatch 198 14.1 Integrated procedures 198 14.2 Causes of damage and loss of plant quality 199 14.3 Factors affecting the overwinter physiological condition of plants 202 14.4 Plant attributes influencing survival 205 14.5 Lifting 207 14.6 Culling, grading and counting 209 14.7 Storage 210 14.8 Insecticide treatment 216 14.9 Packing and despatch 218 14.10 Handling of plants raised in containers 220 15. Legislation and the nursery manager 223 15.1 Forest Reproductive Material Regulations 223 15.2 Seed and plant sales 228 15.3 Seed stand registration and seed collection 230 15.4 OECD scheme for the control of reproductive material moving in international trade 232 15.5 Plant and seed health 233 15.6 Current pesticide legislation 236 15.7 Seed and plant breeding 239 15.8 Other legislation 241

v Appendices I a) The Forestry Authority - list of addresses 247 b) Laboratories undertaking soil analysis 249 II Glossary 250 III Common and botanical names of forest trees 254 TV EEC standards for nursery stock 256 V Conversion factors 260 Index 261

vi Preface

This Bulletin is a revision of the first edition of Bulletin 43 Nursery practice published in 1972. That edition provided an introduction to nursery practice for managers, supervisors and students and had been in steady demand until it went out of print. The preparation of a second edition has provided the opportunity to bring its contents more into line with contemporary develop­ ments in forestry and nursery practice. While the substantial programmes of upland afforestation of the 1970s and 80s have lessened in recent years, there has been an off-setting increased interest in planting at lower elevations and greater emphasis on planting stock for conservation of amenity and wildlife. At the same time, new developments in techniques - such as, for example, container-raised plant production - have widened the range of commercially viable production systems available to the nursery manager. Possibly the most significant long-term development is the increasing availability of seed of superior performance potential, resulting from tree selection and breeding programmes. The large-scale vegetative propagation of plants raised from such seed marks the emergence of the forest nursery industry from being based solely on seed from wild populations to one where, increasingly, the products of genetic improvement will play an important part in forest composition. Associated with increasing use of vegetatively propagated stock is the ability in the nursery to exercise greater control over the growing environ­ ment for plants, both through more sophisticated instrumentation, and through the ability of electronic data capture to provide information to man­ agers in a way that had previously been thought totally impossible. A development of a different sort is the recognition of the need to keep dis­ tinct the variety of seed sources of native Scots pine where these occur within the natural range of the species. Nevertheless, this and the increased use of vegetatively propagated plants from ‘improved’ seed have in common the need for high standards of nursery management and record keeping, to ensure plants are supplied true to name. A further recent development has been a greater understanding of the physiological response of plants to handling in the critical period between lifting in the nursery and delivery to the forest. A dilemma faced by the editors has been whether to mention proprietary products and firms. We concluded that it is more helpful to mention these where relevant, at the same time making it clear that no judgement is to be inferred where other similar products are available on the market. Mention in the text of the Bulletin does not imply endorsement of the particular product or company, nor does omission infer any criticism. This second edition has been prepared along similar lines to the first edi­ tion, except that the authors of the individual chapters are named in the chapter headings. All contributors have been faced with the challenge of pro­ ducing an informative introduction to their particular topic within the space contraints of a single volume. Where readers find they would like more detailed information, it is hoped that the references given will provide rele­ vant sources. Finally, most sincere thanks must be expressed to everyone who has con­ tributed to the content of the revised Bulletin. This includes not only present staff in Forestry Commission and private nurseries, but also all those whose past work has provided the foundation of knowledge and practice on which present methods and understanding are based.

J. R. Aldhous W. L. Mason Forest Nursery Practice

Summary This Bulletin, written by experts in their field, describes techniques involved in successful production of bare-rooted and cell- (small container-) grown stock of the tree species most widely planted in United Kingdom forestry. The subjects covered include: formation of new nurseries; maintenance of the fer­ tility of existing nurseries; procurement of seed; production of seedlings and transplants; production of cell-grown planting stock; the role of mycorrhizas; vegetative propagation; irrigation; weed control; control of diseases and insect and other pests; plant storage and handling; legislation affecting nursery management. References are given to supplementary sources of information.

La Gestion des Pepinieres Forestieres

Resume Ce Bulletin, compose par des experts pertinents, decrit les techniques pour la production reussie des plants a racines nues et des plants en cellules (petits recipients) pour les especes forestieres plus plantees dans Le Royaume-Uni. Les sujets y compris sont: la formation des nouvelles pepinieres; l’acquisition des graines; la production des semis et des plants repiques; la production des plants en cellules (recipients); le role des mycorhizes; la propagation vegeta­ tive; l’irrigation; le desherbage; la lutte contre des maladies, des insectes nuisibles et des autres depredateurs; le stockage et la manutention des plants; et la legislation a l’egard de la gestion des pepinieres. Des references a des sources additionelles d’information sont pourvues.

B aums chulver fahren

Zusammenfassung Dieses Bulletin, da(3 von Experten geschrieben wurde, beschreibt Techniken zur erfolgreichen Produktion von wurzelnackten und in Zellen (kleine Behalter) gezogenen Bestanden der Baumart, die vorwiegend in UK Forsten gepflanzt wird. Die behandelten Themen umfassen: Formierung neuer Baumschulen, Erhaltung der Ergiebigkeit bestehender Baumschulen, Beschaffung von Samen, Produktion von Samlingen und Setzlingen, Produktion von in Zellen gezogenen Bestanden, die Rolle von Mykorrhiza, vegetative Fortpflanzung, Unkrautkontrolle, Bekampfung von Krankheiten, Insekten und anderen Schadlingen, Pflanzenlagerung und - handhabung, Gesetzgebung die den Baumschulbetrieb betrifft. Die Quellenangabe enthalt weitere Informationsquellen. List of Contributors

J. R. Aldhous Former Head of Silviculture Division, The Forestry Commission. Author of Forestry Commission Bulletin 43 Nursery practice (1972). W. L. Mason Head of Silviculture (North) Branch, Research Division, The Forestry Authority.1 (Previously Nursery Silviculturist1) P. G. Gosling Head of Plant Production Branch, Research Division, The Forestry Authority.2 S. C. Gregory Forest Pathologist, Research Division, The Forestry Authority.1 S. G. Heritage Forest Entomologist, Research Division, The Forestry Authority.1 R. L. Jinks Plant Production Branch, Research Division, The Forestry Authority.2 H. M. McKay Plant Physiologist, Research Division, The Forestry Authority.1 A C. Miller Conservator, North Wales, The Forestry Authority; formerly, Manager, Delamere Nursery, Forest Enterprise. J. L. Morgan Silviculturist, Research Division, The Forestry Authority.1 M. F. Proe Plants Division, Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen. D. G. Pyatt Wildlife Ecology Branch, Research Division, The Forestry Authority.1

1 Northern Research Station, Roslin, Midlothian, EH25 9SY. 2 Alice Holt Lodge, Wrecclesham, Famham, Surrey, GU10 4LH. R. G. Strouts Forest Pathologist, Research Division, The Forestry Authority.2 C. Walker Head of Mycorrhizal Research Unit, Research Division, The Forestry Authority.1 C. T. Wheeler Department of Botany, The University of Glasgow. D. R. Williamson Forest District Manager, South Downs Forest District, Forest Enterprise; formerly, Silviculturist, Research Division, The Forestry Authority.2

1 Northern Research Station, Roslin, Midlothian, EH25 9SY. 2 Alice Holt Lodge, Wrecclesham, Famham, Surrey, GU10 4LH. x i i Chapter 1 Nursery policy and planning

J. R. Aldhous

Introduction planting stock falling from about 25% of plan­ tation establishment costs to about 1 2 V2%; Forest nurseries are an essential part of more recently, this cost relationship has been forestry in Britain. Each year for the last 20 maintained for similar bare-rooted stock. years, between 80 and 120 million plants have However, stock resulting from tree-improve- been sent from British forest nurseries to ment programmes, especially where this has extend or restock privately and nationally been bulked up by vegetative propagation, is owned forest. In addition, in many years con­ more expensive to produce, this increased cost siderable numbers of trees have been exported being justified commercially by expectations of to other EEC countries. enhanced growth rates and superior form in In the immediate postwar period, afforesta­ plantations (Gill, 1983; Lee, 1990). tion of bare land dominated planting activi­ ties. In the last decade however, areas being Purpose of this Bulletin restocked annually have increased substan­ This Bulletin is intended as a ready reference tially. In the 1990/91 planting season, for the nursery owner or manager, giving restocking accounted for 49% of the demand guidance on most points of practice relating to for plants and is likely to continue to increase the raising of young trees for planting in the in scale. The ratio of broadleaves to conifers is forest, and describing some underlying princi­ likely to increase in the short term in response ples on which practice is based. to availability of better quality land for It is written on the assumption that the planting, and increased public interest in policy of the nursery manager is to raise good woodland landscapes and wildlife habitat. quality plants at the lowest cost. Little Forest nurseries are certain to continue to allowance is made for the estate owner or the be the main source of new trees for future amenity group who want to raise plants on a British woodland, for although natural regen­ small scale on ground that may not be well eration is the recognised way of restocking in suited to the best growth of young trees. Such many parts of the world, in Britain, it cannot owners are advised to follow the recommenda­ be relied on. Also, forest managers may wish tions in this Bulletin as far as they apply; the to replant either with more productive species, stocks raised will probably grow more slowly or with strains of the same species of while in the nursery, but should be suitable improved quality and vigour raised either in for woodland or forest planting. They will the open nursery, or by one of the more inten­ probably have cost more to produce than in a sive methods described in Chapters 9 and 10. large nursery, though not necessarily more There is, in addition, increased interest in than the purchase price from a reputable native species and in local seed sources of nursery manager. The owner will have had native species. the convenience of having his plants available In the 1950s and 1960s an intensive pro­ whenever he can lift them, and also the satis­ gramme of research resulted in the cost of faction of seeing them grow. No attempt is made to describe practice in Area (000 ha) raising ornamental varieties of trees or the production of large trees for planting as speci­ mens or for landscape work. Throughout this Bulletin, quantities are given in metric units. A table of conversion factors to imperial measure is given in Appendix V.

1.1 Whether to start a nursery

1.1.1 Market prospects Forest nurseries may be managed either to produce plants for sale on the open market, or to produce plants to meet a previously known Year commitment, whether a long-term planting programme or a contract. Many nurseries pro­ Figure 1.1 Private forestry new planting and restocking, 1971-1992. duce for both outlets, and thereby have the income and security from regular contract sales as well as the opportunity to increase the last decade and will continue to increase these sales and profits by selling the rest of as forests planted during the last 50 years are their stock on the open market. cut and replanted, ultimately reaching at least However, careful research into market twice the present annual rate. prospects and a rigorous investment appraisal must always be undertaken before deciding to 1.1.2 The nursery site open a nursery for commercial production. Figure 1.1 shows the annual area planted by The features of a good nursery site for pro­ private woodland owners in Great Britain over ducing bare-rooted stock are described at the period 1971-92 using figures from Forestry length in Chapters 2 and 3. If any of the more Commission Annual Reports. important of these are ignored, costs of pro­ The demand in this period for plants for duction are likely to be higher and growth afforesting privately owned bare land reflects slower than on good sites. the fiscal provisions incorporated in Govern­ Where production is to be exclusively of ment budget legislation and the level of grant stock in containers, such as Japanese paper aid for planting. For example, fiscal changes pots, ‘rootrainers’, plugs, etc., the main in 1972 and in 1988 both led to a sharp drop requirements are reduced to mains power, in demand for plants for bare land afforesta­ good quality water, a level site and ready tion, with a period between 1978 and 1988 of access. sustained increase in planting. More recently, incentives have been increased for planting on 1.1.3 Size of nursery farm land through ‘Better land’ supplements The simplest guide to size in relation to (Forestry Commission, 1993). output is that 1 ha of nursery area gross (i.e. The area of privately owned woodland including paths, fallow, etc), is required for restocked after felling has been much less every 180 000 to 250 000 forest planting stock each year than the annual area of new to be produced. It is seldom economical to planting; also, it has fluctuated less over the start a nursery for less than a regular annual same period. It has increased slowly during production of 250 000 planting stock.

2 Seedbed area season. There are many calls on fallow land. These include: summer lining out of rising 2- For every unit of area cultivated, approxi­ year-old plants, plants from cold stores or mately 60% is sown; the remaining area is from vegetative propagation houses; comple­ taken up by alleys between beds. The number tion of a substantial proportion of the dormant of seedlings produced from fully stocked season lining out programme before conifer seedbeds range from 400 to 1000 per Christmas (some foresters try to complete half square metre (nett sown area) according to by this time); throwing up of seedbeds in the species and season; columns (8) and (9) of autumn or winter in preparation for the Table 6.1 (in Chapter 6) ‘Seed quality, sowing spring; holding over for another year surplus density and expected yields: major conifers’ seedlings or transplants. give average conifer stock in good nurseries, while Table 6.2 ‘Seed quality and seedling pro­ If it is anticipated that there will be regular duction: broadleaves’ gives data for and substantial calls on fallow ground for two broadleaved species. NB: space for alleys or more of these reasons, the proportion of between beds has to be added if using the fig­ fallow land should be increased to 40% of the ures in these tables to calculate gross areas total cultivated area. When planning a for any sowing programme. nursery, it is far better to err on the generous side with the allowance of fallow land; the cost of maintaining surplus fallow is small and is a Transplant area worthwhile insurance. In most nurseries, transplanting is by machine, setting out five or six long lines of Uncultivated ground plants between alleys. This layout allows sub­ sequent tractor-based operations such as pes­ The area occupied by permanent roads, build­ ticide applications, undercutting/wrenching ings, hedges, dumps of materials, machine and mechanical lifting. According to the initial parks and other permanently uncultivated spacing of plants, between 75 and 120 plants areas within the nursery perimeter, taken per square metre (including alleys) must be together, usually amount to between 20 and allowed when planning transplanting areas. 30% of the total nursery area. Separate, Hand lining out, using boards (e.g. the 2 m specifically calculated, additional allowances Paterson board) is still practised locally. This should be made for access to plant cold stores may either reproduce the pattern of lines sim­ and for safety zones around pesticide stores ilar to that from machine lining out or the and fuel stores. boards may be set side by side to make breaks of plants the length of the board and many board-widths wide. In the latter case, the ben­ 1.2 Planning production efit of any more economical use of land has to Forest nursery work requires to be planned be set against more costly hand work applying well in advance, by a person thoroughly expe­ sprays during the season, and hand lifting at rienced in forest nursery work. The benefits of the end of the year. such experience can be expected not only in The relationship of spacing of plants in and any advance planning, but also in the execu­ between rows is shown in Table 6.7. When tion of plans and in timing them in relation to planning nursery areas, it is advisable to plan the day-to-day conditions of the nursery. for 70% usable plants in the lines. Nursery planning, whether of the require­ ments of manpower and machines or of plants Fallow land and materials, can be simplified if records are available from which can be estimated: Between a quarter and a third of the culti­ vated area should be planned to be under • the annual demand for planting stock, by fallow or a green crop at the end of the sowing species, provenance, age and size;

3 • the year-by-year saleable out-turn from Computer-based management and record­ seedbeds and lines, noting also wastage fac­ keeping systems are taking an increasingly tors (percentage of plants that are culled as important role in nursery management. They being below specification, diseased, etc.), offer many possible aids to managers. There and unsold plants; are several systems in use in horticultural • the cost, labour and time requirements of nurseries. One which is specifically tailored to various operations. forest nursery production is produced by ‘Growing Information Systems’, Hyndland, Such records should assist the nursery Glasgow, G12 9JA. However, whatever system manager to determine his future programme, is installed, it must be readily adaptable to give him some idea of what margins of error changing perceptions of need. he should allow for seasonal variations in Management records whether manual or yield and provide the basis for identifying computer-based, can be divided up into: where he should give priority in any attempts to improve efficiency/reduce unit costs. • Plant production Details of seed origin/provenance; amount of seed sown; seedlings lifted; plants lined 1.3 Records out; forest plants lifted; size, or proportions Nursery records can be divided into those in size categories; cuttings inserted in vege­ required by law and those optional records tative propagation programmes; proportion whose value lies in the insight they provide to rooted; proportion successfully repotted/ the nursery manager about his operations. transplanted to be suitable for forest The financial records necessary to prepare planting; storage dates and conditions. accounts so as to meet current company law, • Cash outgoings PAYE and VAT requirements are not dis­ (a) Recurring costs of materials: fertilisers, cussed in this Bulletin. seedbed cover, seed, fuel, pesticides, Obligations under the ‘Forest Reproductive machinery maintenance and running Material Regulations’ are set out in Chapter costs, protective clothing, etc. 15, section 15.1, and those relating to plant (b) Capital expenditure: buildings, site health in section 15.5. These include a improvements, equipment and machines requirement for nursery managers to keep with more than a 1 year life, etc. reliable production records for all the species (c) Manpower costs: wages, salaries, con­ covered by the Regulations. By far the larger tract payments for work done. part of such records needs to be kept for the (d) Overheads: rent/rates on premises, value of the information that is provided for heating and lighting, insurance, interest nursery management, irrespective of FRM on loans, etc., depreciation on capital and plant health requirements. items, VAT, etc. • Operations 1.3.1 Nursery management records (a) Technical: details of those operations The first and most important preliminary is to and conditions in the nursery which decide why and how any given record is wanted, may affect yields and help comparison e.g. to provide a guide as to the financial and of one year’s results with another. These technical efficiency of the nursery, to provide may best be kept in a diary; this should the basis for stock control and sales or to meet be divided by nursery sections so as to statutory requirements for retention of records show readily the events during the (e.g. VAT, Forest Reproductive Material, etc.). season for each section. Records collected without a clear idea of their (b) Legal: details of applications of pesticides purpose are quite likely to have omitted vital and similar operations, where records are points required in a later study. required to be kept under pesticide legis­

4 lation. Records of stocks of species cov­ taking counts have been made. When in ered by the Forest Reproductive Material doubt, nursery managers should enquire what Regulations and for plant health obliga­ is currently available for the computer system tions should be kept in such a way that they have installed in the nursery. the number and disposal of stock of each seed lot initially sown can be audited. 1.3.3 Labelling in the nursery; nursery plans 1.3.2 Stocktaking Customers rely absolutely on the nursery man­ This is a most important operation, normally ager to provide stock which is true to name; at falling due in late summer. For saleable plants, the same time, nursery managers have a legal over-estimates of numbers can lead to over­ obligation to take all reasonable precautions to selling and the need to buy in stock; under-esti­ ensure that the stock offered is correctly mates may lead to wastage. Both alternatives described and stock sold is true to name. (See are likely to result in loss of profits. also Chapter 15, sections 15.1 and 15.8). It is Numbers of stock in the nursery not intended strongly recommended that all blocks of plants for sale in the current year are required for growing in the nursery are both marked and annual valuation/accounting purposes, as well mapped. as for showing whether the future production Labels, while essential, by themselves are targets for the nursery are likely to be met. not enough - there are many instances of In many cases, the nursery manager will these having been disturbed by passing know his stock very well and will know intu­ machinery, visitors/vandals and, occasionally, itively the average stocking in beds and lines; animals and birds. Nursery section maps or nevertheless, it is easy to misjudge. Objectively plans should also be prepared, showing the taken sample counts provide the basis for reli­ position of each lot of seedlings or transplants, able short and long term records of production. so that, should a label be lost or displaced, If time and effort are not to be wasted, any there is an indisputable record as to where stocktaking system must be well designed sta­ any replacement label should go. tistically, in relation to the number and size of In transplant fines of similar species or dif­ samples taken. Advice on sampling systems ferent origins of the same species, it acts as a for stocktaking may be sought from the reminder to men lifting, if the change in identity Forestry Authority, Northern Research is marked by a plant of a totally different genus. Station, Roslin, Midlothian. Lawson cypress makes a good marker plant. A perpetual problem is that nursery sale cat­ All these efforts will be wasted if similar alogues and stock forecasts often have to be pre­ care is not exercised to maintain the identity pared in mid-summer, at a time when many of plants at all stages during handling and plants have still to put on a substantial part of despatch. their growth. The amount of this late growth is often critical in determining the size, grade or usability of the plants concerned. 1.4 Sale of plants Early assessments of potentially saleable Plants may be offered for sale by advertising stocks based on estimates of the percentage in any of the forestry and other journals survival of the number of plants in the ground reaching potential customers. At the same at the beginning of the growing season have time, a price fist or catalogue giving details of subsequently to be reconciled with actual the available species, origins, sizes and prices stocks shown from stocktaking. of plants, must be ready by at least mid­ Wherever computers with appropriate soft­ summer. The fist or catalogue has to be pre­ ware are available, they can speed up the pared, based on early season survival and availability of stock estimates once the stock­ growth as it appears in the nursery, on the

5 assumption that plants will grow normally in plants so as to be able to compare them with the remainder of the season. Every encourage­ the full consignment when received. ment should be given to prospective customers to see the growing stock in the nursery before placing orders. 1.5 Quality of plants Quality in the context of this Bulletin means 1.4.1 Forestry Commission surplus the fitness of plants for planting in the forest plants or woodland, where the intensive after- The Forestry Commission does not sell plants to planting care that can be provided in parks private woodland owners; any surpluses from and gardens is not available. its production are offered to the forest nursery Forest and woodland planting sites vary, trade, to whom enquiries should be made. both inherently in soil and climate, and through the scale and type of cultivation and 1.4.2 Horticultural Trades Association pre-planting vegetation control. Foresters’ demands may vary therefore, according to the The Horticultural Trades Association has a circumstances of the site to be planted and to Forestry Group currently with 32 forest the season of the year. Within this range of nursery members, between them producing demand, however, and given otherwise equal most of the UK forestry planting stock. The treatment, good quality plants have a better group regularly liaises with Government min­ chance of becoming established and getting isters and departments responsible for away to a good start than poor quality stock. forestry policy, keeping to the fore, issues of Nursery managers’ long-term reputation is concern to the forest nursery industry. based on their customers’ perception of this The group meets annually with the quality of stock. Forestry Commission and the Timber Growers There are three main attributes of quality: Association to exchange information on cur­ rent production and market trends. The group • inherent genetic quality; also prepares statistics of production by the • physical characteristics; private sector. At one time, the HTA acted as • physiological characteristics. clearing house for surplus forestry plants but These result partly from the starting mate­ is no longer doing so. rial (seed or cuttings), partly from the way Further details of the Forestry Group can plants are grown in the nursery and partly be obtained from the Horticultural Trades from the way plants are handled between com­ Association, 19 High Street, Theale, Reading mencement of lifting and final planting. RG7 5AH. Much stock which was of good genetic and physical quality in the nursery has deteriorated 1.4.3 Samples to worthlessness through failure to ensure good Any enquirer wishing to purchase any sub­ treatment during lifting, storage and despatch stantial quantity of forest plants should ask (See Chapter 14). for samples. The nursery manager should wel­ Uniformity or otherwise of a batch of plants come requests for samples, and should take is an aspect of quality which can be improved pains to include plants of the full range of the by appropriate grading before despatch. See lot in question; if this is done, much unprof­ last paragraph of section 1.5.2 below. itable argument between the nursery manager and the purchaser about whether the plants 1.5.1 Inherent genetic quality: seed sent were as advertised can be avoided. A origin and improved seed sample of any lot should consist of at least 10 transplants, or 25 seedlings. Seed origins The purchaser should bed out sample Recommended seed origins for the species

6 most commonly planted in British woodlands What nursery managers have to do in are given in Forestry Commission Bulletin 66 response to the regulations is set out in Choice of seed origins for the main forest Chapter 15, sections 15.1 to 15.3. See also the species in Britain (Lines, 1987). references at the end of that chapter.

Improved seed 1.5.2 Physical attributes of plant quality Limited but increasing amounts of seed are These include: becoming available from tested (‘approved’) and • physical dimensions - height, root collar untested seed orchards, derived from selected diameter and the ratio between them (i.e. superior (‘plus’) trees. Trees in tested orchards sturdiness); have undergone rigorous selection, breeding • morphology - stem form, branch habit, and field trial testing, so as to distinguish and leader persistence, foliage condition, root retain trees whose quality derives principally development and shoot:root ratio; and from their superior heritable genetic make-up, • nutrient status. discarding those whose quality derives from favourable local site conditions. For most ‘untested’ seed orchards, this process is still Height under way. See ‘The choices and relative values Height of plants sent out for- planting in the of different seed sources’, Chapter 2 in Forestry forest should exceed the minima given in Commission Bulletin 83 Seed manual for forest Table 1.1. Height is here defined as the dis­ trees (Faulkner, 1992); also further reading and tance from the bud of the leading shoot to the references under Mason, W.L. et al., and Rook, root collar or, in the case of vegetatively prop­ D., at the end of this chapter. agated stock, from the leading bud to the point of root emergence nearest the leading bud. EEC legislation Programmes of origin/provenance research, Root collar diameter seed stand selection and tree improvement, The diameter of the stem at the root collar for when first started in Great Britain, were justi­ plants of a given height depends primarily on fied by their inherent potential value to the amount of growing space they have been national forestry. Subsequently, the same con­ given in the preceding growing season. cepts have been adopted by the EEC and have However, the range of possible root collar been embodied in EEC legislation and diameters does differ from one species to national legislation described in Chapter 15 another, and the commonly planted forest below. species can be grouped into four stem diam­ The tree improvement programmes and leg­ eter classes shown in Table 1.1. Species in islation come together in that: Class I are the most sturdy for a given height, while those in Class IV are slenderest. • the current register of seed stands and poplar stoolbeds; For the species most commonly propagated vegetatively (Sitka spruce and hybrid larch), • the current register of seed orchards; and the stem diameter just above the point of root • the availability of small quantities of Sitka emergence nearest the leading bud should be spruce seed from progeny-tested seed orchards substituted for root collar diameter. for bulking by vegetative propagation; Table 1.2 gives standards for minimum root all now operate within the framework of ‘The collar diameters for various heights of trees Forest Reproductive Material Regulations, when sent out bare-rooted for forest planting. 1977’. The regulations apply both to bare- These standards agree closely with those rooted stock and to container-grown stock satisfying the ‘EEC standard’ under the Forest used for forestry purposes. Reproductive Material directive 71/161/EEC.

7 Table 1.1 Minimum height and stem diameter class Table 1.2 Standards of sturdiness (minimum of transplants for planting in the forest stem diameters for given heights) for transplants sent for planting in the forest. Species grouped by classes Species Minimum height Stem diameter class' shown in Table 1.1 (cm) Height Minimum stem diameter at collar Conifers (cm) Scots pine 15 I/ll Class Class Class Class Corsican pine 10 I 1 II III IV Lodgepole pine 15 II (mm) (mm) (mm) (mm)

European larch 20 III 10 3.5 Japanese larch 20 III 11-15 4.5 3.5 3.0 Hybrid larch 20 III 16-20 5.5 4.5 3.5 3.0 Douglas fir 20 ll/lll 21-25 6.5 5.0 4.0 3.5 Sitka spruce 15 III 26-30 7.5 5.5 4.5 4.0 Norway spruce 15 I/ll 31-35 9.0 6.5 5.0 4.0 36-40 10.0 7.0 5.5 4.5 Noble fir 15 I 41-45 11.0 7.5 6.0 5.0 Grand fir 15 I 46-50 12.0 8.0 6.5 5.5 Western hemlock 20 IV 51-60 14.0 8.5 7.5 6.5 Western red cedar 20 II Lawson cypress 20 III The leading shoot of otherwise vigorous Broadleaves Oak 20 I species such as Nothofagus procera frequently Beech 20 II die back to some extent but normally sprout Ash 25 I from the uppermost live bud and do not lose Sycamore 25 II apical dominance. Sweet chestnut 25 I Vegetatively propagated stock showing Birch 25 III Alder spp. 20 II strong plagiotropism, i.e. the tendency to grow like a side branch, should either be grown on * Where two classes are given, the first class should be for another year in the nursery or should be applied to ‘stocky’ plants and the second to ‘standard’ plants. culled. This also corresponds to the similar distinction in the EEC Branch growth should be normal for the standards. species.

(NB: Table 1.2 includes species not covered by Foliage condition and nutrient status the FRM directive and vice-versa.) Appendix IV During the growing season, plant foliage can gives full details of EEC Plant Standards; see exhibit transitory or long-lasting symptoms of also section 15.1.7. disease, damage or deficiency. These can arise Plate 1 illustrates acceptable quality plants, from: based on visual standards. • nutrient deficiency or excess, Chapter 5, section 5.6 describes standards for seed. • drought, • damage by wind or frost, Shoot development • attack by pests. Conifers when dormant should have a single See Chapters 4 and 13. Plants with poor, main stem and (except for Cupressus, Thuya discoloured or damaged foliage at the time of and allied genera) a single well formed ter­ lifting are normally culled out and discarded. minal bud. Seasonal bronzing of species like western red Broadleaves should similarly have a well cedar is not a defect. formed central main stem and healthy buds. Studies on the nutrient content of nursery

8 stock in British nurseries were carried out in or in transit (see also Chapter 14, section the 1960s but remain valid (Benzian, 1965). 14.2). Expected values of major and some micronu­ trients for conifer seedlings based on this Uniformity of stock work (which analyses needles rather than Batches of plants can be made more homoge­ whole shoots or whole plants) are given in neous by grading. However, this can be over­ Table 4.8. Deficiency symptoms associated done; it is preferable to achieve uniform stock with low nutrient content in needles are given by good nursery practice (Cannell, 1989; in Chapter 4, section 4.3. See also plates in Ritchie, 1989.) Almost always, plants are Benzian, 1965. graded by height categories; occasionally, they may also be graded by sturdiness. Root morphology and shoot:root ratio Grading may be desirable to avoid early In spite of many attempts, it is not yet pos­ variation in plant size in young plantations sible to find any simple objective non-destruc­ leading to some requiring, for example, tive physical assessment of quality of root weeding and some not, or to subsequent morphology and shoot:root ratio. Subjective uneven growth. South and Mason (1993) criteria have to govern practice. describe how in carefully measured studies of For all species, the ideal forest planting performance following planting, smaller plants stock have well-branched root systems carrying never catch up and if anything fall behind as many short fibrous roots, each capable of the plantation reaches canopy closure. quickly regenerating new growing tips. Cannell (1989) warns that in excessively However, there are substantial differences uniform plantations, trees may not be able to between species and it is easier, for example to assert dominance so that the woodland does generate fibrous rooting in spruces than pines. not produce the larger dimension log sizes Roots must not have been stripped of bark. expected in a normal assortment; however, The bigger and better developed the main this danger is not great, given the inherent stem is, the larger and more fibrous should the variation in most planting sites. root system be. A plant with a moderate size main stem and a good root system is more 1.5.3 Physiological attributes likely to become established quickly than a Physiological criteria are only slowly coming plant with a similar root system but larger top. into practical use in British forest nursery prac­ tice. Until 1990, the physical attributes dis­ Shoot:root ratio cussed above, together with a visual assessment The current rule of thumb is that the ratio of of hardening-off/dormancy, have been taken as shoot to root on a dry weight basis should not working substitutes for physiological tests, be more than 3:1. because of the lack of quick on-site tests for physiological condition. See also Chapter 14. Damage overwinter and during handling or storage Hardening off and dormancy Plants must not have been subject to water­ Until the beginning of the 1980s, hardening logging in the winter before lifting as this may off, i.e. the lignification of the current year’s kill the roots without visibly affecting the growth and the development of healthy winter foliage. Such waterlogged plants may start to resting buds, was taken as a visible physical flush shortly after planting out, but thereafter manifestation of internal physiological the tops soon die. changes, indicating that plants could be safely Plants must not have been allowed to dry moved from nursery to forest. Currently, out in the period between lifting and planting almost all bare-rooted plants are expected to in the forest, nor become heated while in store be fully dormant when lifted, dormancy being

9 maintained, where necessary, by cold storage stem form than stock from transplanted (see also Chapter 14, section 14.3). seedlings. (Mason et al, 1989). This is an ephemeral effect of taking cuttings from side Root growth potential (RGP) branches of the parent plant; after a few years in the forest, the inherent vigour and good RGP assesses the ability of plants to grow new form which justified the selection of the parent roots under controlled growth conditions; it has stock for vegetative propagation asserts itself. become an important criterion for defining both the planting season, the time for putting plants Similarly, British Standard 3936, part 4 into and removal from winter cold-storage, and (BSI, 1984) gives some figures for container a potential index of the condition of plants after plants, but these are based largely on Japanese handling (Tabbush, 1985, 1986 a and b, 1987, paper pot production and should not be related to plants from other containers. 1988; Aldhous, 1989; also Plate 3). The present grading standards have to be reassessed for this extended range of types of Electrolyte leakage stock, and where necessary, adjusted for these This techique is being tested as a promising and for plants from any other new plant produc­ rapid and simple test of the extent that roots tion system. have suffered damage allowing leakage of the salts in the cell (McKay, 1992) (Chapter 14, section 14.3). 1.6 Names and ages of plants The names given in Appendix III are used 1.5.4 Quality criteria for other plant throughout the Bulletin. Column 2 of the production systems appendix gives current botanical names. Alternatives to bare-rooted transplants for forest planting are coming into increasing use 1.6.1 Types of plant in British forestry practice. These include: Definitions of types of plant commonly raised in 1. bare-rooted undercut and side-cut seedlings nurseries in the UK are listed in the Glossary raised at low density in seedbeds following (Appendix II); they follow British Standard precision sowing (Chapter 8); 3936, part 4 (BSI, 1984). 2. bare-rooted transplants of cuttings rooted 1.6.2 Age and type conventions in polyhouses, principally of genetically The length of time plants have spent in the improved Sitka spruce and hybrid larch nursery and the treatments they have been (Chapter 10, section 10.2); given follow a well-established convention. 3. container-grown stock, initially Corsican For many years, the alternative techniques pine in Japanese paper pots, but with many available when raising stock for forest other species now being reared in a wide planting were restricted, so that the conven­ range of containers. tion remained simple; however, additional The concepts outlined in sections 1.5.2 and techniques introduced in the last decade have 1.5.3 above for bare-rooted transplant stock led to the need to extend the old convention to raised from seed are likely to apply in principle accommodate the new types of plants. to these other types of stock, and the sturdi­ Forestry Commission Research Information ness figures given in Table 1.2 provide a Note 135 (Samuel and Mason, 1988) sets out starting point for quality standards for the framework for the extended convention undercut and vegetatively propagated stock. now in use in the Forestry Commission. Nevertheless, the criteria and values have not been critically tested for such stock and must Age be applied with discretion. For example, some Age in years is indicated by the sum of figures rooted cuttings of Sitka spruce have a poorer describing the plant.

10 Type and duration of treatment FURTHER READING The approximate duration of treatment of MASON, W.L., DEANS, J.D. and THOMP­ plants is expressed as the time spent sepa­ SON, S. (eds) (1989). Producing uniform rately in the seedbed, cutting bed, transplant conifer planting stock. (Proceedings of a line or container. A numeral shows how long workshop at York, UK, IUFRO working the plant spent undisturbed at each stage, ‘1’ party S3.02-03, Nursery operations.) or ‘2’ representing the corresponding number Forestry 62 (Supplement), 1-314. of growing seasons, parts of a season being MASON, W.L., and GILL, J.G.S. (1986). given as ‘‘A’. Where plants are lined out very Vegetative propagation of conifers as a late in the growing season, it is a matter for means of intensifying wood production in local judgement whether these are better Britain. Forestry 59, 155-172. described as IV2+IV2 or 2+1. MASON, W.L., MANNARO, P.M. and WHITE, I.M.S. (1986). Growth and root development Letters and symbols representing treatment in cuttings and transplants of Sitka spruce Unless preceded by a letter, the first figure in 3 years after planting. Scottish Forestry 40 any plant description is the time spent undis­ (4), 276-284. turbed in seedbeds. ROOK, D.A. (1992). Super Sitka for the 90s. Letters preceding the first figure indicate: Forestry Commission Bulletin 103. HMSO, London. C plants raised from cuttings; P container-grown stock. Symbols following a figure indicate an oper­ REFERENCES ation after the period indicated by the figure: ALDHOUS, J.R. (1989). Standards for asses­ + transplanting sing plants for forestry in the United u undercutting Kingdom. Forestry 62 (Supplement), 13-19. S stumping (applied to willows and BENZIAN, B. (1965). Experiments on nutri­ poplars, usually in addition to trans­ tion problems in forest nurseries. Forestry planting) Commission Bulletin 37. HMSO, London. Two-year-old seedbeds which have been BRITISH STANDARDS INSTITUTION (1984). undercut are normally described as ‘lul’; how­ Specification for nursery stock. Part 4: Forest ever, the ‘u’ is not a reliable indication as to trees. B.S. 3936: Part 4: 1984. British Stand­ the undercutting prescription followed. See ards Institution, London. also Chapter 8. CANNELL, M. (1989). Uniform nursery stock Examples of age and type descriptions: and plantation development. Forestry 62 (Supplement), 263-273. 1-year-old stock: 1 + 0 Cl + 0 Pl + 0 V2 + V2 FAULKNER, R. (1992). The choices and rela­ 2-year-old stock: 1 + 1 l u l V + V Cl + Sl /2 2 tive values of different seed sources. 3-year-old stock: 2 + 1 F/2 + IV2 1 +1 + 1 Chapter 2 in Seed manual for forest trees, 4-year-old stock: 2 + 2 ed. A.G. Gordon. Forestry Commission Information on plant identity numbers is Bulletin 83. HMSO, London. given in Chapter 5, section 5.2. FORESTRY COMMISSION (1993). Woodland Grant Scheme - applicant’s pack. Forestry Commission, Edinburgh. GILL, J.G.S. (1983). Comparison of production costs and genetic benefits of transplants and rooted cuttings of Sitka spruce. Forestry 56 (1), 61-73. LEE, S.J. (1990). Potential gains from geneti­ cally improved Sitka spruce. Research

11 Information Note 190. Forestry Commis­ SOUTH, D.B. and MASON, W.L. (1993). sion, Edinburgh. Influence of differences in planting stock LINES, R. (1987). Choice of seed origins for size on the early height growth of Sitka the main forest species in Britain. Forestry spruce. Forestry 66(1), 83-96. Commission Bulletin 66. HMSO, London. TABBUSH, P.M. (1985). The use of co-ex- MASON, W.L., BIGGIN, P. and McCAVISH, truded polythene bags for the handling of W.L. (1989). Early forest performance of plants. Research Information Note 118/86/ Sitka spruce planting stock raised from cut­ SILN. Forestry Commission, Edinburgh. tings. Research Information Note 143. TABBUSH, P.M. (1986a). Plant handling. Forestry Commission, Edinburgh. Forestry Commission Report on Forest McKAY, H.M. (1992). Electrolyte leakage: a Research 1986, 17. HMSO, London. rapid index of plant vitality. Research TABBUSH, P.M. (1986b). Rough handling, Information Note 210. Forestry Commis­ soil temperature and root development in sion, Edinburgh. outplanted Sitka spruce and Douglas fir. RITCHIE, G.A. (1989). Integrated growing Canadian Journal of Forest Research 16, schedules for achieving physiological uni­ 1385-1388. formity in coniferous planting stock. TABBUSH, P.M. (1987). Effect of desiccation Forestry 62 (Supplement), 213-226. on water status and forest performance of SAMUEL, C.J.A. and MASON, W.L. (1988). bare-rooted Sitka spruce and Douglas fir Identity and nomenclature of vegetatively transplants. Forestry 60, 31-43. propagated conifers used for forestry pur­ TABBUSH, P.M. (1988). Silvicultural princi­ poses. Research Information Note 135. ples for upland restocking. Forestry Com­ Forestry Commission, Edinburgh. mission Bulletin 76. HMSO, London.

12 Chapter 2 Selection, layout and formation of a nursery for the production of bare-root plants

A. C. Miller and J. R. Aldhous

Introduction 2.1.2 Soil depth Careful attention to the selection of a nursery There should be at least 25 cm of readily site will amply repay all the effort involved. workable, well-draining soil; the subsoil must Failure to select a soil that is sufficiently acid also be free-draining. Any pan or compacted inevitably results in costly and unsatisfactory layer must be able to be broken up to main­ production of many commonly planted conifer tain good drainage. species, while selection of sites which are Soils containing many large stones or much unsatisfactory in other respects, e.g. on a gravel should be avoided. Tractor-based heavy soil, weedy, or in frost hollows, will sowing, undercutting and transplanting opera­ sooner or later (and generally, sooner) add to tions are becoming increasingly precise; while the cost of one or more operations or lead to small numbers of stones can be cleared off with unnecessarily high losses. a stone-picker or modified potato lifter behind a tractor, sites with stones that are large enough to throw undercutters or transplanting 2.1 Physical limits for nursery machines out of alignment should be avoided. sites 2.1.3 Rainfall The physical limits within which sites should The mean annual rainfall for the site should be sought are given below. preferably be in the range 700-1000 mm. Sites with a mean rainfall value less than 700 mm 2.1.1 Elevation should only be considered if irrigation will be available at all times. Sites with more than In England and Wales, nursery sites should be 1000 mm annual rainfall should only be sought certainly below 300 m and preferably selected if the soil drainage is excellent. below 100 m above sea level; in Scotland, sites should be below 100 m. The higher the site, the colder it will be at all times of the year, 2.1.4 Previous land use the shorter the growing season and the The previous use of land may influence its greater the chance of the soil being frozen or value as a potential nursery site because of covered with snow when plants are required the effect of some forms of husbandry on soil or other work should be proceeding. While acidity and the amount of weed seed present. plants in nurseries at higher elevations will Young plantation or any other type of wood­ remain dormant later in the spring than those land should not be spurned as possible sites in lowland nurseries, this advantage is offset for a nursery, if the soil texture and acidity by the disadvantages previously mentioned. are right; see Chapter 3, section 3.1.1.

13 The sites most readily converted to suc­ sentative series of samples from any potential cessful forest nursery production in Great nursery site. (See Chapter 3, section 3.3.6 for Britain since 1950 have been on acid, light- instructions on taking soil samples.) Samples textured soils covered with bracken or should be tested for acidity, organic matter heather. and nutrient status. A mechanical analysis is Where the production of poplars is not normally required, except when there is intended, soils classified by texture as sands doubt about the texture, drainage characteris­ should be avoided in favour of soils with a tics or workability of the soil when cultivated. sandy loam texture. Sites found to have soils with a pH of 6.0- Nurseries have sometimes been described 6.5 should normally be rejected unless there according to the previous history of the site, are special circumstances favouring the site as: ‘heathland’, ‘woodland’ or ‘agricultural’. and the soil can readily be acidified. These terms have never coincided exactly with Sites with a soil pH over 6.5 should be any particular soil characteristic and their rejected for the production of bare-rooted names are seldom used in any context of stock. nursery planning or management. At one time it was thought that heathland nurseries would become exhausted and would 2.2.2 Soil texture, workability and need to be replaced after a few years, as the drainage nutrients made available by the initial culti­ Most forest nursery work involving soil move­ vation were used up. However, with attention ment takes place in the winter and early to fertiliser prescriptions, maintenance of soil spring, whenever the weather is mild. The acidity and control of weeds, some nurseries of ideal forest nursery soil should therefore be heathland origin remain productive after two quickly draining and free-working at this time or three decades of cropping. On the continent, of year. It should contain only a little clay and nurseries of similar origin have been in culti­ silt and not too much very fine sand because vation for over 100 years. of its water-retaining properties. In the last 30 years, the large majority of new forest nurs­ eries have been established on sandy or loamy 2.2 Site selection sand soils with a maximum of 10% clay and Within the physical limits given above, the 15% silt; indeed, the soils in many such nurs­ factors to be taken into account when eries have practically no clay at all. Such selecting a nursery are: nurseries have often been most successful and productive, and while the light soils usually • soil acidity (Chapter 3, section 3.2); retain less soluble nutrients compared with • soil texture, workability and drainage; heavy soils, they are usually acid and rela­ • access and services; tively weed-free. • local topography in relation to frost hollows, Light soils quickly lose water from the sur­ exposure and aspect; face 1-2 cm, especially if left loose after culti­ • freedom from weeds, and effective barriers vation. However, crops’ water needs can be against invasion by weeds (Chapter 12); ensured by judicious irrigation. • labour supply; While the organic matter content of nursery • distance from trunk road network. soils is not crucial, a high content of fine organic matter assists retention of nutrients Of these, the first three are the most impor­ tant, but none can be safely ignored. and water, and plentiful coarse organic matter (e.g. as from residues of a fibrous greencrop such as rye-grass) may improve the working 2.2.1 Soil analysis qualities of loamy soils (but see also Chapter It is essential that tests be made on a repre­ 4, section 4.4 on coarse organic matter and

14 seedling germination). In most nurseries on surface should itself be ripped before any sub­ sandy soils, there is at least 3% organic soil or topsoil is spread back over it. Care matter in the soil, and in many Scottish nurs­ should be taken to ensure that the subsoil is eries of this type, the organic matter content not compacted by heavy machinery working may be 10% or more. The organic matter con­ when it is too wet. See also section 2.4.5 tent of loamy soils, especially those which are below. in warmer regions of the country and which Tile drains should not normally be neces­ have been in nursery or arable cultivation for sary for a new nursery site. In normal nursery some time, is usually less than 3% and often management, it is difficult to avoid com­ less than 2%. paction of sandy and sandy loam soils, and A soil very low in organic matter is less able some subsoiling is likely to be necessary from to retain and store plant nutrients, and may time to time. If tiles are put in (for example if require a more intensive ‘little and often’ the lower subsoil drainage is impeded), the nutrient regime, compared with better pro­ tiles must be at least 60 cm deep, and well vided sites. below the depth of any subsoiler that may be If drainage is not satisfactory because of an used in the nursery. It is important that the iron-pan or other compacted layer impeding drains are properly constructed with suitable drainage, the possibilities should be investi­ porous backfill immediately above the drain. gated of initially breaking it up using a sub- If tile drains exist from the previous land use, soiler with a winged tine. This configuration of their position and depth should be mapped as tine is particularly effective in breaking far as possible, to minimise the risk of dam­ indurated layers. aging them in subsequent operations. It is important to distinguish ‘pans’ and similar indurated layers of soil where less dense (and freely draining) soil is within reach 2.2.3 Freedom from weeds of the bottom of the subsoiler, from more sub­ Ideally, the site of a new nursery should be free stantial layers of compact soil which continue from annual and perennial weeds and weed below subsoiling depth so that the lower part seeds. With proper management, (i.e. continued remains a barrier to drainage even though the vigilance and cultivation, application of herbi­ upper part is shattered. cide or hand-weeding to remove any weeds Where surface water from adjacent land before they set seed), such sites can be kept enters the potential nursery site, cut-off or substantially weed-free for many years. The other surface drains or ditches should prevent difference in the direct annual cost of weeding water entering the nursery. Other drains may in a clean nursery compared with a weedy one be needed to lead away water accumulating is significant, though less now thanks to the in the nursery, especially from the permanent weedkillers currently available, than formerly road system and hardstandings around build­ when hand-weeding played a dominant role in ings. nursery weed control. See Chapter 12, for rec­ Any minor hollows where water might ommendations for weed control. accumulate can be filled with soil from adja­ Steps should be taken to minimise the risk cent slightly higher ground leaving a gently of weed invasion. If the nursery is reasonably domed surface so that water drains to the clean, import of plants should be minimised, edges. However, it is vital always to leave at wherever possible transplanting only seed­ least 20 cm of topsoil over all ground that is to lings raised on the nursery. be cropped. Some weeds, e.g. groundsel, have developed If it is necessary to reshape the landform of strains which are resistant to some weed­ any section, the top 25-30 cm of topsoil must killers. By raising and lining out only your be moved to one side while the underlying own stock, import of resistant strains of weeds subsoil is levelled. The lowest exposed subsoil is avoided.

15 Where there is any serious risk of weed should be avoided unless protection by means seeds blowing in from adjacent weedy land, and of internal hedges or shelterbelts can be pro­ it is not possible to persuade the neighbour vided. responsible to manage the land so as to prevent weeds from seeding, a boundary shelterbelt/ Aspect hedge may act as a filter intercepting weed There are various opinions about the best seed. Care has to be taken, however, to keep aspect for a nursery, the only point of agree­ that ground clean, otherwise it could harbour ment being that an easterly aspect should be more weeds than the neighbouring ground! avoided. The reasons are, firstly, that the winds that most damage plants are the cold 2.2.4 Frost hollows; slope; exposure; easterly winds of winter and early spring, and aspect secondly, that if plants are caught by a late These are all features related to local topog­ spring frost, the ill-effects are most acute if raphy. plants are thawed rapidly by the morning sun. Sites with a southern rather than a northern Frost hollows aspect should be chosen for poplar production because of their greater warmth. Avoidance of frost hollows is important to escape the worst consequences of late spring frosts. Frost hollows occur wherever cold air 2.2.5 Access and services can accumulate - in the bottoms of valleys, The nursery must be accessible to large com­ large or small depressions, and where there mercial vehicles, so that plants and materials are barriers to the drainage of cold air down a may be received and despatched and tractors slope. Where trees and shrubs form such a bar­ and implements brought in when required. rier, a gap as least as wide as the trees are The entrance and access to the main buildings high, created at the point in the barrier fur­ should be metalled and able to take traffic in thest down the slope, will enable the cold air to all weathers. If the existing access is not ade­ drain off. Little can be done to remove cold air quate for expected needs, the highway in natural frost hollows and nursery managers authority should be consulted before any spec­ may have to resort to overnight irrigation or ification for a new or improved access is netting or slatting shelters to protect specially finalised. vulnerable stock; see also, Chapter 11, section An electricity supply will need to be three- 11.4.3 and Chapter 13, section 13.1.1. phase if any substantial cold-storage facilities Nurseries located near the coast may find are envisaged, or if high capacity pumps are the influence of the sea reduces the incidence of required for the irrigation system. severe radiation frosts. In addition to a water supply for drinking and sanitation, estimates of water require­ Slope ments for irrigation must be included. These By choice, a nursery should lie on a gentle can be obtained from the calculations neces­ slope of 2-4°, with sufficient gradient to allow sary when preparing plans for irrigation on rain to run off, but without eroding the soil. open ground and for misting in propagation Moderate slopes easily become eroded and are houses (Chapter 11, section 11.4). The avail­ more difficult to work by machine, while com­ ability of water and any restrictions to be pletely flat land may be subject to poor nat­ observed in times of prolonged drought must ural drainage and frosts. be identified, so that plans and costings for the nursery can include provision for bore­ Exposure holes or a private reservoir to supply the Sites which are exposed to strong winds from nursery. any direction, but particularly from the east, Early discussions should be sought with the

16 authority responsible locally for waste dis­ Substantial numbers of plants may be posal; inevitably, there will be some washings required for upland or moorland sites where and waste from pesticides applied as part of spring is late; northerly nurseries have the everyday nursery husbandry. Whether these advantage that their season is more closely can be sprayed on to the soil, processed synchronised to such sites than those in the through a small on-site treatment unit or held south of England. However, cold stores and in a special tank for specialist off-site disposal lorries or trailers with or without chilled will depend on the pesticides expected to be storage make it practical for plants’ dormancy used, the geographical and geological circum­ to be maintained so that they can be distrib­ stances of the nursery site, and the require­ uted when required (Chapter 14, section ments of current legislation (Chapter 15, 14.7.4). As a consequence, the more southerly section 15.6). nurseries can take advantage of warmer growing conditions to produce regularly, good 2.2.6 Labour and supervision quality planting stock in 2 years and, by late- winter cold storage, avoid premature loss of No nursery can be run without a labour force. dormancy in the early part of the planting Their number and terms of employment season. depend on the degree of mechanisation envis­ aged and the availability of other work when the work force is not wanted in the nursery. In 2.3 Layout of nursery practice, the labour requirement ranges from V2 to 1 man-year per hectare of nursery pro­ ductive ground, exclusive of special require­ 2.3.1 Shape of nursery ments for vegetative propagation or other The nursery should be as compact, i.e. as near similar intensive production system. square as possible, and regular in shape so as While it has often proved possible to employ to minimise the length of boundary fence and a substantial proportion of staff seasonally, to reduce the amount of time lost moving from some key personnel (e.g. tractor drivers) must one part of the nursery to another by both be retained all the year round, amounting to labour and supervisors. 25-35% of the total annual labour requirement. There should be one ganger or senior worker 2.3.2 Size and shape of sections for every 8-12 workers, while a forester or These should be related to the method of other supervisor will be required full-time if working, the scale of mechanisation, the need the nursery exceeds 15 ha. The forester or for hedges and the topography of the ground. nursery manager in charge of a nursery, Sections should be not less than 0.5 ha in whether full or part-time, should have had area, and if lining out is by transplanting recent training or up-to-date experience in machine or by plough, sections twice this size nursery work. Nursery management requires (i.e. lha) are preferable so that machines can specialist knowledge and few untrained or get a continuous run of between 100 and 150 m inexperience staff do well in a nursery until before they need to turn. If the nursery is they have gained that knowledge. exposed and hedges are required for local wind protection, they should be parallel to the line of 2.2.7 Access to markets machinery and irrigation runs, the location of Nurseries producing the bulk of their plants which should be decided before hedges are for sale are best sited near the motorway and planted. trunk road network. Geographical proximity Where permanent shelterbelts are to be to potential markets is less important than planted or existing woodland retained as shel­ the time taken for delivery lorries to reach terbelts, these should be outside the nursery their market destination. boundary fences. Some nursery managers arrange the size of • Fertilisers - while fertilisers packed in sections so that in the direction of lining out, the polythene bags can be stored out of doors number of plants filling a full fine across the under a waterproof sheet, there is less risk section is a multiple of 1000; this eases control of theft or vandalism if they are under of piecework payments and lining out pro­ cover. grammes and subsequent stocktaking. • Plants - if large numbers of lifted, bare- root plants are to be held while awaiting 2.3.3 Buildings* grading, packing or despatch, some sort of Nursery buildings should be located in the plant storage is necessary. nursery where most convenient for efficient A cool, very well ventilated shed or management, within constraints imposed by shaded storage area, capable of holding a any planning approval or building bye-law substantial number of plants in co-extruded consent and the need for security of premises black and white polythene bags would meet and their contents. this need; plants have often been kept Buildings should provide the following facil­ under the shelter of a dense canopy in ities: conifer plantations. However, while this last is often well-suited to short-term 1. Offices for the nursery manager and his sup­ storage in upland plantations, it is not rec­ port staff, conforming to the requirements of ommended as the sole means of storage for the current regulations made under the any forest nursery. Offices, Shops and Railway Premises Act, If plants have to be kept dormant beyond 1963, and Health and Safety at Work Act, the time of bud-break, a refrigerated store 1974, in respect of cleanliness, ventilation, will be needed, enabling plants to be lifted temperature, lighting, sanitation, storage of while fully dormant in December/January clothing, etc. (HSE, 1989). and kept in that condition until required 2. Stores for: 3-4 months later; see Chapter 14, section • Machinery and tools - some items in this 14.7. category are costly and are attractive to • Seed - the need for a separate seed store thieves. There must at least be part of any will be determined by the scale and choice machinery or tool store able to withstand of species to be raised in the nursery. All casual attempts at forced entry. If any seed must be kept cool; in addition, any machinery maintenance is anticipated, the seed requiring moist prechilling treatment floor should be concreted and the store will need refrigerated storage where the appropriately equipped as a work area. temperature can be closely controlled. • Petrol and other machine fuels and lubri­ Where there is a coldstore for plants on cants - such a store must conform with the the nursery, it will also usually be suitable Petroleum Spirit (Motor Vehicles etc.) for storage of dry seed and seed being Regulations, 1929 (SR&O 1929/ 952). prechilled. For main-stream conifer and • Pesticides - this must be dry, secure and similar small seeds, there should be suffi­ conform with the requirements of current cient space even in the busiest years. If, pesticide legislation. If only small quantities however, large quantities of bulky seeded of pesticides are ever held in the nursery, a broadleaved species are expected to be secure ‘vault’ store may suffice; see Chapter grown, more careful planning and manage­ 15, section 15.6.5. ment will be required to ensure that space is available in a plant coldstore when needed. If no suitable plant store is available, a * The Acts of Parliament, Regulations etc. quoted here were in force in summer 1993. There is no guarantee that this refrigerator will have to be purchased, or list is comprehensive or that it will remain up to date. coldstore space hired for this purpose.

18 3. Working rooms or working space for: Where possible, a road should also be made • Seed preparation - including separating, round the perimeter of the nursery. This will cleaning and drying any locally collected ensure that machines can get in from both seed, soaking prior to prechilling, stratifica­ ends of all sections unless baulked by ditches tion, hot and cold treatment to induce ger­ or hedges, and will also provide a barrier mination, etc. against weeds encroaching from outside the • Receipt, grading, packing and despatch nursery fence. Permanent roads should not be of plants - this area must be cool and shel­ allowed to be covered with weeds. See Chapter tered; see also Chapter 14, sections 14.5 12 for means of keeping them clean. and 14.6; Roads, together with the associated head­ • Application of insecticide - by dipping or lands, should always be wide enough for trac­ by electrodyn treatment before despatch of tors and implements to be able to turn plants, if specified by the customer (see without damaging plants. The actual dimen­ Chapter 14, section 14.8). sions depend on the equipment in use on the particular nursery. However, for the longer 4. Mess room, washing and separate lavatory items, an overall width of 10 m should be facilities for men and women staff. These allowed for road plus headland. should be up to the standards prescribed On sloping ground, the layout of roads has under the Agriculture (Safety, Health and to take account of the permanent open drains Welfare Provisions) Act, 1956, plus any and the risk of scour and/or soil erosion. Where supplementary facilities required for staff possible, roads should cross the tops and bot­ who have been handling pesticides such as toms of sections so that loads can always be separate storage room for clean and poten­ taken downhill; this will reduce the risk of tially contaminated clothes. compaction of soil or bogging under wet condi­ 5. Readily accessible first aid equipment, tions where tractors are used, and will be less meeting the requirements of the Health fatiguing for staff moving plants, etc., by hand. and Safety (First Aid) Regulations, 1981 (SI Paths and alleys within or between sections 1981/917) and the current code of practice and unmetalled roads, should always be con­ issued by the Health and Safety sidered temporary and should be cultivated Commission (HSC, 1991). whenever necessary. Alleys between seedbeds Some of the above can be combined in one or beds of transplants should be 45-50 cm building if convenient. On private estate or wide to allow tractor wheels to pass easily. company sites where forest nursery produc­ Wider paths, up to twice this width, will be tion is combined with other rural land-based needed where hand barrows and trolleys are businesses, some of these facilities will form to be used regularly, or where stock is part of the overall provision for the site. undercut/wrenched several times in a season.

2.3.4 Roads, paths and alleys 2.3.5 Hedges and windbreaks The buildings should be served by an all- Hedges and shelterbelts have three distinct, weather metalled road connecting to the though often combined, roles: security, visual nearest public road. Permanent roads to screening and a means of reducing wind-flow. nursery sections need only be sufficiently well Traditionally, hedges have been grown to surfaced to carry a tractor and trailer. Often, provide security against incursions by live­ the natural soil, when compacted by traffic, is stock. Such hedges are managed so as to adequate for this purpose, but in nurseries on maintain dense live foliage throughout, but stony soil, any stones collected from the sec­ especially at the bottom of the hedge. tions should be thrown on to the most heavily Hedges providing visual screening are often used roads to reinforce them. taller than stock hedges; nevertheless, dense

19 lower foliage is desirable if the screen is to • Cotoneaster spp., remain effective. • Scots pine (may harbour pine needle dis­ The aim in designing windbreaks and shel- eases), terbelts is to reduce windspeed without gener­ • Prunus spp. in plum growing areas (plum ating additional turbulence. Such belts do not pox virus (Buczacki and Harris, 1981)). provide the security that a dense stock-proof hedge will provide; a dense hedge provides See also, Chapter 13, last paragraph of good shelter in its immediate lee but is ineffec­ introductory section. tive after a short distance because of the tur­ bulence generated as the wind passes over it. Windbreaks Within a nursery, there may be need for For best effect, hedges intended as wind­ hedges for security or as windbreaks, or both. breaks should be 50% permeable to the wind. However, hedges also have disadvantages. Denser barriers increase the turbulence of the They impede the work of machines and take air-stream crossing the windbreak and the up space, they can harbour weeds, pests and benefit to crops is less (Baxter, 1985; Garner, diseases, they can root out into sections, com­ 1988; NSCA, 1985). peting for water and nutrients and, if wrongly sited, can create frost pockets. Hedge maintenance Hedges should be cut, preferably not with ver­ Security hedges tical sides but tapering towards the top. This Where security hedges are required, good will give branches at the base a better chance quality plants should be put in at 50 cm of remaining alive, so that the hedge will not spacing along ground that has been trenched, go thin at the bottom. Hedges should not be dressed with fertiliser as for transplants, plus allowed to intrude into the nursery. They are a liberal application of hop-waste or other more effective as permeable barriers if kept bulky organic manure, if used in the nursery. narrow. The following species make good hedges: Roots of hedge plants may enter cropped areas and compete with plants nearest the • Lawson cypress, hedge. In addition to cutting the hedge to keep • western hemlock, it properly shaped, periodic deep ripping or • tamarisk (for areas near the coast in the hand trenching, parallel and close to the hedge south of England), should be undertaken, to check lateral spread • holly. of roots, taking care not to disturb drains, cables or other services. Unsuitable species include: • beech (may harbour aphis), 2.4 Breaking-in a new nursery • western red cedar (may become infected with ‘Keithia’ (Didymascella thujina)), 2.4.1 Sequence and timing of operations • Monterey cypress (may be killed in severe winters and may become infected with Much the same sequence of operations is Seiridium cardinale, (Phillips and Burd- required whether the site is covered with ekin, 1992)), trees, with heather and bracken or with grass, except that for grass and heather sites, the • Leyland cypress (grows very vigorously, earlier operations are unnecessary. The best requires heavy regular cutting to keep it sequence is: under control, and may also be affected by Seiridium), • removal of trees and scrub; • hawthorn (because of risk of fireblight • removal of aerial parts of woody weeds; (Erwinia amylovora)), similarly, • ploughing;

20 • cleaning (i.e. removal of woody roots); bulldozer fitted with a toothed grubber blade • subsoiling; should be used to push out stumps and scrub. • incorporation of initial application of nutri­ A toothed blade is preferable to a standard ents; dozer blade; it does not disturb the soil more than is necessary and removes less soil with • final cultivation. the roots, so making burning easier. Where If possible, the nursery fence should not be trees are of any size, their crown and stems erected until the cultivations are completed, should be felled before the bulldozing starts, so as to give the greatest degree of freedom of leaving stumps 70 cm to 1 m high, so as to give manoeuvre to mechanical equipment for as the bulldozer good leverage on the root long as possible. However, if the site is heavily system. infested with rabbits, it may be necessary to Where there are only low stumps, stumps fence and commence control operations before can be picked out by excavator using a bucket the final cultivations. Temporary fencing may attachment. Two shallow trenches are made be required where other operations, e.g. road one either side of the stump, severing lateral or major building construction, are not sched­ roots, after which the stump can usually be uled to be complete before the site has been lifted out from the front with minimal soil dis­ broken in. turbance. Ideally, trees should be felled, and stump Alternatively, trees can be winched down and scrub removal completed during the while still standing, either by tractor fitted summer, so that cleaning can go on in suitable with a winch or by hand winch. Within weather until the beginning of the nursery reason, the higher the winch cable can be season when the ground is to be cropped. attached up the tree to be removed, the easier Stones collected during initial cultivations the tree comes down. may be suitable for metalling the main All stumps, roots, brash/lop and top should nursery road. be removed from the cleared site, using a for­ In all the initial operations, as little subsoil warder, or loader and dumper trucks. If such as possible should be brought to the surface. material is to be burned, the fires must be out­ Undesirable compaction of the soil can be min­ side the nursery cultivated area otherwise the imised if every opportunity is taken to clear fungus Rhizina inflata may colonise the site and prepare the site in dry conditions. and, in later years, may kill newly planted stock (Phillips and Burdekin, 1992). 2.4.2 Removal of vegetation If care is taken to pick up and cart off the large bulk of the roots, stumps and brash, and Trees and woody weeds the brash has not been forced into the soil by In all clearing operations, tractors extracting harvesting equipment, the soil can be roto- timber and machinery preparing the site vated to 25 cm and subsequently a stone should not run over brash/lop and top. This picker behind a tractor will clear the will avoid it being pressed into the soil, and remaining woody material. made more difficult to lift from the site. This is the opposite of what many timber har­ Herbaceous vegetation, heather, bracken, vesters may expect, so that they must be etc. specifically instructed on this point. The soil Low woody vegetation such as heather, types selected for nurseries are likely to be bracken, bramble and gorse should be cut by fully capable of supporting harvesting equip­ tractor-mounted swipe or rotary cutter, the ment without a brash mat except for any wet loose vegetation raked up and taken off the depressions on the site. site. Alternatively, if there is only a light cover Where trees and scrub have to be cleared of woody vegetation, it may be reduced to a rather than being sold as timber or firewood, a mulch by a rotary chopper.

21 On heathland and non-woodland sites, the If it is necessary to level the ground surface mat of roots, grass and residues of involving more than a few centimetres change herbaceous weeds and heather must be broken of depth of soil, the top 25 cm of soil should be up. The best means of doing this is to plough to carefully removed from the whole of the area a depth of between 10 and 15 cm. Alternatively affected (i.e. both the ground to be lowered and a very heavy rotovator may be used, followed the ground to be raised). The whole area by a stone picker, as for woodland sites. should then be ripped with a winged tine, lev­ elled, ripped again and the topsoil then spread Grassland back into place. Any grassland should be ploughed to a depth of Sections disturbed in this way should in 20 cm and should not be rotovated, nor should addition to the initial application of mineral the turf be removed from the site. The grass nutrients prescribed following soil analysis, be should be first ploughed as early in the summer given either a heavy application of bulky as possible to give it time to break down thor­ organics immediately after replacement of the oughly. Spraying with herbicide (glyphosate or top-soil, or, preferably, be put under a ryegrass paraquat) a week or two before ploughing may green crop for a growing season. hasten its breakdown and reduce the uneven­ ness of the first crop grown subsequently. 2.4.5 Deep subsoiling/ripping Any patch of couch or similar deep-rooted If there is an iron-pan or other hard layer of creeping weed-grass should be treated chemi­ soil within 0.4-0.5 m of the soil surface which cally, about 2 weeks before ploughing; see may impede drainage or rooting, this may be Chapter 12, sections 12.2 and 12.3. broken up by deep subsoiling with a tine at intervals of 1.2 m across the nursery. After run­ 2.4.3 Cleaning cultivations ning in one direction, a second series of runs should be made at right angles to the first. The soils should next be worked repeatedly, The first operation in a nursery should be alternately ploughing to about 15 cm and har­ undertaken using a winged tine ripper. This rowing or cultivating with spring tines until all requires a greater drawbar pull than is avail­ the coarse woody remnants of stumps, stems able from the tractors standard in forest nurs­ and roots have been removed. Alternatively, a eries, and an 80-100 hp tractor will be stone-picker (e.g. Kverneland) can be used to required. For best effect, the soil must be dry screen out and remove woody material. when any subsoiling is carried out. Once the initial cultivations have been com­ Winged tines are able to lift a greater pleted, a careful watch should be kept for any volume of soil and be more effective in dis­ patches of creeping perennial weeds, e.g. turbing the lower layers of the soil if deep couch, sorrel, which may have survived. If tining is preceded by cultivation or shallow these appear, appropriate steps must be taken tining. Both operations can be carried out at to kill them by spraying and cultivation before the same time if the shallow tines are placed the first crops are sown or transplanted. well forward of the deep tine on the trailor toolbar. See Davies, 1982. 2.4.4 Levelling and grading Sections should slope evenly or, if on a flat 2.4.6 Incorporation of nutrients site, should be slightly domed. During the If a soil analysis indicates that the soil is too cleaning cultivations, a skilful ploughman can acid or is unduly low in phosphorus or magne­ move soil across a section to level out very sium, this can be adjusted by an initial appli­ minor humps and hollows. However, large- cation of lime (for excessively acid soils), scale transfer of top soil must be avoided as ground mineral phosphate (for soils low in denuded areas will produce poorer plants for phosphorus), kieserite or calcified magnesite several years afterwards. (for soils low in magnesium), dolomitic lime­

22 stone (excessively acid soils low in magne­ for setting up open nursery production. They sium) or sulphur for local patches of exces­ are also much more dependent on the success­ sively high pH. The amounts of each to be fulness of the techniques being followed, and applied should be determined on the basis on in particular the yield of well-rooted cuttings soil analysis; see Chapter 3, section 3.3. from stock plants. Nevertheless, preliminary These additions may be made at any time indications are that direct costs in setting up in the winter preceding the first crop, once the for vegetative propagation are of the order of ground has been levelled. Materials should be £100 000 for a production unit aiming to pro­ spread evenly and incorporated by ploughing duce 500 000 saleable rooted cuttings annu­ followed by rotovation. ally. No costs can sensibly be given for access 2.4.7 Final cultivation roads as these depend so much on the partic­ ular circumstances of the nursery location. The nursery site should finally be cultivated either by plough to a depth of 20 cm, or by spading machine or vertical rotovator to a 2.6 Site requirements for depth of 15 cm. If any nutrients have been added, a rotovator incorporates these more nurseries producing other types thoroughly in the soil, but it may be more dif­ of forest planting stock ficult to firm the soil sufficiently, if seedbeds are to be thrown up shortly after rotovation. 2.6.1 Vegetative propagation Where the propagation cycle includes a period 2.4.8 Fencing in open ground, the site requirements for a Only one nursery in a hundred can safely be bare-root nursery also apply to establishing a rim without a rabbit fence, but only a small pro­ new nursery exclusively devoted to vegeta­ portion need a deer fence. See Forest fencing, tively propagated planting stock. Forestry Commission Bulletin 102, pages 6-7 (Pepper, 1992) for fence specifications. 2.6.2 Container systems and fully housed propagation systems Where plant production is entirely inside prop­ 2.5 Costs of formation agating or container houses, there is no longer Recent direct costs (1991) of breaking in new any need to ensure soils with appropriate pH; ground for a nursery have been of the order of however, most of the other factors, including £1100 per hectare for green field sites and good soil drainage also apply. In addition, £5000 per hectare for woodland, exclusive of maintenance of uniform water pressure overheads and the cost of the ground. Rabbit- between and within houses is more important, proof fencing is £2-3 per metre run additional and is facilitated if the ground is sufficiently to this. flat for all the houses to be laid out on the same Irrigation for a large site costs between level on the site. Particular care should also be £1000 and £1500 per hectare. taken to ensure that the water supply will be Industrial buildings are in the range reliable both in quality and quantity. £150-250 per square metre floor area, while the capital cost of cold-storage facilities is of the order £50 per cubic metre of store volume. 2. 7 First crops in new nurseries The facilities recommended for vegetative propagation of Sitka spruce cuttings from 2.7.1 Land freshly taken in from heath­ improved seed orchard seed are described in land or woodland Chapter 10. The initial capital costs of such Where ground, before being taken in, showed facilities are additional to those given above no signs of weeds, there is much to be said for

23 sowing seedbeds on such land. There has been REFERENCES experience over many years of excellent first BUCZACKI, S.T. and HARRIS, K.M. (1981). crops in these circumstances without resort to Pests, diseases and disorders of garden presowing treatment with dazomet; see plants. (Collins Guides series). Collins, Chapter 12, section 12.3.1. Seedling yields London. may be slightly lower if there is a lot of par­ BAXTER, Sheila M. (1985). Windbreaks for tially broken down organic matter in the soil horticulture. ADAS Booklet 2280. MAFF, and the ground cannot be compacted as much Alnwick. as would be wished; however, the risk of DAVIES, D.B. (1982). Subsoiling. ADAS bringing in undesirable organisms, especially Leaflet L 617. HMSO, London. weed seeds is avoided. GARNER, J.R. (1988). Windbreaks for fruit Transplants are obtained from the first crops. ADAS Pamphlet 3150. MAFF, year’s crops of seedlings. Alnwick. No special steps are needed to introduce HSC (1991). First aid at work. Health & mycorrhizal fungi into new nurseries; suffi­ Safety (First-aid) Regulations, 1991. cient inocula are available in the soil and Approved Code of Practice. Revised, 1991. plants pick these up if nutrition and soil pH HMSO, London. are adequate (Levisohn, 1965). HSE (1989). A guide to the Offices, Shops and Railway Premises Act, 1963. Health & 2.7.2 Land formerly under agricultural Safety Executive Booklet HS(R)4. HMSO, crops London. If, however, the site is on former agricultural LEVISOHN, I. (1965). Mycorrhizal investiga­ land or there are reasons to believe there will tions. (Supplementary paper in Experi­ be a significant residual weed seed population, ments in nutrition problems in forest then more immediate management considera­ nurseries.) Forestry Commission Bulletin tions can determine whether to sow seed and 37, Vol. I, 228-235. HMSO, London. line out home production, or whether to NSCA (1985). Trees & shrubs for farm import seedlings for lining out in the first planting. NSCA Leaflet 50. North of year, and similarly, whether dazomet should Scotland College of Agriculture, Aberdeen. be used for controlling weeds in the first year, PEPPER, H.W. (1992). Forest fencing. and if not, what other means of weed control Forestry Commission Bulletin 102. HMSO, should be used. London. PHILLIPS, D.H. and BURDEKIN, D.A. (1992). Diseases of forest and ornamental trees. Macmillan, London.

24 Chapter 3 Forest nursery soils

D. G. Pyatt

To ensure steady output from forest nurseries, becomes impeded, for example if a plough pan first and foremost the soil must be sufficiently or compacted layer is formed by cultivating acid for the crop being raised and sufficiently when the soil is too wet, poor aeration and light and well drained to be workable during slow drainage in the soil may give rise to poor the larger part of the winter. Freedom from plant growth and yield, in spite of the most weeds is an advantage, though less important carefully conceived fertility regime. than formerly because of the availability of herbicides. 3.1.1 Texture Formerly, plants in forest nurseries largely Soil texture is defined by the proportion of depended for their nutrients on what was particles of different size in the soil. stored in the soil. Farmyard manure or lime Sand (particles from 2 to 0.06 mm diameter) might have been applied but this was as much and silt (particles from 0.06 to 0.002 mm) con­ to benefit a greencrop as forest trees. Only the sist mainly of minerals derived from parent soils with better reserves - the traditionally rock unchanged by weathering; in contrast, more fertile soils - could sustain any worth­ the clay fraction (<0.002 mm) consists pre­ while crops. dominantly of colloidal minerals formed as Now it is generally accepted that each crop products of weathering and not found in must be given a plentiful supply of mineral unweathered rocks. The origin or composition nutrients if vigorous stock is to be raised; of the particles does not affect the definition of large nutrient reserves and high organic texture. Thus the sand particles may be matter contents are useful but any conse­ 90-95% quartz - e.g. in soils derived from sed­ quences of deficiences in these properties can imentary deposits; alternatively the sand par­ largely be made good. ticles may include substantial proportions of felspar or mica, for example if derived from granitic rocks, or they may be composed of cal­ 3.1 Physical characteristics cium carbonate as in seashore dune sands The soil is composed mainly of particles where particles of broken seashells abound. derived from the parent rocks together with Clay particles in the soil have two important humus and partly decayed residues of dead properties: the ability to hold or combine with plants and soil animals. The texture (section nutrients required by plants, and the property 3.1.1) of the soil is determined by the propor­ of swelling and shrinking as the soil becomes tions of different sizes of mineral particle; the wetter or drier. This latter property has a major structure (section 3.1.3) of a soil is determined influence on the structure of the soil and the by the extent to which the particles adhere ability of the soil to form aggregates, such as together to form natural aggregates. the ‘crumbs’ composing the surface of seedbeds The growth of crops and their response to at sowing time on loamy or heavy clay soils. fertilisers can be very much affected by the Natural drainage channels in clay soils physical condition of the soil. If drainage occur only between aggregates of particles and

25 are open only when some shrinkage has taken within certain limits by the nursery manager. place in the clay. The spaces between indi­ Soil texture, however, can only be modified at vidual clay particles are minute and when a greater expense than is generally accept­ filled with water do not drain under the force able. Only if the soil is of the right texture is it of gravity. possible to produce successful annual crops of tree seedlings and transplants regularly. Classification by texture On the heavier soils, winter work may The proportions of sand, clay and silt present become impossible in wet periods and frost-lift in each soil can be the basis of an objective soil may also be a serious problem, limiting classification. Several alternative classifica­ autumn lining out. In addition, within the tions have been made; one of the best known, range of soils commonly encountered in forest shown in Figure 3.1, is used by the Soil nurseries, the heavier the texture, the easier Survey of England and Wales (Hodgson, 1985; it is to create a cultivation pan (section 3.1.5). Avery, 1990). 3.1.2 Organic matter and humus Texture of forest nursery soils Organic matter is not taken into account in An ideal nursery soil should be well drained, the standard soil texture classifications. stone-free, and have a maximum of 10% clay Nevertheless humus in the soil holds moisture and 10-15% of silt. Soils within these limits and nutrients as clay does, but without its fall into the texture classes; sands, loamy stickiness. Soils low in clay but relatively high sands and sandy loams. Good nursery crops in organic matter are probably the ideal from can also be grown on soils with less than 10% the point of view of texture for forest nurs­ silt and clay - by definition sands - though eries. more attention has to be paid to the supply of Organic matter in soil varies considerably. nutrients on such soils, and to ensure plants One important practical distinction however is do not suffer from drought. between raw organic matter and humus. Raw Some soil characteristics such as pH and organic matter consists mostly of remains of nutrient status can be modified fairly readily plants, usually partially decomposed, but still retaining part of the original plant structure. During decomposition, the proportion of cellu­ lose and hemicellulose in plant tissues is usu­ ally reduced in relation to the lignin constituent. This lignin breaks down much more slowly and its colloidal, dark-coloured residues form the bulk of what is called humus. Any chemical determination of organic matter may include raw organic matter besides humus proper, as well as the live tissues of soil bacteria and fungi, though these last two sources form a relatively small part of the organic matter so determined. However, colloids derived from bacteria may form an important constituent of humus. Humus swells or shrinks in response to wet •*— % sand fraction 60-2000 pm or dry conditions respectively and thereby Figure 3.1 The composition of the textural classes of assists in establishing and maintaining good soils. (Based on the system used by the Soil Survey soil structure. Raw organic matter can also of England & Wales and ADAS; reproduced with have an important effect on soil structure, permission.) partly by its own physical presence as a dis­

26 continuity in the soil mineral matter and the amount of air or water present, the rate at partly as a site of bacterial and fungal activity which air diffuses and the rate at which water where organic colloids are present in far percolates down through the soil. greater concentrations than normal. In a soil with a good structure, between 40 When a new nursery is established on land and 60% of the volume should be occupied by previously under semi-permanent heathland, pores and V3-V 2 of the total pore space should woodland or perennial grass vegetation, the be filled with air. If the air-filled pores are organic matter content of the soil diminishes reduced to 10% of the soil volume or less, until in equilibrium with the new soil condi­ plant growth becomes impossible. tion associated with annual cropping. The Pore size has a most important effect on the breakdown of the initial ‘surplus’ of organic tenacity with which water is held in the soil. matter may be quite rapid, especially if the In pores with a diameter of less than about soil pH is raised by liming. The improved aer­ 0.03 mm, the water is held with a force ation resulting from cultivation is an impor­ greater than that of gravity, while in pores tant factor stimulating this biological larger than this the water can drain away. decomposition of organic matter. As break­ Thus clay soils with a large proportion of very down proceeds, plant nutrients are released, small pores hold much water while sandy soils thus giving rise to the outstanding growth of have few small pores and retain little. Plants plants in the first years of many heathland extract ‘available water’ from the soil until nurseries. See also Chapter 4, section 4.4. they can get no more, when they reach ‘wilting point’. 3.1.3 Structure Only about 21 mm of water is ‘available’ in the top 15 cm of sands; on heavy clays, up to In contrast to texture, structure describes the 27 mm of stored water is available, while on way the soil particles are aggregated. Soils loamy soils with a high proportion of fine have their individual particles clustered sand, 30-35 mm of water is available. together into crumbs, clods, blocks, etc., (Hodgson, 1985). Plants on very coarse-tex- though in sandy soils these are weakly devel­ tured soils, with a small reserve of available oped and easily break up. The shape and size water are therefore more likely to suffer from of these aggregates principally determine the drought than plants on medium-textured structure. How densely aggregates are packed soils. See also Chapter 11, section 11.2. together also is part of the description of the structure of any soil. The pore-size distribution in soil is deter­ mined partly by the texture and partly by the One, if not the most important effect of a structure, which in the upper layers of culti­ good soil structure is to ensure good drainage vated soils can be markedly affected by man­ and aeration, the gaps between individual agement. In a loamy soil, a crumb structure, aggregates being the main channels for the whether produced by skilful cultivation or by movement of excess water. Loss of structure substantial additions of organic matter, will implies that soil becomes denser, the larger not only increase the amount of pore space but pores disappear and drainage is impeded. See also the proportion of large pores, so also section 3.1.5. improving the natural drainage and surface aeration. 3.1.4 Air and water, pore space and Sandy soils with a high proportion of fine compaction sand are liable to drain more slowly following Soil may be described as a mass of particles, heavy rain or irrigation and to be more liable more or less aggregated together and perme­ to compaction damage if machine-lifting or ated with a network of channels and pores. other operation involving repeated passage of Some fundamental soil properties derive from machines has to take place while the soil is the geometry of this pore space, for example, still very wet. On such soils, checks for com­

27 paction should be made regularly and also Plough pans can easily form and any slow­ whenever there is a suspicion that drainage is ness in disappearance of water following slower than expected. heavy rain or any unexpectedly poor health of Heavy dressings of organic matter can have stock, especially transplants, should immedi­ a marked effect on the moisture-holding ately lead to a test to determine whether a capacity of light soils, and increases of up to plough pan is present. Lodgepole pine trans­ 70% have been reported in agricultural prac­ plants of inland origins seem particularly sen­ tice. A similar effect was observed in the sitive to temporary waterlogging of this sort. woodland nursery at Teindland in Moray, A pan may be detected by digging carefully where regular dressings of hopwaste main­ into the suspect area. The spade should be tained the original exceptionally high organic handled very gently and only a shallow layer matter content and the water-holding capacity of soil removed at a time. A pan will be of the soil, while without hopwaste both have apparent by the occurrence of compact soil at fallen markedly; the stability of the very small a depth of between 10 and 20 cm according to soil crumbs has also been improved. (Table the depth of cultivation. Once the pan is 4.9, page 58; Low and Sharpe, 1973.) passed through, the soil may become less com­ pact again. An alternative method of detection 3.1.5 Plough pans and soil capping is to dig a pit to a depth of 25 to 30 cm, care­ A plough pan is a compacted layer where soil fully expose a clean face on one wall and with aggregates are more densely packed and some a pencil point probe the soil at intervals down may have lost their structure by being rubbed the profile. Any compact layer can be detected and pressed together. by greater resistance to the probe. A cruder Once present, the pan may interfere with alternative is to probe vertically with a sharp free drainage and thus cause temporary strong rod. waterlogging leading to root death, or it may Visually, compacted layers sometimes interfere with root penetration. appear to be lighter or greyer in colour than A pan will usually develop whenever soil is the soil either side. In extreme cases, the pan frequently cultivated to the same depth, gives off hydrogen sulphide (the smell of whether by repeated passes of the plough rotten eggs), and has an olive hue which share and tractor wheel, by rotovating or by rapidly darkens on exposure to air. repeated passes of a plant lifter. Pans are All these methods require a sensitive touch, most readily formed when any of these opera­ but this can be acquired with a little practice. tions is undertaken when the soil is wet. Any nursery forester should acquire the skill There is a strong risk of plough pan forma­ to test for plough pans at the earliest opportu­ tion when ground is repeatedly cultivated nity. during fallow periods to control weeds. This risk can be minimised by ensuring that mid­ Capping season cultivations are to a depth of at least Capping of the soil, i.e. the formation of a thin, 5 cm less than the final autumn ploughing smooth, almost impermeable crust, is common which should be to full cultivation depth. Any after heavy rain, and may be particularly plough pan formed during the summer should common on sandy loams and on silty soils low be broken up before the winter by use of a in organic matter. Water will run off a capped winged subsoiling tine at 0.9-1.3 m intervals. soil more rapidly in heavy storms than if the Winged tines are more efficient and will allow soil surface is loose, thereby rendering the the disruption of the pan in one pass (see rainfall less effective in replenishing soil-mois- Davies, 1982). If a winged tine is not available, ture reserves. Such rapid run-off also occasion­ an unwinged tine should be used, working first ally leads to soil erosion. Otherwise, there is no in one direction and then at right angles to it. evidence that soil capping is harmful in forest The soil should be dry at the time of subsoiling. nurseries. Surface cultivation can break up the

28 cap, but when a vigorous crop of seedlings or pH between 4.5 and 5.0. Spruces, hemlock, transplants is growing, the cap is unlikely to lodgepole pine and larch grow more slowly in be damaging. Capping is less prevalent where soils with a pH much outside this range and, the organic matter content of soil is high and it under otherwise identical conditions, may be is unlikely to be serious in seedbeds where a less than half as tall on neutral soils (pH suitable grit cover is used, or on fallow ground 6.5-7) as on acid soils. Scots pine, Corsican which is cultivated regularly. pine, Norway spruce and Douglas fir are less intolerant of slightly acid or near-neutral soils, though these species still do best in acid 3.2 Soil pH conditions. Western red cedar on the other hand grows better on slightly acid soil (pH Soil acidity or soil reaction is commonly 5.5-6.5) than on acid soil, but this is the only referred to in terms of the pH scale where a commonly planted conifer for which this value in the range 6.5-7.5, measured in water, response has been established. indicates a neutral soil, values from 5.5 to 6.5 There has been little research into the pH indicate slightly acid soil, from 4.5 to 5.5 acid responses of hardwoods while in the nursery. soil, and less than 4.5 very acid soil. Soil pH However, practical experience and limited values of 3.5 or less are rare. Soil pH values research show that seedlings and transplants above 7.5 indicate alkaline soils. of the broadleaved species most commonly In the laboratories of the Forestry Commis­ planted in woodlands, e.g. oak, alder, beech, sion, the Agricultural Development and birch and sycamore, grow well in the nursery Advisory Service and the Macaulay Land Use on acid soils (pH 5.0-5.5) but that poplars and Research Institute, the pH of soil is measured ash require slightly acid or nearly neutral electrically after the soil has been mixed with soils (pH 5.5-6.5) and will not tolerate acid water. Some workers have used solutions of conditions. calcium chloride. Measurements made in cal­ For most crops, an acid soil is therefore cium chloride solution are usually about 0.6 either essential or at least satisfactory. If both less than those made in water. This difference conifers and poplars are to be grown, an acid has to be remembered when examining the pH soil should nevertheless be sought as it is easy response curves given in Forestry Commission to make an acid soil less acid by adding lime­ Bulletin 37 Experiments on nutrition problems stone or chalk but more difficult to acidify a in forest nurseries (diagrams 7-13, pages neutral soil. Some nursery managers have 36-44) (Benzian, 1965). limed a section of an otherwise acid nursery The pH, as determined in the field or labo­ and keep this section solely for the production ratory, varies a little not only with method of of hardwoods. measurement but also with time of year and crop. It will tend to be higher in cool, moist 3.2.2 Changes in pH weather and in winter than in hot dry weather and in summer; it will also be higher The pH of soils is most readily changed by in summer under a crop than under bare liming which raises the pH and makes the soil less acid (see the following section). Liming is fallow. Thus differences in soil pH of less than 0.2 should be ignored. Where possible, com­ usually a deliberate and controlled attempt to parisons should be based on samples taken at influence soil acidity, but the pH of soils can the same time of year and following a similar also be altered by certain fertilisers sometimes crop. For production nurseries, sampling in used in forest nurseries, some fertilisers acidi­ the autumn on fallow land is the ideal. fying soil more rapidly than others. (See sec­ tion 4.2 et seq. for details.) The rate at which soil pH may change 3.2.1 Plant growth and pH depends on the soil texture. The resistance to Most seedling conifers grow best in soil with a change, the ‘buffer capacity’, is largely propor­

29 tional to the organic matter and clay content lime requirement is to be determined, the lab­ of the soil (and in neutral and alkaline soils, oratory must be told the desired optimum pH the carbonate content, but this last is not rele­ for the soils being analysed; the recommenda­ vant to forest nursery soils). A strongly tions resulting from the analysis must be buffered soil is likely to provide a more con­ checked against the values shown in Table 3.1 stant environment for plants than a soil that for the pH and soil textures of the samples. If is weakly buffered; light sandy soils are how­ the ‘lime requirement’ exceeds the value ever usually in the latter category, unless very derived from the table by more than 600 kg well provided with humus. ha-1, the divergence should be discussed with the soil chemist doing the analysis. If in 3.2.3 Making soils less acid doubt, always adopt the lower value of the two. Where the soil is too acid, it can readily be brought to the optimum for the crop by adding Liming materials (See also sections 3.2.1 lime in one of its several forms. For forest and 3.2.4) nurseries, however, several warnings must be given. Firstly, many light sandy soils are The forms of chalk and limestone from the weakly buffered, therefore, the pH of such various geological deposits are, when finely soils may be very readily raised by liming; sec­ ground, approximately equal in value as ondly there is only a moderate range of pH means of raising the pH of soils even though over which optimum growth is obtained. To there may be small differences in the amount these must be added the fact that most weeds of other materials present. are less vigorous on very acid soils. Thus it is Dolomitic limestone provides Mg in addi­ of the greatest importance: tion to lime and can be used where, in addi­ tion to raising the pH, the Mg reserves in the • to apply lime evenly, soil have also to be increased. • not to apply excessive doses, Dolomitic limestone may be taken as equiv­ • to keep if anything on the acid side of the alent weight for weight to ordinary ground optimum. limestone or chalk, and at the same time, The amount of lime required depends on a equivalent weight for weight, to Epsom salts combination of the buffer capacity of the soil - as regards supplying magnesium. this is most readily related to texture - and Magnesian limestone contains less Mg than the extent to which the pH has to be raised. A dolomitic limestone but may be considered as guide which can be used in the absence of any its equivalent for all practical purposes. other information is given in Table 3.1. Soils Basic slag has been recommended in the are grouped in four texture classes. past. However, because of changes in the steel Within each soil texture class, three industry, it is no longer available. columns are given. Use the values in the first column (to raise the pH to 5.0) whenever the Lime-free seedbed grit sections to be treated are likely to be used for In the past, the pH of many nursery soils was conifer production. Values in column two (to raised unwittingly, when grits containing lime raise the pH to 5.5) may be used if the sections were used as seedbed covers and when basic to be so treated are for hardwoods only, while slag or composts made with liming materials the values in column three should only be were applied to greencrops and trees. In used for sections devoted to the raising of recent years, foresters have understood such poplar or ash. dangers and have used lime-free grits, etc. Soils laboratories are also able to determine Periodic checks must be carried out however the ‘lime requirement’ of soil (i.e. the amount to ensure that in particular, the grits cur­ of lime required to raise the pH to a given rently in use for covering seed are lime-free. value) from samples sent in for analysis. If the If in doubt about the suitability of a grit,

30 take a sample (about a tablespoonful), put it is present, acidification is practically impos­ on a clean saucer or shallow bowl and pour sible. Every forester should, therefore, avoid over it a little dilute hydrochloric acid. If the measures which make the soil less acid than grit fizzes or individual particles of the grit is required and, of course, a soil with a natu­ fizz, limestone is present and the grit is rally high pH should never be chosen for a unsuitable. nursery. Hard water has also raised the pH of sec­ Soil without free lime may be acidified over tions which have been heavily irrigated for a period of several years by regular use of several years. ammonium sulphate applied as top-dressings A fuller discussion of the different liming to crops. The ammonium-nitrogen in this fer­ materials available is contained in Whinham, tiliser is either taken up directly by the plant, 1976. or on soils with a pH over 5.5 is converted to nitrate in the soil, leaving the free sulphate 3.2.4 Acidification of soils which is the principal acidifying agent. The While it is easy to neutralise an acid soil, it is nitrate-nitrogen also acidifies as long as it is more costly to acidify a soil when the pH is too not taken up by plants. high. Where a substantial amount of free lime More rapid acidification can be achieved by

Table 3.1 Tonnes per hectare of magnesian limestone, ground limestone or ground chalk to raise the pH of soil to approximately 5.0 (for normal forest nursery production); 5.5 (for sections devoted to hardwoods); or 6.0 (for sections devoted to poplars)

Soil texture class 3 Sands, loamy Sandy loams Silt loams, Clay loams, silty (Soils in class 4 sands sandy silt clay loams, clay but high in loams, sandy organic matter) clay loams

Tonnes lime per hectare to raise soil pH

Soil pH up to up to up to up to up to (suspension in water) 5.05.56.0 5.05.56.0 5.0 5.5 6.0 5.0 5.5 6.0 5.0 5.5 6.0

3.0 5.0 6.3 7.5 6.0 7.6 9.0 8.1 10.1 12.1 10.0 12.5 15.0 11.9 14.9 17.9 3.2 4.5 5.8 7.0 5.5 7.0 8.5 7.3 9.4 11.4 9.0 11.5 14.0 10.8 13.6 16.6 3.4 4.0 5.3 6.5 4.9 6.4 7.9 6.5 8.5 10.5 8.0 10.5 13.0 9.5 12.5 15.5 3.6 3.54.86.0 4.3 5.8 7.3 5.6 7.8 9.8 7.0 9.5 12.0 8.4 11.3 14.3 3.8 3.04.35.5 3.65.1 6.6 4.9 6.9 8.9 6.0 8.5 11.0 7.1 10.1 13.1

4.0 2.5 3.8 5.0 3.0 4.5 6.0 4.1 6.1 8.1 5.0 7.5 10.0 6.0 8.9 11.9 4.2 2.0 3.3 4.5 2.5 4.0 5.5 3.3 5.3 7.3 4.0 6.5 9.0 4.8 7.8 10.8 4.4 1.5 2.8 4.0 1.9 3.4 4.9 2.5 4.5 6.5 3.0 5.5 8.0 3.6 6.5 9.5 4.6 1.0 2.3 3.5 1.3 2.8 4.3 1.6 3.6 5.6 2.0 4.5 7.0 2.4 5.4 8.4 4.6 0.5 1.8 3.0 0.6 2.1 3.6 0.9 2.9 4.9 1.0 3.5 6.0 1.3 4.1 7.1

5.0 1.3 2.5 1.5 3.0 2.0 4.1 2.5 5.0 3.0 6.0 5.2 0.8 2.0 1.0 2.5 1.3 3.3 1.5 4.0 1.8 4.8 5.4 0.3 1.5 0.4 1.9 0.4 2.5 0.5 3.0 0.6 3.6 5.6 1.0 1.3 1.6 2.0 2.4 5.8 0.5 0.6 0.9 1.0 1.3

Note: If the soil contains more than 10% organic matter, use the next higher soil texture class; e.g. if the soil is a loamy sand, the values in the first set of three columns would normally be appropriate. However, if the soil organic matter of such a soil exceeds 10%, use the set of columns headed 'Sandy loams'.

31 a single heavy winter dressing of sulphate of is described in the previous section. Ammo­ ammonia. A dressing of 3750 kg ha-1 has nium nitrate is also likely to acidify soils, but reduced the pH by between 0.75 and 1 unit. not as strongly as ammonium sulphate. The (Benzian, 1965). However, such heavy winter effects of slow release fertilisers depend on dressings may result in excessively high con­ their constituents and no generalised com­ centrations of soluble salts and risk of scorch ment can be made. to plants during the subsequent growing Because pH is so important for plant season. growth and because it can be altered by the Alternatively, soils can be acidified by addi­ nutrient regime, soil samples should be taken, tions of screened rock sulphur, or flowers of at least for pH measurement, every 3 years as sulphur. Rock sulphur has been used success­ a matter of routine. fully in several Scottish forest nurseries. However, the risk of damage in a dry spring is greater with sulphur than with ammonium 3.3 Soil analysis sulphate. In either case, the sulphur is oxi­ Many attributes of the soil can be the subject dised in the soil and forms sulphuric acid. of chemical or physical analyses. However, Sulphuric acid has also been applied direct to only those which can be influenced by man­ soils experimentally. Ferrous sulphate is used agement are discussed below. Permanent in horticulture for acidification but not, so far attributes such as texture (section 3.1.1) while as is known, in British forest nurseries. of critical importance in selecting sites, are of The quantity of sulphur required for acidifi­ small significance in relation to day-to-day cation depends on the pH of the soil and the control of fertility. pH required. In experiments in England, While chemists have been examining agri­ 1250 kg ha-1 of sulphur were required to pro­ cultural soils for many years, forest nursery cure a drop of between 0.75 and 1.0 pH unit, soils have received much less attention. Cooke while in Scotland 500-600 kg ha-1 have had (1967) discusses fully the values and the limi­ the same effect. In some nurseries, the soil tations of soil analysis and emphasises the once acidified has stayed acid while in others risks of extrapolating results from one crop to the pH has slowly drifted back towards its another, or from one soil series to others original value. derived from unrelated parent material. Soils are normally analysed for P, K, Mg, pH and lime requirement. Some laboratories 3.2.5 Maintaining the status quo; and also determine the percentage of organic the effect of nitrogen fertiliser on pH matter. The analytical methods, especially in Several proprietary nitrogen fertilisers are England and Wales, have been based on agri­ available which combine a nitrogen compound cultural crops and agricultural soils; for forest with calcium carbonate, so that the fertiliser nurseries it seems at present best to treat the can be used with little effect on soil pH. results of soil analyses as indicators of any ‘Nitrochalk’ with 15.5% N was used as a top- need to boost reserves in the soil in addition dressing for seedbeds in research programmes to supplying, through fertilisers, the current for many years and had no effect on soil pH. needs of the crop. Currently, however, the content of N in this In paragraphs 3.3.1 et seq., tables are given and similar proprietary fertilisers is higher showing the range of values likely to be and the ratio of acidifying to neutralising con­ obtained when analysing soil for P, K and Mg. stituents changed. Light nursery soils are The two sets of values and indices given are likely to become more acid with repeated use those currently in use by the laboratories most of such compounds, but the rate of change will likely to analyse forest nursery soils, i.e. the be slow. Agricultural Development and Advisory The acidifying effect of ammonium sulphate Service (ADAS) for England and Wales, and

32 the Macaulay Land Use Research Institute in 3.3.3 Magnesium Scotland. The presence or absence of deficiency symp­ The recommendations in paragraphs 3.3.1- toms and results of soil analysis should deter­ 3.3.3 are adequate for sandy loams and loamy mine whether to apply magnesium for each sands of moderate organic matter content crop until the next analysis, or alternatively (say, between 2.5 and 7%). For heavy soils, or whether to apply magnesian limestone both to soils with a much higher organic matter con­ raise pH and increase reserves of Mg. tent, they will be less reliable. It has usually been considered that balance, i.e. a similar analysis index for P, K and Mg, 3.3.4 Interpretation of results of soil is as important as the actual values, and if P analyses and K, or K and Mg are badly out of balance, While a soil analysis is a highly informative then deficiency symptoms are more likely to guide to managers, it is most important to appear in plants. realise that it is not an exclusive basis for rec­ ommendations for any fertiliser regime. The 3.3.1 Phosphorus nursery forester has other sources of informa­ Results of soil analysis for P indicate whether tion which may support or modify recommen­ it is necessary to boost the reserve of P by dations based on soil analyses. The most means of an extra application at the first important of the other sources is the knowl­ opportunity after analysis. edge of the plants’ performance over the last 2-3 years in relation to the fertiliser used. 3.3.2 Potassium This and the knowledge of what can be Forest nursery soils which are light and acid achieved in productive nurseries should give usually contain little K and may have a limited a good idea of the extent by which current capacity to store any reserves. Additional fer­ practice needs to be modified to achieve such tilisers containing potassium should therefore aims as high out-turns of usable 1-year be added as a matter of routine as top-dress- seedlings, 1+1 transplants or undercut seed­ ings for each crop on such soils. Soils con­ lings. The forester should also know whether taining more adequate levels of K will need the plants show deficiency symptoms at any less top-dressing with K or possibly none at all. time during the year. The forester should

Table 3.2 Phosphorus content of soils by analysis

ADAS analysis Action recommended in addition to standard treatment* Macaulay analysis

Analysis results Index Analysis results Indexf (parts per million P) (mg kg~1 P)

0-9 0 Apply 1250 1 <7 VL 075 | kg of ground mineral 7-22 L 10-15 1 625 J phosphate per ha respectively 23-35 SL 16-25 2 Apply | 35-48 S-SL 26-45 3 standard 1 48-109 S 46-70 4 treatment J >109 H only

(ADAS scale goes up to 9 but the higher indices are relevant mainly to glasshouse soils)

* Standard treatment is to add for each crop 60-120 kg ha 1 of P (25-30 kg ha 1 for greencrop); see Table 4.4. t VL, very low; L, low; SL, slightly low; S, satisfactory; H, high.

33 have some idea of how the soil handles, and 3.3.5 Recommendations to apply lime its texture, structure and capacity to retain One particular aspect of soil analysis that nutrients, as well as being aware of features should always be looked at critically and of local climate which affect responses to fer­ checked against Table 3.1 and section 3.2.3 is tilisers, e.g. high summer rainfall or regular any recommendation to apply lime. Many soil spring drought. laboratories are accustomed to handling agri­ Where in doubt, and where information is cultural soils and to applying agricultural not otherwise available, properly designed and standards of lime requirement, and an error laid-out fertiliser trials can provide informa­ could easily occur here. If any lime recommen­ tion leading to more confident prescriptions dation seems excessive, ask for confirmation of for fertility maintenance. the figure recommended, making it quite clear

Table 3.3Potassium content of soils by analysis

ADAS analysis Action recommended in addition to standard treatment* M acaulay analysis

Analysis results Index Analysis results Indexf (parts per million K) (mg kg~1 K)

0-60 0 Top dressing with K essential <12 VL especially on light soils. See Table 4.2 12—42 L 61-120 1 Perhaps top-dress with K 42-66 SL 66-91 S-SL 121-240 2 91-208 S 241—400 3 No top-dressings necessary >200 H 401-600 4

(Index scale goes up to 9)

* Standard treatment is to apply 125-105 kg ha 1 of K in spring to each crop; see Table 4.4. t VL, very low; L, low; SL, slightly low; S, satisfactory; H, high.

Table 3.4Magnesium content of soils by analysis

ADAS analysis Action recommended in addition to standard treatment* Macaulay analysis

Analysis results Index Analysis results Indexf (parts per million Mg) (mg kg ~1 Mg)

0-25 0 Apply 60 kg ha-1 magnesium <12 L to each crop. 26-50 1 Use magnesian limestone 12-24 SL whenever pH has to be raised. See Table 4.3. 51-100 2 Annual magnesium applications 24-36 S-SL probably not necessary. Use magnesian limestone whenever pH has to be raised. See Table 4.3. 101-175 3 >36 S 176-250 4

* Magnesium is not normally applied unless shown to be necessary by foliage discoloration or soil analysis, t L, low; SL, slightly low; S, satisfactory.

34 what is the desired optimum pH for the Normally, each nursery section should be nursery soil. sampled separately unless two or more sec­ tions are of the same soil type have similar 3.3.6 Sampling of soil for analysis drainage conditions and have been treated Before any samples of soil are taken, contact identically for several years. should be made with the laboratory doing the Any subsection or part of a section which analysis. Agreement must be reached about differs visibly from the rest of the section, or when and how many samples are required on which plants regularly grow markedly and the sampling and labelling procedure to better or worse than elsewhere in the section, be followed. Laboratories which may analyse should be sampled separately. forest nursery soils are listed in Appendix lb. It is important to determine the normal The method of sampling likely to be recom­ depth of cultivation, especially in heathland mended is given in section 3.3.7. Samples nurseries. should be taken in the autumn unless other­ For each section to be sampled, the aim is to wise agreed, so that variations according to get as representative a soil sample as possible. the time of year are minimised. It is prefer­ This can be done by collecting about 24 small able that soils should be sampled regularly equal samples from points evenly distributed every 3-4 years. over each sample area. Small sections may be Analysis may take some time; allow for at less intensively sampled, but a minimum of 10 least 6 weeks between sending samples and samples should always be taken. Sections may getting the results. Each section is best sam­ be traversed following a W pattern, and taking pled before greencropping or during bare six samples from each leg of the W; other sam­ fallow, whichever is normally part of the rota­ pling patterns may be used if preferred. tion. Samples should be taken in dry weather, Samples may be taken with an auger or a but if this is impossible, the soil laboratory spade. An auger is preferable and if samples should be consulted before any drying of soil is are to be taken regularly, a suitable tool attempted. In England and Wales, soils are should be obtained for this purpose. Sampling preferred undried. by spade necessitates additional work mixing Any covering letter and accompanying label samples and sub-dividing to reduce the bulky on the soil sample should, between them, give sample to the amount required for analysis. the following details: • Name and address of sender (to whom Sampling by auger results will be returned). There are special soil augers of approximately • Location of nursery if different from above. 3 cm diameter for taking samples; wood • Number of samples sent and source nursery augers of similar size can also be used if the section of each sample. shank is lengthened. Screw the auger into the • Analyses required. soil to the full depth of normal cultivation, pull it out with the soil sticking to it, then • Optimum pH desired for each section. take the soil off and put it in a clean bucket. • Date and reference of previous soil Continue this procedure, as outlined in the analyses. preceding paragraph, until the whole section • Crops and fertilisers since the last analysis. has been covered and sufficient soil collected • Any relevant information, e.g. deficiencies (i.e. about 1 kg). The soil should then be well observed, high summer rainfall, soil map if mixed and put in a polythene or cotton bag. available, soil type if known. Sampling by spade 3.3.7 Method of soil sampling If using a spade, ensure it is clean before sam­ First decide what areas should be sampled. pling, then at each sampling point, dig to

35 expose a smooth face of soil the width of the REFERENCES spade and to the depth of cultivation. From AVERY, B.W. (1990). Soils of the British Isles. this face, remove a slice of soil not more than CAB International, Wallingford. 3 cm thick from the whole depth of the BENZIAN, B. (1965). Experiments on nutri­ exposed face and put it in a clean bucket. All tion problems in forest nurseries. Forestry samples from a given section should then be Commission Bulletin 37. HMSO, London. mixed thoroughly in the bucket and the mixed COOKE, G.W. (1967). Control of soil fertility. sample reduced by repeated halving until Crosby Lockwood & Son, London. about 1 kg soil is left. This should be put in a DAVIES, D.B. (1982). Subsoiling. ADAS strong polythene or hessian bag - the best size Leaflet L 617. HMSO, London. is one which the sample will fill half to two- HODGSON, J.M. (1985). Soil Survey field thirds full. handbook. Technical Monograph 5. Soil For further reading, see Russell, 1988. Survey of England & Wales, Harpenden. LOW, A.J. and SHARPE, A.L. (1973). The long-term effects of organic and inorganic fertiliser regimes at Teindland nursery. Scottish Forestry 27, 287—295. RUSSELL, E.W. (1988). Soil conditions and plant growth, 11th edtn, ed. A. Wild. Long­ mans, London. WHINHAM, N.W. (1976). Lime in agriculture. ADAS Leaflet L 542. HMSO, London.

36 Chapter 4 Plant nutrition

M. F. Proe

Introduction 4.1 Foundations During the last two decades, new systems of The regulation of a balanced nutrient supply production have been introduced into British is one of the nursery manager’s most impor­ forest nurseries. Many of these make greater tant duties. Inadequate nutrient supply can use of cold storage, precision sowing, under­ cause failure in the achievement of production cutting, containerised stock and vegetative targets. No one nutrient is more important propagation. Such diverse production systems than another for plant growth, though in any require a thorough understanding of the prin­ particular nursery one nutrient may be in rel­ ciples of plant nutrition. atively short supply compared with others Pressure for land has now made fallowing because of the local soil type or climate. and greencropping more difficult to incorpo­ rate into nursery management plans. Many 4.1.1 Essential nutrients traditional sources of organic amendments Carbon dioxide and water provide the carbon have disappeared or are so remote from nurs­ (C), oxygen (O) and hydrogen (H) necessary eries that transport costs prohibit their use. for the production of carbohydrates during On the other hand, many new formulations of photosynthesis. In addition, plants require a fertilisers are now available, including slow further 13 mineral elements derived pri­ release and liquid products. marily from the soil. Six of these are required Environmental concerns over loss of inor­ in relatively large amounts - nitrogen (N), ganic fertilisers to drinking water supplies phosphorus (P), potassium (K), magnesium (especially in southern England) threaten fur­ (Mg), calcium (Ca) and sulphur (S). The first ther constraints to nursery management. four nutrients have to be applied deliberately Nutrient regimes in forest nurseries must, in the forest nursery or plants may not grow. therefore, ensure that intensive production Calcium and sulphur are constituents of fer­ can be sustained without long-term soil degra­ tilisers such as superphosphate and are dation. In addition, the supply of nutrients almost always present in the soil in sufficient must be carefully matched to plant demand, quantities to maintain good plant growth. thereby minimising losses through leaching. Trace amounts of seven other elements are Nutrient supply must also be manipulated, in required for growth - iron (Fe), manganese conjunction with production techniques, to (Mn), boron (B), zinc (Zn), copper (Cu), produce stock of correct size specifications and molybdenum (Mo) and chlorine (Cl). These in the correct physiological state to maximise are rarely deficient in British forest nurs­ their chance of survival and rapid early eries. growth when planted out to forest sites. This chapter focuses upon nutritional 4.1.2 Nutritional targets regimes for the production of bare-root The nursery manager should aim to provide a planting stock. balanced supply of nutrients capable of sup­

37 porting healthy and vigorous plant growth while also ensuring adequate root develop­ ment and plant hardiness. Ideally, nutrient regimes should be used in conjunction with other cultural practices such as undercutting and irrigation to maintain growth so that plants reach the optimum size for sale at the end of their final growing season in the nursery. However, in practice, this is not always possible because of the unpredictability of summer temperature and rainfall. These affect both the rate of nutrient Figure 4.1 Plant response to increasing nutrient supply. (Modified from Morrison, 1974) supply from the soil and the rate of demand for nutrients by growing plants. Erring on the cautious side may lead managers to apply Eventually, deficiency becomes so severe that heavier dressings than are necessary. This growth ceases and plants may die. can lead to what has sometimes been referred The general relationship between plant to as ‘luxury uptake’. In this case nutrients nutrient concentration and growth is illus­ may be supplied in excess to plant demand trated in Figure 4.1. Marginal ranges of with no return in increased growth. If the nutrient concentrations for different species effects of over-application of fertiliser are lim­ are given in Table 4.8. These values are based ited to ‘luxury uptake’, the economic penalty upon broadleaved foliage sampled in July/ incurred is small in terms of overall crop pro­ August, or the tops of conifer seedlings taken duction costs. However, over-application of at the end of the growing season. Little infor­ fertiliser can lead to toxicity (‘fertiliser mation exists regarding how these values scorch’), excessive shoot growth both in rela­ change throughout the growing season. In tion to the nursery manager’s objectives and practice, there is seldom enough time to col­ in relation to the size of the root system (poor lect and analyse foliage samples for the pre­ shoot:root ratio). scription of remedial fertiliser applications The concept of ‘luxury uptake’ has been within the same growing season. Foliage questioned in recent years. There is now sub­ analyses can be used, however, to check how stantial evidence that nutrient uptake con­ soil analysis data relate to plant nutrient tinues in late summer and autumn when status in a specific nursery. plant growth may be minimal. Storage of N during winter has been shown to influence growth the following spring in both sycamore 4.1.3 Soil fertility and Sitka spruce (Millard and Proe, 1991a Aspects of soil fertility have already been dis­ and 1991b). Uptake of N and K late in the cussed in Chapter 3. In terms of plant nutri­ season can also increase overwinter frost tion, however, it is through the soil that plants resistance although late season N applications obtain most of their nutrients and some fac­ may induce earlier flushing in the following tors affecting nutrient availability are season, thereby increasing the risk of spring described in the following sections. frost damage (Benzian et al., 1974). Nursery managers should try to prevent Below optimum levels, there is a critical the occurrence of nutrient deficiencies by range in which plant nutrient levels are mar­ matching the supply of nutrients with the ginal and growth may be slightly reduced expected removal from the nursery in planting without any visual signs of deficiency. As stock. This must also take account of any plant nutrient levels decline, visual symptoms applied fertiliser lost from the site by do appear and growth is markedly reduced. leaching, or immobilised within the soil by

38 Table 4.1 Nutrients removed in Sitka spruce Clay particles and well-humified organic (kg ha~1) matter typically possess negative charges. Soil electrical neutrality is maintained by the Crop and nursery Dry matter N P K Ca Mg adsorption of positively charged ‘cations’ (H+,

Sitka spruce seedlings K+, (NH4)+, Ca2+, Mg2+, etc.) that are important Teindland, Moray - 55.0 8.2 41.8 13.2 4.4 for plant nutrition. There are a number of tech­ Wareham, Dorset 3201 48.4 7.7 22.0 19.8 4.4 niques by which soil cation exchange capacity Kennington, Oxford 3938 75.9 12.1 47.3 24.2 4.4 can be measured (Bache, 1976). The most usual method is to displace exchangeable cations Sitka spruce transplants Wareham, Dorset 4435 69.3 11.0 40.7 24.2 5.5 with a saturating salt (e.g. ammonium acetate) Kennington, Oxford 7392 110.0 15.4 66.0 42.9 7.7 buffered to a pH of 7. However, because CEC Devilla, Kincardine - 115.5 14.3 62.7 18.7 7.7 can vary with soil pH, measurements taken often over-estimate the CEC that is operating in forest nursery soils where pH values are competing micro-organisms or through soil usually within the range 4.5 to 6. Target values chemical processes; such processes include, for for some North American forest nursery soils example, phosphorus fixation in which sol­ have been set within the range 7-12 meqg1 uble forms of P react with iron or aluminium soil (Youngberg, 1984). Values in UK nurseries in the soil and become unavailable for plant usually fall within this range. growth (Brady 1974, p.462). Soils with a high cation exchange capacity can retain nutrients in an available form to Nutrient removal plants, so resisting leaching losses following The quantity of nutrients typically removed in fertiliser application. Cation exchange capacity crops of Sitka spruce are given in Table 4.1. increases with increasing organic matter con­ What is actually removed within any partic­ tent, provided this is well decomposed (Figure ular crop will depend upon the soil, plant size, 4.2), and also with increasing clay content. stocking levels, fertiliser regimes and climate. In general, however, quantities of nutrients removed in forest nursery crops are of the Base saturation same order as those removed in the har­ Nutrient availability depends not only upon vesting of cereals, hay or potatoes. The quan­ the cation exchange capacity but also on the tity of fertilisers required to supply these proportion of this capacity occupied by nutrients is comparatively large due to poor nutrient elements as opposed to hydrogen ions recovery of applied nutrients by plants. In an - the base saturation. This, in turn, is extreme case of a sand low in clay and organic largely reflected by soil pH (Figure 4.3). matter, 70% of the potassium applied was lost 20 • from the top 42 cm of the soil profile due to u> O leaching, while only 22% of applied phos­ o • a phorus was either taken up by the plants or Ed) 15 • retained within the top 25 cm of the soil £- a (Bolton and Coulter, 1966). CD a S >° ■ •■ ■ ■ O H a ■ ■ Cation exchange capacity c _ a 2 x 5 ' The extent to which nutrients are retained 0) within a soil in forms available to plants co re depends, to a large extent, upon soil cation O 0 1------1 1 1 1 ' 0 2-1 6 8 ’0 exchange capacity (CEC). Cation exchange Organic matter (%) capacity is conventionally expressed as milli- Figure 4.2 Relationship between cation exchange equivalents per 100 g of soil (meq 100 g_1 soil). capacity and percentage soil organic matter.

39 70

O th e rs 5 0 M g

O th er; M g

3 ■ 03 Base saturation 33% 50% 50% (/) 0) PH 4.5 5.5 5.5 if) CTJ ■ Ca availability Low H igh H igh m 30 Mg availability H igh Lo w M e d iu m

Figure 4.4 Relationship between cation exchange capacity, soil type, base saturation and nutrient availability for three contrasting soils. 10 5 .5 3 have base saturations of 50% and their pH Soil pH values are 5.5. Soil 1 has a base saturation of Figure 4.3 Relationship between soil pH and 33% and, consequently, a lower pH of 4.5. In percentage base saturation. soil 1 the amount of exchangeable calcium is the same as in soil 3 but the availability will The effects of cation exchange capacity and be greater in soil 3 because the proportion of base saturation upon nutrient availability are exchangeable sites occupied by calcium is illustrated in Figure 4.4. The first two soils greater. Similarly, magnesium availability have CECs of 12 meqlOOg-1 soil while the will be greater in soil 3 than soil 2 even third has a CEC of 6 meq 100 g _1. The though the amounts are similar. nutrient holding capacity of the soil depends, In soil analysis, an attempt is made to esti­ to a large extent, on the total cation exchange mate the potential availability of nutrients to capacity. Nutrient availability, however, plants rather than the total soil content. depends more upon the proportion of exchange Nitrogen is rarely analysed since its avail­ sites occupied by each nutrient. Soil 2 and soil ability through a season is very difficult to

Figure 4.5 Soil analysis interpretation: available phosphorus in two soils over a 20-year period.

Year

40 determine from a single analysis, as it takes (Burt, 1988). Nevertheless, solid fertilisers are part in many microbe-related reactions and likely to remain in use as long as bare-rooted not just in cation exchange. stock continues to be produced. To get the best out of them, soil analyses should be based upon regular sampling 4.2.1 Soluble fertilisers together with careful records of fertiliser use Most materials used in forest nurseries are and plant performance. In this way each readily soluble compound fertilisers com­ analysis can be seen in the context of histor­ prising various combinations of nitrogen (N), ical trends within specific nurseries. For phosphorus (P) and potassium (K). The most example, a given value in one nursery may widely used products are nitrogen fertilisers, indicate stable and adequate nutrient levels nitrogen/potassium and phosphorus/potas­ whereas the same value in another may show sium compounds. a rapid decline toward possible deficiency levels within the near future (Figure 4.5). Single nutrient (‘straight’) fertilisers Record keeping should include details of the timing and rates of past fertiliser treatments, any organic materials added to the soil, Nitrogen is usually supplied as ammonium amounts and duration of rainfall and irriga­ nitrate, ammonium sulphate or urea (Table tion and the timing of undercutting and any 4.2). N-fertilisers are often granular or prilled other important cultural operations. for ease of application and are readily soluble in water. The positively charged ammonium ions tend to be held within the cation 4.2 Use of fertilisers exchange complex of soils and are less prone to leaching than are nitrates. Pure ammonium The particular nutritional requirements of nitrate (34.5% N) is slightly acidifying and individual crops vary greatly depending upon this is sometimes counteracted by adding cal­ plant and soil characteristics, together with cium carbonate to provide a neutral fertiliser the type of management adopted. The guide­ with a nitrogen content in the region of 27%. lines given here include a representative Applications of ammonium sulphate are three range of fertilisers used in common practice, times as acidifying as ammonium nitrate. This but each nursery should tailor its fertiliser is due to microbial activity which produces regime to fit its own requirements, normally sulphuric and nitric acids. On soils with rela­ with the help of a soil analytical service. A tively high pH values, ammonium sulphate wide variety of products are currently avail­ can be used to lower the pH gradually towards able to nursery managers. Traditionally, a optimum levels. dressing of phosphorus and potassium has been applied as solid fertiliser before the Prilled urea, which is widely used in plan­ growing season and top dressings of nitrogen, tation forestry, is rarely used in the nursery sometimes with potassium, applied several due to the high concentrations of nitrogen pre­ times during the season. Advances in tech­ sent (44%) and the tendency for losses to occur nology and improved understanding of the through volatilisation. Where urea is used, an relationships between nutrient supply and initial reduction in soil acidity is followed by plant performance have led more recently to subsequent acidification, with an overall net the development and use of both liquid and acidifying effect similar to that of ammonium various types of slow-release fertilisers. nitrate (Brady, 1974). Current trends are towards applying fer­ tilisers through nursery irrigation systems Phosphorus is much less mobile within the (particularly container systems under poly­ soil than highly soluble nutrients such as N thene), thereby achieving a better match and K. Nevertheless, it can be leached from between nutrient supply and plant demand very sandy soils, but, at the other extreme, it

41 can become unavailable to plants by becoming Magnesium, if required, is usually applied as closely adsorbed on clay minerals in the soil. magnesium sulphate. This can be as ‘Epsom Phosphorus is currently applied as phos­ salts’ or in the more concentrated form of phate. Phosphates vary in water solubility kieserite (Table 4.2). If soils are particularly from virtually insoluble, to moderately sol­ acidic then magnesian limestone or dolomitic uble. Water-insoluble forms are, however, limestone can be used. slightly soluble in citric acid. This often pro­ vides the basis for expressing the availability Compound fertilisers of phosphate to plants in such materials. There are several chemical compounds used Phosphorus is usually applied in combina­ as fertilisers which contain more than one of tion with other nutrients but there are some the major nutrients applied in forest nurs­ ‘straight’ phosphate fertilisers (Table 4.2). eries. Potassium nitrate contains both potas­ Superphosphate is the principal phosphate sium and nitrogen. Monammonium phosphate fertiliser currently used. It is manufactured by (MAP) and diammonium phosphate (DAP) treating rock phosphate with sulphuric acid to contain both nitrogen and phosphorus. produce a material containing approximately 30% phosphates, 50% gypsum (calcium sul­ ‘Compound’ fertilisers usually comprise a phate) and 20% impurities. Triple superphos­ number of ‘straight’ products mixed to provide phate is produced by treating the raw rock a number of different nutrients, although phosphate with phosphoric acid to increase potassium nitrate, MAP and DAP may also be the phosphate content more than two-fold. used. Rock phosphate is the least soluble of all Individual formulations vary between man­ phosphate fertilisers and must usually be ufacturers and also change with time. ground to a powder (ground mineral phosphate, Constituents used include potassium salts, or GMP) if it is to become available for plant ammonium nitrate, superphosphates and uptake. Finely ground rock phosphate is most ammonium phosphates. Examples of different effective when added to soils high in organic products currently available are given in matter. Availability of GMP as a powder is now Table 4.3. limited. Coarser material may have a role in maintaining P levels in difficult soils where 4.2.2 Slow-release fertilisers leaching or fixation on to clay minerals is a On sandy, well-drained soils in areas of mod­ problem. Where rock phosphate is used, North erate to heavy rainfall, soluble salts of African sources are preferred and the properties nitrogen and potassium are particularly vul­ of various sources are discussed more fully in nerable to losses through leaching. The usual Forestry Commission Leaflet 63 (Binns, 1975). method of overcoming this problem is to apply ‘Bonemeal’ is an alternative source of P top-dressings every 4-6 weeks throughout the used in horticulture but its high cost usually season thus incurring increased costs of appli­ precludes its use in forest nurseries. cation. An alternative is to use slow-release fertilisers, many of which are now on the Potassium is obtained from mining under­ market. Allen (1984) described the potential ground salt beds and is usually applied as benefits from slow release fertilisers: potassium chloride (muriate of potash) or • better utilisation by the crop due to the potassium sulphate (sulphate of potash). All release rate being more closely related to potash salts used as fertilisers are water sol­ plant demand; uble and have little effect upon soil pH even when applied in large amounts. Occasional • reduced losses from leaching, volatilisation damage to plant tissues has been recorded with or denitrification; potassium chloride and potassium sulphate is • reduced toxicity due to their lower salt now generally preferred for forest nurseries. indices;

42 Table4.2 Single nutrient ‘straight’ fertilisers

Nitrogen

Material Formula %N Properties Uses

Amonium nitrate n h 4 n o 3 34.5 Water soluble crystals - slightly acidifying Top dressings

Amonium nitrate + n h 4 n o 3 + 27 Granular - water soluble: little effect on Top dressings Calcium carbonate Ca C 0 3 soil pH

Ammonium sulphate (NH4)2 s o 4 21 Water soluble crystals: acidifies soil Top dressing

Urea CO (NH2)2 44 Water soluble - prilled initially reduces Basis of many slow but then increases soil activity release N fertilisers

Phosphorus

Material Formula %P2Os Properties Uses (% P)

Rock phosphate Complex 25-35 Insoluble - slow acting. Preferred as Longlasting and used (11-15) ground powder if available to increase soil P status

Super phosphate Ca(H2P04)2 + 18-20 Water soluble powder/granules Seedbeds and Ca S04.2H20 (8-9) transplants

Triple super phosphate Ca(H2P04)2 46 Water soluble granules Quick acting on seed­ (19-20) beds and transplants

Potassium

Compound Formula %K20 Properties Uses (%K)

Muriate of potash - KCI 60 Water soluble crystals Top dressing but can potassium chloride (50) cause foliage scorch

Sulphate of potash - k 2 s o 4 50 Water soluble powdery crystals Top dressing - causes potassium sulphate (42) less scorch than KCI

Magnesium

Compound Formula % MgO Properties Uses (%Mg)

Epsom salts Mg S 0 4.7H20 17 Soluble crystals Restricted to remedial (10) foliage sprays due to cost

Kieserite Mg S 0 4.H20 29 Slowly soluble crystals Applied to soil several weeks (17) before sowing/lining out

Magnesian limestone Mg C 0 3 + 16-21 Slightly soluble powder- Used to correct low soil Mg and dolomite* Ca C 0 3 (10-13) reduces soil acidity levels on acid soils

* Dolomite is composed of approximately 7CaC03 + 6MgC03. Magnesian limestone contains a higher proportion of CaC03.

43 Table 4.3Some currently available fertiliser products

Manufacturer Product Formulation N : P2Os : K20 % % %

Readily soluble fertilisers

Hydro Agri Double Season PK 0 24 24 Check when available in year* NK Silage 24 0 17 Extran 34.5 0 0

ICI Fertilizers Nitram 34.5 0 0 Kaynitro 25 0 16

ICI Horticulture '5 Star' Stabilised N 25 1 0 + 1.5% Mg + trace elements Enmag 4 19 10 + 7.5% Mg

Kemira Nitraprill 34.5 0 0 (formerly UKF) Kayenne 26 0 15

Controlled release fertilisers

Fisons Ficote 70 14 8 Short term 8 1 16 10 10 J CRF Ficote 140 14 8 Medium term 8 1 16 10 10 J CRF Grace Sierra Osmocote Mini 18 6 12 2 - 3 months CRF 18 6 11 5 - 6 months CRF Osmocote 18 11 10 8 - 9 months CRF 17 10 10 12-14 months CRF 16 8 9 + 3% MgO 16-18 months CRF

* PK fertilisers similar in composition to 0:24:24 may also be obtainable from fertiliser blenders, e.g. Scotphos, Ayr.

• lower application costs. nutrient release including gums, oils, waxes, resins, sulphur and plastics. These provide Slow release nitrogen fertilisers are essen­ slow or delayed release by a number of dif­ tially of two types (Sharma, 1979): ferent mechanisms. Water may diffuse • those comprising organic and inorganic through a semipermeable coating causing the compounds of low water solubility; granules to swell and burst the coating. Other • conventional, soluble fertilisers coated with products may have small pores in an imper­ insoluble or slowly soluble materials (some­ meable coating through which the soluble fer­ times referred to as controlled release or tiliser diffuses slowly while in others the CRF fertilisers). impermeable coating is designed to degrade slowly due to chemical or biological action. Nitrogen fertilisers with low solubility include urea-formaldehyde (UF), isobutyli- Apart from slow-release nitrogen fertilisers, dene diurea (IBDU) and magnesium ammo­ studies have also been made into the perfor­ nium phosphate. Rate of release of nitrogen mance of potassium metaphosphate as a slow- from slowly soluble materials depends mainly release source of both phosphorus and upon particle size together with soil conditions potassium. Results of tests in Britain showed and climate. that on the lightest soils it sustained a supply Various materials have been used to coat of K better than potassic superphosphate. It soluble fertiliser granules to control the rate of was not, however, as effective at maintaining

44 soil K levels as was a regime of potassic super­ tilisers in which slurries of solid particles are phosphate in the spring plus a top dressing of kept in suspension by means of suspending K (prilled potassium nitrate) in the summer agents and by regular agitation. Such mate­ (Benzian et al., 1969). rials require specialised skills and equipment Many slow-release fertilisers are now on for their correct application and are not widely the market including Enmag, Gold-N (sul­ used in UK forest nurseries. phur-coated urea), 5-Star Fertilisers, Ficote The use of slow release fertilisers together and Osmocote. Modes of action vary as do with liquid fertilisers provides a possible individual formulations with some including mechanism for matching nutrient supply to trace elements in addition to several of the plant demand, thereby minimising the dan­ major nutrients. If these products are to be gers of excessive salt levels in the soil and used, advice should be sought regarding rates losses due to volatilisation or leaching. of application, timing and use of supplemen­ All the developments in slow-release and tary dressings. liquid fertilisers have been led by demands in the ornamental nursery trade; there has been 4.2.3 Liquid fertilisers little research into optimum regimes for forest In recent years there has been a growing nursery stock. As a consequence, recommen­ interest in the use of liquid fertilisers in forest dations for their use have to be based on nurseries. Early experience suggests liquid extrapolations from the use of conventional fertilisers are every bit as safe as granular fer­ fertilisers in forest nurseries. As a working tilisers when used carefully. They are particu­ rule, slow-acting or soluble fertilisers should larly important for nurseries using irrigation be applied at rates which, for the season as a systems through which liquid feed can be whole, do not exceed the rates recommended applied at frequent intervals. They also give for conventional fertilisers. nursery managers greater choice of rate and time of application and enable a more even 4.2.4 Rates of fertiliser application application of fertiliser to seedbeds and trans­ Fertilisers must be applied to forest nurseries: plants, thus reducing the risk from scorch on • to maintain soil nutrients at levels which young plants. ensure adequate availability to plants; Liquid fertilisers usually contain various • to provide a supply of nutrients to meet cur­ combinations of urea, ammonium nitrate, potassium chloride, ammonium phosphate rent uptake requirements; and ammonium polyphosphates depending • to counteract processes which reduce upon their specific formulation. There is a nutrient availability such as leaching, limit (‘concentration barrier’) to how much of volatilisation and immobilisation within the these compounds can be dissolved into solu­ soil. tion so that liquid fertilisers usually contain The nutrient content of fertilisers offered less nutrient per unit weight than do solid fer­ for sale in the UK has, by law, to be stated. tilisers. The analysis may be expressed in terms of ele­ A wide variety of true solution fertilisers is ments or their oxides. To convert from the now available. When used, particular care oxide to the element the following factors must be taken to control the quantity of spray should be used: applied together with the droplet size and P = P205 x 0.44 nutrient concentration. K = KjO x 0.83 On the whole, liquid fertilisers are more expensive than their solid counterparts. Mg = MgO x 0.60 Attempts have been made to overcome the For example, to calculate how much of each concentration barrier imposed by liquids element 150 kg Scottish Agricultural Indus­ through the development of ‘suspension’ fer­ tries Enmag will supply (6%N, 20% P205, 10%

45 Table 4.4Fertiliser application rates applied before sowing or transplanting (kg of element ha-1)

Nitrogen ' Phosphorus Potassium Crop type Standard Standard High'1' Standard High+

Seedbeds (60) 55-65 65-75 100-120 120-145 Transplants (50) 45-55 55-65 85-100 100-120

* If nitrogen is applied then a slow release formulation should be used. * High rates used if soil reserves low or levels difficult to maintain.

K2O, 8.5% Mg) the following procedures are ratio of phosphorus to potassium together necessary: with some magnesium and a slow-release Nitrogen = (6/100) x 150 = 9.0 kg N form of nitrogen. Phosphorus = (20 x 0.44/100) x 150 = 13.2 kgP Potassium = (10 x 0.83/100) x 150= 12.5 kgK Additional fertilisers Magnesium = (8.5 / 100) x 150 = 12.8 kg Mg Soil nutrients must be maintained so that adequate supplies are normally available. For Initial fertiliser dressings a typical nursery soil (sandy loam with a bulk Forest nursery production can place heavy density at 1.5gem-3) available* nutrients to demands upon soil for nutrients. Each crop 15 cm depth should be of the order 200 kg P, will have its own requirements depending 300 kg K and 100 kg Mg per hectare. These upon species, age, management system, soil would correspond to approximate analysis and climate. In addition, fertiliser recovery values of 90p.p.m. P, 140 p.p.m. K and rates are always well below 100% so that 45 p.p.m. Mg. Once values fall to two-thirds of application rates must exceed rates of removal those quoted above, nutrient availability could in planting stock. be reduced and the higher rates recommended Typical rates of nutrients applied as initial for initial dressings in Table 4.4 should be dressings are given in Table 4.4. Phosphorus used. and potassium are usually applied as readily Where analysis shows available nutrients soluble compound fertilisers. Phosphorus to have fallen below one-half of the levels applications may well last the entire season quoted above then further measures must be whereas on sandy soils with moderate rainfall, taken: potassium top dressings may be necessary to • Ground mineral phosphate will increase supplement the initial application. Where soil phosphorus reserves and, because it is nutrient levels are difficult to maintain, the slow acting, it should have a prolonged higher range of dressings given in Table 4.4 effect. Rates of application should be should be used. If soil reserves are low then, between 500 and 800 kg ha-1 depending once again, higher rates of readily soluble fer­ upon the level of phosphorus reported in tilisers should be used. Nitrogen is rarely the soil analysis. applied before sowing or transplanting, but • Magnesian limestone and kieserite are also slow release formulations can be useful in slow acting and can be used to increase soil reducing leaching and volatilisation losses magnesium levels. Where soil pH is high, early in the season. When used, slow release kieserite should be used in preference to fertilisers should be supplemented by top magnesian limestone. Rates of application dressings later on. Where phosphorus levels to correct soil magnesium levels are are low and potassium satisfactory, Enmag 600 kg ha-1 for magnesian limestone and can be useful as it provides twice the usual 300 kg ha-1 of kieserite. Materials should be applied a few weeks before drilling or trans­ * Extractable with 0.43M acetic acid at 20°C. planting.

46 Table 4.5Top dressing application rates (kg of ele­ soluble fertilisers are to be used or salt sensi­ ment ha-1 y-1) tive species are to be produced (Norway spruce and Abies), then the risk of fertiliser Crop Nitrogen Potassium scorch can be minimised by earlier applica­ tions - approximately one month before the Seedbeds 100-150 50-75 Transplants 75-100 35-50 ground is to be used. Top dressings of nitrogen are usually given Note: A single top dressing should not apply any more than as three or four equal applications during the 25 kg of nitrogen ha '1. season. On soils with low potassium retention • Potassium salts are very soluble and may (sandy with low organic matter and high rain­ fall), NK fertilisers are usually used for one or be quickly leached on very sandy soils, low in organic matter. More frequent top dress­ two top dressings. The traditional pattern of application has been to wait 5-7 weeks after ings should be used if soil potassium levels germination of seedlings (by which time the are low. primary needles/leaves should have appeared) If problems persist then expert advice before making the first application. should be sought. Reasons could include phos­ Thereafter, applications are given at regular phorus fixing soils (Smilde, 1973), low cation intervals of not less than 4 weeks with a final exchange capacity, or heavy rainfall causing application in late August. Transplants should excessive leaching. receive their first dressing in mid-May (pro­ vided a minimum of 4 weeks has passed since 4.2.5 Top dressings transplanting). Thereafter, dressings are Nitrogen and, to a lesser extent, potassium again given at intervals of not less than 4 can be quickly lost from the soil by leaching weeks with a final dressing in late August. in periods of heavy rainfall or by denitrifica­ Fertilisers should not be applied to any crop tion. To minimise such losses, several dress­ during hot weather or when the soil is dry. ings are usually applied throughout the Between consecutive dressings at least 25 mm growing season. Typical rates of application of rain or 12 mm of irrigation should have per year are given in Table 4.5. For nitrogen occurred but if very heavy rain occurs soon responsive species such as larch, Douglas fir, after top-dressing then a second application alder and birch, rates of application should be should be considered to replace any losses due reduced to between half and two-thirds of to leaching. For nitrogen responsive species usual levels. Where liquid fertiliser regimes (larches, Douglas fir, alder and birch) mid­ are used, phosphorus can also be included in season dressings can be omitted. If slow- top dressings, making a corresponding reduc­ release compounds are used as pre-sowing/ tion in the fertiliser applied at the time of transplanting dressings then early top-dress- sowing or lining out. ings may be reduced or omitted. On crops which are to be stood-over then it is usual to 4.2.6 Timing of fertiliser applications apply half of the top-dressings one year and Granular fertilisers can feasibly be spread at half the next. any time of the year. Ground mineral phos­ In recent years, research under carefully phate and low doses of magnesian limestone controlled conditions has shown that much can be applied at any convenient time before greater efficiency of fertiliser use by trees can sowing or transplanting. Soluble compound be obtained by using frequent, low-rate appli­ fertilisers and slow release formulations used cations of nutrients matched to the rate of as initial dressings should be spread and culti­ plant growth (Ingestad, 1977; Ingestad and vated into the top 7-10 cm of soil as near as Lund, 1986). This must, however, be seen in possible to the time of sowing or trans­ the context of increased costs associated with planting. Where large additional dressings of multiple applications.

47 50 -i

Time (days after sowing) Figure 4.6 Seasonal variation of nitrogen in conifers.

While it is not yet possible to predict, with moderate N uptake. Care must be taken in any degree of confidence, the nutrient require­ extrapolating such results to the open nursery ments for a given crop at a given time, it is seedbed where sowing densities differ between becoming clear that the use of a small number species, temperatures are lower and the of equal top dressings during the season is not vagaries of climate must be considered. The the most efficient schedule. Preliminary general pattern of N uptake is, however, likely research on container stock grown in the poly­ to hold with only the absolute values house clearly demonstrated that, for a range changing. Based upon such preliminary infor­ of conifer species, rates of N uptake varied mation it is reasonable to speculate that a markedly during the growing season (Figure nitrogen top dressing regime in which the first 4.6). Rates of N uptake were slow for the first application was reduced to provide only 20% 10-12 weeks, followed by a short period of of the season total N fertiliser, followed by a rapid uptake and a more extended period of second dressing supplying 40%, a third pro-

Time (days after sowing) Silver birch

Sycamore

Sitka spruce Japanese larch

Scots pine

Figure 4.7 Seasonal variation of nitrogen in seedlings. (Data for containerised stock)

48 nursery before implementing these new regimes on a larger scale.

4.2.7 Nutrition and outplanting performance Careful attention to nutrition within the nursery can have significant effects upon yield from plantations through improved survival and accelerated establishment. Evidence sug­ gests that initial seedling size, as influenced by nursery nutrition, can have a strong influ­ ence on early field performance and tree growth (Fisher and Mexal, 1984). Studies in Figure 4.8 Fertiliser release characteristics. North America have shown that needle %N in 2 + 0 Douglas fir and Sitka spruce was posi­ viding 30% and a final dressing in August to tively correlated with survival, total height make up the last 10% may prove beneficial. If and current height growth after 3 years in the more than four dressings can be applied then forest (Van den Driessche, 1984). The same so much the better. study also reported that Douglas fir main­ Information on broadleaves is very limited, tained similar relative growth rates after but the same piece of research mentioned planting out such that any differences in above suggested the pattern of N uptake may seedling dry weights at the time of planting be quite different (Figure 4.7). Demand for N continued to influence growth for several was much greater earlier in the season and years. Late-season applications of nitrogen top dressings should probably reflect this. (after bud set) have also been reported to Seedlings became ‘pot-bound’ approximately 3 advance bud break of Sitka spruce when months after sowing. Further research is nec­ planted out in UK forests, without any delete­ essary to confirm these results in open rious effects upon survival, except in very nursery seedbeds but there is already suffi­ exposed locations where frost damage was cient information to suggest equal top dress­ increased (Benzian et al., 1974). This, in turn, ings throughout the growing season are likely increased height growth during the first to be inefficient. season in the field but differences became There may well be scope for greater use of small in relation to tree size in later years. the more complex slow release fertiliser com­ The increased survival of Douglas fir following pounds developed to provide a closer match late season fertilisation was thought to be a between rate of nutrient supply and plant result of elevated mineral nutrient reserves demand (Figure 4.8). However, it will still be increasing the capacity for root growth, necessary to supplement slow release prod­ although direct evidence for such an effect is ucts, applied at sowing or transplanting, with still required (Van den Driessche, 1985). top dressings later in the season. One suitable In the past it has often been assumed that regime might be to apply 50% of the annual N late season applications of potassium may fertiliser as a slow release at the start of the improve cold hardiness. Benzian et al. (1974) season with a further 30% in early summer showed potassium fertiliser increased growth of and the final 20% as a final top dressing in trees soon after planting on forest sites but August. found no significant effect upon frost damage. These new top dressing regimes are cur­ In a thorough review of the literature, Pellett rently based largely upon theory and prelimi­ and Carter (1981) concluded that adequate nary research on containerised stock. It is nutrition to promote rapid growth, without com­ important to do small-scale trials within the promising the shootrroot ratio, should enable

49 plants to acclimatise to cold better than those Damage by: frost suffering severe nutrient deficiency or supra- insects optimum fertilisation. There is also evidence fungi that potassium is important in regulating plant wind water status through stomatal control and late- Waterlogging of soil season applications may increase drought toler­ Drought ance of transplanted seedlings (Fisher and Sunscorch Mexal, 1984). Other work on Douglas fir, again Pesticides (residues or faulty application) in North America, showed frost hardiness to be more closely related to the ratio of K to N pre­ The first step in determining the cause of sent in tissues, rather than to the level of an any discoloration is always to dig up and individual element (Timmis, 1974). examine carefully a sample of the affected plants, paying particular attention to the roots. Possible causes of observed symptoms 4.3 Nutrient deficiencies and are shown in Table 4.6. remedial fertilisers Pests and diseases, the effects of climate and damage due to weedkillers used in forest nurseries are described elsewhere. 4.3.1 Deficiency and damage Plants markedly deficient in one or more In the course of the growing season, plants nutrients show this by poor growth and by exhibit a range of colours. For most plants, developing characteristically discoloured foli­ these remain within the range of shades of age; foliage may be smaller than normal and green until tints associated with natural leaf in certain extreme cases, shoots may die back. senescence develop. A few species adopt a In addition, plants may be more susceptible to more bronzed or purple hue over winter, damage by frost, drought, insect and fungal namely western red cedar and seedling pines, attack. but for most species the untimely appearance While it is easy to ascribe symptoms to defi­ of red or yellow hues or browning of foliage is ciencies induced in experiments, it is not always a sign of distress due to one, or a combination easy to make correct diagnoses from foliage of the following: symptoms alone, as more than one nutrient Nutrient deficiency may be lacking. Diagnosis usually involves Nutrient excess (fertiliser scorch) weighing up probabilities, taking into account:

Table 4.6 Symptoms and possible causes of deficiencies and damage

Observed symptoms Possible cause

Withering or drying (green) foliage. Weedkiller; sun scorch; fungal attack; insect feeding on roots.

Straw or light-brown foliage (not autumn colours of Fertiliser excess; weedkiller; heat scorch; wind burn; deciduous species). fungal attack; copper deficiency. Yellow, red or purple discoloration; foliage remains fresh. Nutrient deficiency; root damage; lime-induced chlorosis; weedkiller.

Spotting or blotching of foliage. Fungal attack; insect attack; weedkiller.

Dead roots. Waterlogging; fungal attack; dessication or mechanical damage during lining out; maltreatment before lining out; insect feeding.

Visible loss of bark on roots, or loss of foliage. Insect attack; mechanical damage by implement; hail.

Dead root collar (or stem at soil surface) but roots and Weedkiller, sun scorch, fungal attack. stem healthy.

50 • what fertilisers have been put on and Deficiency symptoms when; • rainfall and irrigation in relation to fer­ Needle bearing conifers (pine, spruce, larch, fir, hemlock, etc.) tiliser applications; A general yellowing and reduced growth of • soil characteristics; and, if possible, needles occurs, the extent of which increases • knowledge of the situation with similar with the severity of the deficiency. Very severe crops in other nurseries. deficiency produces short, stiff needles yellow- The following sections outline the major green to yellow in colour. Occasionally the tips roles of each nutrient in plant growth. Visual of needles in seedlings may turn pink or symptoms of deficiency are described for three purple and this is sometimes followed by groups of seedlings (Benzian, 1965; Hacskaylo needle necrosis at the end of the season. et al., 1969; Huttl, 1986; Ingestad 1957, 1959, Needles exposed to full sunlight appear to 1960; Lavender and Walker, 1981; Leaf, 1968; develop more discoloration than those in Morrison, 1974; Stone, 1968; Swan, 1960 and shade. Typically, seedbeds become saucered Worley et al., 1941): with the seedlings at the outer edges being 1. needle bearing conifers based mainly on taller and greener than those toward the descriptions for pines and spruce; centre. Symptoms can be recognised as soon as seedlings are large enough for different 2. conifers which have scale-like leaves based shades of green to be recognised. upon descriptions for western red cedar, and Conifers bearing scale-like leaves (e.g. 3. broadleaves such as birch and elm. western red cedar) A brief description of the fertilisers avail­ Foliage is yellowish, very sparse and stems able for supplying each element is then given. may be reddish in young seedlings. Dying of While recommendations for remedial fer­ the older foliage is conspicuous but there is tilisers are given, these will only restore little shattering (Hacskaylo et al., 1969 - see nutrient levels in plants to the extent that the glossary). plants are physiologically capable of taking them up. For example, foliage showing severe Broadleaves (e.g. birch, elm) deficiency symptoms may not be able to Seedlings become stunted and leaf size may be recover. Also, plants which failed to grow markedly reduced. Foliage is pale green or rapidly because of nutrient deficiency, may yellow with anthocyanin spots developing on resume rapid growth following remedial treat­ the underside. Older leaves die and stems or ment but will not be able to grow faster to petioles that are normally green may take on compensate for the earlier lost growth. pink or reddish colours.

4.3.2 Nitrogen Remedial fertiliser Observed nitrogen deficiencies can develop Role very rapidly when the crop is growing fast and Nitrogen is a constituent of amino acids (the demand for N is large (Figure 4.6). Deficiency basic building blocks of proteins), the nucleic can be corrected by a standard top dressing of acids (RNA and DNA), many metabolic inter­ ammonium nitrate or ammonium sulphate at mediates and is an essential component of 125 kg ha-1 supplying around 25-40 kg ha-1 N). chlorophyll. When nitrogen is deficient, the However, loss of growth may not be recovered. chlorophyll content of many of the otherwise Where nitrogen deficiency symptoms occur green parts of the plant is reduced (Bould et in early/mid season and N top dressings have al., 1983). been withheld to avoid excessive growth,

51 colour can be restored by addition of a light may be slightly reduced in size and a grada­ top dressing in the same season (25 kg ha-1 N). tion in colour can occur from dark green in the Plants left undisturbed into the winter, usu­ older leaves to very light green in the ally green up by the time of lifting. However, youngest. Lower portions of the usually deep if repeated undercutting is proposed, a top green stems turn a dark brown. dressing should be put on deficient plants (and, where possible, watered in) a few weeks Remedial fertiliser before the first undercut. Top dressings of phosphatic fertilisers are rel­ atively ineffective (Van den Driessche, 1980). 4.3.3 Phosphorus If problems are apparent, an early season dressing of monammonium phosphate (MAP) Role can be used at 250 kg ha-1 to supply approxi­ Phosphorus forms high-energy phosphate mately 60 kg ha-1 P, although this may have bonds which are the chief medium for energy little effect in the same growing season. transfer in plants. It also affects the func­ tioning of many enzymes and plays a key role 4.3.4 Potassium in many biosynthetic reactions. Role Deficiency symptoms The processes of photosynthesis, protein syn­ Needle bearing conifers thesis and carbohydrate translocation all require potassium. It is also involved in the Phosphorus deficiency is associated, pri­ osmotic regulation of water conditions within marily, with a reduction in growth. Sitka the plant which, in turn, can affect resistance spruce does not exhibit any characteristic to drying winds and frost. colour symptoms when deficient in phos­ phorus either as seedlings or transplants. Visual symptoms have, however, been Deficiency symptoms reported for a number of other spruce species, pines and western hemlock. Young needles Needle bearing conifers are green or yellow-green while older needles First signs in the seedbed usually appear in develop a purple tinge that deepens with August but can occur as early as June. severity so that in extreme cases all needles of Typically, needle-tip chlorosis occurs and the seedlings may turn purple. Symptoms are typ­ tips may take on a purplish tinge. As the ically patchy over the seedbed. season progresses, the discoloration extends back from needle tips and a range of colours Conifers bearing scale-like leaves may develop including blue-greens, purple, red, reddish-yellow and yellow. Tips may Young foliage retains a good green colour eventually turn brown and necrotic. whereas older foliage and stems develop red­ Symptoms are more pronounced in the dish or purplish tinges during the first year, youngest needles with the discoloration much turning a reddish brown in older seedlings reduced toward the base of seedlings. The and followed by necrosis. The oldest foliage autumnal colours reminiscent of hardwoods dies but does not shatter. help to distinguish potassium deficiency from the ‘hard yellows’ of magnesium deficiency. Broadleaves Earlier in the season, potassium can be distin­ Leaf size appears to be unaffected in birch. guished from nitrogen deficiency because the Foliage becomes dark green with some red­ chlorosis (yellowing) is most marked at the dish/purple discoloration on the underside due young shoot tips, in contrast to nitrogen where to the presence of anthocyanin. In elm, leaves the discoloration is more uniform. Symptoms

52 in transplants are similar and may occur from deficiency may cause needle tip necrosis with June onwards, the previous year’s shoots usu­ occasional bud death, particularly at the time ally being the most discoloured. of autumn frosts.

Conifers bearing scale-like leaves Conifers bearing scale-like leaves Foliage appears sparse and stems become With magnesium deficiency the youngest limper, causing a droopy appearance. Foliage foliage usually remains green but older at the branch tips maintains a good, green branches become yellow or white before colour but older foliage may be necrotic or turning brown and have a tendency to shatter. dying. Many of the lower leaves and branches As a result seedlings develop a tuft of green at turn brown and die. the top with bare branches below.

Broadleaves Broadleaves Chlorosis and necrosis of foliage occurs from In magnesium deficient birch, foliage first the leaf margins inward. There is typically a turns yellow. Leaf margins may become grey sharp boundary between the white/yellow or brown, eventually spreading over the whole chlorotic area and the normal green. After leaf blade and resulting in leaf mortality. chlorosis, leaves become brown and dry. Interveinal chlorosis and curling under of leaf margins can occur in lime while elm seedlings Remedial fertiliser can be very stunted with their leaf size much Dressings of potassium sulphate at a rate of reduced. Oldest leaves are usually most 200 kg ha-1 to supply 84 kg ha-1 K, can be used affected with a typical progression of mottled to correct potassium deficiency. Sulphate chlorosis accompanied by whitening edges rather than muriate of potash is preferable that spread over the blade until it becomes because risk from fertiliser scorch is less entirely white, the green veins being the last (Armson and Sadreika, 1979). regions to succumb.

4.3.5 Magnesium Remedial fertiliser Epsom salts (magnesium sulphate) applied at Role a rate of 150 kg ha-1 (15 kg ha-1 Mg) should Magnesium is an important constituent of reduce or eliminate deficiency symptoms. chlorophyll and its absence reduces the chloro­ Alternatively, plants can be sprayed in July or phyll content of the foliage and slows the August with 14001 ha-1 of a solution con­ processes of photosynthesis. Magnesium is taining 25 g Epsom salts and 0.5 ml of liquid also involved in carbohydrate metabolism, cell detergent per litre of solution. division and energy transfer within the plant.

4.3.6 Calcium Deficiency symptoms Needle bearing conifers Role Magnesium deficiency usually occurs late in Calcium is an important constituent of plant the season, typically from late August through cell walls and a number of different enzymes. to October. Needle tips turn bright yellow and the discoloration develops along the entire Deficiency symptoms length of young needles although this is rare Calcium is an unavoidable constituent of in older foliage. There is, characteristically, many regularly used fertilisers. Deficiencies of very little gradation between bright yellow calcium rarely, if ever, occur in UK forest and healthy green portions of seedbeds, indi­ nurseries and the symptoms reported below vidual seedlings or individual needles. Severe are based upon laboratory studies.

53 Table 4.7Trace element deficiency symptoms

Nutrient Deficiency symptoms Remedy

Role Conifers Broadleaves

Copper (Cu) ‘Tip burn' - needle ends near growing Blackening of leaf Copper sulphate points dry and become straw coloured. tips, then general broadcast dry at Enzyme component In Sitka spruce, onset sudden during marginal scorch of 20 kg ha-' or 10 kg and catalyst dry weather in late summer. youngest leaves. in 2000 litres Very short transition from healthy Inverveinal yellowing water ha-1 in June to affected tissue. Upper needles of follows. Leaf edges and again in July. apparently healthy plants near affected become taut and brittle ones may show spiral twist. If sunny causing cupping of leaves. weather prolonged, growing points On acutely affected plants, may die. the youngest leaves fall, leaving main shoots and side branches bare.

Iron (Fe) Lime-induced chlorosis (iron deficiency) is a well known disorder of acid loving plants when planted on alkaline soils. On a forest nursery, its occurrence indicates that the site is unsuitable and that Constituent of another site should be sought. chlorophyll NB: Zinc toxicity symptoms strongly resemble those of iron deficiency - see under zinc below.

Energy carrier in More or less uniform chlorosis of new Chlorosis in interveinal photosynthesis and foliage eventually, needles and plants tissue; veins remaining respiration become dwarfed. green, often sharply etched. Wholly chlorotic tissues die slowly, producing apical or marginal scorch.

Boron (B) Deficiency in Britain (nursery and forest) limited to two possible cases. Reported from overseas, especially New Zealand. Immobile in plant; meristem areas may be deficient even though levels in foliage appear adequate.

In sugar Death of apical shoots or ‘rosetting’ - Foliage dwarfed and 10-20 kg ha-’ translocation progressive reduction in leaf spacing and discoloured. Uneven borate fertiliser or water absorption size. In pines, shoot, shoot tip or bud mesophyll growth borax. Bulk up with and transpiration die-back abrupt, sometimes preceded by producing blistered sand for even wilting or abnormal growth. appearance; some spp. distribution, or may show interveinal 0.1 -0.2% w/v chlorosis or browning. soluton of 'Solubor' at 1000-15001 ha-1.

Needle bearing conifers Broadleaves Deficiencies of calcium can cause serious Terminal leaves become chlorotic, stunted and injury to meristematic regions. A general delicate. Discoloration occurs first at leaf tips chlorosis is usually followed by needle and then spreads inwards to produce whitened necrosis, especially at branch tips. Severe defi­ leaf margins progressing toward midrib. ciency can lead to the death of terminal buds, Eventually, terminal buds become necrotic. top dieback and excessive resin exudation. 4.3.7 Sulphur Conifers bearing scale-like leaves Good green colour may be maintained in the Role lower foliage but tips of leaders and branch Sulphur is an essential constituent of amino shoots turn brown and become necrotic. acids used in protein synthesis. It also occurs

54 Table 4.7 continued

Nutrient Deficiency symptoms Remedy

Role Conifers Broadleaves

Manganese (Mn) Neither deficiency nor toxicity reported from British forest nurseries.

Difficult to distinguish from Fe or Mg Chlorosis begins near leaf 8 kg ha-1 of deficiency. margin, developing as manganese sulphate Plant respiration Needles chlorotic at emergence, may V-shaped areas extending or chloride in 'green-up' in later months. inward between major 500 litres water ha-' . veins. Symptoms usually develop late in the season.

Symptoms of toxicity include smaller leaves, severe chlorosis, necrotic spots and discoloration.

Zinc (Zn) Deficiency symptoms not reported from British nurseries, but found in culture.

Enzyme Extreme shortening of needles and needle Chlorotic mottling of 5 kg ha-1 zinc systems spacing and general yellowing and interveinal areas. sulphate + 2.5 kg ha-' occasional bronzing of needle tips. Frequently proceeds up calcium hydroxide in stem, associated with 500 litres ha-1 water. leaf-fall. Terminal rosettes may form; severe deficiency causing die-back.

Zinc toxicity has been observed occasionally in forest nurseries, usually associated with the presence of galvanised or zinc coated wire mesh, especially where rolls of netting have remained for several weeks rolled up at the ends of seedbeds. In such localised situations, seedlings may fail to germinate; those that do may be stunted and show a chlorosis similar to that resulting from iron deficiency.

Molybdenum (Mo) Deficiency symptoms not reported in British forest nurseries; amounts required are minute compared with other elements. Availability falls with increasing acidity in soils.

Enzyme system also Chlorosis followed by necrosis of tissue, For N-fixing alders, 200 g ha-' metabolism of beginning at the tip and eventually symptoms resemble N sodium molybdate N-fixing bacteria covering the entire needle. deficiency - pale N leaves as a 0.01% with marginal scorch. solution.

in a number of co-enzymes and is contained in a time, particularly during periods of rapid chlorophyll. growth.)

Deficiency symptoms Broadleaves Plants may be stunted and younger leaves Needle bearing conifers become yellowish green - similar in appear­ Needles may be thin and spindly. General ance to nitrogen deficiency but no anthocyanin chlorosis develops although this is most pro­ discoloration on undersides of foliage. Older nounced in the terminal regions where leaves retain their dark green colour. necrosis may occur. Remedial fertiliser Conifers bearing scale-like leaves Sulphur deficiencies are not known on the Foliage becomes yellowish, especially in range of soil normally encountered in forest younger portions. Older foliage is paler than nurseries. It is frequently applied as an usual, in contrast to iron deficiency in which unspecified constituent of many fertilisers older foliage retains good, green colour. (NB including superphosphates, Enmag and all young foliage tends to become yellowish for ammonium sulphate. If deficiencies are

55 encountered then flowers of sulphur can be with which plants are able to extract nutri­ used at 20-30 kg ha-1 or ammonium sulphate ents from the soil, and translocate them at approximately 100 kg ha-1. More usually, within the plants. sulphur is used as a means to lower soil pH A general guide to the critical or marginal (Chapter 3, section 3.2.5). range of nutrient concentrations (see Figure 4.1) that could be expected in nursery planting 4.3.8 Trace elements (micronutrients) stock is given in Table 4.8. Plants with levels above those given in the Table 4.8 should have Trace element deficiencies in UK forest nurs­ adequate supplies of nutrients whereas values eries have rarely been reported. Most of the below those quoted are usually indicative of information reported in this section relates to nutrient deficiency. The values given in Table induced deficiencies within experiments or to 4.8 are for current shoots in late autumn for experience overseas. Under field conditions it conifers and for the foliage of broadleaved is difficult to diagnose trace element disorders species in midsummer when concentrations due to problems with sample contamination are most likely to be stable (Figure 4.9). and the high degree of variability within plant In addition to the absolute value of foliage tissues. Table 4.7 summarises the available nutrient levels, it is also important to ensure information. the balance between nutrients is correct. Imbalances can occur, for example, between 4.3.9 Tissue analysis levels of calcium and magnesium, nitrogen While soil analysis provides a ‘snap-shot’ of and phosphorus, nitrogen and potassium or the nutrient reserves in the soil, at the time of nitrogen and sulphur all of which may lead to sampling, tissue analysis (or foliage analysis) physiological disorders and unsatisfactory provides a means of assessing the success growth.

Table 4.8Marginal range of nutrient concentrations in forest nursery stock

Major nutrients

N P K Ca Mg S (% oven dry weight)

Pines 1.5-1.8 0.16-0.18 0.6-0.7 0.06-0.10 0.07-0.10 0.15-0.20 Spruces 1.2-1.6 0.16-0.18 0.5-0.7 0.10-0.15 0.06-0.08 0.13-0.18 Larches 2.0-2.5 0.20-0.25 1.0-1.2 0.20-0.25 0.10-0.12 0.16-0.20 Other conifers 1.6-1.8 0.18-0.20 0.7-0.8 0.15-0.20 0.10-0.12 0.16-0.18

Alder, birch, sycamore, cherry, 2.3-2.8 0.18-0.25 1.0-1.2 0.15-0.20 0.10-0.15 0.14-0.20 lime, willow, Norway maple Other broadleaves 1.7-2.3 0.14-0.20 0.7-1.0 0.20-0.30 0.15-0.20 0.16-0.20

Trace elements

Cu Fe Mn B (pg/g)

Pines and spruces 3-5 20-40 20—40 15-30 Other conifers 3-5 40-60 40-60 20-40 Broadleaves 3-5 30-80 30-80 20-40

1. Below marginal levels indicative of deficient status. 2. Above marginal levels indicative of satisfactory status. 3. Conifers = current shoots in late autumn. 4. Broadleaves = foliage in midsummer.

56 0 1 1 1 1 1 0 50 100 150 200 250

Time (days afler sowing) ...... Silver birch

------Sycamore

------Sitka spruce Japanese larch

------Scots pine

Figure 4.9 Seasonal nitrogen concentrations in seedlings.

At present, tissue analysis as a guide to trations are ‘critical’, affecting growth or perfor­ plant health and nutrition in forest nurseries mance without any visible deficiency symptoms. is still in its infancy. There is only an imper­ Information would then be available relating fect understanding of the relationship soil and foliage analyses for each nursery block between the results of soil and tissue analysis, or soil type thus enabling better interpretations and their interaction with season (e.g. rainfall, of analytical results to be made and nursery- temperature, moisture deficit), site (e.g. soil specific fertiliser recommendations to be given. texture and pH), nursery practice (e.g. timing of operations, quantities of fertiliser, irriga­ tion) and incidence of pests and diseases. Taking plant samples Samples are often taken when visual defi­ Before samples are taken for analysis it is ciency symptoms appear with the aim of essential that the laboratory that will conduct either taking remedial action with respect to the analyses be consulted regarding the type the crop sampled or, at least, to prevent any and quantity of sample required, the time at recurrence in future crops. Such samples are which samples should be taken and the way in often taken with little standardisation with which samples should be handled to avoid any respect to tissues sampled or time of sam­ contamination. The amount of material pling. This makes interpretation of results required will depend upon the analyses to be particularly difficult since the evidence that is carried out but where deficiency symptoms available shows considerable variation in are observed, at least two samples should be nutrient concentration throughout the season. taken from apparently healthy areas and two For example, the potassium content of Sitka from those areas where symptoms are spruce seedlings can fall from 3% dry matter apparent. If possible, intermediate levels of in midsummer to 1% or less by late autumn; it deficiency should also be included. For can also vary markedly from one season to analyses of major nutients the tops of suffi­ another (Benzian et al., 1969). cient plants to provide approximately 20-30 g Foliage sampling should be conducted on a of material per sample should be taken while regular basis similar to that carried out for for trace elements considerably more material soils. This is the best method for detecting any may be required. Care should be taken to areas in the nursery in which nutrient concen­ avoid inclusion of soil in the samples.

57 Owing to the range of factors that can affect Table 4.9 Effect of six annual applications of plant nutrition, some within and some out- 63 000 kg ha~1 raw hopwaste on some physical prop­ with the nursery manager’s control, informa­ erties of a sandy loam soil at Teindland Nursery, tion from historical records can be crucial in Moray diagnosing problems. A summary of such information should always accompany sam­ Percentage Percentage organic Moisture microaggregate ples sent for analysis. matter equivalent stability

Control 11.0 20.8 11.4 4.4 Soil organic matter Hop waste 18.0 29.3 15.0 Soil organic matter comprises three principal Least significant 3.7 3.4 2.4 components: (1) live microbes, flora and fauna difference at 0.1% within the soil; (2) plant, animal and microbial residues in various stages of decomposition; crops incorporated into the soil, break down and (3) humic substances representing the very rapidly during the initial stages of final stages of a series of predominantly bio­ decomposition. During this phase, bacteria chemical reactions (Davey and Krause, 1980). involved produce a number of polysaccharide In the soil, free-living micro-organisms use gums that enhance soil structure. This is illus­ organic matter as a source of both energy and trated in the microaggregate stability figures nutrients necessary for the synthesis of their given in Table 4.9. The high metabolic activity own tissues. Energy is obtained through the within the soil can also result in the suppres­ process of respiration during which the carbon sion of various pathogens due to elevated contained in organic matter is oxidised to carbon dioxide levels and the production of carbon dioxide and then liberated into the air. certain antibiotics within the soil. This period Thus, there is a natural tendency for organic of high activity may last for several weeks and matter contents of soils to decline unless they during the first week or two soil oxygen may are continually replenished. become limiting and lead to the production of Nursery management practices tend to a range of volatile organic compounds and increase the rate at which soil organic matter is acids which can be toxic to germinating seeds decomposed. Tillage of the soil increases aera­ and young plants (Aaron, 1976). These sub­ tion by reducing soil bulk density; it also kills stances break down rapidly once oxygen levels and buries most residual vegetation, hastening return to normal but care should be taken to its break-down. Adequate moisture supply also ensure that seed is not sown into soil that has enhances microbial activity, thus accelerating received additions of readily decomposable the processes of decomposition of residues com­ material in the preceding 10 days. Composts pared with drier soils, or those in which mois­ or peat produce no such problems because ture contents are sufficiently high to cause they have already undergone this initial phase reduced aeration. Within certain limits, micro­ of rapid decomposition. bial activity increases with increasing soil tem­ As decomposition proceeds, fungi predomi­ perature and the elevated temperatures found nate as celluloses and eventually lignin are in forest nurseries compared with those in slowly degraded. Over periods of many years, forests usually result in increased biological humus is formed which differs physically and activity. Microbes also require various nutri­ chemically from the original material from ents for growth and these are frequently avail­ which it was derived. able in forest nurseries where comparatively Humus and partly decomposed organic heavy fertiliser regimes are used. matter affect soil properties in a number of important ways: 4.4.1 Properties • It is dark coloured at the soil surface, Fresh organic material, particularly green absorbs more of the sun’s heat and so

58 Table 4.10 Nutrient contents of various bulky organics (from FC Bulletin 37, Tables 80 and 81)

Percentage moisture Percentage in dry matter content or fresh material Organic matter N P K Mg

Hopwaste 84-87 85-89 4.8-5.1 0.9-1.3 0.2 0.4

Peat 47 93 2.1 0.0 0.1 - Sawdust 44 99 0.2 0.0 0.1 0.0

Bracken/hopwaste compost 72-81 70-83 3.2-3.9 0.5-0.9 1.3-2.1 0.3

Straw/hopwaste compost 73-82 66-78 3.6—4.3 0.9-1.0 0.4—0.8 0.4

Farmyard manure 76 75 2.2 0.3 2.8 -

Sewage sludge 20-55 39-42 1.6-2.8 1.4-2.3 0.3-0.4 -

increases ambient soil temperatures with lowing the application of materials with high consequent effects upon the rate of biolog­ C:N ratios. ical activity. In contrast, soil organic amendments can • Water retention within soils has been increase phosphorus availability by directly shown to be directly related to total organic supplying phosphate and by the eventual matter content. This is especially important chelation of insoluble iron and aluminium in nurseries with sandy soils and low clay phosphates into more available forms. This contents. latter process can be significant in newly • Humus can also combine with clays to sta­ established nurseries on podzolic soils in bilise soil structure. which the B horizon’s considerable potential for phosphate fixation can be counteracted by • It has a high cation exchange capacity and organic soil amendments. Trace element avail­ in most forest nursery soils it is the organic ability may be affected by additions of organic fractions that contribute the largest share matter either through changes in soil reaction of cation exchange sites. (pH) or by the chelating properties of soil • The influence of soil organic matter on organic matter. Boron availability, for cation exchange capacity makes it a major example, has been shown to be highly corre­ factor affecting the buffering capacity of a lated with soil organic matter content soil in relation to changes in soil acidity (Martens, 1968). Similar results have been resulting from the use of inorganic fer­ obtained for extractable copper in Scottish tilisers or hard irrigation water. agricultural soils (Berrow and Reaves, 1985). • Soil organic matter can also have direct Results from a number of long-term experi­ effects upon the availability of nutrients for ments comparing inorganic to organic plant uptake. nutrient regimes have usually failed to show Table 4.10 shows the analysis of a range of significant differences between treatments. bulky organic soil amendments. The only result reported consistently was a The addition of nitrogen-rich, coarse reduction in seedling numbers on beds organic matter can enhance nitrogen avail­ receiving bulky organics in the year of sowing. ability in forest nurseries. However, materials Such reductions could be due to increased low in nitrogen, or with a high C:N ratio like fungal action perhaps in response to the large sawdust, reduce availability due to immobili­ amounts of added nitrogen. Alternatively, sation by microbes during early phases of bulky organics may interfer with the capillary decomposition. Supplemental inputs of inor­ rise of water in sandy soils where good consoli­ ganic nitrogen may, therefore, be required fol­ dation is vital to satisfactory germination. In

59 this context, Benzian (1967) reported difficulty Crops can be grown on the land and incorpo­ in consolidating seedbeds at Wareham when rated into the soil (greencropping) or materials the quantity of added organic matter was can be brought into the nursery from outside. increased to 751 ha-1 y_1. Transplants growing on light sandy soils 4.4.3 Greencrops were found to benefit from incorporation of The incorporation of greencrops has been bulky organics (Benzian, 1967). It therefore claimed to improve the humus content of soils seems logical on sands and very light loams and to provide a readily available supply of (which form a large proportion of forest nutrients for the succeeding crop. However, nursery soils) to recommend the application of the nutrient supply can only be increased sig­ bulky organics to transplants and to grow nificantly if the organic matter in the incorpo­ seedlings using inorganic fertilisers plus any rated greencrop is broken down quickly, residues from the manuring of transplants. whereas to build up humus in the soil such Such a regime should benefit from organic organic matter must be fairly resistant to residues without incurring associated losses decomposition. If the greencrop is ploughed on seedbeds. under while still soft and green, plant mate­ rial will be broken down rapidly with the risk 4.4.2 Optimum levels of losing any nitrate so released by leaching Levels of organic matter in soils vary from before the planting of a tree crop in the fol­ nursery to nursery and it is difficult to provide lowing spring. There is also some evidence guidelines for optimum values. Although the that the decomposition of nutrient rich individual attributes of soil organic matter are organic matter can act as a ‘primer’ and well known, experiments studying the perfor­ increase the rate of breakdown of native soil mance of seedlings grown with and without organic matter (Broadbent, 1947; Hallam and additions of bulky organics have tended to be Bartholemew, 1953). If, on the other hand, inconclusive with no definite evidence of greencrops are allowed to mature then fibrous improved performance compared with those matter, low in nitrogen, will be formed in the using inorganic fertilisers alone (Aldhous, later stages of growth. These will persist in 1972; Benzian, 1965; Benzian et al., 1972; Low the soil and immobilise nitrogen during their and Sharpe, 1973). Soil organic matter content breakdown, perhaps at a time when plants is determined, to a large extent, by the soil fac­ could advantageously use more nitrogen. tors of moisture, temperature, fertility and tex­ The risk of production of coarse woody ture. Organic matter tends to accumulate materials and immobilisation of nitrogen under conditions where the soil is fertile and during their consequent decomposition may be the growing season long, moist and cool avoided if nitrogen fixing species are used for whereas a long, moist, warm growing season the greencrop. Symbiotic associations with N favours decomposition. Clay tends to associate fixing bacteria allow these plants to utilise closely with humus, retarding breakdown by atmospheric sources of nitrogen unavailable to soil microbes so that fine-textured soils usually most plants. As a result, the soil N capital have higher organic matter contents than increases and such increases can offset conse­ coarse-textured soils in similar climatic loca­ quent immobilisation during decomposition. tions. In areas with moist, mild winters sapro­ Coarse N fixing species include peas, lupins phytic fungi are active almost all year and and oil-seed rape. organic matter levels can be very difficult to maintain. Organic matter contents above 10% sometimes occur in British forest nurseries but Recommendations for greencrops usual levels lie between 2 and 8% (Figure 4.2). Greencrops must be suited to the pH of the There are two basic methods of increasing nursery. Mustard is likely to fail if the soil pH organic matter contents of forest nursery soils. is less than 5.5; oats do best at a pH above 5.5

60 and are likely to fail at any pH less than 5.0. mately 25tha_1 to seedbeds and 12.5 t ha-1 to Blue or yellow lupins and also ryegrass grow transplant lines. More recent recommendations well at the range of pH optimum for most have been toward applying 25-40 t ha-1 to lines conifers. Lupins are more expensive than oats. and none to the seedbeds owing to possible See also Chapter 7, section 7.3 for details of reductions in seed germination following appli­ Rhizobial inoculation. cations of bulky organics (see section 4.4.1 Lupins should be sown in May or June at above). If this recommendation is followed and 450 kg ha-1. This and all other greencrops seedbed applications are reduced then 50 kg should be raised on ground given more phosphorus per hectare should be 45-55 kg ha-1 N, 50-65 kg ha-1 P and 70-95 kg included in the pre-sowing fertiliser dressing on ha-1 K before sowing. The crop should be the seedbeds and one or perhaps two additional ploughed in no sooner than the time flowers top-dressings of nitrogen used. When available, first open but before seeds have set. On very hopwaste is a very suitable organic material for light soils, seedlings of yellow lupins grown as use in forest nursery soils. However, it has a greencrop have suffered because of excessive become increasingy difficult to obtain. uptake of P when grown on ground given superphosphate (Warren and Benzian, 1959). Bracken-hopwaste compost Oats should be sown in May at 400- 500 kg ha-1 of Yielder or Castleton potato oats. At the beginning of the post-war period of These should be ploughed in when the ears intensive research into plant nutrition in are visible but still green. forest nurseries, which culminated with the Ryegrass can be used as either a summer or publication of Bulletin 37 (Benzian, 1965), it autumn grass crop. The early crop should be was necessary to establish a satisfactory, sown in April at 33 kg ha-1 of perennial rye­ widely available ‘standard’ compost against grass, or 22 kg and 11kg, respectively, of which to assess experimental fertiliser regimes. Bracken-hopwaste compost became perennial ryegrass and Italian ryegrass. It should be cut regularly and ploughed in, in this standard material. However, in practice, late August. The late crop should be sown in it is no longer made, being replaced where a late August or early September depending on bulky organic supplement is required, by site. If the autumn is mild and grass is sown uncomposted hopwaste. too early, top growth of ryegrass can become so luxuriant as to be an embarrassment by the Bark chippings and sawdust time it should be dug in as a preliminary to The direct use of organic residues such as bark lining out. At this time, the greencrop should chippings and sawdust, which contain much be no more than 10-15 cm high. woody tissue, can deplete the supplies of avail­ able nitrogen in the soil during their decompo­ 4.4.4 Imported organic materials sition. If these materials are composted and supplementary inorganic fertilisers added then Hopwaste the resulting material is suitable for use in Hopwaste is a well proven material providing forest nursery soils although, as for any com­ substantial amounts of nitrogen and phos­ post, the cost may be high. Suitable methods phorus. It is a waste-product from breweries for composting bark have been described in where the hops are boiled to extract flavouring detail by Solbraa (1979). Additions of nitrogen, and can be applied directly to the soil as a superphosphate (with sulphur) and, probably, weed-free organic amendment. There is no ben­ micronutrients are necessary to attain max­ efit from composting hopwaste which, if kept at imum rates of decomposition. Solbraa recom­ the nursery, should be stored under cover to mends adding to the compost 2.0 kg rrr3 of minimise loss of nutrients by leaching. Tradi­ urea and 1.5-2.0 kg m-3 of superphosphate tional rates of application have been approxi­ together with 0.2 kg rrr3 fritted trace elements

61 (e.g. SAI FTE-253A). Moisture content and forest nurseries up to 1945 but fell out of aeration should be maintained by regular favour because it was a major source of weeds turning of the compost and irrigation. For piles and because lime was mixed with the manure of 4-5 m3 this entailed turning the compost up in the farmyard. When this was applied in to four times. The compost was considered forest nurseries, growth of conifers could suitable for use once the temperature within sometimes be depressed on all but the most the pile fell below 20°C, usually after 4-6 acid nursery soils. Its use has increased weeks. Modern methods of composting using recently due to difficulties in obtaining other microfloral inoculations and careful control of suitable materials and changes in farm hus­ the environment may reduce this time quite bandry practices which have reduced these considerably (Campbell et al., 1990a and causes for concern. 1990b). Peat Sewage sludge Acid peat has been used only occasionally as a The use of sewage sludge as a fertiliser and supplement to forest nursery soils. In one soil amendment has received increasing atten­ nursery on a heavy textured soil, it was con­ tion in recent years due to rising costs of fer­ sidered to have improved the working proper­ tilisers and environmental problems of sewage ties of the soil and to have acidified it. sludge disposal on agricultural land. Sewage sludge has rarely been used in forest nurseries Litter for several reasons. Broiler house litter has been used successfully • Its high water content makes it expensive in at least one forest nursery but care must be to transport. taken to avoid scorch from the ammonia gen­ • It may be very unpleasant to handle. erated from fresh piles of such material, and • It may be a major source of weed contami­ to ensure that the litter is totally free from nation. carcasses. • It may contain varying amounts of trace elements and heavy metals. Mushroom compost New methods of processing sewage can now Spent mushroom compost appears to provide provide, at a cost, a solid, easily handled and an alternative material for use as a soil nearly odourless end product that is weed and organic matter amendment. The lime content disease free. Certain elements are, however, of such material should be analysed to ensure found in concentrations approximately 40 times that no detrimental effect upon soil pH is greater than in soils, particularly copper, tin and likely to occur. In one nursery the soil pH was zinc (Berrow and Weber, 1972). Zinc, especially, increased by over one unit for at least 4 years is present in sewage sludges in a highly soluble following application. form often exceeding 500 times that found in the Other materials may become available in soil. Additional problems may arise due to high the future. A comprehensive chemical analysis levels of nickel and manganese. Sewage sludge should be obtained, and advice sought, before should only he considered for use in the nursery any decision is taken to use a new material. if the supplier can guarantee a sustained supply, entirely free from toxic heavy metals and noxious materials such as broken glass. REFERENCES AARON, J.R. (1976). Conifer bark: its proper­ Other materials ties and uses. Forestry Commission Forest Record 110. HMSO, London. Farmyard manure ALDHOUS, J.R. (1972). Comparison of org­ Farmyard manure was used extensively in anics and bulky inorganics on seedbeds

62 cropped annually for thirteen years. In BINNS, W.O. (1975). Fertilisers in the forest: a Nursery practice (1st edtn). Forestry guide to materials. Forestry Commission Commission Bulletin 43. HMSO, London, Leaflet 63. HMSO, London. 147-152. BOLTON, J. and COULTER, J.K. (1966). ALLEN, S.E. (1984). Slow-release nitrogen Distribution of fertiliser residues in a forest fertilisers. In Nitrogen in crop production. nursery manuring experiment on a sandy ASA-CSSA-SSSA, 677 South Segoe Road, podsol at Wareham, Dorset. In Report on Madison, WI 53711 USA, 195-206. forest research for the year ended March ARMSON, K.A. and SADREIKA, V. (1979). 1965. Forestry Commission. HMSO, Forest tree nursery soil management and London,90-92. related practices. Ontario Ministry of BOULD, C„ HEWITT, E.J. and NEEDHAM, Natural Resources, Toronto. P. (1983). Diagnosis of mineral disorders in BACHE, B.W. (1976). The measurement of plants. Volume 1. HMSO, London. (170 pp.) cation exchange capacity of soils. Journal of BRADY, N.C. (1974). The nature and proper­ the Science of Food and Agriculture 27, ties of soil. Collier Macmillan Publishers, 273-280. London. BENZIAN, B. (1965). Experiments on nutri­ BROADBENT, F.E. (1947). Nitrogen release tion problems in forest nurseries (2 and carbon loss from soil organic matter Volumes). Forestry Commission Bulletin during decomposition of added plant 37. HMSO, London. residues. Soil Science Society of America BENZIAN, B. (1967). Manuring young Journal 12, 246-249. conifers: experiments in some English nurs­ BURT, A.C. (1988). Media and mixes for con­ eries. Proceedings, Fertiliser Society 94, tainer-grown plants. Unwin, London. (309 pp.) 5-37. CAMPBELL, C.D., DARBYSHIRE, J.F. and BENZIAN, B„ BOLTON, J. and MAT­ ANDERSON, J.G. (1990a). The composting TINGLY, G.E.G. (1969). Soluble and slow- of tree bark in small reactors - self-heating release PK fertilisers for seedlings and experiments. Biological Wastes 31, 145-161. transplants of Picea sitchensis. Plant and CAMPBELL, C.D., DARBYSHIRE, J.F. and Soil 31, 238-256. ANDERSON, J.G. (1990b). The composting BENZIAN, B„ BROWN, R.M. and FREE­ of tree bark in small reactors - adiabatic MAN, S.C.R. (1974). Effect of late-season and fixed temperature experiments. top-dressings of N (and K) applied to conifer Biological Wastes 31, 175-185. transplants in the nursery on their survival DAVEY, C.B. and KRAUSE, H.H. (1980). and growth on British forest sites. Forestry Functions and maintenance of organic 4 7 , 153-184. matter in forest nursery soils. In Pro­ BENZIAN, B„ FREEMAN, S.R.C. and PAT­ ceedings of North American Forest Tree TERSON, H.D. (1972). Comparison of crop Nursery Soils Workshop, July 28 to August rotations, and of fertiliser with compost, in 1, 1980, Syracuse, New York, 130-165. long-term experiments with Sitka spruce FISHER, J.T. and MEXAL, J.G. (1984). (Picea sitchensis) and other conifers grown Nutrition management: a physiological in English forest nurseries. Forestry 46, basis for yield improvement. In Seedling 55-69. physiology and reforestation success, eds BERROW, M.L. and REAVES, G.A. (1985). M.L. Duryea and G.N. Brown. Martinus Extractable copper concentrations in Nijhoff/Junk, The Netherlands. Scottish soils. Journal of Soil Science 36, HACSKAYLO, J., FINN, R.F. and VIMMER- 31-43. STEDT, J.P. (1969). Deficiency symptoms of BERROW, M.L. and WEBER, J. (1972). Trace some forest trees. Ohio Agricultural elements in sewage sludges. Journal of the Research Development Centre. Research Science of Food and Agriculture 23, 93-100. Bulletin 1015. (68 pp.)

63 HALLAM, M.J. and BARTHOLEMEW, W.V. demography and the seasonal internal (1953). Influence of rate of plant residue cycling of nitrogen in sycamore (Acer addition in accelerating the decomposition pseudoplatanus L.) seedlings in relation to of soil organic matter. Soil Science Society nitrogen supply. New Phytologist 117, of America Journal 17, 365-368. 587-596. HUTTL, R.F. (1986). Forest fertilisation: MILLARD, P. and PROE, M.F. (1991b). results from Germany, France and the Storage and internal cycling of nitrogen in Nordic countries. Fertiliser Society, relation to seasonal growth of Sitka spruce. London. (40 pp.) Tree Physiology 10, 33-43. INGESTAD, T. (1957). Studies on the nutri­ MORRISON, I.K. (1974). Mineral nutrition of tion of forest tree seedlings. I. Mineral conifers with special reference to nutrient nutrition of birch. Physiologia Plantarum status interpretation: a review of literature. 10, 418-439. Department of the Environment, Canadian INGESTAD, T. (1959). Studies on the nutri­ Forestry Service, Publication No. 1343, tion of forest tree seedlings. II. Mineral Ottawa, Canada. (74 pp.) nutrition of spruce. Physiologia Plantarum PELLET, H.M. and CARTER, J.V. (1981). 12, 568-593. Effects of nutritional factors on cold hardi­ INGESTAD, T. (1960). Studies on the nutri­ ness of plants. Horticultural Review 3, tion of forest tree seedlings. III. Mineral 144-171. nutrition of pine. Physiologia Plantarum 13, SHARMA, G.C. (1979). Controlled-release fer­ 513-533. tilisers and horticultural applications. INGESTAD, T. (1977). Nitrogen and plant Scientia Horticulturae 11,107-129. growth; maximum efficiency of nitrogen fer­ SMILDE, K.W. (1973). Phosphorus and tilisers. Ambio 6, 146-151. micronutrient metal uptake by some tree INGESTAD, T. and LUND, A.-B. (1986). species as affected by phosphate and lime Theory and techniques for steady state applied to an acid sandy soil. Plant and Soil mineral nutrition and growth of plants. 39,131-148. Scandinavian Journal of Forest Research 1, SOLBRAA, K. (1979). Composting of bark. III. 439—453. Experiments on a semi-practical scale. LAVENDER, D.P. and WALKER, R.B. (1981). Reports of the Norwegian Forest Research Nitrogen and related elements in nutrition Institute 34 (15), 387^439. of forest trees. In Proceedings Forest STONE, E.L. (1968). Microelement nutrition of Fertilisation Conference, eds S. P. Gessel, R. trees. A review. In Forest fertilisation .... M. Kenady and W. A. Atkinson, Wash­ theory and practice. Tennessee Valley ington, USA University of Washington, Authority, Muscle Shoals, Alabama, 15-22. 132-175. LEAF, A.L. (1968). K, Mg and S deficiencies in SWAN, H.S.D. (1960). The mineral nutrition of forest trees. In Forest fertilisation ... theory Canadian pulpwood species. 1. The influence and practice. Tennessee Valley Authority, of nitrogen, phosphorus, potassium and Muscle Shoals, Alabama, 88-121. magnesium deficiencies on the growth and LOW, A.J. and SHARPE, A.L. (1973). The development of white spruce, black spruce, long term effects of organic and inorganic jack pine and western hemlock seedlings fertiliser regimes at Teindland nursery. grown in a controlled environment. Pulp and Scottish Forestry 27, 287-295. Paper Research Institute of Canada, MARTENS, D. C. (1986). Plant availability of Woodland Research Index 116. (66 pp.) extractable boron, copper and zinc as TIMMIS, R. (1974). Effect of nutrient stress related to selected soil properties. Soil on growth, bud set, and hardiness in Science 106, 23-28. Douglas-fir seedlings. In Proceedings of MILLARD, P. and PROE, M.F. (1991a). Leaf North American Containerised Forest Tree

64 Seedling Symposium, eds R.W. Tinus, W.I. Franco) seedlings. Forest Science 31, Stein and W.E. Balmer, Great Plains 485—496. Agricultural Council Publication No. 68, VAN DEN DRIESSCHE, R. (ed.) (1991). 187-193. Mineral nutrition of conifer seedlings. CRC VAN DEN DRIESSCHE, R. (1980). Health, Press, Boston, USA. vigour and quality of conifer seedlings in WARREN, R.G. and BENZIAN, B. (1959). relation to nursery soil fertility. In High levels of phosphorus and die-back in Proceedings of North American Forest Tree yellow lupins. Nature (London) 184, 1588. Nursery Soils Workshop, July 28 to August WORLEY, C.L., LESSELBAUM, H.R. and 1, 1980, Syracuse, New York, 100-120. MATTHEWS, T.M. (1941). Deficiency VAN DEN DRIESSCHE, R. (1984). Relation­ symptoms for the major elements in ship between spacing and nitrogen fertilisa­ seedlings of three broad-leaved trees. tion of seedlings in the nursery, seedling Journal of the Tennessee Academy of mineral nutrition, and outplanting perfor­ Science 16, 239—247. mance. Canadian Journal of Forest YOUNGBERG, C.T. (1984). Soil and tissue Research 14, 431—436. analysis: tools for maintaining soil fertility. VAN DEN DRIESSCHE, R. (1985). Late- In Forest nursery manual: production of season fertilisation, mineral nutrient bareroot seedlings, eds M.L. Duryea and reserves, and retranslocation in planted T.D. Landis. Martinus Nijoff/Dr W. Junk Douglas-fir (Pseudotsuga menziesii (Mirb.) Publishers, The Hague, 75-80.

65 Chapter 5 Seed

P. G. Gosling and J. R. Aldhous

Introduction Contents of the seed manuals are summarised below.

The use of seed from stands of high inherent Subject Bulletin 59 Bulletin 83 quality is widely recognised as the best means (broadleaves & (forest trees) of ensuring fast-grown and healthy planta­ ornamentals) tions capable of yielding good quality wood. Flower, fruit & seed Seed guaranteed to have been collected in development Chapter 3 Chapter 6 nationally registered seed orchards or seed Collection methods & Chapter 4 & Chapters 7 & stands* may be two or three times more times Appendix 3 8 expensive than seed collected from unregis­ Extraction & processing Chapter 4 Chapter 9 tered stands of unknown quality. The higher Seed yields Appendix 4A Table 9.1 Storage Chapter 5 & Chapter 10 cost is due to the additional labour and super­ Appendix 5 vision needed to ensure that the seed is true Testing Chapter 6 Chapter 11 to its description, and for seed orchards, the Seed & plant identity - Chapter 4 cost of their management. Nevertheless, even number systems the highest of these seed costs adds little to the cost of newly established plantations, and this is amply covered if the plantation raised from the registered seed grow only a few per­ 5.1 Choice of seed origin cent faster than plantations from unregistered seed (Faulkner, 1992; Gill, 1983; Lee, 1990; 5.1.1 Improved seed Rook, 1992.) Much effort has gone into ‘tree improvement’ through selection and testing programmes. As Forestry Commission seed manuals a result, supplies of seed are available from open-pollinated seed orchards and from con­ Two current Forestry Commission publica­ trolled pollination of genetically superior tions describe in detail, many aspects of seed parent trees in the tree improvement pro­ collection, storage, handling, etc., relevant to gramme. Unfortunately, lack of resources has the forest nursery manager. restricted work in the UK to a very small Forestry Commission Bulletin 59. Seed number of species. manual for ornamental trees and shrubs Seed of Scots pine is available from (Gordon and Rowe, 1982). ‘approved’ and untested seed orchards in rea­ Forestry Commission Bulletin 83. Seed sonable quantity. For Sitka spruce, increasing manual for forest trees (Gordon, 1992). amounts of ‘approved’ seed are available; ini­ Nursery managers are recommended to tially, most of this is reserved for vegetative include both volumes in their collection of propagation programmes. The yield of hybrid readily available reference books. larch from open pollinated seed orchards has been much less than anticipated; however, * For explanation of terms, see glossary (Appendix II) and supplies of seed from controlled pollination in also Chapter 15, section 15.1. polyhouses should become commercially avail­

66 able in small quantities in the mid 1990s. This Lodgepole pine No simple recommendation; see footnote is also being reserved for vegetative propaga­ to table. tion programmes. Sitka spruce Queen Charlotte Islands is a well-proven Wherever seed from such improved sources general purpose seed source. For is available and appropriate, it should be the favourable sites in Wales and southwest England, origins in Washington and grower’s first choice and nursery managers northern Oregon may be used; for very should ensure that stocks are on offer. exposed and frosty sites in north Scotland, Nevertheless, for many species, such improved consider Alaskan origins. Improved seed seed is not yet in production, so that the from seed orchards is also available. grower will have to seek stock from home­ Nonway spruce For timber production, eastern Europe grown or imported seed. Romania, Poland, the Czech and Slovak republics; for Christmas tree production, south Germany (German seed zone 5.1.2 Home-grown seed 84013). If home-grown seed is being sought, as a first European larch Carpathian and Sudeten Mts of the Czech principle, seed should be chosen from the very and Slovak republics (native stands); if not best stands in the locality where it is intended available, low elevation stands in Austria and Germany. to plant, ensuring that these are ‘registered’ when relevant (see Chapter 15, section 15.3). Japanese larch Suwa region of Nagano (elevation 1500-1800 m); if not available, Nikko If such seed is not available, the second choice region of Tochigi (1500 m) and plantations should be from the nearest registered seed on Hokkaido. source on a similar site. Failing a local regis­ Douglas fir Washington coast and foothills of W. slope tered source, information on other registered of Cascades (US seed zones 012, 030, sources may be obtained by consulting the 041,202, 241,403,411,412). register of seed sources held at the Forestry Grand fir Olympic Peninsula and Puget Sound (US Authority national offices, addresses of which seed zones 030, 202, 212, 221, 231, 241); are given in Appendix I. if not available, Vancouver Island (British Columbia zone 1020). 5.1.3 Origins of imported seed Noble fir Larch Mountain, Oregon, 975 m, (US seed zones 042, 440, 452). If only imported seed is available, the origins given in Table 5.1 are to be preferred. Western Vancouver Island (BC zone 1010); if not hemlock available, coastal Washington (US zones 030, 012, 011), or Queen Charlotte Isles. Table 5.1 Suggested sources of seed when home- For sheltered sites in northern Britain, Alaskan origins are hardiest but grow collected registered or improved sources are not more slowly. available Western red Washington Olympic Mts below 150 m cedar (US Zone 030, 012, 011, 221); if not Species Suggested source available, Vancouver Island, e.g. BC zone 1020. Scots pine Should not normally need to be imported because seed-orchard seed available. Oak, pedunculate Registered seed sources in woodland in Where grant-aid is linked to use of sessile northern France and northwest Germany. particular local native sources of SP, the Beech Belgium (Foret de Soignes); if not avail­ requirements of the relevant grant able, any registered seed source in schemes must be observed. Belgium, Holland, northern France or Corsican pine For southern sites, registered stands in northwest Germany. Corsica: second choice France, region Birch, downy Western european sources from low 01 (2A) or 01 (2B). For planting north of the silver elevation at latitudes similar to Britain. Midlands, seed from second generation Calabrian CP stands in Belgium (e.g. More detailed information can be found in: Forestry Com­ Koekelare) or France (e.g. Les Barres) are mission Bulletin 66 Choice of seed origins for the main forest also suitable. species in Britain by R. Lines (HMSO, 1987).

67 5.2 Seed identity numbers 5.2.2 Identity numbers for seed collected in Great Britain Forestry managers have for many years, used numbering systems as brief alternatives to General collections names describing the origin of seed, both in the Great Britain is divided for general seed collec­ United Kingdom and elsewhere. The advent of tion purposes into four regions of provenance, seed stand registration under EEC legislation, numbered 10, 20, 30, 40. These are shown in has given a further impetus to establish systems Figure 5.1. Within any region of provenance, that indicate the quality as well as the location seed may have been obtained from ‘registered’ of origin or provenance of seed lots. Systems in or ‘unregistered’ stands. Registered stands of a current use in Europe, USA and Canada, and species in a region of provenance are serially those used in the past in the United Kingdom, numbered; the source identity consists of the are described comprehensively in Chapter 4 of region of provenance number followed by the Bulletin 83. The following is a summary of cur­ registered stand serial number. rent practice in the United Kingdom. Seed from unregistered sources is given only the region of provenance number; it could 5.2.1 The Forestry Commission seed have been derived from a single stand or from identity number system a number of unregistered stands within the Seed Identity Numbers currently being allo­ region of provenance. cated have three parts: species name; crop year; source. While called identity ‘numbers’, letters or names may also be incorporated.

Species name The species name is an essential part of a seed identity, without which it is unlikely to be unique.

Seed crop year The first two digits of all Forestry Commission identity numbers denote the ‘seed crop year’, 1st August - 31st July. This is identified by the last two digits of the calendar year in which the crop year begins, e.g. the first two digits for seed collected in January 1991 is ‘90’.

Source The letters and digits that follow the seed crop year indicate whether the seed was grown in Great Britain or was imported and whether the seed is from a tree improvement pro­ gramme or other special category. The letters and digits indicating source are enclosed in a bracket with supplementary information following.

68 For example: SS 88(1006) denotes Sitka by ‘NT’ if the testing programme for the spruce collected in crop year 88 in stand 6 of orchard is not yet completed, e.g. SP 90(A70) region 10; denotes seed from seed orchard 70 the compo­ POK 89(40) denotes pedunculate oak col­ nents of which have been approved. SP lected in crop year 89 from unspecified stands 87(NT45) denotes seed from Scots pine seed (or stand) in region 40. orchard 45 for which tests have not yet been completed. A small number of Scots pine seed orchards Native Scots pine are composed of clones from native sources. Within the range of native Scots pine, approxi­ The letter ‘N’ is then added followed by the mately 40 woodlands in seven collection zones native pine zone number. are included in a national register (Forestry SP (NT37)N2 denotes Scots pine seed from Commission, 1993). The collection zones are seed orchard 37, this being made up of clones shown in Figure 5.2. Seed collected from such collected from within native tree region 2 (see stands is indicated by the initial letter ‘N’ (i.e. Figure 5.2). native), followed by a digit showing the zone number followed by two digits for the stand; Hybrid larch e.g. SP 89(N502) is native Scots pine seed col­ Collections of seed from orchards of mixed lected in crop year 89 from stand 2 of zone 5. clones of Japanese and European larch are sometimes made from clones of one species only. Improved seed from seed orchards The letters “E’ or ‘J1 are used to indicate this. Seed orchards in Britain are numbered con­ HL 84(NT8)E denotes seed from hybrid larch secutively from 1 within each species. Seed seed orchard 8 from European larch cones only. from such orchards is identified by that number. This is preceded by ‘A’ if the compo­ Family mixtures for vegetative propagation nent clones in the orchard have been approved Mixtures of seed from controlled pollination of as a result of a completed test programme, or proven genetically superior families are now used for the commercial production of rooted cuttings. These mixtures are numbered sequentially starting with 0001, and prefixed by the letter ‘M’. SS 85(M0014) is mixture 14 from controlled pollination of tested families of Sitka spruce.

5.2.3 Identity numbers for imported seed For imported seed lots, name and crop year conventions are the same as for home col­ lected seed. The source information for imported seed is based on the Universal Decimal Classification (UDC) code for countries or parts of countries and is placed within brackets. A list of the more important UDC codes for countries from which seed is imported can be found in the current Forestry Commission Seed Catalogue or Forestry Commission Bulletin 83 Seed Figure 5.2 Native Scots pine seed collection zones. manual for forest trees.

69 In addition, details of region of provenance 5.3.2 Legislation governing purchase provided for the exporting country may be pro­ and sale of seed vided, following the bracketed digits. For Trade in tree seed is covered by legislation, of example: which the most immediate is the Forest (492)3 region 3 of the Netherlands, Reproductive Material Regulations; see Chapter (436)VII/4 region VII/4 of Austria, 15, section 15.1 and also section 15.8.2. (711)C4 coastal zone 4 of British The Forest Reproductive Material Columbia, Regulations affect fewer species than had (795)051 zone 051, Oregon been included in the earlier, now repealed, (8331) Malleco province, Chile 1920 Seeds Act. Species currently covered are listed in Table 15.1 (page 224). 5.2.4 Lot numbers 5.3.3 Classes of seed Lot numbers may be allocated where, for oper­ ational reasons during collection, handling, Seed is classified in current seed catalogues storage or processing, seed which would other­ as: wise have had a single identity number has ‘unregistered’ become divided. ‘registered’ - either from ‘selected seed stands’ or from ‘seed orchards’ (either ‘untested’ or ‘approved’). 5.3 Procurement of seed Registered seed conforms to that category of seed under the Forest Reproductive By far the largest quantities of seed sown by Material Regulations, but is extended for con­ nursery managers are purchased. The prin­ venience and consistency to species not cov­ ciple exceptions are the larger seeded ered by the regulations, but which may for broadleaved and ornamental species within example be marketed under OECD rules. See easy reach of a nursery. Chapter 15, sections 15.1 and 15.4. For recommendations for methods of han­ The bulk of conifer seed used in forestry dling, extraction and storage of locally col­ plantations falls into the ‘registered/selected’ lected seed, see Forestry Commission category. Some seed is also available from Bulletins 59 and 83. ‘approved’ and from ‘untested’ seed orchards. For details of administrative procedures to Legally, both types of seed have to be placed be followed under the Forest Reproductive with ‘selected’ seed lots because there are cur­ Material Regulations for species covered by rently no EEC categories ‘approved’ or those regulations, see Chapter 15, section ‘untested seed orchard seed’. In practice, how­ 15.3. ever, ‘approved’ seed should be considered equivalent to the EEC ‘tested’ seed while 5.3.1 Sources of seed ‘untested’ should be considered intermediate Seed may be purchased either from seed mer­ between ‘selected’ and ‘approved’ (Chapter 15, chants or from the Forestry Commission. A section 15.1.2). list of members selling tree and shrub seed Seed of oak and beech is from time to time may be obtained from the Horticultural available from registered seed sources; how­ Trades Association, 19, High Street, Theale, ever, trees do not bear seed crops every year, Reading, Berks, RG7 5AH. nor can seed be stored easily from one year to Prospective purchasers from the Forestry the next. Consequently, in many years, unreg­ Commission should write for a current seed istered seed sources have to be used (Chapter catalogue to: Plant and Seed Supply Branch, 15, section 15.1.5). Seed Trading, Alice Holt Lodge, Wrecclesham, Seed of other broadleaved species comes Farnham, Surrey, GU10 4LH. almost entirely from unregistered stands.

70 5.4 Collection and extraction of requires equipment and facilities not usually available in forest nurseries. For details of the seed conditions required for long-term storage of While these topics were described in detail in seed of conifers and broadleaves, see Bulletin the first edition of this Bulletin, the tech­ 59, Chapter 5, or Bulletin 83, Chapter 10, and niques of collection and extraction are now the references given there. fully covered in the seed manuals - Forestry A list of the broadleaved forest and orna­ Commission Bulletins 59 and 83 (see page 66; mental species classed as ‘orthodox’ and there­ also Chapter 15, section 15.3.1). fore suitable for long-term storage is given in Appendix 5 of Bulletin 59. 5.5 Seed storage Seed of all conifers used for timber produc­ tion in the UK and many other conifers 5.5.1 Orthodox and recalcitrant seed besides, are ‘orthodox’ and similarly, can be Seeds of a very wide range of food and other stored in suitable conditions for long periods plants, fall into two main groups: ‘orthodox’ (Bulletin 83, Chapter 10.) and ‘recalcitrant’ (Roberts, 1973). Orthodox seeds can be stored successfully 5.5.3 Short-term storage for long periods at low temperatures and low When seed has been received in good condition moisture contents; the lower the moisture con­ from a seedsman and needs no treatment for a tent and the temperature, the longer viability period before it is prepared for sowing, it is maintained. should be stored as described below. The moisture content at which orthodox seeds are stored is based on an assessment of their initial moisture content, anticipated Orthodox seed storage period and the cost of drying. Orthodox seed should be stored in airtight Recalcitrant seeds do not follow this pat­ containers at +2°C. The moisture content of tern of response and die if their moisture con­ most commercial conifers used in the UK tent is reduced below some relatively high should be 6-8% (% fresh weight); broadleaved value. They are shed at moisture contents of species such as ash, cherry, hawthorn and between 50 and 30%, and their quality deteri­ rowan traditionally are stored with a moisture orates as they lose moisture. While most com­ content of 10-15%. monly a characteristic of seeds of tropical Where orthodox seed does not require plantation crops, temperate species such as immediate pretreatment for sowing but is not oak, sycamore, sweet and horse chestnut come in a condition for storage (e.g. if it has been into this category. collected locally, for example, and has a high As a broad rule, most species of a genus moisture content), it will usually be necessary behave similarly - either all are orthodox or to allow it to dry, spread out thinly where all recalcitrant. However, there are a number unheated air can freely move over it (see of exceptions, for example, the genus Acer Bulletin 59, pages 18 and 19). includes orthodox and recalcitrant species. If the moisture content (as a percentage of Also, while classed as ‘orthodox’, Fagus seed is fresh weight) and total weight of the fresh in practice difficult to condition for long-term seed have been determined at the nursery, storage. While there are reports from France and the moisture content required for satisfac­ that it has been achieved on an experimental tory storage is known, the target weight of the scale, long-term storage of beech seed is not seed when ready for storage can be calculated: yet practised commercially (Gosling, 1991). Weight when ready for storage =

5.5.2 Long-term storage Weight of fresh seed x (100 - initial moisture content %) Preparation of seed for long-term storage (100 - intended moisture content %)

71 Recalcitrant seed mancy. The current recommendation is to combine storage and pretreatment, keeping Recalcitrant seeds cannot be reliably stored the seeds at 28-32% moisture content and without some loss of germination. The best 0-5°C temperature. This moisture content is that can be hoped for is that storage condi­ high enough to enable seeds to lose their dor­ tions can be controlled to keep deterioration mancy but not so high as to permit radicle within acceptable limits. growth (Gosling, 1991). Conditions which lead to drying should be avoided; but it is important to remember that at high moisture content seed like acorns will continue to respire and hence generate heat. 5.6 Seed testing It is therefore essential to maintain good air While purchased seed should be supplied with circulation to keep temperatures low, thereby a test certificate, nursery managers may wish also minimising the risk of spread of fungal to have a test done on seed they have collected, infection. or may wish to have a previous test confirmed Storage in a cold store (0 to +2°C) where a or may need a test to check on whether seed high humidity is maintained is the best that is that has had to be stored has maintained its readily available on many nurseries. viability. Traditionally, acorns when collected were If the species comes under the Forest spread over the floor of a vermin free, well Reproductive Material Regulations and the ventilated shed, in a layer 15-25 cm thick. For seed may be offered for sale, testing must be the first 6-8 weeks or until they appeared sur­ carried out at an Official Seed Testing Station face dry, they were turned frequently, daily at on properly taken samples. first then every 2-3 days to minimise develop­ Seed tests fall into two groups: ment of mould as the acorns ‘sweated’. 1. tests of physical quality Subsequently, they were regularly lightly purity sprinkled with water to minimise further weight of 1000 pure seed drying. The temperature in such stores was moisture content; kept down by ensuring the store was always 2. tests of physiological quality well ventilated (Anon., 1962). germination Many hundreds of tons of acorns have been viability. stored by this method. Nevertheless, storage of acorns in a cold store is likely to be superior Seed test certificates give the results of to the older method. standardised tests of these qualities, carried Seeds of recalcitrant species such as oak out in nationally approved laboratories to the often sprout prematurely. While this is an standards of the International Seed Testing indication that the seed should be sown as Association (ISTA). soon as is reasonably possible and with care, it should not cause undue concern as such large- 5.6.1 Seed sampling for testing seeded species have enough stored food Any seed sample to be submitted for testing reserves to allow the surviving embryo to must be representative of the whole. No matter resume growth even if the radicle is broken how accurate the technical work in the testing off. laboratory, the results can only show the quality of the sample submitted for analysis. Short-term storage of beech Beech seed presents difficulties in nursery Mixing before sampling planning because of the variable dormancy of Before sampling, the whole bulk seed lot must seed lots. It may require anything between 4 be as uniform as possible. If significant differ­ and 20 weeks pretreatment to overcome dor­ ences can be observed, either the seed must be

72 Table 5.2 Prescriptions for seed sampling Table 5.3Seed testing: fees (as at 1.10.93); min­ imum sample weight; maximum seed lot weight; purity (a) Seed lot in sacks or other containers standards

Number of Minimum number of containers to be EEC Fee for Minimumi Maximum Maximum containers sampled (Samples to be taken from at species statutory sample seed lot impurities % least 5 positions) in the lot seed weight weight by weight ** test (£) (grams) (kg) % 1-5 (inclusive) Each container 6-14 Not less than 5 containers Silver fir £75* 240 0.1% At least one container in 3 15-30 Beech £11 Ot 1000 50 j 0 0.1% 31—49 Not less than 10 containers 50 or more At least 1 container in 5 European larch £75* 25 _ 0.5%§ Japanese larch £100* 25 - 0.5%§ (b) Undivided bulk seed lot Norway spruce £75* 40 - 0.5% Sitka spruce £100* 25 1000 0.5% Weight of bulk seed Austrian and Number of positions Corsican pine £75* 100 - 0.5% Exceeding Not exceeding to be sampled Scots pine £75* 40 - 0.5% Weymouth pine £75* 90 - 0.5% _ 50 kg Not less than 4 60 kg 1500 kg Not less than 5 Douglas fir £100* 60 - 0.5% 1500 kg 3000 kg At least 1 for each 300 kg Red oak £95 500# - 0.1 %H 3000 kg 5000 kg Not less than 10 Pedunculate 5000 kg 20000 kg At least 1 for every 500 kg oak £95 500# 5000 0.1 %H Sessile oak £95 500# - 0.1% ! remixed or it must be treated as two or more • Seed test: purity; weight of 1000 pure seeds; germination without prechilling. uniform seed lots. t Seed test: purity; weight of 1000 pure seeds; viability by Where a uniform seed lot has been divided tetrazolium method; germination with prechilling, between a number of sacks or containers for t Seed test: as for * plus germination with prechilling. storage or transport, these must be sampled § Purity test standard allows 1% of other Larix seed. 1 Purity test standard allows 1% of other Quercus seed. as specified in Table 5.2. Where it is not • Minimum number of acorns to be submitted in sample. divided, samples should be taken as in Table ** Maximum permitted percentage by weight of fruits and 5.2. seeds of other forest tree species. Where there are more than five containers in a lot, the containers to be sampled should be selected at random, if possible, using a walking the fastest available means. Samples for mois­ stick sampler. Where the seed is stored in bulk, ture content tests must be sent in moisture- samples should be taken with a stick sampler proof containers. at random throughout the bulk, from at least For the United Kingdom, seed may be sent the number of positions indicated in Table 5.2 for testing to: The Official Seed Testing (see Bulletin 83 for fuller details). Station, The Forestry Authority, Research Division, Alice Holt Lodge, Wrecclesham, Sample size Farnham, Surrey, GU10 4LH. Samples should be of a weight that will con­ With each sample, there should be tain a minimum of 5000 seeds (500 for enclosed: Quercus spp., minimum weight for Fagus spp. • full name and address of sender; 1 kg). Minimum weights for species covered by regulations are included in Table 5.3. • species name; • date of sampling; Sample despatch • stock number or reference; Samples should be sent in rigid containers by • quantity of seed represented by sample;

73 • a statement of whether the seed is or has cedure, the moisture content percent of the been kept in cold storage; seed is: • number of Master or other Certificate of (fresh weight - dry weight) x 100 Provenance, or if not available, details of fresh weight seed provenance; This will be a sufficient guide to the moisture • tests required; content of locally collected seed, to indicate • remittance for cost of tests. whether the seed requires any further drying before storage. Seed test fees Fees for seed tests (at October, 1993) are 5.6.3 Tests of physiological quality included in Table 5.3. There are broadly two types of tests of physio­ logical quality, ‘germination’ tests and ‘via­ 5.6.2 Tests of physical quality bility’ tests. The germination test, as its name implies, Purity measures the proportion of seeds in a given sample that is capable of germination under The object of the purity analysis is to deter­ standard test conditions. mine the percentage by weight of four frac­ Alternatively, one of a range of viability tests tions: may be made which permit seeds to be classi­ • seed of the species under test; fied as either alive (i.e. viable) or dead, the • seed of other forest species; inference being that live seeds are capable of • other seed; germination. Seeds with some live tissue, but • inert matter. also significant amounts of dead tissue are usu­ ally counted as dead/incapable of germination. The maximum impurities (content of fruits The choice of test depends on circumstances and seeds of other forest species + inert and in particular, whether there is any statu­ matter) permissible in any seed lot covered by tory requirement for certain tests to be made, the FRM Regulations is given in Table 5.3. and how soon the nursery manager wants to sow the seed. Weight of 1000 pure seed The germination test directly measures the The weight of 1000 pure seed is an expression characteristic which the nursery manager of seed size and is determined by weighing a wishes to reproduce in the nursery, but it takes counted number of seeds time. Viability tests may be sought if seed has The weight of 1000 pure seed is required, to be sown as soon as possible, or because the together with figures for purity percent and seed is dormant and the full germination test the results of the germinability or viability results will not be available for many weeks. tests, to calculate the number of germinable or For example, ash, cherry, beech, hawthorn, viable seeds per kilogram for any seed lot. rowan and lime can require between 6 and 18 months low temperature pretreatment to over­ Moisture content come dormancy; the germination test at a Control of moisture content is essential if seed higher temperature may take a further 6 weeks. is to be stored successfully. The moisture con­ tent of seed is expressed as a percentage of the 5.6.4 Germination tests fresh weight of the seed. In its simplest form, i.e. without any seed pre­ A method of determining moisture content treatment, a laboratory germination test con­ in the nursery, using a balance and an infra­ sists of incubating seeds under standard red lamp to dry seed quickly, is given in conditions, as near optimal as possible, until Bulletin 59, pages 18 and 19. From such a pro­ no more seeds germinate.

74 Non-dormant seeds normally take between be dried and therefore have a very limited 2 and 5 weeks. At the end of the test, germi­ storage life. nated seedlings are classified as normal or Occasionally, viability tests may be applied abnormal and ungerminated seeds are classi­ to the faster germinating species without fied as fresh, empty or dead; see Gordon, 1992 storage problems, such as pines and spruces, for details of germination testing procedures. but only if very quick results (less than 2 However, a simple test of untreated seed is weeks) are required. inadequate for most conifer seeds, and also for broadleaves such as alders and birches Cut test because such seeds exhibit shallow dormancy The cut test is the simplest, oldest and crudest (see section 5.7.1). method of assessing the potential performance Pretreatment by 3-4 weeks of cool moist of seeds or fruits. It relies on the fact that only chilling at 3-5°C is necessary for such species. full and physically undamaged seeds have the The treatment breaks any shallow dormancy potential to germinate. and conditions the seed to be able to achieve When seeds or fruits are cut open, some the maximum rate of, and total percentage may be entirely empty; in others the embryo germination when transferred to germination may be present but is immature, shrivelled, test temperatures. For seeds that may be shal­ mouldy or insect damaged. Clearly, none of lowly dormant, therefore, the whole test proce­ these is viable. The only fruits and seeds dure to assess germination capacity usually which are viable are those which appear takes about 8 weeks. clean, full, firm and apparently healthy. Although the cut test can be applied to any Double tests of germination seed, it is most commonly applied to oaks, Wherever there is doubt about the potential horse and sweet chestnut. effect of 3—4 weeks prechilling, ‘double’ tests • It gives a rapid viability estimate on fruits are performed - with and without pretreat­ that are notoriously short lived. ment. Hence, two germination capacity assess­ ments are obtained. Comparison of mid-test • The resultant partially dissected fruits can and end-of-test germination figures show be transferred to a suitable germination whether pretreatment stimulated, or reduced medium where the pericarp removal (a part germination, or whether it left it unaffected. of the cut test) acts as a ‘pretreatment’ Advice is given on seed test certificates on the which speeds up germination. basis of this test. Pretreatment is recommended where, in Interim report based on cut test the test, pretreatment clearly increased total In Great Britain, the Official Seed Testing germination by the end of the test period. It is Station routinely provides customers also recommended where, although there was requesting tests on these species with an no clear benefit at the end of the germination interim report based on the cut test results, the test period, during the test, pretreated seed germination test results following a few weeks germinated more quickly than untreated seed. later. The cut test report normally states: • total percent viable, including sprouted; 5.6.5 Viability tests The tetrazolium (TZ) and excised embryo (EE) • percent sprouted (and therefore viable); tests are normally applied to those species • total percent dead, including insect dam­ where the combined time to pretreat and ger­ aged; minate seeds is longer than 8 weeks. The ‘cut’ test, is applied to ‘recalcitrant’ • percent insect damaged (and therefore not seeds (see section 5.5.1 above), which cannot viable).

75 Tetrazolium (TZ) test How to use seed test certificate data to In this test, seeds are soaked in a colourless obtain best performance from tree seed solution of 2, 3, 5 triphenyl tetrazolium chlo­ An example of a Forestry Commission Seed ride (TZ). Live tissues turn red, their cells Test Certificate is shown in Figure 5.3. Most having the enzymes capable of converting the of the contents are self-explanatory. However, colourless TZ salt to an insoluble red product. a few minor comments can be made. The pattern of red staining on the seeds is then used to distinguish live (viable) seeds Quality for sowing into containers and for from dead. precision sowing Germination and viability data on the test cer­ tificate are expressed as percentages. In this Excised embryo tests form they can be used to assess whether a Embryos are surgically removed from seeds seed lot is suitable for precision sowing, or any and maintained under conditions similar to cell or container method of intensive plant those for germination. Viable embryos either production. See Chapter 8, section 8.2.1 for remain firm and fresh or actually show visible undercut production and Chapter 9, section evidence of growth or greening over the course 9.5.1. for discussion of alternatives when it of incubation. Non-viable embryos show signs appears that an appreciable number of cells or of decay. containers will be unstocked if one seed is sown per cell and no other seed is available. 5.6.6 Seed Test Certificates Nursery managers purchasing seed must be Appraisal of seed quality familiar with the results of seed testing as Germination and viability percentages com­ presented on Seed Test Certificates. All bined with purity and seed weight results Official and most Advisory Seed Test indicate the overall quality of the seed and Certificates issued in the United Kingdom provide the starting point for calculating include the following information: sowing densities, and a basis for comparing • number of Seed Test Certificate; different seed lots. • purity (percent); • germination percent; Pretreatment • number of live seeds per kilogram (of seed Pretreatment recommendations are given as supplied); under ‘General remarks’ on the test certifi­ cate. The majority of broadleaf species (but • number of seeds capable of germinating, not alders, birches, oaks and chestnut) exhibit per kilogram; seed dormancy and for such species, pretreat­ • weight of 1000 pure seeds in grams; ment is strongly recommended. • year in which the seed ripened; Where the certificate relates to shallowly • whether the seed has been kept in cold dormant species, the results of an ISTA storage. ‘double’ test will be given; see section 5.6.4 on Species covered by the 1977 FRM Regulations, page 75. when marketed, must be accompanied by a current ‘Supplier’s Certificate’. This includes 5.6.7 Seed tests for species not covered the information from Official Seed Test by the Forest Reproductive Material Certificates, listed above. In addition, the Regulations ‘Suppliers Certificate’ must include the The tests described above can be undertaken for description ‘EEC Standard’, or a statement any other forest species. Such tests are carried that sub-standard seed has been authorised out to the same standards and at the same cost, for marketing (Chapter 15, section 15.2.1.). and are supported by ‘Official’ certificates.

76 TEST CERTIFICATE The Official Seed Testing Lab. SENDER OF SAMPLE The Forestry Authority, Research Division Alice Holt Lodge, Wrecclesham, Farnham Surrey, GU10 4LH

Seed description Genus and species : Common name : Ident No. : Master Certificate of Provenance no. : OR Licence to Market no. : Region of Provenance : Place of Provenance : Place of origin : Altitude (metres) : Date of sampling : Date of sample receipt: Quantity represented :

Test results Test Certificate no. :

It is hereby certified that the results of the official test are as follows:

Purity analysis(full) Purity : Other forest seed : Weight of 1000 pure seed : Number of pure seeds/kg : Germination test No pretreatment (Results at day 21) : Normal germ. + Abnormal germ. + Fresh = Viability Pretreatment (Results at day 21 after 21 days pretreatment) : Normal germ. + Abnormal germ. + Fresh = Viability Number of germinable seeds/kg : Number of viable seeds/kg : Viability test % Viable by i) Tetrazolium: ii) Excised embryo: iii) Cut test: (Sprouted: ) (Insect damaged: Number of viable seeds/kg : Remarks on foreign seed : Remarks on pure seed : Ave. % empty : Moisture content Remarks on inert m atter: Wing Pieces, Broken Seed, Resin, Organic Matter, Cone Parts. General remarks This seed will not benefit from pretreatment. Officer in charge Date

Figure 5.3 Sample seed test certificate.

77 Advisory tests for seed 5.6.8 Correlation of laboratory test For seed of species where the quantity of seed results with field emergence is small, ‘advisory’ tests may be more appro­ A germination test measures the maximum priate as they require less seed and the fees germination percentage attainable by a seed are lower. For current fees, contact the Official lot under standard laboratory conditions Seed Testing Station. which are near ideal. Tree seeds are however The efficiency of an advisory test will depend notorious for germinating less well when con­ to a very large extent upon the efficiency of the ditions are not ideal; seedling yields in the sampling. The sample should be truly repre­ nursery similar to germination percentages in sentative of the bulk, containing seed and inert the laboratory are extremely rarely achieved matter in their true proportions. The size of the because conditions, temperatures in partic­ sample is at the discretion of the grower but for ular, are seldom optimal and because seed­ all except the bulky broadleaved species one lings once emerged have to survive the containing between 200-2000 seeds (with hazards of the growing season. accompanying inert matter) is adequate. Viability test results are an even more indi­ Samples of the larger seeded species should not rect measure of potential seed performance. contain fewer than 100 seeds. All results will be given in terms of ger- Local ‘field survival factors’ minable or viable seeds per kilogram depending A ‘field survival factor’ for an individual on the test applied. When results are supplied sowing can be obtained by dividing the as the number of viable seeds per kilogram, pro­ number of usable seedlings available for viding pretreatment is optimal and nursery con­ transplanting at the end of the season, by the ditions reasonable at the time of sowing, a number of germinable or viable seed sown. similar number of seeds should germinate. The implementation of nursery production plans, and specifically, sowing programmes, Quick information test (for results in are more secure if long-term records of about 14 days) nursery performance are available. This advisory test employs ISTA prescribed analyses but is applied to fewer seeds than are used in an Official test, and always relies on a Table 5.4 Field survival factors - common conifers ‘viability’ test. Quick information tests cannot (numbers in 000) be applied to species with very small seeds, Average Average number Field e.g. alders, birches. number of of usable survival It must be specified in writing when rapid germinable seedlings factors results are desirable and a quick information seeds test is required. The Seed Testing Station will per kg 1+0 2+0 1+0 2+0 then endeavour to meet reasonable deadlines. Scots pine 140 80 75 0.6 0.55 Corsican pine 55 30 - 0.6 - Moisture content test Lodgepole pine 270 160 135 0.6 0.5 European larch 60 33 - 0.55 The moisture content of tree seeds is a useful Japanese larch 100 60 - 0.6 - property for potential purchasers to know. Hybrid larch 50 28 - 0.55 - Seeds of most species possess greater longevity Douglas fir 70 38 32 0.55 0.45 at low moisture levels, and obviously the higher Norway spruce 110 85 80 0.6 0.55 Sitka spruce 320 170 150 0.55 0.45 the moisture content the less seed and the Grand fir 20 8 7 0.4 0.35 more water is being purchased per unit weight. Noble fir 12 5 4 0.4 0.35 Moisture content results are determined by Western hemlock 420 180 170 0.45 0.4 drying the seed and assuming that any loss in Western red cedar 500 225 210 0.45 0.4 weight reflects a loss of water. Lawson cypress 230 100 90 0.45 0.4

78 Table 5.4 contains field survival factors, Table 5.5Techniques to overcome seed dormancy based on long-term averages from Forestry Commission nurseries. 1. Outdoor overwintering of moist seed (stratification). 2. Cold treatment of moist seed at c. 2.5°C (prechilling). 3. Alternate warm (c. 20°C) then cold (c. 2.5°C) treatment 5 .7 Seed dormancy of moist seed, under controlled conditions. 4. Mechanical scarification of hard coated seed. Mature seed of most woody plant species from 5. A short immersion in hot (c. 70°C) or even boiling water. temperate zones frequently exhibits dormancy. 6. Treatment with a corrosive chemical, e.g. sulphuric acid. 7. Treatment with non-corrosive chemicals, e.g. KN03, A dormant seed is one that can be shown to be KCN, NaOCI, H20 2. alive, but will either not germinate at all, not 8. Treatment with plant growth substances, e.g. gibberellic germinate promptly, or only germinate over a acid. narrow range of environmental conditions. In dormant seed lots, significant numbers of indi­ term storage at the normal moisture content vidual seed remain dormant under conditions for dry storage (6-8%) do not lose dormancy. normally suitable for germination. This can be This is in complete contrast to cereal grains a serious handicap both to reliable plant pro­ which do lose dormancy in dry storage. Tree duction and to seed testing. seeds which respond to prechilling must be chilled under moist conditions for dormancy to 5.7.1 Breaking dormancy be broken. In order to bring about the germination of a Deep dormancy dormant seed lot, a suitable ‘dormancy Species which do not germinate at all until breakage’ procedure or ‘pretreatment’ has to pretreated and require in excess of 8 weeks be identified and applied, before seed testing moist prechilling to bring about any response, or sowing in the nursery. are commonly referred to as ‘deeply’ dormant. Table 5.5 lists several alternative pretreat­ As an example of deep dormancy, Figure 5.4 ment procedures which overcome dormancy of illustrates the results of germination tests at a temperate tree species. However, no one pre­ range of temperatures with a lot of beech seed. treatment is universally effective and for some The unchilled seed was incapable of germi­ species, even when the most suitable pretreat­ nating at any temperature; 15 weeks moist ment has been selected, differences in for prechilling stimulated germination and 19 example, seed moisture content, duration of pre­ weeks was even more effective (Gosling, 1991). treatment, etc., can materially affect its success. The most effective and widely used dor­ Shallow dormancy mancy-breaking pretreatment is to ‘prechill’ Shallowly dormant seed lots respond to seed, i.e. to expose imbibed (moist) dormant prechilling but do not require the duration of seed to low temperatures - i.e. between 2° and treatment necessary for deeply dormant species. 5°C. Figure 5.5 illustrates the response of a ‘shal­ The optimum duration of prechilling lowly’ dormant seed lot. Untreated, the seed depends largely on species; however, the geo­ reaches is best performance over a narrow tem­ graphical location, the environmental condi­ perature range; with 3-6 weeks’ moist chilling, tions under which seed has developed and this range is considerably widened. In practice, matured, time of collection, and how seed has this implies that pretreatment enables seed to been processed and stored may also affect the germinate well over a range of weather condi­ depth of dormancy and hence the period of tions, and not only in the best. prechilling required. 5.7.2 Seed prechilling Dry storage and prechilling In laboratory seed tests, small quantities of dry Dormant, orthodox tree seeds, kept in long seed placed on moist filter paper and incubated

79 at 3-5°C take up water slowly and commence coarse sand or peat and sand, and to store the pretreatment once their moisture content has stratified seed in a vermin-proof well-drained increased sufficiently. For commercial produc­ pit out of doors (Anon., 1960). The naturally tion, full scale versions of this procedure have occurring low soil temperatures in the winter long been practised. months are normally sufficient to meet the seeds’ chill requirements; however, soil tem­ Stratification peratures closely reflect the winter and early Traditional methods of large scale pretreat­ spring weather, and in mild early springs ment (stratification) are to mix seeds in suit­ seed can be found to be germinating sooner able sized containers with a well-drained but than is desirable. Wherever out of door strati­ moisture retaining medium such as peat or fication is practised, it is essential to examine seed regularly and to be prepared to sow if germination appears imminent.

Prechilling instead of short-duration stratification In the last 20 years, prechilling has largely replaced stratification especially for shallowly dormant species requiring shorter pretreat­ ment periods. This has been due to the wider availability of refrigerated storage to regulate temperature, and the availability of polythene bags which make good containers for han­ dling and storing moist seed; moisture loss Temperature °C during pretreatment is restricted to accept­ ■ = unchilled; ♦ = prechilled at 2°C for 15 weeks; able levels if bags are loosely tied at the neck.

▲ = prechilled at 2°C for 19 weeks. Pretreatment of species requiring long- Figure 5.4 The effect of pretreatment on germination duration pretreatment of beechnuts at different temperatures. For the longer periods of pretreatment neces­ sary for deeply dormant species, pretreatment may be carried out in a refrigerated store so that close control of temperature is main­ tained. However, a stratification medium is also necessary; • the medium retards drying more effectively over the longer pretreatment periods required; • it helps check the spread of any fungal infection, should it break out; • it provides a greater mass to absorb heat from any seed respiration and reduces the risk of the temperature of the seed rising. Temperature °C

■ = unchilled; ▲ = prechilled for 3 weeks at 4°C; The drawbacks to using a moisture retain­ ing medium are: □ = prechilled for 6 weeks at 4°C. • peat and sand add considerably to the Figure 5.5 The effect of pretreatment on germination weight and volume of seed during pretreat­ of Sitka spruce seed at different temperatures. ment.

80 • any excess moisture present in the medium 5.7.3 Varying the period of pretreatment enables seeds which lose their dormancy for deeply dormant species first to absorb water and begin to germi­ Different deeply dormant seed lots of the same nate. These prematurely germinated seeds species often exhibit different depths of dor­ can be killed by mechanical damage during mancy. Thus, the recommended duration of sowing. If they do survive, their early emer­ prechilling based on average requirements may gence will accentuate any unevenness of be too short or long for any particular lot. growth in the seedbed. Similarly, within a lot of seed, individual seeds can require different periods of pretreatment in Prescriptions for the prechilling of shal­ order to bring about subsequent germination. lowly and deeply dormant seeds are given in Where a seed test has been carried out and a Table 5.6. pretreatment prescription given with the test

Table 5.6 Prescriptions for prechilling shallowly and deeply dormant seed

Shallowly dormant Deeply dormant

Preparation

1. Divide seed bulk into conveniently sized lots for pretreatment, taking into account: total quantity of seed; sowing density; total area of seedbeds and where natural breaks will occur in relation to sowing areas and programme; the risk that larger volumes of seed may heat up during pretreatment by respiration.

2. Place conveniently sized seed lots into suitable pretreatment containers. Polythene bags able comfortably to hold about four times the seed volume are ideal, but need rigid support from a bucket, drum or box during operations 3-5 below.

Soaking

3. Carefully add about three volumes of cold water (at about 5°C) to one volume of seed. Ensure that none of the seeds adhere to the sides of the container or remain unwetted.

4. Place the now soaking seeds in refrigeration at about 5°C for 48 h to imbibe.

5. Drain off excess water - either decant, or poke holes in the bottom 5. Drain off excess water without making holes of the bag (as long as the seed is big enough not to escape!). in the bag.

DO NOT LEAVE STANDING WATER IN THE BAG - local waterlogging will drown seeds, act as a site for bacterial or fungal growth, and may also encourage premature germination of some seeds.

6. Lightly tie the neck of the bag, leaving a large air space above the 6. Mix the now imbibed seeds with moist peat and seeds. This will allow aeration without excessive drying. A length sand. First mix approx. one volume of peat to of plastic pipe can be used as a breather tube, and the open end one volume of sand, moistening it so that when of the bag gathered around it. squeezed, it does not quite release free water. Mix about one volume of seed to one volume of the peat/sand mixture. Lightly tie the neck of the bag, leaving a large air space above the seeds.

Prechilling

7. Return the now moist seeds to about 5°C to begin their period of 7. Return the mixture of peat, sand and seed to prechilling. about 5°C to begin their period of prechilling.

8. Aim to prechill for at least 3 weeks, but not more than 10 weeks, 8. Aim to pretreat each deeply dormant species removing seed when sowing conditions are considered suitable. for the duration of each warm/cold period recommended in Bulletin 59, Appendix 7. The warm storage of these treatments should beat 15-20°C.

9. Open bags once a week, gently mix the seeds and check for signs of either mould growth or premature germination.

81 Table 5.6 continued

Shallowly dormant Deeply dormant

Surface drying before sowing 10. At the end of the dormant period, the seed, still in lots for sowing, 10. Surface drying is not necessary for deeply should be surface dried. dormant seed. Seed will surface dry if spread thinly on towels, newspapers or trays, in a room which is either naturally well ventilated, or ventilated with the help of an electric fan. NEVER USE AN ELECTRIC FAN-HEATER. Occasionally, gently stir seeds to ensure even surface drying. Surface drying is complete when the seeds just begin to flow freely enough to pass sowing machinery. NEVER CONTINUE DRYING BEYOND THIS STAGE: NEVER APPLY ARTIFICIAL HEAT. Overdrying &/or heating reimpose dormancy and may ultimately kill the seed if internal drying is severe.

Temporary storage before sowing of surface dried seed 11. If soil conditions in the nursery deteriorate when sowing should be 11. Sowing programme delays are an insignificant in progress, pretreated seed should be put back into store in its part of the time necessary for deeply dormant surface dry state, in loosely tied polythene bags ± plastic breather seed pretreatments, therefore special tube, and stored at about 5°C until required. procedures for temporary storage are Most surface dried seed can be stored refrigerated in this way unnecessary. Seed should be left in pre­ for a few weeks, but should be checked at least weekly for mould treatment until conditions in the nursery are growth and premature germination. suitable for sowing.

Sowing

12. Surface dry seed can be either broadcast, drill or precision sown. 12. Seed can either be sown with the pretreatment medium, or sieved from the medium and broadcast, drill or precision sown. results, it is simplest to follow the recommenda­ sieving) and sow them. Return the seed to tion. Because of variation with a seed lot, a pro­ store and repeat the process at frequent portion of the seed may germinate prematurely intervals until no more seeds germinate. and may be lost but this is usually very small, Exposed radicles of chitted seed are very sus­ especially if a check examination has been car­ ceptible to mechanical damage; such seed ried out in the 2-3 weeks before sowing. must be handled very gently if this is to be Where test results for a seed lot are not avail­ avoided. Option 3 is also very time consuming able (e.g. because there has not been time for a and is only worth considering for very valu­ test to be completed), there are three options: able seed or when seed of the variety is in 1. Adopt the standard pretreatment recom­ short supply. mendations. 2. Commence pretreatment as though the seed 5.7.4 Monitoring pretreatment were an average lot, but from 4-6 weeks To assess whether pretreatment is pro­ before the nominal end of the treatment gressing successfully, take a representative period, inspect the seed regularly, waiting sample of 100-200 seeds at least 4 weeks until about 10% of the seed has chitted before the anticipated sowing date and incu­ before sowing, expecting that the remaining bate the sample under moist conditions at seeds are now close to germinating. room temperature (15-20°C). The germination 3. Inspect the seed regularly during the latter which occurs within about 4 weeks is a good stages of pretreatment and at suitable inter­ indicator of how effectively the pretreament is vals, remove chitted seed (by flotation and/or progressing.

82 FURTHER READING GORDON, A.G. and ROWE, D.C.F. (eds) YOUNG, J.A. and YOUNG, C.G. (1992). Seed (1982). Seed manual for ornamental trees of woody plants in N. America. Dioscorides and shrubs. Forestry Commission Bulletin Press, Portland, Oregon, USA. (Revision of 59. HMSO, London. US Forest Service Handbook 450.) GORDON, A.G. (ed.) (1992). Seed manual for forest trees. Forestry Commission Bulletin REFERENCES 83. HMSO, London. GOSLING, P.G. (1991). Beechnut storage: a ANON. (1960). Collection and storage of ash, review and practical interpretation of the maple and sycamore seed. Forestry Com­ scientific literature. Forestry 64 (1), 51-59. mission Leaflet 33. HMSO, London. LEE, S.J. (1990). Potential gains from geneti­ ANON. (1962). Collection and storage of cally improved Sitka spruce. Forestry acorns and beech mast. Forestry Com­ Commission Research Information Note mission Leaflet 28. HMSO, London. 190. Forestry Commission, Edinburgh. FAULKNER, R. (1992). In Seed manual for LINES, R. (1987). Choice of seed origins for forest trees. Forestry Commission Bulletin the main forest species in Britain. Forestry 83. HMSO, London. Commission Bulletin 66. HMSO, London. FORESTRY COMMISSION (1993). List of ROBERTS, E.H. (1973). Predicting the storage native Scots pine seed collection areas. 1st life of seeds. Seed Science and Technology L June 1993. The Forestry Authority, 499-514. Edinburgh. ROOK, D.A. (ed.) (1992). Super Sitka for the GILL, J.G.S. (1983). Comparison of production 90s. Forestry Commission Bulletin 103. costs and genetic benefits of transplants HMSO, London. and rooted cuttings of Sitka spruce. Forestry 56 (1), 61—73.

83 Chapter 6 Production of bare-root seedlings and transplants

W. L. Mason

This chapter covers all operations involved in late autumn or early winter. See Chapter 3, the production of seedlings and transplants, section 3.2.2, and Chapter 4, section 4.2.4. producing 1+1, 2+1, IV2 + IV2 and similar It is normally preferable to apply bulky transplanted stock. It starts with seedbed organics to land to be used for transplanting preparation and sowing density, and finishes rather than for seedbeds. However, if organics with transplant spacing and maintenance. are to be used, any bulky organic matter such The nutrient requirements of seedlings are as hopwaste or peat should be spread evenly given in Chapter 4, while weed control in late autumn or winter by agricultural dung- methods are described in Chapter 12. spreader, or by hand. Uneven distribution Undercutting systems are considered sepa­ leads to uneven growth in the subsequent rately in Chapter 8. season. After spreading, the organic material should be ploughed or rotovated into the top 15 cm of the soil. Any bulky organic matter Seedling production used must be weed and lime-free. See Chapter 4, section 4. The normal sequence of cultivation is to 6.1 Preparation of the ground for plough to 20-30 cm depth using a chisel sowing plough, followed by rough harrowing to break up any clods and rotovation to prepare a fine 6.1.1 Cultivation of the seedbed area tilth. Ploughing normally takes place in the and incorporation of bulky organic autumn with any clods left to weather over­ manures winter. Harrowing and rotovating occur in the spring. Where the seedbed area has carried a pre­ Ploughing at depths of more than 30 cm is vious crop, the ground should be sprayed with undesirable since it may bring subsoil to the a contact or translocated herbicide soon after surface. lifting to remove any weeds. See Chapter 12, If there is any compacted soil horizon or section 12.3. Fallow land should be treated in cultivation pan, this should be broken up with the same way. The ground should be ploughed a winged tine before the ground is ploughed. in late autumn to level the area and give the soil time to weather overwinter. If ground is ploughed too early in the autumn, weed seed 6.1.2 Size of seedbeds will germinate and weeds will grow and Beds are normally 1.1m wide with alleys or spread during mild spells in the winter unless paths between beds 0.5 m wide. This bed controlled by herbicides. width is traditional, being just narrow enough Magnesian or ordinary limestone, ground to permit easy handweeding from either side. mineral phosphate or any other material pre­ However, it is also well suited to the distance scribed to adjust pH or to correct a nutrient between tractor wheelings and the width of deficiency should be spread on fallow land in the wheels. Beds are raised above the alleys

84 which define them and provide drainage to pack down as hard as possible over the channels so minimising erosion of the sown winter and early spring. However, where the area by storm water. Where the annual rain­ soil is loamy, it is essential to fork up the sur­ fall is no more than 1000 mm, raising the face of the newly made beds as roughly as pos­ beds 5-8 cm is sufficient. With an annual sible to allow the soil to dry out and ensure rainfall over 1000 mm beds need to be raised maximum exposure to frost, so that a good to 10-15 cm. tilth is obtained.

6.1.3 Throwing up seedbeds 6.1.4 Partial soil sterilisation The method will depend on the size of the Partial soil sterilisation is a useful tool in nursery. Mechanical equipment is normally seedbed management. Pretreatment of the used for most of the work. However in smaller formed seedbed area with dazomet in the nurseries, some or all the work of preparation autumn before sowing can reduce weed ger­ may have to be done by hand. mination during the following season and can In larger nurseries, and especially where increase seedling growth (Williamson et al., soils are light, beds should be thrown up 1993). Part of the benefit from soil sterilisa­ using two potato-ridger ploughs set at a dis­ tion is due to an increase in available ammo­ tance of 1.6 m apart centre to centre. A nium nitrogen. While partial soil sterilisation wooden board or pair of metal bars should be may control pathogens such as nematodes fixed between the ridgers to level off the bed (and is recorded as having done so), such con­ to an appropriate height. In this way beds are trol of itself is not sufficient to explain the both thrown up and levelled in a single opera­ effects observed. See discussions in Benzian, tion. Suitable ridgers can be made by 1965, pp. 137-163; also, Aldhous, 1972, pp. removing the centre unit of any three-unit 159-161. It is sensible practice for seedbed potato ridger which fits the three-point areas to be sterilised at regular intervals (e.g. linkage of the nursery tractor. The additional 3-4 years) to prevent build-up of pest popula­ bar, or bars, to level off the bed can usually be tions. made locally and various forms are in use in different parts of the country. When using this implement, it is important that sufficient Recommended procedure for seedbed soil is moved from the edges of the bed to the sterilisation with dazomet middle, otherwise the subsequent rolling only In forest nurseries with responsive soils, consolidates the edges of the bed and leaves seedbed sterilisation with dazomet should be the middle loose. It is also possible to use spe­ carried out in autumn (preferably early to late cialist bed forming machinery to prepare the October) before the soil temperature has fallen beds. appreciably below 7°C at a depth of 15 cm. Where beds have to be prepared by hand, Spring application is generally not feasible the beds should be marked out 1.1m wide because the need to wait until the soil temper­ with 0.5 m alleys between beds. Garden lines ature is high enough together with the length are run out to mark the edges of the beds, and of the treatment period would delay sowing soil is thrown from the alleys on to the beds by unacceptably. spade, each bed on either side of the alley Before sterilisation, the area should be receiving a spadeful alternately. ploughed and cultivated to provide a reason­ Beds may be thrown up at any time during able tilth, but seedbeds should not be thrown winter or early spring while the soil is work­ up at this stage. At the time of treatment, the able; the sooner they are prepared, the better. soil must be moist but not wet; moisture is nec­ Where the soil is very sandy and does not essary for the chemical breakdown of dazomet, require frost in order to obtain a tilth, beds but the presence of excess soil moisture leads may be rolled or raked level and should be left to uneven distribution of the sterilant gas as

85 well as making soil working difficult. hand or by fertiliser distributor. It should be The prilled dazomet should be broadcast incorporated in to the topmost 5-10 cm of the over the soil surface at 380 kg ha-1. Uniform bed by light raking or rotovation before the distribution is essential and is best achieved bed is finally consolidated. Fertiliser has using a machine such as the Sisis ‘Truspred’ sometimes been pressed into the surface by (hand-drawn) or ‘Lospred’ (tractor-mounted) roller at the time of final bed preparation, but spreader. The material is incorporated into this is a practice which in dry conditions can the upper 15-20 cm of the soil by thorough reduce germination because of the close prox­ rotovation; the area is then sealed by rolling imity of seed and fertiliser resulting in salt with a heavy smooth-surfaced roller to leave damage to the emerging radicle. There is no the soil surface firm and without cracks. (On consistent benefit to be obtained by leaving small areas, polythene sheeting weighted the application of fertiliser to the last down with soil (Plate 2), or water could be moment; it can be applied any time in the 9 applied after rolling to provide a more com­ weeks before sowing. plete seal, but this is not usually practicable In studies of placed fertiliser in drills in for large-scale use.) relation to band-sown seed, drills of fertilisers Not less than 4 weeks after application of containing potassic superphosphate substan­ the chemical, the soil can be opened up by fur­ tially reduced the seedling yield per kilogram ther rotovation to release any residual gas. of seed, although the seedlings that were Great care should be taken to avoid culti­ obtained were appreciably larger than those vating deeper than the treated zone and so from broadcast-sown beds in which the fer­ bringing up unsterilised soil. Where release tiliser was mixed evenly with the soil. Fewer cultivation is carried out before the onset of losses occurred with placed phosphate than winter, seedbeds can then be thrown up with potassium sulphate. roughly to weather over winter. However, there is no reason why the treated area should not be left undisturbed until early spring if 6.1.6 Consolidation and tilth this accords with local practice, provided that Correct control and timing of cultivation oper­ release cultivation is carried out at least 2 ations to achieve well consolidated seedbeds is weeks before seed sowing. an essential prerequisite for seedbed manage­ Before final seedbed preparation, a ‘cress ment. Inadequate consolidation or creation of test’ should be used to check the soil for a cultivation pan can each seriously reduce freedom from residual gas. The test procedure seedling growth and development. is detailed in a leaflet provided by the sup­ Beds must be well consolidated before pliers of dazomet, and compares cress germi­ sowing so that soil moisture can reach the sur­ nation in sealed jars containing soil samples face layers by capillary action and prevent from the treated area and from adjacent germinating seed from drying out in warm dry untreated land. weather. This is especially important for conif­ erous and small seeded hardwood species. One 6.1.5 Incorporation of inorganic effective and simple test is to press the surface fertilisers of the bed firmly with the flattest part of a For a full discussion of the quantities of fer­ clenched fist. Consolidation is adequate when tilisers to apply see Chapter 4, section 4.2. no more than a moderate indentation (i.e. Inorganic fertiliser is generally applied in 1 cm deep) can be made. It is important that granular form, the rate depending on the consolidation is uniform throughout the upper nutrient content of the particular brand 15 cm of a bed and that there is no compaction selected and the requirements of the crop and or ‘plough pan’ which will impede water move­ the levels of nutrient reserves in the soil. ment. The creation of a pan is a particular Granular fertiliser can be spread either by risk if the soil is worked when too wet since all

86 the benefit of the previous winter’s weathering 6.2 Preparation of seed for can be lost by compression and aggregation of sowing soil crumbs. Seed should be ordered for delivery well in Beds which will be consolidated soon after advance of sowing so that the necessary pre­ they have been thrown up should have a roller treatments can be given. This is particularly weighing 100-250 kg drawn one or more times important with deeply dormant species where over the bed according to the soil type, after up to 26-30 weeks of stratification may be which no further raking should be necessary. required. Seed certificates should be checked Suitable rollers may be adapted from agricul­ carefully to ensure that a given seed lot is not tural rollers; these should be wide enough to damaged by pretreatment (e.g. pine seed lots cover a single seedbed and be arranged to fit where germination is reduced by moist the three-point linkage of the tractor. A spe­ prechilling). cially manufactured hollow roller, the weight of which can be varied between 120 and 350 kg by adjusting the amount of water 6.2.1 Storage awaiting sowing inside, is also available. Short-term storage methods are described in Chapter 5, section 5.5.3. Long-term seed On very sandy soils, beds thrown up early storage regimes are fully described in Forestry and consolidated naturally should be dis­ Commission Bulletins 59 and 83 (Gordon and turbed as little as possible before sowing. The Rowe, 1982; Gordon, 1992). natural consolidation following exposure to winter and early spring rain can scarcely be equalled by rolling beds which have been loos­ 6.2.2 Seed pretreatment ened or which were newly thrown up shortly Recommendations for pretreatment are given before sowing. Particular care must be taken in Table 5.6, p.81, and Chapter 5, section 5.7. when incorporating inorganic fertilisers not to Careful handling of seed is essential if cultivate too deeply and lose the benefit of optimum germination is to be obtained and natural consolidation. thought must be given to the management of the cold store or refrigerator to ensure space is On loamy soils, a fine tilth has to be created available for seed to be pretreated. Seed in the top 5-8 cm of soil immediately before should be inspected regularly to check for the consolidating. This can be achieved by presence of fungal pathogens, that moisture working the soil with a small rotary culti­ content is correct and that premature chitting vator, or with a rotovator or spading machine is not occurring. It is also important to mon­ attached behind a tractor. Rotary cultivators, itor the temperature of the pretreatment envi­ or rotovators if used when the soil is too wet ronment regularly to check that refrigerators can create a plough pan through the are maintaining the required temperature. ‘smearing1 action and downward pressures of the blades of these machines. This is less of a risk with spading machines. On loamy soils, 6.2.3 Seed dressings the interval between preparation of a fine In agriculture and horticulture, it is common tilth, consolidation of the soil and sowing must practice to dress seeds with a fungicide, insec­ be kept to a minimum. If heavy rain inter­ ticide or repellent. In forest nurseries, the venes after cultivation but before consolida­ most serious and widespread losses of seed in tion, the soil often loses its structure, becomes the past were often due to depredations by saturated with water and handles like por­ birds, and to a lesser extent, mice. Formerly, ridge, and if dry weather follows, may set seeds were regularly dressed with red lead, hard. In these circumstances, the soil should believing that this gave some protection be roughly forked up while moist and left to against small birds, etc. However, in very dry out again. many nurseries, this was found not to be the

87 case and physical protection by netting 6.3.2 Factors affecting sowing density became the principal protection against birds. Recommendations for the density of sowing of One advantage of red leaded seed was that the commonly used conifer and broadleaf it showed up clearly against the soil and gave species are given in Tables 6.1 and 6.2. The the sower an indication of how evenly he was density at which seed should be sown depends sowing. However, lead compounds are not con­ on many controllable factors such as the vari­ sidered environmentally desirable as seed ation in species and seed quality, the known dressings and the use of red lead is no longer productivity of the nursery, local techniques recommended. (e.g. drill or broadcast sowing), and preference Currently, the large majority of nurseries for either 1-year or 2-year seedling stock. sow mechanically and find that a seed In contrast, seasonal factors such as distrib­ colourant is not essential. Also, much of the ution of summer rainfall and critical spells of seed is pretreated and often just chitting; in drought cannot be predicted, yet they also this condition it is much more susceptible may have a profound effect on nursery yields. than dry seed to mechanical damage during Because of these uncontrollable factors, it is the additional handling and is best sown not possible to make precise forecasts of without a seed dressing. seedling yields from given densities of sowing. An estimate of the average total yield of seedlings is given in columns 8 and 9 of Table 6.3 Sowing 6.1 and column 8 of Table 6.2. It must be realised however, that figures are averages 6.3.1 Date of sowing and that variations of ±25% are commonplace. The correct timing of sowing is a most impor­ tant part of seedling production. For instance Germination I survival factor and field if seed is sown too early in a cold spring, ger­ survival factor mination can be slow and, although the It will be apparent from Tables 6.1 and 6.2 that seedlings may grow to a good size by the end more germinable seeds are recommended to be of the season, the yield will be low and the sown per square metre (columns 6 and 7) than crop variable. If sown too late in a dry spring, are expected as seedlings at the end of the germination may be lower than expected. The season. The ‘Germination Survival Factor’ normal date of sowing in Britain is between (column 12) is the number of live seedlings at early March in southern England and mid the end of the season, expressed as a percentage May in northern Scotland. Actual dates will of the number of germinable seeds sown. The depend upon the season, seed pretreatment, difference is accounted for by the seeds which do the target crop (i.e. 1 or 2 year seedlings) and not germinate, are eaten by birds, killed by local nursery factors such as the availability of fungi, etc. If nursery managers find that consis­ irrigation and the risk of spring frosts. tently they obtain better or poorer yields of The temptation to leave sowing until lifting seedlings at the end of the season than are given has been completed must be resisted, unless it in the tables, they should make an appropriate is the policy to produce 2-year-old seedlings, adjustment to the sowing density in subsequent and a regular high germination of late-sown years. The ‘Field Survival Factor’ mentioned in seed can be guaranteed. Lining out and section 5.6.8 is the ‘Germination Survival planting programmes will scarcely be affected Factor’ reduced by whatever allowance is appro­ by the delay while seedbeds are sown, but if priate in the nursery for culls. In Table 5.4 15% sowing is late, it will often make the difference of live seedlings have been allowed as culls. between seedlings that can be lifted after 1 Nursery managers should always critically year and those that have to be grown on for 2 examine the reasons for a particular ‘Field years. Survival Factor1 to see whether it can be

88 improved, either by reducing the proportion of slight overcrowding is inevitable if seedbeds unusable seedlings produced, or by increasing are not to be understocked in all except the the overall consistency of germination. most favourable seasons. There is no evidence that the yield of usable plants is reduced in Changes in recommended sowing densities good seasons because of high seedling density The densities listed in Tables 6.1 and 6.2 are following sowing at the densities recom­ designed to give fully stocked seedbeds in mended; the percentages of culls may be some­ average seasons in productive nurseries and what higher, but the total number of usable should be used if individual calculations for plants from a given number of germinable each seed lot are not to be made. The conifer seeds is usually above average in a good densities represent a substantial reduction on season in spite of apparently crowded beds. the densities prescribed in the previous edi­ The figures for numbers of pure seeds, ger­ tion of this Bulletin (Aldhous, 1972; Table 23). mination and/or viability percentage are This reduction reflects the major impact that derived from laboratory tests. They represent bird netting and the use of pre-emergence her­ an adjustment to the tables in the previous edi­ bicides to eliminate weed competition have tion of this Bulletin to allow for more recent had in raising seedling yields. They also information (e.g. Gordon and Rowe, 1982). reflect increasing recognition that allowing The broadleaved species given in Table 6.2 wider spacing between seedlings produces include only those commonly grown in forest sturdier and better quality planting stock. In nurseries. Recommendations for minor broad­ seasons when germination and growth are leaved species can be obtained by referring to good, even these spacings may be too close due Gordon and Rowe (1982, Appendix 6a) or to seedlings being taller than average or too extrapolating from the most appropriate densely stocked, or both. However, periodic species listed in Table 6.2.

Table 6.1 Seed quality, sowing density and expected yields: major conifers

Common name Seed qualities Sowing density Expected yield in productive nurseries for standard seed; Average Germination Number of num ber o f Total number Average height Germination number of pure percentage germinable germ inable seeds seedlings per of usable survival seeds per kg seeds per kg per rrf (1000s) rrf at end of seedlings at end factor (%) (1000s) season (1000s) of season (cm) Standard Low n o 2+0 1+0 2+0 1+0 2+0 (!) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

Scots pine 165 85 50 140 0.9 0.8 0.6 0.5 5-10 8-15 60-70 Corsican pine 70 80 50 55 0.6 0.5 0.4 0.3 4-8 8-15 60-70 Lodgepole pine 300 90 50 270 0.9 0.8 0.6 0.5 5-10 8-15 60-70 European larch 170 35 15 60 0.8 (0.7) 0.5 (0.4) 10-20 (12-25) 50-60 Japanese larch 250 60 30 100 0.7 (0.6) 0.5 (0.4) 10-20 (12-25) 60-70 Hybrid larch 210 25 10 50 0.8 (0.7) 0.5 (0.4) 10-20 (12-25) 50-60 Douglas fir 88 80 50 70 0.8 0.7 0.5 0.4 7-15 10-20 50-60 Norway spruce 145 80 50 110 1.0 0.8 0.7 0.5 4-8 10-15 60-70 Sitka spruce 400 80 50 320 1.0 0.8 0.6 0.4 4-8 10-15 50-60 Grand fir 45 40 15 20 1.0 0.8 0.5 0.4 4-8 7-15 40-60 Noble fir 40 30 15 12 1.0 0.8 0.5 0.4 4-8 7-15 40-60 Western hemlock 650 65 30 420 1.2 1.0 0.7 0.6 4-8 7-15 50-60 Western red cedar 850 60 30 500 1.2 1.0 0.7 0.6 4-8 7-15 50-60 Lawson cypress 460 50 30 230 1.2 1.0 0.7 0.6 4-8 7-15 50-60

Notes: 1. Figures in brackets refer to species which are rarely sown for 2+0 production. 2. Germination survival factor gives an estimate of average survival factors. 3. Note that columns 8 and 9 are total numbers including unusable seedlings.

89 Table6.2 Seed quality and seedling production: broadleaves

Common name Average Number of Average Average Average number Average Average Average Number of germinable/ yield of seedling of seeds purity germination viability germinable or viable seeds seedlings height at per kg (%) (%) (%) viable (v) seeds sown per per kg 1+0 (cm) per kg rrf (1) (2) (3) (4) (5) (6) (7) (8 )t (9)

Common alder 770 000 85 40 — 250 000 2000 66 000 5-20 Italian alder 410000 85 30 - 108000 2000 60 000 5-20 Grey alder 1 500 000 80 25 - 300 000 2000 60 000 5-20 Red alder 1 400 000 75 55 - 575 000 2000 60 000 5-20 Ash 13 000 90 60 65 7 800 (v) 600 2 500 10-25 Beech 4 500 97 60 70 3 000 (v) 500 1 300 10-20 Silver birch 1 900 000 30 25 - 150 000 2000 100 000 5-20 Downy birch 3 500 000 30 30 - 320 000 2000 105 000 5-20 Bird cherry 20 000 99 - 75 14 700 (v) 800 1 000 10-25 Wild cherry 5 000 99 75 80 4 000 (v) 800 1 000 10-25 Horse chestnut 100 100 80 85 90 (v) 120 45 15-25 Sweet chestnut 240 100 80 65 175 100 110 10-30 Wych elm 90 000 95 45 - 37 000 600 20 000 10-20 Hawthorn* 11 000 95 - 70 7 900 (v) 2000 1 300 10-20 Hazel 800 100 70 60 480 500 200 10-15 Holly 35 000 99 80 75 22 000 1200 9 000 5-15 Hornbeam 25 000 96 45 65 14 500 600 3 000 5-10 Large-leaved lime 8 500 97 70 75 6 500 1000 550 10-20 Smalled-leaved lime 30 000 95 70 80 22 000 1000 2 000 10-20 Field maple 13 500 92 55 70 8 900 (v) 500 3 300 5-20 Norway maple 6 500 85 40 70 3 900 (v) 350 2 000 15-30 Sycamore 9 000 90 40 60 5 000 (v) 250 2 200 15—40 Pedunculate oak 250 99 80 80 220 (v) 250 180 10-20 Red oak 300 99 80 85 240 (v) 250 160 10-25 Sessile oak 300 100 80 85 270 (v) 250 180 10-20 Rowan 290 000 96 70 85 245 000 (v) 2000 8 000 10-25 Whitebeam 55 000 89 - 65 31 000 (v) 2000 2 200 10-25 Nothofagus obliqua 115000 90 25 - 25 500 700 5 200 10-25

Nothofagus procera § 90 000 89 25 - 20 500 700 6 000 10-25 Common walnut 100 100 80 85 85 40 55 10-25

Notes: * Hawthorn figures are for Crataegus monogyna and should be adapted for other species, t Column 8 includes usable and non-usable seedlings. § Now re-named Nothofagus nervosa. 6.3.3 Calculation of seedbed sowing Adjustments to the normal broadcast area sowing area are given below; drill sowing for For seed for which there are germination test undercutting is covered in Chapter 8, section data, the normal broadcast sowing area per kg 8.2.2. of seed may be calculated by dividing the 1. Low quality seed: should the germination number of germinable or viable seeds per kilo­ percentage fall below the value given in gram from the test results by the number of column 4 of the table, the calculated area germinable or viable seeds per square metre per kg should be reduced by 20%; in Tables 6.1 or 6.2. This gives the figures for sowing area in m2. If estimates of both ger­ 2. Local experience: experience in a particular minable and viable seeds are available, the nursery may indicate that growth, or ger­ former should always be used since this pro­ mination and survival of a particular vides a better indication of seedling yield. species, is consistently higher or lower

90 than normal. This may be allowed for as minable or viable seeds per kilogram and is not follows: used directly in the sowing density calculations. (a) if seedlings of any particular species at 1 year or 2 years are regularly 20-35% 6.3.4 Broadcast sowing taller than average (for conifers, see The aim of broadcast sowing is to distribute columns 10 and 11, Table 6.1), increase the seed as evenly as possible over the sown area sowing area per kg by 33%. If regularly so that each seedling has as similar a space as 35-50% taller, increase the sowing area per possible in which to grow. All broadcast kg by 66%; conifer and hardwood seed are sown on to (b) where the germination/survival factor of raised seedbeds. During the season, the edges conifer sowings regularly departs by 20% or of beds usually crumble away and any more from the value given in column 12, seedlings growing there may be lost; hence it the sowing area should be increased or is advisable to leave 8 cm unsown on each decreased in proportion. edge of the bed. The sowing techniques described below can Example 1 be used for most conifer and many smaller hardwood seeds. There are exceptions; strati­ To determine the sowing area for 1 kg of Sitka spruce seed with 70% germination and fied seed is damp and bulky and so is not easily sown by machine, and may have to be 300 000 germinable seeds per kilogram, to be sown by hand* The large seeded hardwoods sown broadcast to produce 1-year seedlings: which are covered with soil cannot be sown by First step, calculate sowing area at normal the machines designed for conifer seed and broadcast sowing density: the techniques for such seed are described at Sowing area = Number of germinable seeds per kg the end of this section. Recommended number of germinable seeds per m2 Broadcast sowing by hand

= 300000* Where seed is sown by hand, it may be sprin­ 1000t kled or cast over the bed, so that it does not fall beyond the edges of the bed, or it may be = 300 m2 per kg cast or thrown diagonally across the bed so * Figure available with seed, that some of the seeds rebound from a wooden t Column 6: Table 6.1 ‘bouncing’ board between 20 and 60 cm high by about 1 m long. The board is held vertically Example 2 with one edge on the margin of the sowing To determine the sowing area for 0.5 kg of area and is moved along as sowing proceeds. rowan seed with 85% viability and 240 000 Best results come from casting seed but small­ viable seeds per kilogram, to be sown broad­ winged seed like that of Lawson cypress or cast to produce 1-year seedlings: birch can only be sprinkled. Sowing area = Number of viable seeds per kg Whether or not a board is used, best results Recommended number of germinable seeds are obtained if the seed for a bed is divided per m2 into two equal parts and one part sown

= 240 000 working from one side and the other from the 2 000 other side of the seedbed. Uniform sowing by hand can only be achieved by practice and = 120 m2 per kg novices must expect some unevenly distrib­ i.e. 60m2 for 0.5 kg uted seed.

In both examples, note that germination or via­ Broadcast sowing by machine bility percent is used in the calculation of ger­ The machines most commonly used for seed

91 sowing were originally designed to spread fer­ in bands between 2 and 5 cm wide and tiliser and sow lawn seed. They are tractor 15-20 cm apart. Bands can be prepared using drawn and essentially consist of a hopper on a pair of plough shares set very shallow to wheels (Plate 4). At the base of the hopper is a open a trench on the first pass and spread a moving belt which carries seed out at a rate shallow covering of soil in the next. There are regulated by a metal slide or grate. Seed is specialist machines available for this task. brushed off the belt to ensure uniform distrib­ ution. Do not use the same machine for both 6.3.6 Rolling after sowing seed sowing and applying fertilisers since fer­ If the seed bounces up while being covered tiliser corrosion to the metal slide can cause with grit after sowing, it should be pressed the rate of seed sowing density to be wrong. into the surface of the soil either by a light Prechilled seed should be air dried just roller, approximately 20 cm in diameter (Plate enough to flow without sticking; if the seed is 5) or by a light board 10 cm wide fitted to a too moist, then the seed will be clumped on broom handle. This is probably more neces­ the bed. sary where grit cover is spread by hand than where a machine is used, the reason being 6.3.5 Larger broadleaved seed that when covering by hand the grit has fur­ Whereas almost all other forest tree species ther to fall and hits the ground with greater are best sown on the soil surface and covered momentum. with sand or grit, the seed of the larger seeded broadleaves such as oak, beech and sweet 6.3.7 Grit covering chestnut are best sown and covered with a Seed covered with coarse sand or fine grit ger­ 2.5^4 cm thick layer of soil. minates more quickly and gives higher yields When broadcast sowing by hand, seed can than if nursery soil is used. If the nursery is be spread over the surface of the bed before sheltered, coarse sand is quite suitable but in the alleys are dug and the soil from the alleys many nurseries, sand may be blown off by can then be spread evenly over the seed. The wind and a fine grit passing a 3-5 mm sieve is alleys so formed may be 10 cm below the preferable. Table 6.3 gives examples of the seedbed surface. If there is more soil than is particle size distribution of several grits that required to cover the seed, the surplus may be have been successfully used in Britain. taken evenly away from the sowing area using In some localities, 6 mm grit is readily rakes or ‘cuffing boards’, i.e. flat boards available but this grade of grit should only be roughly 10 x 50 cm on the end of long handles. used if nothing finer can be obtained. Where Large broadleaved seeds may also be sown there is a choice between crushed flint and a

Table 6.3Particle sizes of grits that have proved successful in forest nurseries (percentage of particles in each size category)

Name Particle size (mm) <0.425 0.425- 1.00- 2.00- 2.80- >4.75 1.00 2.00 2.80 4.75

1. Leighton 1.5 5.9 30.0 51.9 9.2 1.5 Buzzard 2. Quartzag 3.4 0.7 0.6 9.5 64.7 21.1 3. Edzell 3.0 10.0 19.0 28.0 22.0 10.0 4. Aukley 19.9 15.0 12.3 26.2 17.5 9.1

Notes: 1. All grits are light coloured and have no free lime. 2. The first grit (a washed river gravel) is probably the best in terms of uniformity. The others tend either to have too much fine material (e.g. sample 4) or too much large material (samples 2, 3).

92 rounded material of approximately the same from view. On average, one tonne of grit size, the latter is preferable, especially in should be expected to cover about 80 m2 of weedy nurseries, as workers’ fingers may be conifer seedbed. cut by sharp edges on the crushed flints. Grit is normally applied using a grit box It is essential that the grit is free from silt which fits on the three-point linkage of a and from lime. It is also preferable to use a tractor (Plate 6). The grit runs out through an light-coloured grit rather than a dark one. If adjustable slit at the bottom of the box. The the grit is silty, it will cake and may reduce depth of grit is controlled by the combination the germination of seedlings; if it contains of speed of the machine travelling over the lime, it will ultimately ruin the nursery by ground and the width of the adjustable slit. making the soil pH neutral or even alkaline This normally spreads a layer of grit over the when it should be acid (section 3.2.3). If in whole width of a bed. However, where seed is doubt, add vinegar or dilute hydrochloric acid sown in drills, baffles or stops can easily be to a sample of the grit; if it fizzes, it contains made and fitted by the nursery manager so too much lime to be used with safety. that only sown drills are covered and the The colour of the grit affects the tempera­ remaining inter-row space left uncovered; the ture at the seedbed surface; black or dark-grey cost of grit is quite substantial and the saving grit can be several degrees warmer at the soil by this simple modification is well worth surface on a hot day than a very light coloured having. grit. This could make the difference between When covering by hand, the grit should be little injury and severe heat injury to conifers shovelled on to 6 mm mesh riddles or sieves at the root collar. Table 6.4 illustrates the held chest high and shaken so as to distribute effects of particle size and colour on the yields the grit evenly over the nearer half of the bed, of seedlings in a hot summer. In the experi­ the other half being covered from the other ment from which these results are taken, alley. maximum temperatures, recorded just under the grit, were 49°C and 55°C for the white and 6.3.8 Protection against birds and mice dark grey grits respectively. Seed-eating birds (e.g. finches, pigeons) can The quantity of grit required depends on the cause serious damage to germinating size of the grit and the size of the seed. As a seedlings (Tee and Petty, 1973). Failure to rough guide, the depth of covering required guard against this type of damage is a major should slightly exceed the length of the seed on reason for low stocking in seedbeds and it is a its longest axis. This should be sufficient to false economy not to protect seedbeds. The cover the seed so that it disappears completely most effective measure is to cover beds with a

Table 6.4Effect of the colour and size of grit used as a seedbed covering on the yield of Sitka spruce seedlings per m2: Kennington Nursery, Oxford 1955

Colour o f grit Grade of grit Fine Medium Coarse Number Height Number Height Number Height (ITT2) (cm) ( r r r 2) (cm) ( rm 2) (cm)

White 763 4.6 821 4.6 293 3.1 Light grey 307 1.5 425 3.1 377 3.1 Dark grey 305 1.5 274 1.5 274 2.5

The white grit was a quartz from St Austell, Cornwall, the light grey material was a granitic sand from Penmaenmawr, Gwynedd, and the dark grey material a basalt from Clee Hill, Shropshire. The particles in the fine material ranged from 0.2 to 2 mm diameter, the medium from 2 to 6 mm while the coarse particles were more than 6 mm in diameter.

93 2cm (3A inch) plastic mesh (‘bird netting1) deficit), lower nutrient leaching and more which is supported on wire hoops made of No favourable soil moisture conditions when com­ 8 or 10 gauge galvanised wire (see Plate 8). pared with uncloched control beds. For Bird netting should be laid over the beds instance, a 12°C increase in daily maximum within 1-2 days of sowing. Care should be air temperature was recorded under clear taken to peg down the netting at the side of polythene cloches during May-August com­ the seedbed. The netting can be removed once pared with controls (Biggin, 1983). Minimum the first true leaves of the seedlings are well temperatures were also increased, but only by developed and the seed caps have been dis­ about 1°C. The effect of these higher tempera­ lodged. Bird-netting is not necessary if tures is to speed germination and growth. seedbeds are covered with cloches or floating Thus, 50-100% increases in germination per­ mulches (see below), except for large seeded centage and height over controls were broadleaves where crows can pierce the mulch reported by Biggin (1983) when lodgepole sheet to get at the seeds. pine, Corsican pine, Douglas fir, Japanese Mice can also be a serious pest of seedbeds, larch and Sitka spruce were grown under particularly with large seeded species such as clear polythene cloches for 16 weeks after oaks, chestnut and Macedonian pine. The sowing. problem can be particularly bad on seedbeds A wide range of types of polythene and of adjoining hedges, woodland or disused ground. fabric materials have been tested to examine Bird netting will not serve as adequate protec­ their effect upon seedling growth. However, tion and baited spring-traps must be laid at those in general use are clear polythene, intervals along the beds. The traps should be ‘white’ polythene and woven polyester fabrics inspected daily and rebaited as required. Mice (e.g. Agryl P17 or Vlies). The fabrics differ are rarely a problem once seedlings have from polythene sheet in being porous to air passed the first true leaf stage. and water; consequently the magnitude of the temperature increase is less. The same is true 6.3.9 Cloches and floating mulches of various types of ‘breathable’ polythene The main objective of seedbed management is sheeting which have holes or slits at intervals to obtain rapid and uniform germination. in the sheet. The porous fabrics and perfo­ Delayed or inadequate germination can result rated polythene sheets are best used as in patchy stocking and variable seedling size, floating mulches whereas the standard neither of which can easily be corrected. (unperforated) polythene sheets are to be pre­ Frequently the germination rate is restricted ferred as cloche covers. White polythene by cold temperatures, particularly on heavier should be used if the crop species is thought to soils and/or in more northerly nurseries. One be sensitive to high temperatures (see below) way of compensating for this is to use poly­ since the temperature increase is generally thene or woven fabrics to improve the seedbed rather less under this type of cover (Biggin, microclimate. When such materials are laid 1983). flat on the surface of the bed, they are called ‘floating mulches’ (Plate 9). If they are raised Cloches off the bed and supported on wire hoops in the Cloches are normally supported by wire hoops same way as for bird-netting they are termed or similar supports in the same way as bird ‘cloches’. These are somewhat akin to ‘low tun­ netting. In profile, the cloche describes a flat­ nels’ used in horticulture (Plate 7). tened semi-circle above the bed, standing Transparent polythene cloches and translu­ some 30 cm above the centre of the seedbed. A cent mulches provide a favourable microcli­ heavy duty polythene is best used, since mate for germination and growth as a result lighter gauge material may be damaged by the of higher soil and air temperatures, higher rel­ wind. The cloches should be put on as soon as ative humidity (i.e. lower vapour pressure possible after the completion of sowing, grit­

94 ting and herbicide application. Normal pre­ over the seedbed after the completion of sowing fertilisers are used. Cloches should be sowing, gritting and herbicide application. used with sterilised seedbeds so that weed Sheets of material can be laid over one or competition is minimised. If the weather has more beds as convenient and are dug into the been dry, then the bed should be well irrigated alleys. It is not so critical to ensure the bed is before the cloche is put on. The sides of the moist before covering with a mulch because cloche should be dug into the alley and well the materials used are porous to water and secured so that an airtight seal is achieved irrigation can be applied if dry conditions and to prevent the cloches lifting in the wind. occur. Mulches are normally removed once the An extra 25 cm of alley between seedbeds germinating seedlings have started to lift the must be allowed to ensure that the polythene cover off the surface of the bed. It is important can be dug in. Once the polythene has been not to delay removal since the growing tips dug in, the cloche should be left undisturbed can be damaged if they penetrate the fabric of for around 8-16 weeks depending upon the the covering sheet. Materials with circular or crop and management objectives. The shorter slitted perforations are not recommended as period will only promote germination, whereas floating mulches on conifer seedbeds since the longer will also increase growth. The only leading shoots of the crop will frequently problems that are likely to occur are from emerge through the perforations and make it weed regrowth and the cloche drying out. If impossible to remove the cover without large weeds develop, then the polythene damage to the seedlings. should be lifted, the weeds removed by hand The provision of a favourable germination and the polythene replaced. The soil moisture environment under cloches or floating status can be easily checked by looking at the mulches can result in extremely high seedling polythene on warm days. Under such condi­ yields. Experience over more than 5 years in tions there should be a film of condensation all Forestry Commission northern research nurs­ over the inner surface of the polythene as a eries suggests that, using cloches on pine result of water vapour condensing on the seedbeds, yields of 90-100% of the germinable cooler polythene. If this film is not present, seed are attainable. The good germination and then humidity within the cloche is too low and rapid early growth mean that sowing densities young seedlings could be damaged. The solu­ should be reduced over normal recommenda­ tion is temporarily to remove the cloche (but tions to prevent seedlings becoming too not in very warm conditions), irrigate and spindly. Recommendations are given in Table then replace the polythene. 6.5, based upon experience with conifers. Seedlings grown under cloches have to be There is limited experience with broadleaves; carefiilly hardened-off to prevent physiological both oak and birch have shown good response, stress from windy or warm conditions after but beech has proved sensitive to high temper­ cloche removal. Removal should ideally take atures. A floating film may give useful protec­ place in cool weather or in the evening. tion against frost where autumn sown seed Irrigation may be necessary to prevent wilting. has germinated and there is no other shelter. Cloches should never be kept on after the begin­ Cloches or floating mulches should be seri­ ning of August because of the risk of seedlings ously considered by any nursery manager who being damaged by an early autumn frost. seeks to improve seedling yields and produce If seedlings appear to be suffering from more uniform crops. The use of cloches is par­ fungal attack, the cloches should be removed ticularly appropriate in northern nurseries for the season and appropriate fungicides where the increase in seedling growth can applied. ensure that crops are of transplantable size in one year. Floating mulches could be used on Floating mulches many nursery sites in Britain where the more •As noted earlier, floating mulches are laid flat modest temperature increase that is produced

95 Table6.5 Sowing density for conifer species under cloche cover

Species Sowing Remarks (germinable seed per rrf)

Scots pine 400 Clear polythene cover Lodgepole pine 400 Clear polythene cover Corsican pine 450 Clear polythene cover Macedonian pine 500 Sitka spruce 600 White polythene cover (germinating seedlings can be 600 Norway spruce damaged by warm conditions) Douglas fir 600 Larch spp. 600

(Other species: a general rule of thumb is to use between 25 and 50% of normal densities) NB: Densities for floating mulches should be slightly higher than those used for cloches. can provide rapid, uniform germination. This frost and of irrigation against frost are may be of particular importance with tech­ described in Chapter 13, section 13.1 and niques such as drill sowing. However, the Chapter 11 section 11.4.3 respectively. interested manager will need to spend ade­ quate time determining the technique that is 6.4.3 Top dressings most appropriate for a particular crop and Nitrogen top dressings will normally be nursery. required to promote seedling growth. In many nurseries, top dressings of potassium fer­ 6.4 Subsequent care tilisers are also likely to be beneficial. The quantities to apply are set out in Chapter 4, After beds have been sown and covered, Table 4.5 and section 4.2.5, while the timing of weeds, insect, animal or fungal pests must all top dressings is prescribed in Chapter 4, sec­ be controlled, and shelter or watering pro­ tion 4.2.6. The danger of scorching seedlings vided as necessary, together with appropriate by applying inappropriate fertilisers such as fertiliser top-dressings. potassium chloride and urea must be remem­ bered. 6.4.1 Weed and pest control The control of weeds and of pests is of para­ Irrigation mount importance both for the best growth of Adequate irrigation is an essential part of the crop sown and for subsequent crops. modern nursery management; planned sched­ Growing crops should be inspected frequently ules of fertiliser application and undercutting to check for any signs of damage. Details of regimes can only be relied on to produce the techniques for control of pests are given in designed size and type of crop if irrigation is Chapter 13 and of weeds are given in Chapter available to make up for deficiencies in the 12 (see also Williamson et al., 1993). pattern or amount of summer rainfall. Detailed consideration of irrigation is given in 6.4.2 Protection against sun and frost Chapter 11. In normal years, damage from sun is a rare occurrence in British nurseries. Untimely 6.4.4 Special methods of seedling frosts can be a more serious source of damage. production Building up a good knowledge of the local Production of containerised seedlings is cov­ microclimate is the key to avoiding damage ered in Chapter 9. For other techniques (e.g. from frost. The use of shelters against sun and Dunemann beds), the reader should consult

96 the previous edition of this Bulletin (Aldhous, ploughed or rotovated in a few weeks before 1972). lining out. Organic matter can be spread and ploughed in the autumn, but the longer the interval between spreading and transplanting, Transplant production the more nutrients in the organic matter will be lost by breakdown and leaching before transplanting. 6.5 Transplanting The objectives of transplanting or ‘lining out’ 6.5.4 Ploughing in crop residues are to provide greater space for young plants to If the ground has been under seedbeds or develop, and to encourage the formation of a lines, it will normally need to be ploughed to more fibrous and compact root system, together level out paths between seedbeds or strips of with a higher ratio of root to shoot than would transplants and to bury any remaining plants. develop if seedlings were allowed to grow This operation can be combined with either of undisturbed in seedbeds. It also gives an oppor­ the two preceding operations if convenient. tunity for grading and culling seedlings to pro­ duce more uniform transplants. 6.5.5 Lining out following late green­ crop 6.5.1 Preparation of ground Where a greencrop of rye grass has been sown Ground for lining out must be free-working late in the summer and is no more than and not hard or compacted. In many nurs­ 10-12 cm tall, this may be ploughed in as eries, it is preferable to cultivate only as much lining out progresses; it should otherwise be ground each day as is required for that day’s ploughed in or cultivated 2-3 weeks before­ lining-out. On very sandy soils, there is little hand; this may be necessary where the crop harm in cultivating more than a day’s ground has grown more than expected (e.g. because of at a time but on heavier soils, heavy rain can mild winter weather) and is too bulky to be destroy the tilth of unplanted ground. ploughed in as part of the lining out process. The sequence of operations preceding lining out depends on the type of previous crop, 6.5.6 Incorporation of inorganic when it was lifted, the soil condition and pre­ fertilisers dicted weather. In most circumstances, inorganic fertilisers should be spread not more than 3 weeks 6.5.2 Late autumn ploughing before lining out. They do not need to be If the ground has been fallow, or has carried a ploughed in and can be worked in as lining out greencrop or for any reason has been cleared progresses, or they can be rotovated in shortly in the autumn, it should be ploughed in beforehand. Inorganic fertilisers supplying the October or November and left rough. Any crop’s nutrients for the season should not be annual weeds will be buried and the ground applied as early as the autumn if plants are to will be in a state to benefit from weathering be lined out in the spring following. However, by frost and rain during the winter. Any any lime or remedial additional fertilisers may dressing of ground mineral phosphate or mag­ be applied at that time. nesian limestone, etc., prescribed to correct On very sandy soils, Norway spruce and nutrient deficiencies should be applied before grand, noble and European silver fir trans­ this ploughing. plants lined out in late spring may be dam­ aged by normal rates of inorganic fertilisers, if 6.5.3 Ploughing in bulky organic matter prolonged dry conditions follow shortly after If hopwaste or other bulky organic manure is lining out. This risk is minimised by to be applied, this should be spread and spreading the inorganic fertiliser no later than

97 mid-March, even though the plants in ques­ Table 6.6 Recommended growing area for trans­ tion may not be lined out for several weeks; plants alternatively the regime outlined in section Average height Recommended 4.2.6 may be adopted. expected at lifting growing area (cm) (cm2)

6.6 Plants for transplanting <20 75-100 20-40 100-125 40-60 100-150 6.6.1 Spacing >60 125-200

Plants which are overcrowded in the lines or The growing area available to plants should be determined in the seedbeds become drawn and spindly by the size they are expected to reach at the time of lifting. and do not survive forest planting as well as sturdy plants; adequate nursery spacing is Table 6.7 Number of transplants per unit area essential. See Tables 6.6. and 6.7. (excluding area of alleys) at different spacings There are two factors in plant spacing, the No. of plants per 100 m2 area and the shape of the growing space. Spacing Spacing between rows (cm) What little critical work has been done on of plants 15 17.5 20 22.5 transplants in forest nurseries shows, as one in row (cm) would expect, that a greater growing area increases the size of the plants produced, par­ 3.75 17800 15 240 13 330 11 850 5.0 13 330 11 430 10 000 8 890 ticularly the root collar diameter. In a series of 7.5 8 890 7 620 6 670 5 930 experiments, doubling the growing space from 10.0 6 670 5710 5 000 4440 75 to 150 cm2 per plant increased the stem diameter of plants by an average of 20-30% but height by only 5-10%. The shape of the 6.6.2 Lifting for transplanting growing space had little effect on plant size; nevertheless plants tended to be sturdier Seedlings when planted with a square rather than a rec­ Seedlings are usually lifted by hand from the tangular spacing (i.e. more space between seedbeds and transplanted either at the end of plants with rows closer together compared their first, or during or at the end of the with the same area per plant, but plants second growing season. Seedlings less than closer in the row and the rows further apart). 4 cm tall are too small to be handled easily In practice, mechanisation of transplanting and quickly, and are usually discarded. If and subsequent operations are so greatly facil­ more than 40% of all seedlings in a bed are itated by a standard spacing between rows less than 4 cm tall, the whole bed should be that the only easy variation is of the distance grown on for a second year. Nevertheless, spe­ between plants. Current practice is to space cial circumstances may justify planting such rows at 17.5, 20 or 22.5 cm with plants at 3.7, small plants, and experience has shown that if 5 or 7.5 cm in the row. handled with care, many will survive and Plants to be lifted after one growing season grow well. Small plants should not be trans­ may be grown at a closer spacing than if they planted until the risk of frost-lifting has past. are expected to remain in situ for two growing Often only a proportion of seedlings in a seasons. (This assumes that the 1-year (+1) bed are large enough to be handled easily plants will not be as big at the end of the while the remainder are too small for han­ season as plants 2 years in the lines (+2). If dling. A decision has to be taken whether to the 1-year plants are expected to be the same lift the seedbed and waste a proportion of the size at the end of the year as other +2s, they seedlings or to let the bed stand over, and pos­ should be given similar growing areas.) sibly be undercut, with the risk that bigger

98 plants may grow too large while the smallest damp moss, or in polythene bags or by heeling are suppressed. The decision will depend on the plants in. Plants in clear polythene bags factors such as the need for plants, whether must always be kept out of direct sunlight; see leaving the beds will make cultivation of Chapter 14, sections 14.2.6 and 14.5. Plants adjoining land difficult, and a prediction of the can also be placed in cold store to reduce the risk of disease - in particular grey mould - risk of desiccation. spreading if the seedlings become too dense. A third possibility is that the whole bed can 6.6.4 Grading of seedlings for be loosened using a lifter passed at 15-20 cm transplanting deep so that the larger plants can be picked Grading of usable seedlings is the separation out without excessive stripping of roots and before lining out into two or more size cate­ the small ones left. This technique is most gories. This is worthwhile if there is such a suited to beds where up to 30% of the seedlings wide range in the heights of seedlings that the are clearly larger than the rest, as may occur smaller plants need an extra year to grow to a when seed germinates over a long period usable size compared with larger plants. instead of germinating all at once. Often a pro­ Seedling grading should also be carried out if portion of the smaller seedlings get buried the variation in size is such that two grades during the loosening or subsequent lifting. may be produced from the transplant lines. Studies have shown that grading at the Lifting transplants seedling stage will produce more uniform In the same way as seedbeds can be picked transplant beds with limited requirement for over, so transplants which have been in lines a final grading. If grading is required, for 1 or 2 years can be sorted at lifting into seedlings should normally be separated into those large enough for the forest and those too only two grades. short or too spindly for planting out. (See also Chapter 14.) While there is no evidence that 6.6.5 Time of transplanting segregation of seedlings by size has any It is possible to lift plants of cold temperate penalty in terms of genetic potential, seedling species at almost any time of the year and size being determined primarily by seed size transplant them with success. However, so and date of germination, repeated segregation much care has to be given to plants moved of transplants can result in only the least vig­ during the growing season to ensure good sur­ orous stock as the residue held in the nursery. vival that in practice most plants are lifted in Normally, plants should be re-transplanted the dormant season, i.e. after the time in late only once. At the end of the second period in autumn when shoot growth has ceased, shoots the lines, stock should either be sent to the hardened off and winter buds formed, and forest or should be burned. Exceptions to this before the time when the buds have begun to rule should only be made for stock solely for swell in the spring. During this dormant amenity planting where larger than normal period, plants, ideally, should be lifted and plants are required, and in the rare cases transplanted immediately without temporary where late spring frost has caused extensive storage. However, where there are a large damage to shoots and there is a reasonable number of plants to be lifted at one time, chance of recovery, given another year in the these must be stored safely until they can be nursery. transplanted. (See Chapter 14.) If it is likely that planting will continue after the normal 6.6.3 Handling seedlings after lifting time of bud break, the plants involved should Roots of all plants to be transplanted must be lifted while still fully dormant and should always be protected from drying by placing be kept in a cold store until needed. (See the plants in buckets or boxes lined with Chapter 14, section 14.7.4.)

99 The best time for lifting and transplanting practised in England unless the plants have is in late February and March in England and been cold stored. Unless irrigation is avail­ Wales, and in March and early April in able, the timing of summer transplanting is Scotland (see later for summer lining out). By very dependent upon rainfall. The plants this time, the worst of the winter weather has resulting from mid-summer transplanting are usually passed, the soil is moist and the roots frequently better than those left for 2 years have not yet started to grow. Ideally, average and then lined out. This technique reduces the soil temperatures for planting should be risk of late-season attack by Botrytis (grey nearing 5-6°C so that root growth will begin mould) damaging densely-stocked second year soon after transplanting. If transplanting is seedbeds. done in autumn or winter on soils that retain There are three prerequisites if summer moisture, there is a risk of seedlings being lining out is to be a regular feature of nursery lifted out of the ground by frost. production: Deciduous species such as larch, oak, beech 1. sufficient fallow land for the work to pro­ and other hardwoods should be lined out first, ceed without interfering with plants for followed by the pines and then by the spruces, early autumn transplanting or early silver firs (Abies species), Lawson cypress, throwing up of seedbeds; hemlock and western red cedar. Douglas fir 2. a labour force that is not already fully occu­ should always be left to last - indeed it is pied by a weeding programme or other sometimes said that this species should be essential work; transplanted just as the buds break. Corsican pine should be transplanted before the end of 3. adequate irrigation. March although good results have also been obtained with autumn lining out. 6.6.7 Nutrient regime for transplants Monterery pine (Pinus radiata) is a warm This is fully discussed in Chapter 4, sections temperate species and must not be lined out 4.2.4 et seq. See also Tables 4.4 and 4.5. or planted at the soil temperatures found in the forest in the UK in winter. In the few experiments in the south of England on date 6.7 Technique and methods of of planting, almost all plants of this species lining out lined out in February or March have died while 90-100% survival has followed planting There are several methods for transplanting in September and 60-80% survival was found seedlings and each has its particular merits after planting in May. The reason for this dif­ and requirements. However, all of them ference is thought to be due to cold soil tem­ require certain standards. peratures in spring. Pinus radiata can be transplanted without difficulty in many coun­ 6.7.1 Position of plant tries with Mediterranean or sub-tropical cli­ Plants must be set upright with roots radi­ mates and would appear to require warm soil ating symmetrically downwards from the root if newly transplanted stock is to grow well. collar. The stems of plants set askew will straighten up but the base of the stem will 6.6.6 Summer transplanting remain curved and the young trees will be In northern nurseries, many species can be more difficult to plant in the forest. Similarly, transplanted with great success in late June, plants set with all roots bent towards the hori­ July or August after the spring growth has zontal in one direction will shoot satisfactorily hardened off, provided the soil is moist at the but their roots will remain and grow in the time of transplanting. This technique can only position in which they were placed and will be used for seedlings in their second growing thicken and harden in this shape. Such root season, and for this reason it is not commonly systems are often described as ‘hockey stick

100 Plate 1. Four types o f Sitka spruce planting stock. Left to right: cutting (C 'h + V h), containerised seedling (PI + 0), transplant (V h + V h), undercut (1 u 1). (50182)

Plate 2. Soil sterilisation using Dazomet. Polythene sheet seal being spread; edges are covered by soil, turned over by small shares one in each alley. (A3184)

Plate 3. Plants from root growth potential test, in position in gutter; white roots are clearly visible in one and weakly developed in the other. (38107) Plate 4, Seed being sown broadcast by Sisis Lospred. (E8835)

Plate 5. Light seedbed roller for pressing seed into soil surface, showing: i) roller, ii) scraper to remove adhering soil, iii) brush to break any surface crust formed by rolling. (39771)

Plate 6. Covering seedbeds with grit. (39769) roots’ and may persist after planting in the which are loose take longer to become estab­ forest with detrimental effects on stability, lished and are also more likely to suffer especially in the pines, larches and Douglas drought injury in dry weather through inade­ fir. These root deformations are not acceptable quate contact between roots and soil. If under the British Standard for Forest Nursery simazine or other herbicides are used to con­ Stock (BSI, 1984), nor EEC standards (EEC, trol weeds and the soil is loose, these can be 1971; EEC 1974). Straight plants with good washed down by rain into the rooting zone of roots can be grown provided the trench, notch the crop plants rather than into the top or slit made is vertical and not sloping and is 1.5-2.5 cm in which weeds germinate, thereby wide and deep enough to accommodate the increasing the risk both of crop damage and of roots of the plants being handled. The collar inadequate weed control. should be at or just below the soil surface. Good supervision is essential if this standard 6.7.4 Hand laying is to be achieved. The risk of root distortion The simplest system requires no more than a during transplanting can be reduced by trim­ garden line and a dibble with which to make a ming any roots longer than 10-15 cm. Such hole and put in seedlings one by one. trimming does not affect subsequent perfor­ Alternatively, a V-shaped trench 13-15 cm mance. deep may be dug with a spade, one face of the trench being vertical. Plants are then placed 6.7.2 Prevention of drying of the roots in position by hand against the vertical face. Roots of seedling forest trees will die if Each plant is secured in place individually by allowed to dry out and this can occur in a very pressing a handful of soil against the roots to short time on a warm breezy spring day. Once hold them to the trench until a 1—1.5 m length lifted, plants must therefore be kept in boxes, of trench has been set with plants when the buckets, polythene bags or crates, etc., out of trench is filled in, and the ground to the side the sun and wind until required. Plants must consolidated by treading and levelled. not be left out of the ground in lining out boards or in open bags at any time. 6.7.5 Lining out, using boards Plant roots are sometimes dipped in water In the board system, plants are laid side by or in a slurry of soil and water but, though side on a board until it is full, when a second this practice can be traced back to ancient board (or lid) is secured so that the plants are Greek times, there is no clear evidence that in gripped between the two boards and can then Britain the proportion of plants surviving is be moved to the trench. The two parts may be increased. Materials such as alginates and hinged together or free. The two types of waterholding polymers which make water boards most widely used are the 10 ft (‘Ben more viscous are currently on the market. Reid’) hinged board and the 6 ft 4 inch Roots dipped in viscous or ‘thickened’ water (‘Paterson’) unhinged board (approximately retain more of it on roots than if plain water 3 m and 2 m long respectively). These are dis­ had been used. However, this and other forms cussed in full in the previous edition of this of dipping are costly and are only likely to be Bulletin. effective if conditions are otherwise unsuitable for lining out, i.e. dry soil or severely drying 6.7.6 Transplanting machines winds. Almost all transplanted planting stock is lined out by machine, of which there are several 6.7.3 Firmness in the ground types in use in forest nurseries. Following transplanting, plants must be firm The most successful types are based on the enough in the ground that they cannot be ‘Accord’ and ‘Super-prefer’ (Plate 11) trans­ uprooted by a gentle, steady pull. Plants planter units. All units have a planting wheel

101 into which plants are placed like spokes with growth of the crop is not hampered by compe­ the roots projecting beyond the margin of the tition for nutrients or moisture. If weeds are wheel (Plate 12). Plants are gripped in place on prevalent, herbicides should be used for con­ the wheel either by soft rubber or by a spring- trol (see Chapter 12, section 12.4, or loaded catch, and are held firmly until in posi­ Williamson et al., 1993). If for any reason tion in the ground when they are released. A these cannot be used, the same freedom from narrow parallel-sided trench is opened by a weed competition can be achieved by regular share and closed by compacting wheels imme­ and very frequent light cultivations of the soil diately the plants are released. The machines surface, using tractor-mounted tines, brush using spring-loaded catches are preferable hoes or rotary hoes, supplemented by hand since they provide a more precise spacing and weeding of weeds growing between plants in planting depth and therefore a more uniform the lines. quality of plant. The ‘Super-prefer’ units give It is bad management, and disastrous in five rows to the standard seed-bed whereas the the long term, to allow the number of weeds to ‘Accord’ provides six rows. build up towards the end of the year. While The advantages of transplanting machines such weeds will undoubtedly by buried when are that they eliminate both the hard manual the ground is ploughed following clearance, work of digging trenches and the need to fill and while it is also true that the transplants boards. They are also capable of very high themselves will suffer little, nevertheless rates of work, but: many weeds will release viable seeds, espe­ • Transplanting machines travel very slowly cially the annual meadow grass Poa annua, and have to be drawn by a tractor fitted groundsel Senecio jacobea and willowherb with a low reduction gear box. Self-pro­ Epilobium sp. Such seeds will germinate in pelled versions of both machines are avail­ subsequent years and cumulatively increase able. the weeding problem and costs of control. • While the workers avoid the bulk of the physical labour of carrying and digging, they have little scope to move and can get very FURTHER READING AND REFERENCES cold, even though screens may be fitted to ALDHOUS, J.R. (1972). Nursery practice. give some protection from the wind. Forestry Commission Bulletin 43 (first edi­ Plants raised following mechanical trans­ tion). HMSO, London. planting have been satisfactory except where ALDHOUS, J.R. and GLEDHILL, H. (1960). roots have dragged back on the share on Temperatures at the soil surface. Journal of entering the ground, when plants with a the Forestry Commission 29, 48-50. ‘hockey-stick’ root system have developed. ALDHOUS, J.R. (1962). A survey of Dunemann This trouble may be reduced by enlarging the seedbeds in Great Britain. Quarterly share by deepening by 3-5 cm, and by Journal of Forestry 56 (3), 185-196. ensuring that any unduly long roots are cut BENZIAN, B. (1965). Stunted growth and the off. effects of partial sterilization and related treatments. Experiments on nutrition in 6.7.7 Irrigation and transplants forest nurseries. Forestry Commission Bulletin 37, Vol. 1, 134-163. HMSO. London. See Chapter 11, sections 11.4.1-11.4.3. BENZIAN, B. (1979). Nutrition of young conifers and soil fumigation. In Root dis­ 6.8 Tending eases and soil-borne pathogens. Part Proceedings First International Congress of Plant Pathology, London 1968, eds T. A. 6.8.1 Weed control in transplant lines Tousson et al. University of California Elimination of weeds ensures that there the Press, 222-225.

102 BIGGIN, P. (1983). Tunnel cloches - develop­ FAULKNER, R. and HOLMES, G.D. (1954). ment of a nursery technique for growing Placement of fertilisers. Report on Forest conifers. Forestry 56(1), 45-59. Research 1953, 20. BRIND, J.E. (1965). Studies on the effect of FAULKNER, R. (1953). Notes on choosing a partial sterilization on the soil micropopula­ suitable conifer seedbed cover with some tion. (Supplementary paper in) Experiments recent experimental results used for illus­ on nutrition problems in forest nurseries. tration. Scottish Forestry 7 (4), 121-124. Forestry Commission Bulletin 37, Vol. 1, FAULKNER, R. (1953). Summer, autumn or 206-209. HMSO, London. spring lining out. Scottish Forestry 12, BSI (1984). Nursery stock. Part 4 - Specifi­ 127-134. cation for forest trees. BS 3936: part 4. GORDON, A.G. (ed.) (1992). Seed manual for British Standards Institution, London. forest trees. Forestry Commission Bulletin EDWARDS, M.V. (1953). Effects of partial soil 83. HMSO, London. sterilization with formalin on Sitka spruce GORDON, A.G. and ROWE, D.C.F. (eds) and other conifer seedlings. Forestry Com­ (1982). Seed manual for ornamental trees mission Forest Record 16. HMSO, London. and shrubs. Forestry Commission Bulletin EDWARDS, M.V. and HOLMES, G.D. (1951). 59. HMSO, London. Effect of height and diameter on growth TEE, L.A. and PETTY, S.J. (1973). Survey of and survival of planted-out seedlings. losses of first year conifer seed and seedlings Report on Forest Research 1950, 22-23. in Forestry Commission nurseries 1972. EEC (1971). Council Directive No. 71/161/EEC Forestry Commission Research and Devel­ on external quality standards for forest opment Paper 103. Forestry Commission, reproductive material marketed within the London. community. Official Journal of the Euro­ THOMPSON, S. (1980). The growth of lodge- pean Communities, L87, 17.4.71, p.14. pole pine seedlings raised under clear poly­ EEC (1974). Council Directive No. 74/13/EEC, thene cloches at five seedbed densities. amending Directive No. 71/161/EEC, on the Canadian Journal of Forest Research 10, external quality standards for forest repro­ 426-428. ductive material marketed within the com­ WILLIAMSON, D.R., MASON, W.L., munity. Official Journal of the European MORGAN, J.L. and CLAY, D.V. (1993). Communities, L15, 18.1.74, p.12. Forest nursery herbicides. Forestry Com­ FAULKNER, R. (1957). Experiments on seed­ mission Technical Paper 3. Forestry Com­ bed compaction. Report on Forest Research mission, Edinburgh. 1956, 113-123.

103 Chapter 7 Mycorrhizas, actinorhizas and rhizobia

C. Walker and C. T. Wheeler

Some soil organisms interact with plants to drought stress and provide protection from improve nutrient availability or uptake, or to some pathogens (Harley and Smith, 1983). provide protection against pests or pathogens. The three main types of mycorrhizas found These may act indirectly (e.g. free-living on tree roots are ectomycorrhizas, endomycor- nitrogen fixing bacteria, phosphate mineral­ rhizas and ectendomycorrhizas (Walker, 1986, ising bacteria, and antibiotic producers), or 1989 b). Ectomycorrhizas and ectendomycor­ directly (some symbiotic species of bacteria, rhizas occur principally with members of the actinomycetes, or fungi). Except for legumi­ Pinaceae (e.g. pines, firs, Douglas fir, western nous nitrogen fixers, commercial preparations hemlock, larches and spruces), the Fagaceae of such organisms are not available in Great (beeches and oaks), and the Betulaceae Britain, though there are recommendations (birches and alders). Endomycorrhizas form for introducing nodulating bacteria to nursery with most other hardwoods (notably maples, beds of alders. including sycamore, cherry, ash and planes) Although there are currently only limited and on members of the Cupressaceae and prospects for using these micro-organisms in Taxodiaceae. A few species, such as alders and nurseries, the background information willows, can have all three kinds on the same included in this chapter may help the nursery root system. manager to assess future developments. 7.1.1 Ectomycorrhizas Ectomycorrhizas are formed mainly by basid- 7.1 Mycorrhizas iomycetes such as the many species of Boletus Mycorrhizas are specialised structures which and Amanita (many of the common toadstools develop where certain fungi colonise the tis­ found in the forest belong to ectomycorrhizal sues of fine roots of plants (Figure 7.1). The fungi) and a few ascomycetes (truffles are ecto­ fungi assist in the mineral nutrition of the mycorrhizal ascomycetes). These fungi can be plant in exchange for carbohydrates and other grouped loosely by the age of the plants with necessary substances, such as vitamins. This which they form mycorrhizas (Mason et al., mutually beneficial relationship is termed 1986). Some are found mainly with young ‘symbiotic’ or a ‘symbiosis’. The fungal hyphae plants and are termed ‘early stage’ fungi. permeate soil more intimately than plant Others, known as ‘late stage’ fungi, occur only roots, and take up nutrients which they with relatively mature trees, and are not found transfer to plants, thus effectively increasing in nature with seedlings. The early stage fungi the soil volume exploited by the rooting are those which may be of interest to the system. Because of their rapid turnover, nursery manager. Some ectomycorrhizal fungi hyphae more readily respond to changes in are host-specific. For example, Suillus grevillii soil conditions than do the roots. Their main is found only with larch. Most early stage action is to enhance mineral nutrient uptake fungi, however, are not specific to host. (especially phosphorus), but they may reduce One of the most common early stage ectomy-

104 Figure 7.1 a. Drawing of a longitudinal and cross- section at an ectomycorrhiza. b. Perspective drawing representing a portion ot an arbuscular mycorrhiza. (Only the outer cells of part of the root are drawn.) c. Sitka spruce seedling, control treatment (C) with non-mycorrhizal roots. d. Sitka spruce seedling with mycorrhizal roots following inoculation with Laccaria proxima (L).

corrhizal fungi is Thelephora terrestris. The fruiting body of this fungus is velvety, of var­ ious shades of brown, and often fan-shaped (Phillips, 1981), hence its common name of ‘earth fan’. This fungus may form fruiting structures around the stem and lower needles of young conifers in the nursery, a habit which has lead to the erroneous conclusion that it is pathogenic. Because of this, it was once known as the ‘smothering fungus’, and attempts were made to eliminate this helpful symbiont. Thelephora is often found in nurseries together with the two other early stage fungi, Laccaria proxima and L. laccata. These, and other early stage fungi, can improve growth of young trees in both nursery and forest soils (Holden et al., 1983; Thomas and Jackson, 1983).

105 7.1.2 Ectendomycorrhizas the production of short roots. Nursery man­ agers can help to ensure a well-balanced, myc­ Ectendomycorrhizas are particularly common orrhizal root system, even though no active in nurseries, especially with pines. They seem inoculation is carried out, by keeping soil aera­ to be adapted to high-nutrient or stressful sit­ tion high, reducing use of fungicides to a min­ uations. They are formed mainly with species imum, and by applying only as much inorganic of Discomycetes which may be found fruiting fertiliser as is absolutely necessary. Endo­ in nursery beds or on the surface of soil in con­ mycorrhizas too help in producing high quality tainers (Molina and Trappe, 1984). They may planting stock. Normal nursery practice results be beneficial in nurseries, but little is known in the loss of AM inoculum, and if endomycor- about their role in the forest (Castellano and rhizal plants are desired, then active inocula­ Molina, 1989). tion with soil containing propagules of AM Ectomycorrhizas and ectendomycorrhizas fungi will be necessary. can be seen with a magnifying glass because the fungus forms a sheath around the root tip, 7.1.4 Recent advances suppresses root hair formation, and usually modifies the morphology of the short roots. Recently, there has been an upsurge of They can, however, be distinguished with cer­ research into the more practical aspects of the tainty only by microscopical observation of cut production and use of mycorrhizal inocula sections, since the chief distinction between (Marx et al., 1984). Mostly, this has been with them is in whether the fungus penetrates the pines and Douglas fir (ectomycorrhizal species), cortical cells (ectendo-) or merely grows but there has also been progress with citrus between them (ecto-). and other endomycorrhizal plants. Nevertheless, commercial use is limited. In the southeastern United States, some nurseries 7.1.3 Endomycorrhizas now routinely introduce the fungus Pisolithus There are several types of endomycorrhiza, tinctorius into seedbeds before sowing loblolly but the one likely to be found with trees is pine (Pinus taeda). Spore-based inocula of both usually known as an arbuscular mycorrhiza ectomycorrhizal fungi and AM fungi are avail­ (AM). This type of symbiosis can only be able in the USA, as is vegetative mycelium of detected by chemically clearing and staining ectomycorrhizal fungi for incorporation into roots for observation under a microscope, since seedbeds or containers (Castellano and Molina, no sheath is formed, and root hairs are not 1989). Such products are not yet available for suppressed. The fungal partners in AMs are ectomycorrhizas in Great Britain, recent Zygomycetes. They do not have obvious attempts at production and marketing having fruiting bodies, but produce large spores in failed. In France, experiments with Douglas fir the soil. There are no airborne spores, their and Norway spruce have shown that inocula­ spread being by either root-mycorrhizal con­ tion in the nursery with a suitable strain of tact (e.g. by transplantation of colonised ectomycorrhizal fungus can lead to both reduc­ plants), by movement of spores by small ani­ tion of root disease and enhanced forest perfor­ mals, or by transport in soil (e.g. by water, mance. Trials are being carried out in wind or humans). There seems to be little independent nurseries, and have shown great host-fungus specificity with AM fungi, though promise. Favourable results, however, are there is some evidence that different strains of restricted to relatively warm soils, where a fungus can produce different growth pathogen problems necessitate fumigation of responses with the same plant species. nursery soils. This is an important factor in the The presence of a well-developed root system success achieved. Commercially available on nursery stock is an essential aim of the inoculum of AM fungi is now available through nursery manager. Ectomycorrhizas and ecten­ AGC (see address in section 7.3), but has not domycorrhizas contribute to this by enhancing yet been tested in forest nurseries.

106 Recent experiments in Great Britain seedlings. Unless the soil is later fumigated, they will then remain in the soil and become During the past decade, research has been available to future seedlings. carried out into the introduction of ectomycor­ rhizas to Douglas fir and Sitka spruce seedlings, both in seedbeds and in containers 7.2 Non-leguminous nitrogen (Walker, 1987; 1988; 1989 b). fixers Mycorrhizas have been successfully estab­ lished in undercut beds of Douglas fir by use These organisms may be symbiotic or free- of spores of the DF-specific fungus Rhizopogon living (Fitter and Hay, 1987). The importance vinicolor (Walker, 1989 a). However, although of the latter is not well understood, and they there have been some minor successes, gener­ are not likely to be used in the management of ally results have been discouraging with Sitka forest nurseries. spruce. In one experiment, for example, car­ Actinomycetes in the genus Frankia form ried out in the south of England in a disused nitrogen fixing nodules with a wide range of sandy nursery, seedling growth was consider­ perennial woody species, distributed between ably stimulated by the addition of mycorrhizal some 24 different genera in eight plant fami­ fungi (Thomas and Jackson, 1983). On the lies. Such plants are now usually designated other hand, when the same fungi were tried in ‘actinorhizal plants’, to distinguish them from more typical nurseries in the north of Britain, leguminous species nodulated by Rhizobium. no growth effects were obtained (C. Walker, Casuarinas are widely planted and economi­ unpublished; Wilson et al., 1990). cally important examples of actinorhizal Plant handling can damage mycorrhizas. plants in the tropics and sub-tropics. In tem­ Evidence from root growth potential tests perate regions, species of the genus Alnus con­ shows that one of the results of poor plant stitute the most widely used actinorhizal trees handling is a reduction in the number of but species such as the Russian olive active mycorrhizas (see also Chapter 14). (Elaeagnus) and sea buckthorn (Hippophoae) There are no immediate prospects of using are utilised for land reclamation/stabilisation mycorrhizal inoculation as a routine in the and others for fruit production (Wheeler and nursery. Nevertheless, as progress is made in Miller, 1990). other countries, products may become avail­ able in Britain, and, in theory, they could be 7.2.1 Nitrogen-fixing nodules formed beneficial. The nursery manager should keep on alders by species of Frankia a ‘weather eye’ open for announcements in the The nodules formed following infection with horticultural press, but initially should Frankia are perennial structures and can beware of commitment to anything other than achieve cricket ball or larger size as a result of a trial, of any commercial products that seasonal growth. Nodule masses so formed on become available. Advice on the latest situa­ a plant may contain one or several Frankia tion can be obtained from the Forestry strains that can vary widely in effectiveness in Authority Research Division at the Northern nitrogen fixation (Hooker and Wheeler, 1987). Research Station near Edinburgh. The continued growth of the nodules ensures When land which has not been under recent the persistence over several years of the sym­ tree cover is converted to nursery use, it is biosis with the Frankia strain(s) responsible likely that there will be few, if any, ectomycor­ for the initial infection. This is of particular rhizal fungi in the soil. Natural invasion advantage for the nitrogen nutrition of the through ‘spore rain’ will be slow and patchy. host plant if the infecting strain is of high Such sites should be used for lining out before effectiveness. establishment of seedbeds. Mycorrhizal fungi Frankia is a slow growing micro-organism will then be transferred with the transplanted compared with Rhizobium or some ectomycor-

107 rhizal fungi and techniques for its isolation ment and growth of transplants on nitrogen from nodules and its culture in the laboratory deficient sites from which Frankia is absent, have been developed only during the last 12 e.g. spoil reclamation areas. years (Lechevalier and Lechevalier, 1990). Strains of Frankia isolated from nodules of an Recent research in Great Britain actinorhizal plant can vary widely in their Strains of cultured Frankia, effective on competitiveness and effectiveness for nodula- alders, have been identified for use in Britain tion, even when re-inoculated on to plants of (Hooker and Wheeler, 1987) and their applica­ the same species (Wheeler, McLaughlin and bility has been proven at Forestry Commis­ Steele, 1981; Hooker and Wheeler, 1987). sion research nurseries, near Edinburgh, Many Frankia strains are promiscuous in their Lothian, and Farnham, Surrey (Wheeler et al., infectivity and can nodulate plants of species 1991). Inoculated plants can be sent from the in families different from that from which they nursery as 1+0 seedlings instead of, as is more were isolated. Sometimes this can result in a usual, 1+1 transplants. Enhanced growth satisfactory symbiosis, but in other cases, it compared with uninoculated controls can be may be less efficient, or even completely inef­ observed for at least 3 years following out- fective. Often, poorly effective nodules are pro­ planting on mine reclamation sites (McNeill et duced on plants introduced into areas al., 1989 and 1990). It is important that alders containing well nodulated plants of different destined for planting out on reclamation land species of the same genus (Hall et al., 1979). are well nodulated. Frankia is often found in natural plant communities where actinorhizal species have 7.2.2 Availability and recommendations been absent for many decades (Arveby and Huss-Danell, 1988). Its introduction to such for application of inoculum areas may be as spores, as these can be widely Techniques for the large scale inoculation water- or wind-dispersed. Frankia may also with Frankia are available in countries such survive in a vegetative condition by sapro­ as Canada for the inoculation of alders phytic growth in association with the roots of (Perinet et al., 1985). The market in Britain is non-nodulated species such as birch not sufficiently large to justify the investment (Smolander et al., 1990). Survival seems to be required for such a venture but interested poorest in highly organic soils such as peats readers are referred to Benoit and Berry (Arveby and Huss-Danell, 1988). It is not (1990) for further details. Nodulation with unusual, therefore, for nursery soils where crushed nodules is an easy and successful alders are to be grown to contain Frankia technique, however, and it is recommended which will give rise to nodules, of varying that seedbeds be treated in this way until effectiveness in nitrogen fixation, on the roots commercial inoculum is available. of seedlings grown in unsterilised seedbeds. If Healthy nodules, free of blackening or alders are grown in the nursery for some time, obvious fungal attack, should be collected from then the levels of Frankia in the soil will grad­ an existing stand of the appropriate species. ually increase. However, not all nursery soils The nodules should be freed of roots, washed contain Frankia, or the strains present may well with running water and, with a blender, be poorly infective or ineffective in fixation. In homogenised in water (preferably not tap- addition, even if a nursery soil contains water, which usually contains chlorine). The Frankia, sterilisation of the seedbed before resulting mixture should be strained through sowing will prevent nodulation of the muslin or a fine sieve to remove large parti­ seedlings until the organism is re-introduced. cles and the liquid retained. Approximately 10 Poor nodulation of seedlings in the nursery g fresh weight of nodules should be ample to will reduce seedling growth and vigour and treat 10 m2, when diluted in 9 litres of water. may seriously affect the successful establish­ It should be applied to the seedbed with a

108 watering can, fitted with a coarse rose. The Rhizobia exhibit some specificity for nodu­ inoculum can be applied successfully to the lation of particular plants, e.g. R. loti nodu­ seedbed at sowing or, in drought conditions, lates lotus, R. leguminosarum biovar trifolii shortly after seed germination. Some inocu­ nodulates clover; Bradyrhizobium spp. nodu­ lated plants should be retained in the nursery late lupins, though cross inoculation often in 30 cm pots containing nursery soil mixed occurs between groups of Rhizobia. with ‘Perlite’ to act as a future source of nod­ Many legumes are nodulated effectively by ules. While a plant may have only 1-2 g nod­ the natural populations of rhizobia present in ules after one year’s growth, nodule weight the soil. Thus, R. leguminosarum nodulates should have increased to 10 g or more per peas, and occurs widely in British soils, as do plant by the third year. New potted plants strains that will nodulate shrubs such as should be established each year to provide a broom or gorse. As with Frankia, a crushed continuous supply of nodules as the older preparation of effective nodules (recognised by trees outgrow their pots. Alternatively, a per­ their pink colour on slicing) can be used for manent hedge of inoculated alders can be inoculation. However, effective rhizobia may established in the nursery from which nodules be absent from the area to be planted and be can be gathered as required. unavailable locally. Consideration of the type Although a small amount of mineral of rhizobia required for inoculation of nursery nitrogen aids nodulation by reducing stress on stock is then important, particularly if out- the seedling before infection and thus encour­ planting is to be to a nitrogen poor location. aging the development of functional nodules, Unlike Frankia, commercial inoculum has it should be emphasised that nodulation is been available for legumes for many years, sensitive to excess fertiliser nitrogen and that There is an American supplier (The Nitragin even very small amounts of ammonium Company, Liphatec, Milwaukee), and at least nitrate can inhibit nodulation of some acti­ one company in Britain, AGC MicroBio norhizal plants (Righetti and Munns, 1982). It Division, NPPL Building, Rothamsted is unlikely that the nitrogen content of most Experiment Station, Harpenden, Hertford­ nursery soils will be so low as to require the shire, produces such a product. These firms application of fertiliser before seeding. produce catalogues of strains available for Application of phosphorus will aid nodulation purchase. Inoculum is usually supplied in a and soil pH also is important in the nodula­ peat-based carrier. It can be applied by incor­ tion process, although many alder species can poration into the soil or by coating the seed tolerate a wide pH range from pH 4.0-7.5 before sowing. Instructions are supplied with (Dixon and Wheeler, 1983). the inoculum ordered but application of a min­ imal bacterial number must be achieved for successful nodulation. Small-seeded species 7.3 Legumes and their nitrogen- require at least 10 000 bacteria per seed while large seeds, such as soybean, will require as fixers many as a million bacteria per seed to ensure Nitrogen fixing root nodules on legumes are inoculation. formed by symbiosis with bacteria (termed The main uses of legume inoculation in the ‘rhizobia’) belonging to the family Rhizo- UK are likely to be with leguminous green biaceae. Two genera, Rhizobium and Brady- cover crops, e.g. clovers and annual lupins. rhizobium, are of particular interest for Although several legume trees such as temperate forestry. Of these, the former is Laburnum or Robinia are grown as ornamen­ better known. The best known of the latter, B. tals, their use in forestry is limited. Cytisus japonicum, nodulates soybean, but bradyrhi- can have an important role in reclamation zobia also nodulate many of the legume tree work (Skeffington and Bradshaw, 1980) and species (Allen and Allen, 1981). in biomass production (Wheeler et al., 1987).

109 Tree lupins have been used successfully for HARLEY, J.L. and SMITH, S.E. (1983). Mycor­ sand dune rehabilitation in Australia and rhizal symbiosis. Academic Press, London. New Zealand, and as nurse crops, e.g. for HOLDEN, J.M., THOMAS, G.W. and JACK­ conifers on china clay wastes in Cornwall SON, R.M. (1983). Effect of mycorrhizal (Thomas, 1988). It should be noted that many inocula on the growth of Sitka spruce strains of Rhizobium are ineffective at soil seedlings in different soils. Plant and Soil acidity lower than pH 4.5-5.0. 71, 313-317. HOOKER, J.E. and WHEELER, C.T. (1987). REFERENCES The effectivity of Frankia for nodulation and nitrogen fixation in Alnus rubra and ALLEN, O.M. and ALLEN, E.E. (1981). The Alnus glutinosa. Physiologia Plantarum 70, Leguminosae. A source book of characteris­ 333-341. tics, uses and nodulation. Macmillan, London. (812 pp.) LECHEVALIER, M.P. and LECHEVALIER, H.A. (1990). Systematics, isolation and cul­ ARVEBY, A.S. and HUSS-DANELL, K. (1968). Presence and dispersal of infective ture of Frankia. In The biology of Frankia and actinorhizal plants, eds C.R. Schwinzer Frankia in peat and meadow soils in Sweden. Biology and Fertility of Soils 6, and J.D. Tjepkema. Academic Press, New 39—44. York, 35-36. BENOIT, L.F. and BERRY, A.M. (1990). MARX, D.H., CORDELL, C.E., KENNEY, D.S., Methods for production and use of acti­ MEXAL, J.G., ARTMAN, J.D., RIFFLE, norhizal plants in forestry, low mainte­ J.W. and MOLINA, R.J. (1984). Commercial nance landscapes and revegetation. In The vegetative inoculum of Pisolithus tinctorius biology of Frankia and actinorhizal plants, and inoculation techniques for development eds C.R. Schwinzer and J.D. Tjepkema. of bare-root tree seedlings. Forest Science Academic Press, New York, 281-294. Monograph 25. CASTELLANO, M.A. and MOLINA, R.J. MASON, P.A., WILSON, J., LAST, F.T. and (1989). Mycorrhizae. In The container tree WALKER, C. (1986). The concept of succes­ nursery manual, Volume 5, eds T.D. sion in relation to the spread of sheathing Landis, R.W. Tinus, S.E. McDonald and mycorrhizal fungi on inoculated tree J.P. Barnett. Agricultural Handbook 674. seedlings growing in unsterile soils. Plant Washington DC: U.S. Department of Agri­ and Soil 71, 247-256. culture Forest Service. McNEILL, J.D., HOLLINGSWORTH, M.K., DIXON, R.O.D. and WHEELER, C.T. (1983). MASON, W.L., MOFFAT, A.J., SHEPPARD, Biochemical, physiological and environ­ L.J. and WHEELER, C.T. (1990). Inocula­ mental aspects of symbiotic nitrogen fixa­ tion of alder seedlings to improve seedling tion. In Biological nitrogen fixation in forest growth and field performance. Arboriculture ecosystems: foundations and applications, Research Note 88/90/SILN. DoE Arbori- eds J.C. Gordon and C.T. Wheeler. cultural Advisory and Information Service, Martinus Nijhoff/W. Junk, The Hague, Famham, Surrey. 107-171. McNEILL, J.D., HOLLINGSWORTH, M.K., FITTER, A.H. and HAY, R.K.M. (1987). Envi­ MASON, W.L., SHEPPARD, L.J. and ronmental physiology of plants, 2nd edtn. WHEELER, C.T. (1989). Inoculation of Academic Press, London. Alnus rubra seedlings to improve seedling HALL, R.B., McNABB, H.S., MAYNARD, C.A. growth and forest performance. Forestry and GREEN, T.L. (1979). Toward develop­ Commission Research Information Note ment of optimal Alnus glutinosa symbioses. 144. Forestry Commission, Edinburgh. Botanical Gazette 140 (Suppl.), S120-S126. MOLINA, R.J. and TRAPPE, J.M. (1984).

110 Mycorrhiza management in bareroot nurs­ rhizas. Proceedings of the Royal Society of eries. In Forest nursery manual: production Edinburgh 93B, 117-129. of bareroot seedlngs, eds M. L. Duryea and WALKER, C. (1988). Mycorrhizas. Report on D. Landis. Martinus NijhoffTDr W. Junk, forest research 1988, 37. HMSO, London. The Hague. WALKER, C. (1989a). Friendly fungi poised to PERINET, P., BROUILLETTE, J.G., FORTIN, boost nursery growth. Horticulture Week J.A. and LALONDE, M. (1985). Large scale 205 (1), 18-19. inoculation of actinorhizal plants with WALKER, C. (1989b). Mycorrhizas. Report on Frankia. Plant and Soil 87, 175-183. forest research 1989, 40. HMSO, London. PHILLIPS, R. (1981). Mushrooms and other WHEELER, C.T. and MILLER, I.M. (1990). fungi of Great Britain and Europe. Pan Current and potential uses of actinorhizal Books, London. (288 pp.) plants in Europe. In The biology of Frankia RIGHETTI, T.L. and MUNNS, D.N. (1982). and actinorhizal plants, eds C.R. Schwinzer Nodulation and nitrogen fixation in and J.D. Tjepkema. Academic Press, New Purshia: inoculation response and species York,365-385. comparisons. Plant and Soil 65, 383-396. WHEELER, C.T., HELGERSON, O.T., SKEFFINGTON, R.A. and BRADSHAW, A.D. PERRY, D.A. and GORDON, J.C. (1987). (1980). Nitrogen fixation by plants grown Nitrogen fixation and biomass accumulation on reclaimed china clay. Journal of Applied in plant communities dominated by Cytisus Ecology 17, 469-477. scoparius L. in Oregon and Scotland. SMOLANDER, A., RONNKO, R., NURMIAH- Journal of Applied Ecology 24, 231-237. LASSILA, E.L. and HAAHTELA, K. (1990). WHEELER, C.T., HOLLINGSWORTH, M.K., Growth of Frankia in the rhizosphere of HOOKER, J.E., McNEILL, J.D., MASON, Betula pendula, a non-host tree species. W.L. and SHEPPARD, L.J. (1991). The Canadian Journal of Microbiology 36, effect of inoculation with either cultured 649-656. Frankia or crushed nodules on nodulation THOMAS, G.W. and JACKSON, R.M. (1983). and growth of Alnus rubra and Alnus gluti­ Growth responses of Sitka spruce seedlings nosa in forest nurseries. Forest Ecology and to mycorrhizal inoculation. New Phytologist Management 43, 153-166. 95,223-229. WHEELER, C.T., McLAUGHLIN, M.E. and THOMAS, R.J. (1988). A review of the use of STEEL, P. (1981). A comparison of symbi­ nitrogen-fixing shrubs and trees in agro­ otic nitrogen fixation in Scotland in Alnus forestry and farm forestry systems in N. glutinosa and Alnus rubra. Plant and Soil Europe. Research and Development in 61, 169-188. Agriculture 5, 143-152. WILSON, J., INGLEBY, K. and MASON, P.A. WALKER, C. (1986). Mycorrhizas in forestry - (1990). Ectomycorrhizal inoculation of Sitka has inoculation a future? Forestry and spruce; survival of vegetative mycelium in British Timber 15 (5), 20-21. nursery soil. Aspects of Applied Biology 24, WALKER, C. (1987). Sitka spruce mycor­ 109-115.

Ill Chapter 8 Production of undercut stock

W . L. Mason

Chapter 6 describes a traditional bare-root only possible with fast-growing species (e.g. production system where seed is sown at high larches, radiata pine) in southern Britain. In density (800-1500 seeds per m2). The resul­ the final season before lifting, a sharp blade is ting seedlings are lifted after one or two passed horizontally through the seedbed to growing seasons and lined out (‘transplanted’) sever the tap-root and any other roots below a at low densities at 100-150 plants per m2. given depth. The initial undercutting is often These transplants are then grown on for a fur­ followed at intervals by further manipulations ther period before being lifted and dispatched of the root system by ‘wrenching’. This to the forest. The purpose of this two-stage involves passing a blade at an angle (c. 35° production system is to provide strong, sturdy front to rear) through the bed at or just below plants with adequate root fibre that can with­ the depth of the undercut. Wrenching breaks stand planting in the forest better than off any secondary roots growing down below untransplanted seedlings. the initial undercut and stimulates prolifera­ This traditional system has a number of tion of root fibre (Sharpe et al., 1988). Drill drawbacks. Firstly, seedlings in broadcast sown beds may also be sidecut. seedbeds invariably are unevenly distributed, It is important to differentiate between creating localised interplant competition and ‘multicut’ stock purposely produced by resulting in appreciable variation in seedling regimes like the above, and ‘casual under­ size. Secondly, all methods of transplanting, if cutting’ carried out as a last minute decision done badly, have a tendency to produce trees to check excessively vigorous plants or to with a swept, J-rooted root system. This dis­ attempt to salvage unsold stood-over stock. tortion can make trees difficult to plant and Plants produced by these ‘casual’ undercutting could cause serious stability problems in regimes will not be of the same quality as pro­ species with limited potential for adventitious duced following the recommendations in sec­ root regeneration. Finally, transplanting is a tion 8.3 below. labour-intensive operation and is an addi­ The purposes of planned and managed tional hazard in the production system, undercutting are: exposing seedlings to the risk of damage • To promote and manipulate root develop­ during the lifting and lining out process. ment so that the maximum amount of root fibre is produced in the upper layers of the soil. This ensures that as much of the root 8.1 Potential of undercutting system as possible is recovered at lifting. An alternative approach to bare-root trans­ • To control height growth so plants achieve plant production is to sow seedlings for under­ a desired specification. cutting, at about a quarter of the density of • To decrease the shootrroot ratio so that conventional seedbeds (e.g. 200 seeds per m2). postplanting check is reduced. The resultant seedlings are usually grown on • To avoid the risk of producing transplants for two seasons. A 1-year production cycle is with distorted roots.

112 8.1.1 Root response to undercutting The root system has to be regenerated to The speed of root regeneration after undercut­ maintain adequate supplies of water to the ting is largely dependent upon soil tempera­ shoots. Studies have shown that, after under­ ture, being faster at higher soil temperatures. cutting, there is a substantial increase in the This implies that, under British conditions, flow of photosynthate and nutrients towards undercutting should normally take place in the undercut root system (e.g. Rook, 1971). June or July, which tend to be the warmest This change in the pattern of distribution of months of the growing season. The later plant foodstuffs will continue until the root undercutting is delayed into the autumn, the system is regenerated. slower and more limited will be the amount of root response obtained that year. 8.1.2 Plant quality and forest When undercutting, the lower part of the performance root system is severed, reducing the supply of Because of a more favourable shootiroot ratio, water to the shoots. An imbalance rapidly increased sturdiness and the greater amount develops between the demand and supply for of fibrous roots, undercut conifer planting water particularly during summer, moisture stock has generally been found to be superior stress develops in the shoots and growth is to transplant material in most recent British reduced. Figure 8.1 shows patterns of shoot experiments. Since 1985, some 30 forest water potential (a measure of moisture stress) experiments have been established with Sitka during the weeks following undercutting of spruce, Douglas fir, lodgepole pine, Scots pine, Sitka spruce. Each point shows the maximum Corsican pine, Japanese and hybrid larch level of moisture stress recorded during a 24- (Mason, 1988). In nearly all instances, the hour period and is the mean of ten samples. undercut stock has out-performed the trans­ The values show that undercut plants are sig­ plants in terms of either survival and/or early nificantly more stressed than non-undercut height growth. The differences have tended to plants for at least 2 months after undercutting. be most notable with species that are consid­ ered difficult to establish such as Douglas fir or Corsican pine. 2 5 /6 ______3 / 7 ______1 1 /7 ______1 2 /6 ______3 / 9 Undercut stock has also shown greater resistance to the stresses imposed by storage 0.7 and other aspects of the handling system. This 0.8 improvement in performance appears to 0.9 reflect the greater fibrosity of the root system, l + 10 5- (M P a ) K1 making the plant more resistant to different

| 1.2 levels of damage. Various aspects of forest I 13 performance of undercut stock are discussed t 1.4 by Deans et al. (1989); Mason et al., 1989; * 1.5 McKay and Mason (1991); Nelson and Howes (1991) and Sharpe et al. (1990). The undercut plants used in these experi­ U lr |r Ir Ir W IrW

• ------• = lu l Sitka spruce ments were produced using the intensive

0 ------o = i + i Sitka spruce undercutting regimes described later in this

U = undercutting chapter. (MPa) Mega pascals Ir = irrigation W = wrenching 8.1.3 Physiological effects of undercutting Figure 8.1 Shoot water potential (ij/) of undercut (1 u 1) and non-undercut (1+1) Sitka spruce during the last During the growing season, the amount of third of the growing season. height growth made by a seedling will be

113 influenced by the moisture and nutrients water stress. While the critical levels of being supplied via roots. Thus, a seedling plant moisture status before or after under­ grown under dry conditions with limited cutting have not been well defined, the art nutrients will be shorter and have poorer of successful undercutting regimes is to foliage nutrient status than one grown under bring plants close to the point of wilting moist fertile conditions. The former will also without letting them die. tend to have a larger root system in relation to the shoot size since more of the products of photosynthesis (‘photosynthate’) are diverted 8.2 Sowing for undercut to developing a root system to supply the production plant’s requirement for water and nutrients. The main difference between sowing for Undercutting is intended to divert photosyn­ undercut production compared with transplant thate from shoot growth to the creation of a regimes is the much lower sowing densities superficial and much branched root system. used in the undercut system. Table 8.1 gives The nursery manager has four key ways to recommended densities for precision sowing of influence the root system through the effect of a representative range of the major conifer and undercutting: broadleaved species. The figures assume that 1. The depth at which the initial undercut is the seed lots are of high quality with over 90% made - the shallower the undercut the germinability or viability. The density chosen more intense the moisture stress the plant will depend upon the quality of seed lot, the undergoes. Earlier work that showed inade­ equipment available for sowing, the ability to quate response to undercutting was gener­ maintain favourable germination conditions in ally the result of undercutting at depths the seedbed, and the number and sturdiness of (e.g. 15 cm) where only a small amount of usable seedlings desired per m2. root was removed with only a very short­ In general terms, at lower densities (i.e. term effect upon the plant. wider spacings), plants will have greater root 2. The timing of the first undercut and any collar diameter in relation to their height and subsequent operation - it should occur in will have larger root systems with more fibre high summer so that the soil is warm (see Deans et al., 1989). In precision sown enough to allow root regeneration. beds, densities are calculated on actual 3. By wrenching and sidecutting to continue the manipulation of the root system so that Table 8.1 Sowing densities for precision sowing for roots develop in the upper layers of the soil undercut production with some conifer and and in a configuration which is convenient broadleaved species for lifting and planting. Continued root dis­ turbance until the end of the growing Species Density season ensures that photosynthate con­ (seeds per m2) tinues to be channelled towards the root system. Corsican pine 150 Scots pine 150 4. Finally, regulation of irrigation is essential Larches 200 for effective application of undercutting Sitka spruce 200 regimes. Without remedial irrigation, plants Douglas fir 200 can die if the undercut is followed by dry, Birches 200 warm weather. However, it is also a mistake Sycamore 150 Beech 150 to overwater undercut stock since there is Oaks 125 some evidence that physiological quality at the end of the season is improved if the Note: Assumes seed lots with over 90% germinability/ plants have been subjected to moderate viability.

114 number of seeds sown rather than number of seek to destone any sections where stone may germinable seeds. be a problem, before sowing takes place. Clearly, the low sowing densities used in Standard agricultural destoners are perfectly undercut systems mean that any failure in acceptable, provided these lift the stones on a germination because of poor seed, poorly belt so that they can be deposited in a trailer cleaned seed, temperature, drought, bird pre­ and removed. Destoners that bury stones in dation, mouse damage, etc., can be very costly. the alleys or under the wheelings should not Table 8.2 shows how the recommended den­ be used. sity for Douglas fir can be adjusted to take account of seed lots with lower germinability. 8.2.2 Seed sowing Similar calculations can be undertaken for the A range of mechanical sowers is available for other species. In general, it is not worthwhile use in the production of undercut plants. The sowing seed lots with less than 60% germina­ simplest option is to use the broadcast sowers tion for undercut production without first used in conventional seedling production but attempting to upgrade the seed quality by to sow at a lower average density. The main removing any empty or damaged seeds. If seed problem with this approach is the inability to is sown at relatively high density (e.g. 400 control lateral spread of seedling roots, and seeds per m2) and high germination results, also a risk of uneven seed distribution so that then it is advisable to respace the seedlings to individual plants do not have uniform growing a lower density at the end of the first season. space. A better approach is to sow the seed in If this is not done, then plant quality will bands (‘drills’) along the length of the bed. suffer, with the trees being tall and spindly Depending upon the sower used, between six with poor root development. and eight drills can be obtained on a 1 m wide seedbed so that a side cutter can be used to 8.2.1 Freedom from stones sever roots crossing between drills. A further Successful conditions for growing undercut advantage of sowing in drills is that weed plants require that the upper soil horizons are growth between the rows is more readily con­ free of large stones than might deflect an trolled. undercutter blade. This is to ensure that the undercutter can be kept at a constant depth in Conifers the soil. If stones or other large objects such as root debris are present, the undercutter will Most drill sowers available on the British ride up over them and cut off roots very close market were designed for use in agriculture to the surface. Plants treated in this way will and they are not very easy to use with tree often die or at best will have very inadequate seeds. The main exception is the Matco-Fahse root systems. The nursery manager should Mini-Air which can sow up to six drills on a preformed seedbed, and gives reasonable spacing between seeds of conifers. Table 8.2 Sowing density for seed lots of differing The most accurate conifer seed sower on the germinability for precision sowing of Douglas fir British market is the Summit Precision Sower (see Front Cover and Plate 13) which was Germination Target density Germinable (%) (seed per m2) seeds per m2 designed in New Zealand for sowing Pinus radiata and has been successfully adapted for >90 220-200 180-200 use with a range of British conifer species. 81-90 250-220 198-225 This machine can make and sow a seedbed in 71-60 285-250 177-228 one pass. A vacuum inside the sowing drum 61-70 320-285 174-224 <61 do not sow for ensures that seed for each drill is held on the undercutting without drum for controlled delivery to the soil at reg­ upgrading seed lot ular intervals (Plate 14).

115 Whatever seed sower is used, it is impor­ considered before sowing if the particular tant that the seed purity be high since seed nursery section was weedy under the previous wings and other debris can easily clog orifices crop. or metering mechanisms and result in blank A standard pre-emergence herbicide should drills on the seedbed. It is worth checking that be applied immediately after sowing and fur­ a sower can cope with a particular species by ther application of herbicide may well be nec­ carrying out a small preliminary test. essary during the first season to ensure that no weed growth becomes established. Weed Broadleaves control during the second season can be less Large seeded broadleaves are treated rather intensive, using a standard transplant differently, shallow drills being opened in the product at the beginning of the season and fol­ bed surface and seeds being fed down funnels lowing this at a later date by mechanical to the drill which is then covered over. inter-row hoeing to remove any surviving weeds (see also Chapter 12, section 12.4). Drill spacing Drill-sowing for undercut production must be 8.3 Recommended undercutting carried out with particular care since the regimes placing of the rows affects all aspects of subse­ quent management. Wind can be a serious The following recommendations are largely problem since seeds can have 5-20 cm to fall based upon experience with conifers at the before making contact with the soil. Strong Forestry Commission nursery at Wykeham in winds can blow the light seeds during their North Yorkshire. The nursery soil is a stone- fall so that they lie outwith the drill. If seed free, coarse loamy sand derived from Jurassic has to be sown under windy conditions, heavy passage beds and irrigation is available from polythene skirts should be fixed round the an adjacent reservoir. While the basic princi­ drill to shield seed from the wind. Care is also ples should apply to all species and nurseries, necessary when sowing on side slopes since they may need to be adapted to particular sit­ the sower can ‘crab’ or move downhill and uations. become misaligned so that outside rows on one side are too close to the edge of the bed and 8.3.1 Time of first undercut are destroyed in subsequent operations. The initial undercut should take place in June or July of the second season with exact timing 8.2.3 Tending depending upon the growth of the plants. Most other aspects of seedbed preparation and Earlier undercutting is possible if the aim is to management follow the procedures outlined in reduce the rate of height growth. However, in Chapter 6. Seed is sown on the top of the such circumstances it is better to have an ini­ seedbed and covered with grit in the normal tial undercut, leave the root systems to regen­ manner, except for large seeded broadleaves erate for 6-8 weeks and then restart in late which are drilled into the top layers of the soil. July to early August. Depth of undercut Presowing fertilisation and first year top should be around 8 cm; shallower depths risk dressing regimes should follow the standard severely damaging the plants, while greater prescriptions for the nursery. depth will not give adequate conditioning. Careful weed control is essential for suc­ cessful management of a precision sowing and Subsequent operations undercutting regime. Since the seedlings are Undercutting should be followed after 2-3 sown at wide spacing, they are particularly weeks by wrenching at 10-15 cm depth (i.e. vulnerable to weed competition in the first below the initial undercut) and this should be growing season. Soil sterilisation should be repeated at similar intervals until early

116 Plate 7. Seedbeds under polythene continuous cloches. (J.R. Aldbous)

Plate 8. Seedbed being covered with polythene netting against birds showing: i) hoops to hold netting above bed, man feeding them out, ii) netting roll on rotating spindle, tii) netting edges being secured (with pegs). (39386)

Plate 9. Seedlings grown under floating mulch, showing mulch being removed. (W.L. Mason) Plate 10. Preparation for machine lining out. Tractor hauling: i) rotovator, preparing tilth, ii) Cambridge roller to ensure adequate compaction, Hi) smoothing rollerto provide even surface for planting. (A3087)

Plate 11. Transplanting using Super-prefer. A general view showing shelter for workers against wind and cold. (E8833)

Plate 12. Inserting seedlings into holders on rim o f planting wheels. (38222) Table 8.3End of season height as a percentage of 8.3.2 Fertilisation of undercut stock height at time of first undercutting in four conifer A common observation is that undercut and/or species for two growing seasons wrenched plants develop pale, chlorotic foliage Species Percentage height in the later part of the final growing season 1986 * 1987f (Coker, 1984). This response occurs because nutrients, particularly nitrogen, are redistrib­ Scots pine 103 109 uted from the foliage to the regenerating root Corsican pine 110 system. This symptom may take at least a Sitka spruce 185 Douglas fir 180 165 month to develop after undercutting and fer­ tiliser regimes should anticipate the problem Data are from Wykeham nursery. rather than wait for it to develop. This * 1986: trees were first undercut on 2/7 followed by response is also found in other species such as wrenching on 4/8; 19/8; 5/9; 19/9; 6/10; 29/10. Scots pine and Douglas fir. t 1987: trees were first undercut on 16/7 (SP) or 31/7 (DF). Wrenching on 21/8; 3/9 and 14/9. Figure 8.2 (see also Table 8.4) shows how nitrogen deficiency develops in undercut Sitka October. In some tap-rooted species (e.g. spruce over the course of a growing season. A Corsican pine, oaks), it may be necessary to standard regime of nitrogen applied at regular undercut the crop for a second time if intervals was unable to maintain N status in wrenching does not remove roots regenerating the undercut seedlings even though it was downwards from the tap-root. Where beds adequate for plants that were not undercut have been drill sown, one or two sidecuttings (2+0). By contrast, a more generous regime will also be necessary during the period from with five applications of nitrogen in liquid July to October to prune roots growing across form, four applied at close intervals following the drills. undercutting, was able to maintain and Sidecutting can be undertaken using discs improve the nitrogen status of the foliage. set to a depth of 15 cm passing between drills This high nitrogen regime involved the appli­ (Plate 17). cation of over one-and-a-half times as much The crop’s response to undercutting and elemental N as the standard regime. wrenching should be monitored closely. It can Other results suggest that increasing the take up to 3—4 weeks before roots show any amount of nitrogen top-dressing by a factor of sign of response to undercutting in July. The 1.5-2.0 compared with transplant stock is a best way of monitoring the crop is to lift reasonable rule-of-thumb to adopt. However, plants with a spade at weekly intervals to there is no evidence to suggest that levels check upon root development. Beds should be should exceed 150 kg Nha-1 in one growing irrigated if the leading shoots of the crop show season. Fertiliser should be applied in small signs of wilting. doses in a ‘little and often’ approach. The effect of undercutting upon height Application of nitrogen in a liquid form will growth varies with species. Conifers which enhance the speed of uptake provided it is make a single flush of growth such as Scots adequately diluted. Care should be taken to and Corsican pine make little growth after the avoid formulations involving urea, since these initial undercut, whereas those capable of can scorch plants particularly when they are growth throughout the season (e.g. larches, under stress following undercutting. Douglas fir) may grow another 5-10 cm in Deficiences of P, K and Mg have not been height after the initial undercut (Table 8.3). observed in British nurseries on undercut The difference is species response means that stock given standard nutrient regimes. undercutting on its own cannot always be However, P and K deficiencies are noted in the used to control height growth, and that fertili­ literature (Racey and Racey, 1988). Where sation regimes must also be considered. levels of these elements tend to be marginal, a

117 Figure 8.2 Response to undercutting of Sitka spruce plants in their second season of growth: nitrogen status of foliage.

Symbols O • and a show treatment values on date foliage sampled

—O 2 + 0 seedlings not undercut—standard N a ______A lu l seedlings once undercut — standard N

— • lu l seedlings once undercut — high N

Table 8.4Response of Sitka spruce 1u1 plants to undercutting: nitrogen status of foliage (see Figure 8.2). Details of regimes

18 June Kay-nitro (25-0-16) at 75 kg ha -1 to standard 8 August Nitrogen liquid feed to high N treatment treatments. (70 litres ha-1). Nitrogen liquid feed (35-0-0) at 70 litres ha "1 18 August Kay-nitro to standard treatment to high N treatment. (75 kg ha-1). 2 July Undercut standard and high N treatment. 19 August Wrench standard and high N treatments. 16 July Nitrogen liquid feed to high N treatment (70 litres ha-1). 29 August Nitrogen liquid feed to high N treatment (70 litres ha-1). 1 August Nitrogen liquid feed to high N treatment (70 litres ha-1). 4 September Kay-nitro to standard treatment (75 kg ha-1). Kay-nitro to standard treatment (75 kg ha-1). 5 September Wrench standard and high N treatments. 4 August Wrench standard and high N treatments. 19 September Wrench standard and high N treatments. 7 August Side-cut standard and high N treatments (70 litres ha-1). 6 October Wrench standard and high N treatments.

Notes: 1. 2+0 plants received the standard regime. 3. Mean height of plants at the end of season was; 2. Standard treatment received 75 kg elemental 2+0 non-undercut-21.3 cm; 1 u 1 standard- N ha -1 over season; high N received 120 kg 16.2 cm; 1 u1 high N - 17.4 cm. elemental N ha -1 over the same period.

118 Table 8.5A provisional fertiliser regime for precision since sharp sands will rapidly blunt a blade sown undercut conifer stock being produced on a 2- while smoother soils have little effect. Soil year cycle conditions at the time of undercutting are also important. In dry spells, the soil in the upper Basal fertiliser Top dressing horizons can be quite hard so that the under­ cutting blade has difficulty in moving through Year 1 PK plus other nutrients N applied at 50-100 kg the bed. In such situations, the blade will bow at recommended rate for element ha -1 over the season. towards the centre so that seedlings in the the section following soil Two to four applications. middle are undercut at perhaps only 2 cm analysis. K applied at 75 kg ha -1 K20 at depth. This problem can be avoided either by the end of season. loosening the soil before the start of undercut­ Year 2 ting by passing a lifting blade through the soil PK applied in spring at N applied at 100-150 kg below the target undercut depth or by side 1 /2—3/4 of rate applied the element ha -1 at 5-6 intervals previous year. Applied over the season. K applied at cutting or by irrigating the beds before under­ between rows and 75 kg ha -1 K20 at the end of cutting. Up to 12 mm of water should be incorporated. season. applied if the latter approach is adopted. Plate 17 illustrates a disc side-cutter. sensible precaution is to apply a supplemen­ At the end of the final growing season when tary dressing at the beginning of the second plants have been intensively undercut and growing season. This can be incorporated into wrenched, the upper 8-10 cm of the seedbed the soil by applying it in bands between the may be quite loose, so that it is possible to lift rows and using the sidecutters or a rotary plants easily by taking the leading shoot brush hoe to mix the fertiliser into the top between the thumb and forefinger and pulling layer of the soil. the plant from the soil with only limited root Table 8.5 sets out a fertiliser regime for damage. The looseness of the soil can cause dif­ precision sown and undercut conifer stock ficulties when plants are lifted using a single­ based upon experience at Wykeham. There row lifter. This is because successful operation are a number of areas that still require confir­ of such machines requires firm soil in front of mation, particularly the role of late season the plough share if there is to be a regular flow top-dressing in alleviating nitrogen deficiency. of plants taken up by the lifting belts. One solu­ However, the nursery manager should realise tion to this problem is to use some form of that undercutting regimes require additional whole-bed lifting system to harvest the plants. nutrient inputs compared with transplant pro­ Such a system has the added advantage of duction, and that production of chlorotic reducing the risks of soil compaction that are plants is not inevitable. the result of single row lifters travelling every part of the seedbed. Alternatively, a heavy 8.3.3 Mechanical aspects of application of irrigation 2-3 weeks before undercutting lifting may settle the soil back around plants Successful undercutting can only be achieved sufficiently to enable lifters to work. if adequate equipment is used (van Dorsser If long lateral roots remain, which will and Rook, 1972). The prerequisites are a impede subsequent planting, these should be sharp, reciprocating (i.e. side to side action) carefully trimmed back to 15-20 cm (Nelson blade which can be carefully maintained at and Howes, 1991). the proper depth (Plates 15 & 16). Sharp blades ensure that root systems are cut 8.4 Use of undercutting with cleanly and not dragged. Blunt blades often do not cut roots, but drag them so that a swept other systems root system results. Soil texture has an impor­ In southern Britain, it is possible to produce tant effect on the need to resharpen blades faster growing conifers and many broadleaves

119 on a V2UV2 production cycle. Most aspects of ficult soil. It is also important to recognise that this system follow the general principles dis­ the system involves more intensive distur­ cussed for 2-year undercut production. bance of the plants than is usual in traditional However, the key factor is to sow early (March bare-root production. Correct application of the to April at the latest) and to force the early system requires a good grasp of the principles height growth using floating mulches, so that of plant growth, physiology and nutrition, plus the seedlings are tall enough to start under­ sensitivity to seasonal variation. cutting in July or early August at the latest. If this is not done, then the nursery manager runs the risk of either producing very small REFERENCES plants (if not brought on) or of producing COKER, A (1984). Nitrogen status of Pinus taller plant with poor root systems (if not radiata seedlings after undercutting: undercut effectively). Neither will make satis­ changes in total, soluble and insoluble factory planting stock. nitrogen. New Zealand Journal of Forestry There is no major reason why undercutting Science 14(3), 277-288. cannot be used in transplant lines to improve DEANS, J.D., MASON, W.L., CANNELL, the quality of the root systems. However, for M.G.R., SHARPE, A.L. and SHEPPARD, this to be done effectively, it is desirable that L.J. (1989). Growing regimes for bare-root the transplants are lined out on to a raised stock of Sitka spruce, Douglas fir and Scots bed. This makes it easier to operate the under­ pine. I. Morphology at the end of the cutter at the correct depth. It is very much nursery phase. Forestry 62 (suppl.), 53-60. more difficult to operate a reciprocating MASON, W.L. (1988). Precision sown and undercutter on flat transplant lines since the undercut conifer planting stock. I. Quality arms of the blade tend to plough up the alleys and performance. Forestry Commission and the undercutter may be damaged. Research Information Note 129. Forestry Otherwise, a fixed blade may be used. Commission, Edinburgh. MASON, W.L., SHARPE, A.L. and DEANS, 8.5 Implications for nursery J.D. (1989). Growing regimes for bare-root stock of Sitka spruce, Douglas fir and Scots management pine. II. Forest performance. Forestry 62, The results of forest and plant handling exper­ (suppl.), 275-284. iments generally indicate that a precision McKAY, H.M. and MASON, W.L. (1991). sown and repeatedly undercut and wrenched Physiological indicators of tolerance to cold (or ‘multicut’) plant is a superior product to the storage in Sitka spruce and Douglas fir conventional bare-root transplant. The fact seedlings. Canadian Journal of Forest that the labour-intensive transplanting opera­ Research 21, 890-901. tion can be eliminated means that it is possible NELSON, D.G. and HOWES, R.E.J. (1991). to produce a plant of better quality at a Root pruning of planting stock after lifting. reduced cost. However, this requires full Forestry Commission Report on forest stocking, which in turn depends upon use of research 1991, 9. HMSO, London. good quality seed, high germination and sur­ RACEY, J.E. and RACEY, G.D. (1988). Under­ vival being achieved, leading to evenly spaced, cutting and root wrenching of tree seedlings: well-stocked seedbeds. The system also an annotated bibliography. Ontario Min­ requires good quality nursery soil (i.e. stone- istry of Natural Resources. Forestry free loamy sands on level or uniform sloping Research Report 121. (78 pp.) ground) with adequate irrigation to allow ROOK, D.A. (1971). Effect of undercutting and undercutting at the most appropriate time. wrenching on growth of Pinus radiata D. The system cannot be successfully employed in Don. seedlings. Journal of Applied Ecology all nurseries, particularly small units with dif­ 8,477-490.

120 SHARPE, A.L., HOWES, R.E.J. and MASON, VAN DORSSER, J.C. and ROOK, D.A. (1972). W.L. (1988). Precision sown and undercut Conditioning of Radiata pine seedlings by conifer planting stock. II. Nursery regimes. undercutting and wrenching: description of Forestry Commission Research Information methods, equipment and seedling response. Note 132. Forestry Commission, Edinburgh. New Zealand Journal of Forestry Science SHARPE, A.L., MASON, W.L. and HOWES, 17, 61-73. R.E.J. (1990). Early forest performance of roughly handled Sitka spruce and Douglas fir of different plant types. Scottish Forestry 44 (4), 257-265.

121 Chapter 9 Container production of tree seedlings

R. L. Jinks

The majority of forest tree seedlings are raised Container production offers opportunities on open-ground nurseries and are dispatched for the more precise control of growth through in a bare-root condition; however a small but the regulation of mineral nutrition, spacing, increasing number of plants are produced in temperature, irrigation, light intensity and containers, the technique having a place for day length. Such scheduled production should producing plants for smaller planting schemes lead to more uniform and reproducible growth and for stock of special genetic quality (Mason as long as stock is not overcrowded. This and Biggin, 1988; Mason and Hollingsworth, chapter describes the equipment and tech­ 1989; Mason and Jinks, 1990). A container- niques required for the production of tree grown plant is one which has been raised in a seedlings in modular trays. cell, bag or pot filled with an artificial growing medium and has growing medium sur­ rounding the roots when the seedling is 9.1 Container systems planted out. The term ‘cell-grown’ is often There are several types of proprietary con­ used to distinguish tree seedlings raised in tainer systems which are specifically designed modular trays from the larger container for growing tree seedlings, most of these have plants which are produced for ornamental originated in North America and Scandinavia. planting and which are grown for more than A detailed discussion on the types of container one year on the nursery. available in the United States and Canada Although container seedlings can be more can be found in Landis et al. (1990); (see also expensive to grow than bare-root stock, the Hollingsworth and Mason, 1989). root systems are less likely to be damaged The Japanese paper pot is a degradable during lifting and transport, and planted container system which is used in the UK for seedlings may have a better chance of survival the production of Corsican pine seedlings. The in certain situations. Container production paper is bonded together with a soluble adhe­ also offers several advantages for the nurs­ sive forming a honeycomb pattern of cells; the eryman. The production period is short, pots are readily separated and are planted allowing a quick response to changes in with the paper still surrounding the media demand; if necessary two or more crops could and roots. Three different grades of paper are be sown each year in appropriately equipped available which have different breakdown nurseries. Nurseries exclusively producing times, the medium resistance, F grade, is suit­ containers, whatever their size, are not con­ able for forestry use. The Ecopot system is fined to sites with a suitable soil type and similar to Japanese paper pots except that the there is less risk of a build up of soil problems. paper is coated with a layer of plastic and is However, a higher capital investment is stripped off the root plugs at planting. required in growing facilities and ancillary Most of the non-degradable systems are equipment (e.g. polytunnels, irrigation sys­ made from moulded plastic or polystyrene. All tems, benching, etc.). have slits or ribs on the inner walls of the cells

122 to prevent root coiling and they have large density of the leaf canopy. However, the larger holes at the base for drainage and to volumes of the cells which are selected for encourage air pruning of roots when the trays these species usually result in a wider spacing are placed on mesh covered benches or pallets. between the cells in the trays. Exact relation­ The cells are arranged in pre-formed plastic ships between cell volume, spacing and trays (e.g. Rigipots and Styroblocks) or as growth have yet to be determined for most hinged books (Rootrainers) and are offered in species grown under UK conditions. a range of cell volumes and numbers of cells Besides the important biological considera­ per tray (Plates 18-20). tions, other factors have also to be considered Several factors influence the choice of con­ when selecting a suitable container system. tainer system. The design of the cells must be Systems such as paper pot containers are used biologically suitable for growing tree seedlings only once, a fresh supply being required for and must include features for preventing root each crop of tree seedlings. Most plastic tray coiling and for encouraging root pruning at systems are designed to be used for raising the base of the cells. The cell volume must more than one crop, the tree seedlings can be match the final size of the seedling and this dispatched either in their trays or removed will be a function of both the species being from them at the nursery and packaged for grown and the duration of the growing period. transport to the customer. If plants are sent Volumes of 50-100 cm3 appear adequate for out in the trays, a reliable procedure is needed most conifers, while larger volumes of up to to ensure their prompt return to the nursery 300 cm3 are appropriate for many broadleaved after planting. The trays should also be robust species. In ‘Honeycomb’ systems with water- enough to withstand any mistreatment after permeable walls such as Japanese paper pots, they have left the nursery. Reusable trays water is able to move laterally between pots, have to be cleaned, sterilised and then stored compensating to some extent for any uneven­ until required for the next crop. Trays can be ness of watering in the polyhouse. cleaned by scrubbing or with high pressure The spacing between the cells also influ­ hoses, and they should be sterilised by dipping ences the morphology of the seedlings, partic­ in a suitable solution recommended by the ularly the root collar diameter (RCD). tray manufacturer. Although close spacing maximises the number of seedlings able to be grown in a tunnel, some unwanted consequences may result from such 9.2 Nursery facilities spacing. Many of the facilities and items of equipment • It increases the competition for light required for the efficient production of con­ between neighbouring seedlings, reduces tainer-grown seedlings are typical of any seedling dry weight and RCD and may intensive horticultural nursery. Further ‘draw up’, i.e. increase seedling height (e.g. details on nursery layout and facilities can be Timmis and Tanaka, 1976); found in Stanley and Toogood (1981) and • it can encourage the development of shade Macdonald (1986), only the particular require­ leaves, and cause the production of dis­ ments for growing trees being emphasised in torted stems, particularly along the edges of this section. the trays; • close spacing may also encourage fungal 9.2.1 Plastic tunnels and glasshouses diseases and create problems with watering Container seedlings are most commonly broadleaved species and faster growing grown in plastic tunnels. Glasshouses are conifers. equally suitable though more expensive. The Most broadleaved species require a wider tunnels can be either arranged as a series of spacing than conifers because of the width and separate structures or linked together as

123 multi-span tunnels to enclose a much larger water uniformly to the growing crop in a rea­ area. They should have wide doors to permit sonable time. Hand watering is only practical easy access for tractors and other equipment when production is on a very small scale. It is and the sides should be near vertical to allow very important that the irrigation water is full use of the covered area. evenly applied to ensure that all seedlings The floors of the tunnels should be isolated receive adequate water since the cells of many from the soil by covering with porous mate­ container systems are isolated from one rials such as woven plastic sheets, gravel, or another so that there is no transfer of water chipped bark, or even concrete block. Bare soil from wetter to drier cells. An inefficient irriga­ will turn to mud under the frequent irrigation tion system will result in some cells being regime and traffic inside the tunnels. overwatered while others remain dry. Uncovered soil will also encourage the devel­ Overwatering causes leaching loss of nutri­ opment of weeds and diseases. ents; sufficient to bring about short-term waterlogging may encourage development of Ventilation disease. The effects of irregular water distrib­ ution can often be seen as rings or zones of Tunnels and glasshouses for raising tree uneven seedling growth within a tunnel. seedlings must have an efficient ventilation Irrigation systems in polyhouses fall into system to prevent heat injury during sensitive two categories: mobile and fixed systems. stages of production such as germination and Further information on the design principles early seedling growth. Adequate ventilation is of irrigation systems can be found in Landis et also needed for promoting hardening-off of the al. (1989). crop after the seedlings have reached their required size. The sides of tunnels should be clad with a netting material which extends Mobile irrigation systems well above the height of the crop and sup­ Mobile systems consist of a horizontal boom porting benching, to provide side ventilation. with a series of regularly spaced nozzles. The Wind-up polythene skirts should also be boom is moved back and forth above a group of installed so that the tunnel can be closed up in benches by an electric motor. These systems colder weather to maintain warmer tempera­ produce an even distribution of water and the tures for seedling growth. Tunnels which have nozzle types can be interchanged for different variable roof vents are also available. A more purposes such as applying pesticides. The expensive but flexible option is to install quantity of water which is delivered is deter­ forced ventilation using thermostatically-con- mined by the nozzle output per unit of time trolled electric fans. The ability to shade areas and the speed and number of passes which the within a tunnel will also reduce the heat load boom makes over the crop. on containers during hot weather, particularly during germination. Fixed systems Fixed overhead systems consist of a series of 9.2.2 Irrigation and liquid fertilisation irrigation lines with sprinklers or nozzles systems inserted at regular intervals to form a grid The volume of the cells used for raising tree pattern (Plate 21). The distribution of water seedlings is small and this limits the amount tends to be less even than for mobile booms of water which can be stored between irriga­ but fixed systems should prove satisfactory if tions. Hence, frequent irrigation is required they are properly designed, installed and during hot weather, particularly when the maintained. Fixed systems can waste more crop has a large leaf area. Tunnels must be water than boom systems and drips falling equipped with an efficient irrigation system from the nozzles on to the cells beneath after which has the capacity to deliver sufficient the irrigation has been switched off can also

124 be a problem. It is recommended that advice is allow groups of trays to be readily transported sought from an experienced irrigation supplier by fork lift. The supporting system must be or consultant about the design of an appro­ constructed of durable material and capable of priate irrigation system to ensure that the withstanding the weight of full trays of system fully meets the requirements for recently watered containers (Plate 22). raising tree seedlings. The performance of any irrigation system 9.2.4 Hardening-off and holding areas should be tested regularly to check both the Once stock has reached its desired size, it can quantity of water being applied and the distrib­ be hardened off and held outside the tunnels ution pattern. This can be simply done by before despatch. If moved outside during the catching water applied in a given period of time growing season, some species may make more in a series of containers with similar size aper­ growth before the end of the season. ture, arranged in a grid pattern throughout a A suitable standing area should be con­ tunnel or bay. The results of such tests provide structed with a clean base, equipped with irri­ essential information for timing the duration of gation and wind protection. Alternatively, irrigation and also should identify any dry spots houses can be fitted with sides that can be which may need supplementary hand watering wound up or removed; this avoids the need to or modifications to the sprinkler pattern. find an additional hardening-off area. Container seedlings are most commonly fer­ tilised by applying liquid feed through the irri­ 9.2.5 Mixers and other machinery gation system either at every watering or at Operations such as mixing the growing less frequent intervals. A range of dilutors and medium, filling trays and sowing seed can be injectors of varying degrees of sophistication carried out manually, but for a larger scale of and cost are available for use in horticulture production some or all of these procedures can and the principles of operation of the different be mechanised. These operations should be types are discussed by Bunt (1988) and Landis carefully integrated together into an efficient et al. (1989). The injection system must be production line which makes the best use of compatible with the irrigation system and is labour and materials and prevents bottle­ usually installed on a by-pass line so that necks forming. either irrigation water or liquid feed can be Suitable buildings are of course required for applied through the irrigation system. housing these operations and also for the storage of trays, ingredients for growing 9.2.3 Benching and pallets media, etc. One of the features of growing tree seedlings in containers is that the roots are air pruned at the base of the cells. This prevents roots 9.3 Growing media from growing out of the containers and can A good quality growing medium is essential also promote the development of a more for successfully raising tree seedlings in con­ fibrous root system. Seedling containers are tainers. The medium should: designed with large drainage holes and must • drain well after irrigation and so be well have an unrestricted air space beneath the aerated; trays to permit air pruning. The trays should be raised at least 15 cm above the ground by • hold adequate reserves of water for plant supporting them on mesh benches, trestles, or growth after irrigation; by some other means which exposes the base • have a pH appropriate for the species being of the cells to air. Benches which are at about grown; waist height are convenient for manual opera­ • hold reserves of mineral nutrients; tions such as thinning seedlings, while low • be free from harmful insects, diseases and mesh-covered pallets placed on the ground weeds;

125 • be free flowing to allow cells, particularly Table 9.1 Growing media suitable for use with a small ones, to be filled easily whether man­ liquid feed programme ually or mechanically; Bulk Ingredients (%) • retain its physical structure during the life­ For general use: time of the crop and not decompose. Medium grade sphagnum peat 100

Thus a medium suitable for growing tree For overwintering: seedlings in containers has to have an ade­ Medium grade sphagnum peat 75 quate physical structure which is determined Perlite or vermiculite 25 by the bulk ingredients used in the mix, and it Fertilisers (kg n r3) also has to have an appropriate nutrient con­ Ground magnesium limestone 2.5 tent which is determined by the amounts of Ammonium nitrate 0.2 added fertilisers. Detailed information on the Superphosphate 0.75 Potassium nitrate 0.4 physical and chemical properties of growing Frit WM 253A 0.3 media are presented in Bunt (1988) and Landis et al. (1990). Growing media can either be bought in which will drain after irrigation and provide ready mixed or made up on the nursery from aeration (AFP - the ‘air filled porosity’). The the basic ingredients. Proprietary media have more decomposed sedge peats are best avoided several advantages including the saving of since they are too fine and can become water­ time, labour and facilities needed for making logged; these peats also tend to break down up the media at the nursery. However, on-site quickly and so lose their physical structure. mixing allows more flexibility in adjusting the Fibrous peats should also be avoided for use in composition of the medium to include new small cells since they can make filling cells materials and recommendations; the grower difficult. Suitable medium grade peats are can also experiment and adapt his mix to suit clean to handle; peats which leave the hands particular situations and crops. Mixing on a dirty are too decomposed to make good media. small scale can be carried out by hand but Up to 25% of a relatively coarse amendment mixing by machine is far more efficient. It is is often included in container mixes to change important not to over-mix a medium since this the physical properties of the medium, particu­ can destroy its physical structure and also larly if a crop will be exposed to rainfall during damage the coating of any controlled-release winter. Materials which contain fine particles fertilisers in the mix. Two typical mixes which (<0.5 mm) should not be used since they will have been found suitable for use in containers reduce the AFP of the peat and so increase the are shown in Table 9.1. risk of waterlogging. The main materials used as amendments include perlite, vermiculite, 9.3.1 Bulk ingredients pine bark, and sands and grits.

Peat Perlite The main bulk ingredient used in container Perlite is available in several grades and the media is peat, and this is often amended with seed grade is suitable for container media. a coarse material such as perlite. It is likely Perlite does not contain any plant nutrients that other materials will be developed as an nor does it absorb them from added fertilisers. alternative to peat in the future. Relatively Mixes containing perlite have a lower AWHC undecomposed, medium grade sphagnum and are well aerated. peats are generally suitable as they have a high ‘total pore space’ (TPS). Such peats have Vermiculite a high ‘available water holding capacity’ Vermiculite is also available in several grades (AWHC), yet there are sufficient larger pores and it contains some available nutrients such

126 as potassium and magnesium and can absorb the response of container seedlings to the these and other nutrient ions such as ammo­ addition of lime to container media before nium nitrogen from added fertilisers. The detailed recommendations can be made. industrial grades used for insulation are not However, the pH of container media should suitable for horticultural use. Vermiculite has not be allowed to increase above 5.5 to reduce a high total porosity and can hold water and the risk of chlorosis developing. The amount of air; while the particles are less stable than lime required to raise the pH of a medium perlite, they should last long enough for tree depends on the types and quantities of mate­ seedling production. rial used in the mix. Mixes containing a large proportion of an amendment such as perlite Other amendments will require less lime than one composed pre­ dominantly of peat. The lime requirement also Particles of pine bark can also be used as an varies between different types of peat (Bunt, amendment; such bark must be stacked and 1988). The quantities listed in Table 9.1 are aged before use, to eliminate any toxicity. applicable to Irish sphagnum peat. Coarse lime-free sands and grits can also be Low lime rates should also be specified used in container mixes; in horticulture, these when ordering proprietary mixes; media for­ are usually added to increase the weight of a mulated for growing ericaceous plants such as mix but this is generally not desirable in Rhododendron spp. should be suitable. If forest seedling production. dolomitic limestone is completely omitted from a medium, then it is important to include 9.3.2 Base fertilisers magnesium and calcium in the liquid feed.

Lime and pH Micronutrients Peat is a naturally acidic material and the pH The micronutrient elements such as copper of growing medium is commonly raised by the and iron which are required by plants in very addition of ground limestone. Ground dolo­ small amounts are usually added to the mitic limestone is often used because it sup­ medium either in a slow-release form as pow­ plies magnesium as well as calcium for plant dered glass frits or as soluble chemical salts. growth. It is common practice to maintain the Some controlled-release fertilisers also contain media pH between 5.5 and 6.5; the lower micronutrients. value is often recommended for growing conifers while the nearer neutral pH is Nitrogen, phosphorus and potassium advised for raising broadleaves. However, (N, P, K) there is evidence that for many species there In most soil-less media, all seedlings’ require­ is no advantage to liming organic media above ments for nitrogen, phosphorus and potassium pH 5.5 (Wright and Niemiera, 1987), and it have to be supplied as fertilisers. However, if has been suggested that the addition of lime­ all of the fertiliser requirement was applied as stone should be discontinued since pH adjust­ soluble fertilisers at mixing, the resulting high ment and the supply of calcium and levels of dissolved salts in the medium would magnesium can be efficiently carried out by impair germination and damage seedlings. In liquid feeding (Landis et al., 1989). addition, these nutrients are not readily In some situations the addition of dolomitic retained by soil-less media and so will be lime can have an adverse effect on growth. leached out if excess irrigation water is Douglas fir seedlings can develop distorted applied. In practice, these elements can be and chlorotic shoots in media containing applied either as slow-release fertilisers sup­ dolomitic lime (Dangerfield 1978; Dumroese et plying their nutrients over a period of time or al., 1990). by frequent feeding with a dilute solution of More research is needed to investigate fully soluble fertilisers.

127 A small amount of soluble fertiliser is often crop can be precisely controlled and varied to included in the mix to provide a starter supply suit different stages of growth with little risk of nutrients for early seedling growth before of damaging plants through over-fertilising. liquid feeding commences. Suitable fertilisers However, the nutrient solution has to be include ammonium nitrate, superphosphate evenly applied to the seedlings; a well- and potassium nitrate; these are added in designed irrigation system and injector or quantities which are unlikely to cause salt dilutor is therefore essential. Liquid feeding injury provided that the medium is not also requires some skill to mix the stock solu­ allowed to dry out. tions and to monitor the performance of the feeding programme. Controlled-release fertilisers There are several proprietary liquid feeds available and these are convenient to use Coated controlled-release fertilisers (CRF) can because the concentrated feed is already pre­ also be used as either a base dressing in com­ pared as a powder or liquid. The concentrate bination with a liquid feed programme, or as is dissolved or diluted to make a stock solution the main source of the major elements. which is then injected into the irrigation Several formulations are available, designed water at the required dilution. The alternative to last from 3 to 19 months. The rate of to proprietary feeds is to make up the concen­ release from these fertilisers is governed by trated stock solutions on the nursery from sol­ the nature of the coating and by temperature; uble chemicals. This is cheaper and allows the release rate increases at warmer tempera­ more flexibility in the amounts of nutrients tures. Because of the small size of tree which are applied to the crop. In addition, the seedling containers, it is difficult to obtain an pH of the nutrient solution can also be even distribution of the relatively few large adjusted by using acids such as nitric acid as fertiliser granules required in each cell. one of the ingredients. However, two formulations o f ‘Osmocote’ have There are three criteria which have to be a smaller granule size than other CRFs and so considered in selecting or formulating a liquid permit a more even distribution of granules feed programme: between cells. Two longevities are available: 2-3 month (18-6-12) and 5-6 month (18-6-11). • the composition of the feed; Once a CRF has been incorporated in the • the balance between the elements in the mix, the grower has little control over the feed; supply of nutrients since the fertiliser will • the concentration at which the solution is continue releasing nutrients until the fer­ applied to the seedlings. tiliser salts have become depleted. New formulations of controlled-release fer­ 9.4.1 Composition tiliser come out on the market from time to Most solutions will contain N, P and K, and time and it is always advisable to test any many will include Mg, Ca, S and micronutri­ new material or procedure on a small scale to ents. Micronutrients should not be required in determine if there are any potential problems the nutrient solution if these have been or whether the new product offers any signifi­ included (e.g. as frit) in the growing medium cant advantages. unless a deficiency is subsequently diagnosed. Similarly Mg may not be required if dolomitic 9.4 Liquid feeds limestone has been used as the source of lime. The irrigation water may contain significant Applying nutrients as a solution through the concentrations of certain nutrient ions such as irrigation system is the commonest method for N 03“, Ca++, and Mg++ and these should be fertilising container tree seedlings. The taken into account when formulating the feed; amounts of nutrient which are applied to the a detailed description of the appropriate calcu­

128 lations can be found in Landis e t a l. (1989). seed purity is particularly important if the The form of nitrogen in the solution can also seed is to be sown by machine and is not to be important; both the ammonium and nitrate clog it. Seed should be correctly pretreated to forms should be present, the proportion of break dormancy and to promote rapid, even ammonium-N not exceeding 50% of the total germination. Regimes for seed pretreatment nitrogen concentration (Landis e t a l., 1989). are covered in Chapter 5, section 5.7.

9.4.2 Nutrient balance 9.5.2 Seed sowing Imbalances in the proportion of the nutrient It is essential that a high proportion of the elements can affect the pH of the medium and cells produce a usable seedling and each cell also cause interference in the uptake and util­ must be sown with at least one germinable isation of certain ions, or even lead to the seed. Unfortunately the percentage germina­ development of nutrient toxicity if certain tion of tree seed seldom approaches 100% and, nutrients are in great excess. The ratios of particularly with some broadleaved species, nutrients are usually set relative to nitrogen the final percentage germination can be quite and the ratios of 100N:15P:80K determined by low and unpredictable. There are four options Ingestad (1979) are often used in nutrient for achieving high stocking rates in con­ solutions for applying to container tree seed­ tainers. lings. In proprietary feeds the phosphorus and • Seed with a high germination capacity, can potassium contents are expressed as the pro­ be sown mechanically at the rate of one portion or percentage of the oxides P205 and seed per cell (Plate 23). K20 in the concentrate, while the nitrogen content refers to the proportion of elemental • Cells can be sown with more than one seed N. (Factors for converting from the oxide to and the seedlings thinned to a single plant the elemental form are 0.436 for P205 to P and per cell. This method is suitable for many 0.83 for I^O to K). conifer species where the percentage germi­ nation of a seed lot is reasonably pre­ 9.4.3 Nutrient concentration dictable from laboratory tests. Table 9.2 gives simple guidelines. For a more detailed The concentration of the final diluted solution discussion of multiple seed sowing, see is usually expressed as the concentration of Tinus and McDonald (1979), Schwartz nitrogen in the feed in p.p.m. (parts per mil­ (1993), and Wenny (1993). lion). Typical concentrations range from 50 to 200 p.p.m. N, the choice of concentration • Multiple sowing is not practical for trees depending on the stage of growth and the fre­ which have large seeds because of the quency of feeding. When applying nutrients narrow diameter of the cells. Seed of these with every irrigation, 50 p.p.m. may be species can be allowed to begin germination applied during the establishment phase and during pretreatment (chitting), the germi­ the concentration increased to 100-150 p.p.m. nating seed can then be separated out at during the period of rapid growth. The higher intervals and sown into the cells. concentrations of 150—200 p.p.m. are applied when feeding at less frequent intervals. Table 9.2 Number of seeds to sow per cell as a function of percentage germination

9.5 Seedling production Percentage germination Seeds per cell

9.5.1 Preparation of seed for sowing 85-100 1 It is important that the highest quality seed is 75-85 2 obtained for container production both in 60-75 3 terms of purity and percentage germination; (Source: Tinus and McDonald, 1979)

129 • Seed of species whose percentage germina­ and doors, if they are left open for ventilation, tion is very low or unknown, for example must be covered with bird-proof netting until exotic species, can be germinated, after pre­ the seedlings have fully emerged. Baited traps treatment, in seed trays and the seedlings should also be set out among the trays to can then be pricked out into individual cells. catch rodents. The procedure for sowing seed into containers depends on the size of the seed, whether it has Control of temperature been pretreated and, if appropriate, on its The seed of many species will begin to germi­ stage of germination. nate at relatively cool temperatures normally experienced at sowing times between March and May. Earlier sowing dates usually require Small ungerminated seed provision for frost protection to prevent Small seed which is sown directly into the freezing injury in cold weather. High tempera­ cells should first be surface dried in air after tures after mid-May can limit later sowing pretreatment; this makes it more freeflowing unless the trays can be kept cool by shading and easier to handle. The seed is sown on to and venting. the surface of the growing medium and then The environment has to be carefully con­ covered with a layer of lime-free grit to a trolled during germination and early seedling depth equivalent to the thickness of the seed growth, in particular the temperature and the to prevent drying out. The sown trays can be moisture relations of the germinating seed. covered with white polythene sheet or a woven The temperature of seed sown in containers polypropylene sheet to maintain high humidi­ can fluctuate widely since the upper layer of ties. The covers are usually removed once the medium, which is where the seed is situ­ about 10% of the seeds have germinated. ated, experiences the largest variation in tem­ perature. Similarly, most of the water lost by Chitted seed evaporation from cells occurs at the surface of Chitted seed should be sown as soon as signs the medium and so these layers can also of germination are visible, usually when the undergo wide fluctuations in moisture con­ seed coat splits and the radicle begins to tent. emerge. The cells should be partially filled To prevent damage occurring to the germi­ with growing medium to leave sufficient room nating seed, the growing medium temperature for the seed and its covering of compost. The should not be allowed to fall below 0°C or chitted seed should be placed on to the surface exceed 30°C. It is important to measure the of the medium with the radicle pointing down, temperature of the medium, rather than just the cells are then filled with media sufficient the air temperature, to determine if measures just to cover the top surface of the seed. If ger­ have to be taken to reduce the heat load on mination is allowed to progress too far when containers. In tunnels, the temperature of the the seed is chitting then great care must be medium may be several degrees higher than taken not to damage the emerged radicles and the air temperature during hot weather the seedlings will have to be carefully pricked because of the absorption of solar radiation by out into the medium. Cells sown with chitted the medium surface and the trays, especially seed are not normally covered with polythene if they are made from dark coloured plastic. or other materials since the seedlings should Medium temperature can be easily checked by emerge at a rapid rate. measuring the temperature at 1 cm below the surface using a hand-held electronic ther­ mometer. Protection Several steps can be taken to cool the Sown seed must be protected from predation growing medium and reduce the rate at which by birds, squirrels and rodents. All side vents the surface layer of the medium dries out.

130 Covering the surface of the medium with light Control of irrigation coloured grit will reflect part of the incoming Container-grown seedlings require frequent radiation; covering the trays with white poly­ irrigation during hot weather because of the thene or a spun polypropylene material will limited water-storage capacity of the cells. also reduce the heat load at the medium sur­ There are several methods for determining face as well as help retain moisture. Light when to irrigate. The simplest method is by coloured trays will reflect some of the incident careful observation of the growing medium heat radiation and so be cooler than dark and the condition of the seedlings. The mois­ coloured trays. Trays made from insulating ture status of the medium is assessed by materials like polystyrene will conduct less observing the ease with which water can be heat into the medium than thinner denser squeezed from a sample of medium and plastic trays. Tunnels should be adequately relating this to the status of the seedlings. ventilated and can be shaded externally with This method is widely practised but does shade-cloth in very hot weather. Frequent light require experience and is subjective. irrigations during hot weather are required to replace water lost by evaporation. A high water A more objective method for measuring the content in the medium not only keeps the ger­ moisture status of the medium is to weigh a minating seed moist but also provides a source sample of trays, since the weight will decrease of water for lowering the temperature of the as water is lost by transpiration and evapora­ growing medium by evaporative cooling. tion. This technique requires a reasonably accurate weighing machine such as a pan bal­ ance on to which a tray can be placed or a 9.5.3 Seedling establishment spring balance from which trays can be hung. During the earliest stages of seedling growth, it The trays are first weighed after excess irriga­ is important to avoid overwatering since tion and when drainage has ceased. This reduced aeration in the medium can adversely determines the ‘saturation’ weight. The trays affect root growth. Similarly ‘damping ofF may are then weighed at regular intervals until it also become a problem. Liquid feeding is often is determined that the seedlings require started when the first true leaves have watering, this weight is the weight at which emerged, the original dressing of soluble fer­ irrigation should be initiated. The water tiliser providing enough nutrients for the early status of the seedlings can be determined stages of seedling growth. The exact time to either by examining the seedlings or, more start feeding will depend on the species, the accurately, by measuring the water potential amount of base fertiliser included in the (degree of water stress) of the seedlings using medium and the amount of leaching that has a pressure bomb (Landis et al., 1989). To avoid occurred from excess irrigation. Species with problems of waterlogging or leaching of nutri­ large seeds can make appreciable growth using ents, trays are not normally irrigated to or stored reserves and so are less dependent on beyond full saturation weight unless excess the amounts of nutrients available early on. salts are being flushed out of the medium. The ‘irrigation’ weight can also be calculated from 9.5.4 Seedling growth the water-release curve of the particular growing medium; this is a physical measure­ Once seedlings have become established they ment made in a laboratory, of the availability enter a period of rapid growth; correct irriga­ to plants of water in the medium. tion, fertilisation and environmental control are essential to ensure the production of quality seedlings. High temperatures and Control of liquid feeding humidities must be avoided, seedlings must The frequency with which liquid feed is not be exposed to water stress or allowed to applied during growth depends on the rate of become nutrient deficient or over-fertilised. nutrient uptake by seedlings (i.e. the growth

131 rate) and the rate at which nutrients are lost taken to promote the cessation of growth, to from the growing medium by leaching. Ideally encourage the onset of dormancy and to the concentration of soluble nutrients in the increase the hardiness of shoots and roots. medium should not be allowed to fluctuate Many species will cease growth and set bud widely; consequently, infrequent applications naturally during late summer and such of a high concentration feed should be avoided. seedlings should be encouraged to remain dor­ If more nutrients are applied than the mant by stopping liquid feeding or switching seedlings can absorb, the concentration of sol­ to a low nitrogen feed, reducing watering and uble salts can increase to high levels and by maintaining cooler temperatures either by cause salt damage to seedlings. To avoid this ventilation or by moving the plants out to a problem, containers should be periodically suitable outdoor standing area. over-irrigated to ensure that a proportion of Other species can continue growing well the nutrient salts are flushed out to prevent into autumn if they remain in a productive salt build up. The application of nutrients at a environment under protection. This can delay moderate concentration (50-100 p.p.m. N) shipment and may also reduce the degree of with every irrigation is the simplest way of frost resistance of the plants. Hardening-off maintaining a relatively constant supply of can be encouraged in several ways, such as by nutrients in the growing medium. reducing or stopping the nutrient supply, and In the UK, nutrients are more commonly by exposing seedlings to mild drought, short applied at a higher concentration (150-200 days, and cool temperatures. A common and p.p.m. N) in the liquid feed at set intervals relatively simple method for promoting dor­ between irrigations, typically once or twice mancy is to reduce or stop liquid feeding weekly during periods of active growth. during late summer and to move the seedlings However, time-tabled feeding may not always outside the tunnels to a prepared standing supply adequate amounts of nutrients. It is area. The combination of declining day length, advisable, therefore, to check the nutrient cooler temperatures and reduced nutrient status of the growing medium periodically supply encourages the development of dor­ before applying liquid feed, to determine if the mancy. frequency of application is adequate. Exposure of seedlings to drought can also hasten bud set in certain species such as Nutrient status of the growing medium Douglas fir. However, the drying of the medium has to be carefully controlled to avoid The concentrations of specific elements in damaging the seedlings. Ideally, the water samples of growing medium can be analysed status of the seedlings during drying should by a soil science laboratory or by using a pro­ be carefully monitored by measuring shoot prietary nutrient analysis kit. Laboratories water potentials with a pressure bomb, but in usually provide guidelines for the interpreta­ practice the water status of the medium and tion of the analytical results. Very low concen­ seedlings is usually assessed subjectively. trations of nutrients would indicate that Long periods of cloudy weather can reduce feeding is too infrequent, assuming that the the rate of transpiration and so greatly concentration of nutrients in the solution is increase the time taken before seedlings correct and that the feed is being applied become exposed to mild water stress. Uneven evenly for long enough. High concentrations of drying of trays across a tunnel can also be a nutrients would suggest that too much feed is problem since some trays may dry more quickly being applied by the fertiliser programme. than others and so require hand watering. Artificial reduction in day length using 9.5.5 Conditioning seedlings blackout systems offers a precise method for Once seedlings have reached their desired size inducing dormancy in species such as spruces during mid to late summer, steps must be and Douglas fir. The advantages of using pho-

132 Plate 13. Precision drill sowing by Summit sower, iii) (end visible, to right of white plate) vacuum showing: roller which picks up seed at predetermined i) vacuum pump on tool frame immediately behind spacing from tractor, iv) eight seed (rays, ii) smoothing roller, v) rollers pressing seed into soil surface. (39375)

Plate 14. Seed sown using the precision sower. (A1002) Plate 15. Undercutting. View from rear showing undercutter out of the ground with vertical reciprocating arms and trough shaped shares to restore the edges of seedbeds after the disruption by the reciprocating arms. (E8272)

Plate 16. Undercutting. View showing at far end of bed from left to right: i) depth control wheel, ii) vertical coulter cutting track for Hi) small disc loosening soil ahead of vertical reciprocating arm carrying undercutting blade. (39556)

Plate 17. Vertical discs cutting laterals between drilled seedlings. Position of discs controlled by steersman seated on tool-frame. (39550) toperiod to induce dormancy over drought and The insulation provided by polystyrene nutrient stressing are that seedlings are not trays will also reduce the rate of heat loss stressed, crop response is uniform, and it is during cold weather and should be considered relatively easy to impose blackout treatments for nurseries where seedlings are likely to be (Eastham, 1990). exposed to sub-zero temperatures for long periods. 9.5.6 Winter protection If container seedlings have to be held at the 9.5.7 Handling and despatch nursery over winter it is important to protect Cell-grown plants have the advantage over them from freezing injury. The roots are par­ bare-rooted stock that the growing medium ticularly susceptible to damage because the greatly reduces the risk of root damage roots of many young trees and shrubs are less between nursery and permanent planting site. frost resistant than the shoots; typically roots Nevertheless, in other respects, the plants are injured when media temperatures fall require the same care and protection as for below -5 to -15°C (Studer et al., 1978). bare-rooted plants. These requirements are Several features of container design fully described in Chapter 14. increase the risks of frost damage during cold weather. Factors such as shallow depth and the isolation of the individual cells can REFERENCES increase the danger of media temperatures BUNT, A.C. (1988). Media and mixes for con­ falling to damaging levels. The most certain tainer-grown plants: a manual on the way of preventing winter injury is to over­ preparation and use of growing media for winter seedlings in tunnels provided with sup­ pot plants. Unwin Hyman, London. plementary heat to prevent temperatures DANGERFIELD, J.A. (1978). Influence of falling below 0°C. lime incorporated in soil mix on growth of If seedlings have to remain in unheated Douglas-fir. Fisheries and Environment tunnels or outside during freezing weather, Canada Bi-monthly Research Notes 34 (1), there are several measures which can be 1- 2 . taken to reduce the risk of freezing injury DUMROESE, R.K., THOMPSON, G. and occurring. It is important to ensure that the WENNY, D.L. (1990). Lime-amended growing medium is well watered before the growing medium causes seedling growth onset of freezing weather. While ice is distortions. Tree Planters’ Notes 41 (3), forming, heat is released (the latent heat of 12-17. fusion), which prevents the temperature of the EASTHAM, A.M. (1990). Regulation of seedling medium from falling below 0°C. The root tem­ height in container-grown spruce using pho­ perature will only fall below 0°C when all the toperiod control. In Target Seedling water has become frozen, hence the higher the Symposium: Proceedings, Combined Meeting water content, the longer this delay will last. of the Western Forest Nursery Associations; Trays should be packed tight together and 1990 August 13-17; Roseburg, Oregon. Eds placed directly on the ground to reduce heat R. Rose, S. J. Cambell, and T. D. Landis. loss and allow heat to be conducted into the Gen. Tech. Rep. RM-200. US Department trays from below. Surrounding the trays with of Agriculture, Forest Service, Rocky Moun­ straw bales and covering them with materials tain Forest and Range Experiment Station, such as polythene sheets, fleece, or a reflective Ft Collins, CO. (286 pp.) thermal screen, will also reduce the rates of HOLLINGSWORTH, M.K. and MASON, W.L. radiative and convective heat loss. Any snow (1989). Provisional regimes for growing con­ which may cover trays overwintered outside tainerised Douglas fir and Sitka spruce. should not be cleared away since snow is an Forestry Commission Research Information excellent insulator. Note 141. Forestry Commission, Edinburgh.

133 INGESTAD, T. (1979). Mineral nutrient MASON, W.L. and JINKS, R.L. (1990). Use of requirement of Pinus sylvestris and Picea containers as a method for raising tree abies seedlings. Physiologia Plantarum 45, seedlings. Forestry Commission Research 373-380. Information Note 179. Forestry Commis­ LANDIS, T.D., TINUS, R.W., McDONALD, sion, Edinburgh. S.E. and BARNETT, J.P. (1989). Seedling SCHWARTZ, M. (1993). Germination math: nutrition and irrigation, Vol. 4 of The con­ calculating the number of seeds necessary tainer tree nursery manual. Agriculture per cavity for a given number of live Handbook 674. US Department of Agri­ seedlings. Tree Planters’ Notes 44 (2), culture, Forest Service, Washington, DC. 19-20. (119 pp.) STANLEY, J and TOOGOOD, A. (1981). The LANDIS, T.D., TINUS, R.W., McDONALD, modern nurseryman. Faber and Faber, S.E. and BARNETT, J.P. (1990).Containers London. and growing media, Vol. 2 of The container STUDER, E.J., STEPONKUS, P.L., GOOD, G. tree nursery manual. Agriculture Handbook L. and WIEST, S.C. (1978). Root hardiness 674. US Department of Agriculture, Forest of container-grown ornamentals. Hort- Service, Washington, DC. (88pp.) Science 13, 172-74. LUCAS, R.E. and DAVIS, J.K. (1961). Rela­ TIMMIS, R. and TANAKA, Y. (1976). Effects tionships between pH values of organic of container density and plant water stress soils and availabilities of 12 plant nutri­ on growth and cold hardiness of Douglas fir ents. Soil Science 92, 177-182. seedlings. Forest Science 22, 167-172. MacDONALD, B. (1986). Practical woody TINUS, R.W. and McDONALD, S.E. (1979). plant propagation for nursery growers. How to grow tree seedlings in containers in Batsford, London. (669 pp.) greenhouses. Gen. Tech. Rep. RM-60. US MASON, W.L. and BIGGIN, P. (1988). Com­ Department of Agriculture, Forest Service, parative performance of containerised and Rocky Mountain Forest and Range bare-root Sitka spruce and lodgepole pine Experiment Station, Ft Collins, CO. seedlings in upland Britain. Forestry 61 (2), WENNY, D.L. (1993). Calculating filled and 149-163. empty cells based on numbers of seeds sown MASON, W.L. and HOLLINGSWORTH, M.K. per cell: a microcomputer application. Tree (1989). Use of containerised conifer Planters’ Notes 44 (1), 49-52. seedlings in upland forestry. Research WRIGHT, R.D. and NIEMIERA, A.X. (1987). Information Note 142. Forestry Commis­ Nutrition of container-grown woody nurs­ sion, Edinburgh. ery crops. Horticultural Reviews 9, 75-101.

134 Chapter 10 Vegetative propagation

W . L. Mason and R. L. Jinks

Introduction Over the last two decades there has been increasing interest in propagating vegeta­ Vegetative propagation is the term used to tively other tree species (e.g. Mason and describe the production of plants by asexual Keenleyside, 1988) for three main reasons. means. Propagules are placed in an environ­ 1. Tree breeders are increasingly able to iden­ ment favourable for development so that each tify genotypes which are more vigorous or becomes an independent plant. Techniques have better form or timber quality or which include the rooting of cuttings and layers, are more disease resistant than the wild grafting and budding, separation and division. populations. These improved genotypes are Cuttings are usually made from shoots but generally available only in very small quan­ roots may also be used. The original seedling tities (perhaps a few thousand seeds) and plant from which vegetative propagules are therefore they cannot be grown from seed in taken is known as the ‘ortet’; the cuttings commercial quantities. taken from a particular ortet are known as ‘ramets’. The attraction of vegetative propaga­ 2. Propagation systems have improved consid­ tion is that all the ramets are genetically iden­ erably so it is now possible to maintain tical to the ortet and potentially have similar unrooted cuttings safely in humid condi­ form, timber quality, foliage colour and so tions for several months while new roots forth. The resulting population of plants with develop. the same genotype is known as a ‘clone’. 3. We have a better understanding of the Plants of tree species that are used in influence of the age of the donor plant upon British forestry have generally been raised the rootability of the cuttings (Davies et al., from seed. The basic reason for this is that 1988). Thus, cuttings taken from plants less there are only a few species which can be veg­ than 3-4 years old from seed can be rooted etatively propagated without the use of com­ fairly easily even though those taken from paratively sophisticated propagation facilities. older plants can be difficult to root. Species which can be easily rooted using stem A wide range of forest tree species besides cuttings include poplars, willows, London poplars and willows, in Britain have been suc­ plane, some elms, Lawson cypress, western cessfully propagated using juvenile cuttings in red cedar, clones of Leyland cypress, intensively managed facilities (see Table 10.1). Cryptomeria japonica, coast redwood and Thus cuttings could theoretically be used on a giant sequoia. Until recently, the only genera much wider scale for producing forest planting where vegetative propagation was of impor­ stock. However, cuttings cost around 1.5-3 tance in producing forest planting stock in times more per plant to produce than conven­ Britain were the poplars and willows. Species tional seedlings. Therefore their use is nor­ in these genera possess latent root primordia mally justified only where the material in their stems which makes it relatively easy propagated offers sufficient genetic superiority to root cuttings in the ground. over unimproved seedlings to compensate for

135 Table 10.1 Tree species of commercial forest section (the balsam poplars) are readily propa­ interest in Britain which have been successfully prop­ gated from hardwood cuttings. In the Leuce agated using juvenile stem cuttings section, the white poplars can also be propa­ gated from hardwood cuttings, but the aspens Conifers Broadleaves and their hybrids are more difficult and are usually propagated from root cuttings. Sitka spruce Sessile oak Norway spruce Pedunculate oak Hybrid larch Red oak 10.1.2 Hardwood cuttings European larch Sycamore Poplars can be marketed in different forms Japanese larch Beech depending on their intended purpose. Stocks Lodgepole pine Lime spp. Scots pine Birch spp. can be raised and sold as 1 or 2-year old Corsican pine Gean rooted cuttings, and these are often used for Macedonian pine Ash wide spaced planting. Poplars required for Western hemlock Nothofagus spp. high density planting such as for biomass, Douglas fir Common alder particularly the more recently introduced Grand fir Red alder clones, or for new stool beds, are sold as Noble fir Sweet chestnut unrooted cuttings or sets for direct insertion A/ofes:1.A revised version of Table 3 in Mason and Gill into the ground at the planting site. (1986). Poplar cuttings and plants used for forestry 2. Successful is defined as more than 60% rooting. purposes in the UK must be produced from stool beds which have been officially approved the increased price. This cost differential also and recorded in the National Register of Basic means that some of the more intensive (and Material under the Forest Reproductive more expensive) propagation techniques used in other areas of horticulture may not be justi­ fiable. Table 10.2 List of poplar clones currently acceptable for registration under the Forest Reproductive Material Regulations, 1977

10.1 Propagation of broadleaves Preferred clone name Poplar parentage

10.1.1 Poplars Fritzi Pauley P. x trichocarpa Scott Pauley P. x trichocarpa Most poplars raised commercially are propa­ Columbia River P. x trichocarpa gated from hardwood cuttings taken during Trichobel P. x trichocarpa the winter. Poplars can also be propagated Balsam Spire P. trichocarpa x P. tacamahaca from seed, from softwood and root cuttings, (formerly TxT 32’) and by grafting or budding. Raising from seed and grafting are generally only used in tree Canescens P. alba x P. tremula breeding programmes. Softwood and root cut­ Casale 78 (formerly 1-78) P. deltoides x P. nigra tings are used for propagating those species Eugenei P. deltoides x P. nigra Gelrica P. deltoides x P. nigra which do not root readily from hardwood cut­ Heidemij (indistinguishable P. deltoides x P. nigra tings. Softwood cuttings are particularly from Laevigiata) useful for bulking up the numbers of a scarce Robusta P. deltoides x P. nigra clone in a short time. Serotina P. deltoides x P. nigra A detailed discussion on the taxonomy and Primo P. deltoides x P. nigra production of poplars can be found in Jobling Ghoy P. deltoides x P. nigra (1990); see also Potter et al. (1990). Generally Gaver P. deltoides x P. nigra all the poplars in the Aigeiros section (the Gibecq P. deltoides x P. nigra black poplars), apart from some forms of Beaupre P. deltoides x P. trichocarpa Populus deltoides, and in the Tacamahaca Boelare P. deltoides x P. trichocarpa

136 Material Regulations 1977. At present there anual shoot is often too thin for making cut­ are 18 clones of poplar which are acceptable tings. Cuttings are prepared from the well- for registration under these regulations. These budded remaining parts of shoots. Cuttings are given in Table 10.2 (see also Chapter 15, taken from the bases of shoots may be too section 15.3.4). thick for easy insertion into soil, and may be Poplar cuttings may be prepared at any slower to shoot since many of the lateral buds time during the dormant season from 1-year- may already have produced shoots during the old fast grown shoots. Suitable shoots are best first year. The top cut of the cutting should be produced on specifically managed stock plants made about 1 cm above a bud, while the basal (stools), although shoots from 1-year-old cut should be made close to or just below a rooted cuttings or other sources such as cop­ bud. Cuttings can be stored before use or dis­ pice may also be acceptable. patch in a cold store at +3 to 4°C. They must be enclosed in a labelled air-tight polythene bag to prevent water loss. Cuttings can also be Stock plants / stool beds stored outside by placing them upright and Stock plants are established either by direct completely covering them in coarse sand. insertion of hardwood cuttings or by planting Cuttings which are to be rooted in the rooted plants at a spacing of at least 1 x 1 m in nursery are usually inserted into the ground the nursery; the shoots are cut back to the in late winter to allow roots to form before the ground annually during the winter to buds break in the spring. Cuttings can be encourage the development of vigorous new directly inserted if the soil has been suitably shoots. Areas where such poplar stock plants prepared. The cuttings should be pushed in are growing are normally called ‘stool beds’. vertically until the top cut surface is at soil Many of the hybrid poplar clones are difficult level; subsequent soil settlement and some to distinguish apart in the nursery. All stool erosion will usually expose enough of the cut­ beds must be clearly labelled and the layout of ting to allow the rows to be readily identified. the beds must also be recorded on maps. Spacings for inserting cuttings vary from as Individual clones should be planted in sepa­ close as 30 cm within rows and 80-100 cm rate rows to reduce the risk of mixing up cut­ between rows, to 50 x 100 cm for the more vig­ tings or sets from different clones when orous clones. However, a spacing of 50 x 50 cm cutting the shoots in winter. If more than one is commonly used. clone has to be planted in a row, it is impor­ The new shoots on rooted cuttings grow tant to leave a clear marker between clones, very vigorously and can reach heights in such as a large post, to emphasise the excess of 150 cm in the first year. Where more boundary. During the summer, stool beds than one shoot emerges, the shoots should be should be checked for the growth of rogue singled to the straightest and most vigorous plants which may arise from rooted pieces of stem when the shoots are about 25 cm long. discarded shoots left after winter pruning and One-year rooted cuttings which have not cutting or from a previous stool bed. Any reached a suitable size can be grown on for a rogue plants should be removed or treated further year in the nursery. The shoot system with herbicide to avoid the risk of producing can be stumped back and the root stock trans­ batches of cuttings of mixed clones. planted in the winter to yield a source of cut­ tings and eventually to produce plants with Cutting preparation 1-year-old shoots on 2-year-old root systems. In British nurseries hardwood poplar cuttings are usually 20-25 cm long, with a diameter of 10.1.3 Poplar - softwood cuttings 10-20 mm at their midpoint. Cuttings with a All of the poplar species and cultivars which top diameter of less than 8 mm usually do not are raised commercially in nurseries in root well and so about the top third of the Britain can be propagated successfully from

137 leafy summer cuttings. However, this is a tings should be collected in the early morning more expensive method for propagating and stored away from direct sun in opaque poplars than rooting winter-dormant woody polythene bags. Cuttings may be very soft at cuttings because rooting softwood cuttings the beginning of the summer and require an requires more attention and equipment. efficient misting system to prevent wilting. Nevertheless the leafy summer softwood cut­ The lower leaves are usually removed from ting technique is a particularly useful means the cuttings before they are inserted into a of rapidly increasing stocks of selected clones well drained rooting medium such as 1:1 peat: because of the rapid rate at which new roots coarse sand or peat:vermiculite. The base of are produced, typically after only 2 weeks, the the cuttings can be dipped in a proprietary high rooting percentages which can be hormone rooting powder to increase the rate obtained, and the large numbers of small cut­ of rooting. Cuttings are also treated with a tings which can, if necessary, be prepared fungicide to prevent rotting. from suitable shoots. Leafy cuttings can be Cuttings can either be inserted 3-5 cm rooted throughout the summer with little apart in trays or in individual containers. The decline in percentage rooting and 90-100% high rooting percentage which can be achieved rooting can be achieved with poplars from the with softwood cuttings makes the direct inser­ sections Aigeiros and Tacamahaca. Rooting of tion of single cuttings into one litre containers softwood cuttings is a particularly successful a particularly efficient method of production method for propagating P. x canescens (grey because it eliminates the need to pot-up plants poplar) and other poplars in the section Leuce. after the cuttings have rooted in trays. Peat:grit (3:1) amended with a low rate of con­ Propagation facilities trolled release fertiliser has been found to be a suitable rooting and growing medium. An intermittent mist system is required if high Cuttings inserted towards the end of summer percentages of rooted softwood cuttings are to are best rooted in trays and potted-up the fol­ be achieved. Mist installed in cold frames, lowing spring; potting-up in autumn may not glasshouses and polytunnels have all produced allow sufficient time for the recently rooted acceptable results. Bottom heat is not required plants to become established before winter. for summer propagation; however, shading is After insertion, the misting frequency essential for maintaining the turgor of cuttings. should be set quite high to prevent wilting, Maintaining light levels (total shortwave) at and the cuttings should be well shaded to about 3M Jnr2day_1 using Loach’s (1988) avoid excessive water loss. After rooting the shading scheme has produced successful cuttings should be weaned-off by reducing the rooting of even very soft tip cuttings. Further misting frequency and gradually increasing details on propagation systems and their man­ the ventilation around the cuttings. agement can be found in Hartmann, Kester and Davies (1990) and MacDonald (1986). Cuttings rooted in trays should be potted up as soon as possible after rooting to avoid the roots becoming too entangled. Cuttings Cutting preparation which have been rooted in containers should Softwood cuttings should be collected from be given occasional liquid feeds to maintain vigorous shoots on stock plants which are cut plant quality; however, too much fertiliser can back each winter. The cuttings are taken from promote excessive growth for the size of con­ current shoots and are usually 10-15 cm long tainer. and are cut just below a node; however cut­ The methods described here, while featuring tings as small as single-node cuttings can be poplars, can also be used for many other successfully rooted. It is very important to broadleaved species raised from cuttings taken prevent the cuttings from losing water before during the growing season, while tissues are they are inserted in the rooting medium; cut­ soft.

138 10.1.4 Aspen propagation from roots rows and lifted after one year to produce a Aspen (P. tremula L.) is a difficult species to usable plant. Cuttings with shoots shorter root using stem cuttings. However, it suckers than 50 cm are best transplanted and grown quite readily from the root system and this on for a further year. Sets are cut from shoots feature can be adapted by the nursery man­ on stools and are usually 2.5-3 m long. They ager to provide planting stock of desired ori­ are planted at spacings of 30-60 cm x gins (Hollingsworth and Mason, 1991). 60-90 cm and grown for 1 or 2 years according The simplest method is to dig up suckers in to size and growth rate or may be planted out the forest with a sharp spade, making sure direct into woodland. Many willows can also that sufficient root is recovered to support the be successfully propagated from softwood cut­ shoot. These suckers can then be potted up at tings and raised in containers. the nursery to grow on for a year before being planted out in the forest. The main problem is that this will only provide a small number of 10.2 Propagation of conifers plants. An alternative system involves the collec­ 10.2.1 Pr opagation facilities tion of roots from trees in the forest in late It is possible to root conifer cuttings in a tradi­ winter and bringing them to the nursery. The tional propagation frame with whitewashed roots are then cut into lengths of 15-30 cm glass and hand watering to maintain required and are placed in seed trays in a greenhouse levels of humidity. However, this is a labour in a sphagnum moss peat:vermiculite 1:1 mix­ intensive method which is generally not appro­ ture to promote suckers. The suckers are har­ priate for propagation of more than a few hun­ vested in early spring when 4—10 cm long, dred cuttings. Most commercial propagation of with a scalpel or sharp knife, by cutting just conifer cuttings takes place in polythene green­ above the point where the suckers leave the houses using some form of intermittent mist root. They are immediately inserted into a irrigation (Plate 24). In this propagation freely draining substrate in an intermittent system, the leaves are sprayed intermittently mist propagation unit. Up to 30 suckers may and are effectively cooled through the evapora­ be produced per metre of root. Cuttings root tion of the applied films of water (Loach, 1988). within 2-3 weeks, after which they should be The lowered leaf temperature reduces the potted up and grown on for the remainder of vapour pressure difference between the inte­ the season. It is quite possible to produce 1- rior of the leaf and the surrounding air, and so year-old plantable stock using this technique. restricts the rate of water loss from the cut­ tings and maintains them in a turgid condi­ 10.1.5 Willows tion. Under mist, much of the water that is lost Many aspects of the propagation of willows by evaporation is not internal tissue water but are similar to those used for poplars. Willows external applied water. can be planted as sets, hardwood cuttings or The essential features required in a mist rooted plants. propagation unit are the polyhouse, the mist Care must be taken not to mistake flower irrigation and controls, ventilation and some buds for vegetative buds. A substantial pro­ form of basal heating to promote rooting and portion of some current shoots of shrubby wil­ prevent frost damage. General details of mist lows may be occupied by flower buds, such propagation facilities can be found in a material being unsuitable for cuttings. number of standard horticultural texts (e.g. Hardwood cuttings are usually 20 cm long and MacDonald, 1986). The following comments 12-25 mm thick with a single healthy vegeta­ are specific to our experience with propagation tive bud about 1 cm from the top (White, of Sitka spruce and hybrid larch (Mason, 1990). Hardwood cuttings can be inserted 1989; Mason, 1992; Mason and Keenleyside, 30 cm apart within rows and 60 cm between 1988).

139 Any normal type of commercial polyhouse is are commercially available for producing suitable for propagating conifer cuttings. Both intermittent mist. Before making a final deci­ single and multispan houses can be used, but sion in favour of a mist system, the water the latter are to be preferred since they pro­ supply should be checked for pH, free lime and vide more constant air temperatures within mains pressure. A hard water supply (> 130 the house. Either a clear or a white polythene p.p.m. free CaC03) should be acidified using cover can be used; the latter will provide nitric acid injected into the irrigation water shade and will therefore reduce the risk of (Landis et al., 1989). A pressure of around scorch damage on unrooted cuttings. 50-60 p.s.i. is desirable to ensure a fine mist Additional shading may prove necessary spray with uniform distribution. The ideal during May-August to prevent high air and mist system should be sensitive to ambient leaf temperatures increasing the rate of water conditions and provide a variable frequency of loss and, if exceeding 30°C, also damaging the misting according to evaporative demand cuttings. within the house. There should be no mist applied overnight when humidity within the 10.2.2 Temperatures in the propagating house will remain at near 100%. house The target specification should be that 10.2.4 Fogging air temperatures within the house remain Alternative systems for propagating conifer between 5°C and 30°C; relative humidity cuttings include those based upon ‘fog’. should average 95% during rooting, but can be Fogging systems involve the creation of clouds reduced to 50-60% when the cuttings are of fine droplets less than 20 pm in diameter, weaned. For this to be achievable, the facility which hang within the polyhouse. This main­ must have some form of background heating to tains a stable, high humidity environment and prevent frost damaging the cuttings or the irri­ because less water is deposited on plants and gation system. High temperatures are normally growing medium, reduces the amount of controlled by forced air ventilation using fans, nutrient loss in the cuttings when compared and by shading. Fans should be set to come on with mist irrigation. Very good rooting can be at temperatures between 25. and 30°C. Damp obtained in a fogging unit. It is an expensive pads or similar devices should be placed over system requiring high pressures (> 100 p.s.i.). the louvres where the fan draws air into the At present fogging is probably best seen as a house. This prevents dry air being drawn into research tool or as a technique for rooting very the house and reducing the humidity to low, soft cuttings which would be prone to water potentially damaging levels. If a propagation stress, e.g. micropropagation material. facility is operating under very warm condi­ tions, there is always a trade-off to be made 10.2.5 Types of cuttings and time of between ventilating the house to keep the crop collection/insertion cool, and maintaining high humidity and leaf Two types of cutting are normally distin­ wetness to prevent the crop drying out. In this guished in conifers. Hardwood (winter) cut­ situation, shading can help by reducing inci­ tings are collected in early spring before the dent light intensity and the temperature build­ buds have broken; the cutting consists of up in the house. Attempts to cool a house by tissue laid down in the previous growing very frequent misting are often unsatisfactory season. Softwood or summer cuttings are since the rooting substrate may become satu­ taken in July when shoots are in active exten­ rated for long periods, creating anaerobic condi­ sion growth; the cutting consists of tissue laid tions at the base of the cuttings. down in the current growing season. Sometimes cuttings are taken in late August- 10.2.3 Mist September after resting buds have formed; A wide variety of irrigation control systems these are known as semi-hardwood cuttings.

140 Hardwood cuttings are generally favoured 10.2.7 Preparation and management of by commercial nurseries propagating conifers cuttings for forestry. The use of dormant material Cuttings are normally collected with secateurs reduces the risks of handling damage so that (Plate 25). These should have a scissor-type the cuttings can be safely cold-stored for short rather than the anvil type action to prevent periods before insertion. crushing of the shoots. Provided the material The normal size of cutting used is 8-10 cm. is juvenile, there is no need to strip the Both tip (i.e. with a terminal bud) and base needles, wound the base of the cutting or (no terminal bud) cuttings can be rooted. The apply rooting hormone in order to achieve latter are particularly useful in achieving high good rooting performance. Such techniques multiplication rates. It is important not to col­ are expensive and increase the cost of pro­ lect thin, wispy cuttings since these are easy ducing the cuttings. They are of use only to damage during insertion and produce poor where the nursery manager is attempting to root systems. build up stocks of a desirable genotype that is hard to root. 10.2.6 Management of mother plants Conifer cuttings can be successfully rooted Successful rooting of cuttings is influenced by in a wide range of substrates provided they nutrition of mother plants in the season before give adequate support to the cutting and good collection and insertion. Regimes should avoid drainage. The substrate needs to be adjusted the production of cutting material with either to the type and intensity of misting regime a very low or high nutrient status. The former being used. Thus, successful propagation are too deficient to root satisfactorily and the under a system where there are long bursts of latter too soft to handle easily. It is particu­ water applied at regular intervals will require larly important to maintain adequate nitrogen a coarser, better drained substrate than one status in the stock plants since this is an where misting is linked to evaporative important nutrient for both root initiation and demand. A substrate that has given good subsequent root development. The target results over a number of years is 1 part should be to maintain adequate nitrogen sphagnum moss peat : 1 part composted pine levels (see Fig. 4.1 and Table 4.8) throughout bark: 1 part perlite (special seed grade, the season before collection of cuttings. average size 1-3 mm) on a volume basis, all Nursery managers should maintain mother mixed together. plants of desirable genotypes in a juvenile Normal practice is to root conifer cuttings in state and collect cuttings over a number of trays of the rooting substrate or in rooting years. There are two ways of achieving this. beds. The former are generally easier to The first is to create a ‘hedge’ of mother plants manage. Assuming a crop of hardwood cut­ of the desired genotype. These are cut back tings is inserted in March, callus development annually to a height of about 25 cm above is seen at the base of the cutting in May with ground and allowed to grow back. Cuttings root initiation shortly thereafter. At this stage, are collected from this regrowth. The second the misting intensity should be reduced at reg­ method is to use ‘serial propagation’ where ular intervals as the cuttings develop self-suffi­ cuttings are collected from the previous crop of cient root systems. The first roots that develop cuttings (known as a ‘cycle’), this procedure are typically white and fleshy and are termed being repeated over a number of cycles. ‘water-roots’. These are brittle and easily dam­ Preliminary results have suggested that serial aged. An indication that propagation has been propagation is more effective than hedging in successful is when the roots turn brown and maintaining juvenility in Sitka spruce. fibrous, similar to those of a seedling. However, it is not yet clear whether either Fertilisers can be incorporated into the sub­ technique will maintain cuttings in a juvenile strate but this is probably of little benefit state indefinitely. unless the aim is to produce 1-year-old forest

141 usable material. Cuttings are generally inca­ and lined out into a bare-root nursery, and pable of taking up external nutrients until grown on for a further 18 months when the new roots have been initiated. A heavy cuttings should be 30—40 cm tall. At this misting regime will also leach nutrients out of stage, plants may either be used a source of the substrate before they can be taken up. further cuttings or they can be dispatched for Cuttings propagated under mist become forest planting. Blackwood (1989) has nutrient-deficient because of leaching of the describes a commercial two-cycle propagation foliage and of remobilisation of nutrients system of this type with a multiplication towards the rooting zone. For example, con­ factor per ortet of 400 usable rooted cuttings centration of N, P and K in Sitka spruce cut­ (see section 10.2.9 following). tings declined by 51%, 61% and 37% An alternative approach is to root the cut­ respectively, after 3 months under mist com­ tings in seedling containers of the type pared with initial values. described in Chapter 9. The advantage of this Once mist frequency has been reduced at technique is that handling costs resulting the start of weaning, regular liquid feeding from transplanting to the open nursery are should begin to restore the nutrient status of eliminated. In addition, plantable cuttings can the cuttings. Fertiliser should be applied be produced in one year, reducing the time either once or twice a week with a balanced taken to produce bulk stock for planting. NPK feed at concentrations of around Propagation in containers uses similar tech­ 200 p.p.m. N. niques to propagation in trays or rooting beds, The high humidity present in mist houses with one or two exceptions. These include can result in serious fungal attacks, particu­ incorporating a limited amount of small larly by Botrytis spp. Cutting material should prilled controlled release fertiliser in each cell be treated with an approved systemic fungi­ to boost growth after rooting. It is also neces­ cide 7-14 days before insertion. Once the crop sary to lift up the containers after rooting to has been inserted, the cuttings should be air-prune the cuttings and promote fibrous sprayed at weekly intervals as a prophylactic root development. measure. It is essential that different products be used in sequence to guard against a build­ 10.2.9 Sitka spruce vegetative up of resistance in the pathogen to a partic­ propagation ular fungicide. The crop should also be Facilities have been established in the period inspected regularly and any diseased material 1989-91 at the Forestry Commission nursery removed. Particular points to watch out for at Delamere, Cheshire, for large scale produc­ are disease developing on damaged tissue, or tion of vegetatively bulked up planting stock of under the bud scales of opening buds if they genetically improved Sitka spruce from limited do not fall off. Fungicide, fertilisers and any supplies of seed (Plate 27). other products should always be applied in the Table 10.3 gives details of the operations evening with the mist switched off for up to 12 involved. These are spread over a 6-year period hours after application. This will ensure that and involve three phases of production, each of the chemicals are absorbed, while the time of 2 years. application guards against any risk of scorch. Phase 1 starts with germination of the improved seed in small containers and inten­ 10.2.8 Production system sive growth of the resulting seedlings, potting The current method of producing rooted into larger containers during the first season conifer cuttings is to collect and insert the (Plate 28). Plants are grown on under an inten­ hardwood cuttings in March and to maintain sive regime and should be at least 1 metre tall them in the polyhouse until July-August. At by the end of the second growing season. At this stage, the bulk of the crop should be well this stage each seedling should be well enough rooted (Plate 26); the cuttings are then lifted furnished with side branches for the whole

142 plant to be cut up and yield on average 80 cut­ tion) commences in February/March at the tings per plant. All of this phase is carried out beginning of the fifth year and is similar to the in polyhouses, the larger containers being on first cycle rooted stock production. Plants are capillary sand beds. cut to yield the maximum number of cuttings Phase 2 (first cycle rooted stock production) and these are inserted into a mist propagation commences in February/March at the begin­ unit, rooted cuttings being lined out in July/ ning of the third year, when cuttings are August of the fifth year for growing on until taken. These are inserted into a mist propaga­ the end of the sixth season, when they should tion unit where they remain until July/August be suitable for forest planting. of that year, when the cuttings that are well At this stage, the plants will not look the same rooted are lined out in open nursery ground. as conventional transplants. The rooted cuttings No attempt is made to maintain the identity of do not have such well developed lower lateral the individual original seedling trees from branches as conventional stock, because they which the cuttings were taken. lack the ring of buds associated with the ter­ Lined out cuttings remain in the open minal bud of a 1-year-old seedling. Some needles ground for the remainder of the year of which developed while cuttings were rooting may planting and all the following year. By this also be smaller than usual, reflecting the effect of time, they should have grown to the size of diversion of nutrients from shoot to root growth conventional forestry planting stock. Each at that time. These differences should be pointed plant should be big enough to yield about 9-10 out to potential customers with the assurance cuttings per plant. that the genetically improved stock will grow Phase 3 (second cycle rooted cutting produc­ better than plants from unimproved seed.

Table 10.3 Standard two cycle propagation system for Sitka spruce (source, Mason 1992)

Stage Year Month Operation Comments

February/March Seed stratification 3 -4 weeks moist prechilling at 2°C.

March/April Sow seed 1 seed sown per cell in containers (100-200 ml cell capacity). Container substrate is sphagnum moss peat:vermiculite 3:1 by volume with Ficote 70 16:10:10 at 1.5 kg n r3, ground limestone at 1 kg n r3, magnesium limestone at 2 kg n r3 and fritted trace elements at 0.3 kg nv3.

April—July/Aug Germinate and Maintain seedlings in a polythene greenhouse under natural grow on seedlings daylength at target temperatures of 20/15°C day/night with permitted maxima/minima of 30/5°C. Supplementary weekly liquid feeding using balanced NPK at 200 p.p.m. N will be necessary in July and August.

July/August Pot on seedlings This should be done when seedlings are about 15 cm tall. for stock plants Pot seedlngs into 4-litre containers with substrate of sphagnum moss peat:ground pine bark:grit in 6:3:1 ratio by volume. Incorporated basal fertiliser of Osmocote 18:11:10 (0-9 months) at 3 kg n r3, ground lime at 1.2 kg n r 3, magnesium limestone at 2.4 kg n r 3 and fritted trace elements at 0.3 kg rrr3. The role of the bark is to keep the substrate open and to provide a buffer against sudden release of nutrients in high temperatures. No liquid feeding should be required until May/June of year 1.

0-1 August-May Grow on stock Maintain polythene greenhouses frost-free overwinter. Keep plants plants spaced out so that laterals do not touch. Keep stock plants in polyhouse.

143 Table 10.3 continued

Stage Year Month Operation Com m ents

May Pinch out leaders This is best done with the fingers to prevent damage. Any and side-shoots plants of poor form should be culled out. of stock plants to promote branching

May/June-Sept Stock plant Feed up to twice weekly throughout the period of active growth management (target (late May-August) using a high N product (e.g. NPK 2:1:1) at is plants up to 200-250 p.p.m. N. Change to NPK 1:1:1 weekly feeding at 100 cm tall) 200 p.p.m. N in September and October. Feed to run-off to ensure that substrate is at correct nutrient balance. Target nitrogen levels in foliage should be > 1.5% dry weight. Use a con­ ductivity meter for monitoring leachate. Water plants regularly (i.e. daily) especially during warm conditions. Respace plants at inter­ vals to ensure laterals do not touch and cutting quality is maintained. 1-2 October-Feb Overwintering stock Can be done either in a frost free polyhouse or plants can be overwintered outside. If the second option is taken, the plants must be transferred outside before October to guard against early frosts. Roots may have to be protected against freezing temperatures. February/March Prepare to collect Spray all plants with a systemic fungicide (e.g. 0.1% thio- first cycle cuttings phanate methyl) 14 days before collection to guard against Botrytis infection.

10 February/March Collect first cycle A standard length of 8 (±2) cm is used. Both tip (with terminal bud) cuttings and base (no terminal bud) cuttings are collected. Only collect from wood laid down in the previous year (i.e. year 1). Minimum diameter of cuttings should be c. 2 mm (i.e. cuttings should with­ stand gentle bending between thumb and forefinger). Keep cut­ tings cool and shaded after collection. They can be cold-stored (+1°C) in polythene bags for 2-3 weeks without damage. 11 March Insertion of cuttings Insert to 3 cm depth in seed trays or similar that are 7 cm deep. Ideal spacing between cuttings is 4 cm, but 3 cm is acceptable. Seed trays should be placed on rooting benches or on fine sand. This prevents waterlogging at the base of the medium. Substrate should have an air filled porosity of >15%. Sphagnum moss peat:pine bark:grit (2-3 mm) or perlite in a 1:1:1 ratio by volume is our preference, but other alternatives are acceptable if they pro­ vide support and maintain good drainage. No rooting hormone is applied before insertion; stripping of basal needles is also unnecessary. No fertiliser is incorporated in the substrate. 12 March-June Propagation of Rooting trays are placed in a mist propagation unit under natural first cycle cuttings daylength. A white polythene cover or other shading is desirable to diffuse direct sunlight and reduce the risk of scorch. Target rel­ ative humidity levels are 90-95% during daylight hours. Peak misting frequency is a 5 s burst every 1-2 min. Mist frequency should be controlled by a device linked to ambient evaporative demand. Use fan ventilation to keep temperatures < 30°C. Fans should have moist pads on the outside to prevent dry air being sucked into the house. Fungicides are applied weekly in rotation to prevent Botrytis attack. Apply fungicides (and fertilisers) under dull conditions or in late evening to avoid scorch. Switch off the mist for 6-12 h after application. Start of callus initiation at base of cuttings 6-10 weeks after insertion.

144 Table 10.3 continued

Stage Year Month Operation Comments

13 2 June/July Weaning of cuttings After 50-70% of the crop has root initials, mist frequency should be reduced at weekly intervals until only one or two waterings per day are required. Burst length is increased so that there is a ‘watering’ rather than 'misting' regime. Raise trays of rooting plants to promote air pruning and encourage root proliferation within the tray. Start liquid feeding once weaning has begun, to counteract nutrient leaching during propagation. Use a 1:1:1 NPK feed at 200 p.p.m. N applied at 4 litres solution n r2 twice a week. Weaning is near completion when white fleshy roots ('water roots’) have been transformed into brown fibrous roots.

14 2 July/August Lift and line out Cuttings should be lined-out in a bare-root nursery using standard cuttings lining out machinery. Space at 10 cm (50 plants m~2) within rows to encourage branching. Apply normal basal fertilisers before lining out. Discard any poorly rooted or misshapen cuttings before lining out.

15 2/3 August-May Care for lined out Lining out should occur early enough so that cuttings make new cuttings root growth to guard against risk of frost lift. Normal herbicide regimes after lining out.

16 3 May-October Maintenance of Apply a balanced 1:1:1 feeding regime to provide around 100 kg lined out cuttings of elemental N ha-1 over the growing season. If possible apply (target is plants little and often to maximise height growth and yield of second 40-50 cm tall) cycle cuttings.

17 3/4 October-Feb Overwi ntering

18 4 February/March Collect second Attempt to collect as many tip cuttings as possible to guard cycle cuttings against risks of double leaders from basal cuttings.

19 4 March-July/Aug Propagation and Regimes are identical to first cycle. weaning of second cycle cuttings

20 4 July/August Line out second As for first cycle except that spacing is now 5 cm cycle cuttings ( = 100 plants n r 2).

21 4/5 August-May Maintenance of As for first cycle. lined out cuttings

22 5 May-October Culturing of cuttings One-two light top dressings of N (25 kg elemental N ha-1 in total) for forest planting before undercutting at 8 cm in July. Follow by fortnightly or (target is plants 3-weekly wrenching until end of growing season. Apply additional 25-35 cm tall) N and K to maintain nutrient status. Total of 50-75 kg of elemental N ha-1 over season.

23 5/6 Nov-March Lifting of cuttings, Remove any double leadered plants. Plants with slight (up to grading and dispatch 15-20°C deviation from vertical) stem bend are acceptable. Otherwise treat as normal forest planting stock.

24 6 Spring Forest planting

Notes: An alternative stock plant regime is to replace stages 4-8 inclusive with one where the stock plants are potted on in outdoor raised beds. These beds are 30 cm high and 1 m wide with a substrate of sphagnum moss peat:composted pine bark:grit in 1:1:1 ratio by volume. 16-18 month Osmocote 16:9:9:3 (Mg) is added at 4 -6 kg n r3, ground lime­ stone at 3.0 kg n r 3, and trace element frit at 0.3 kg n r3. Plants are spaced at 25 cm within and between rows. Target stock plant height is 50-75 cm. This system will give a lower yield of cuttings (30-40 per plant) compared with the standard polyhouse regime (60-70+ per plant) but it is less demanding on maintenance, especially watering.

145 Production areas stock, production is an ongoing rolling process, The following figures provide an approximate so that at any one time, there will be crops at working guide to the numbers of plants and each stage of growth. To maintain this scale of size of propagating facilities required to pro­ sustained production, approximately 500 m2 of duce and sustain an annual production of 1 capillary house for seedling production, and million rooted cuttings of genetically improved 4200 m2 of mist propagation house are origins, suitable for planting in the forest, required. However, because there is an based on a 6-year production cycle. inevitable build-up over the first 5 years, the The numbers are very dependent on the capital investment in facilities can be spread success of rooting of cuttings and achieving over 4 years, the larger part of the mist unit good survival in transplant lines. The factors requirement only coming into use at the shown are averages based on limited experi­ beginning of the fifth year. ence; a few minutes spent on the same Production implications of any changes in sequence of calculations using other factors technique involving cutting spacing or addi­ immediately illustrates the importance of tional time spent in polyhouses when space is striving for reliable high rooting percentage of already fully allocated have to be carefully cuttings and high percentage survival and examined if the system is not to be disrupted. growth following transplanting. Nevertheless, there are obvious advantages in shortening the production time period so that Production planning for 1 million rooted developments to that end should be expected plants suitable for forest planting - the 6-year at some time. production cycle 1st year • Seed to yield 2300-2500 seedlings; 4000 10.3 Overview and future seeds should be sufficient, sown 1 seed per developments 100-200 ml capacity cell. It seems likely that vegetative propagation of • Space in capillary bed house to accommo­ tree species will continue to increase in impor­ date 2500 seedlings potted on into 4 litre tance as more superior genotypes are identi­ containers, maintained so that the plant fied by tree breeding selection and testing laterals do not touch. programmes. More species are likely to be 2nd year propagated by cuttings, including selected Space to provide same specification as previ­ clones of the major broadleaves. As propaga­ ously (but plants larger). tion techniques continue to improve, one can expect that the differences in price between 3rd year cuttings and seedlings will become less. The • Mist propagation area to accept 190 000 use of vegetative propagation may become as (180 000-200 000) cuttings. important in forest nursery practice as it has • Lining out area to accept 170 000 rooted in other areas of horticulture. cuttings. 4th year 10.3.1 Micropropagation Space to grow transplants on. An allied technique that is becoming increas­ 5th year ingly important is micropropagation. This • Mist propagation area to accept 1400 000 technique uses small pieces of tissue such as cuttings. excised shoot, embryos or cells. The tissue is grown on a medium, usually containing • Lining out area to accept 1250 000 rooted growth promoting substances, in sterile condi­ cuttings. tions in a test-tube or similar container. The Once committed to this type of planting micropropagule proliferates shoots which are

146 then subdivided to yield further material in a S.E. and BARNETT, J.P. (1989). Seedling multiplication cycle. It may prove possible to nutrition and irrigation. Vol. 4 of The con­ multiply the selected genotypes by up to 1000 tainer tree nursery manual. Agriculture times in a year using these techniques. Handbook 674. US Department of Micropropagation can be used to mass produce Agriculture, Forest Service, Washington, stock plants of selected genotypes which are DC. (119 pp.) then repropagated by stem cuttings. This com­ LOACH, K. (1988). Controlling environmental bination of techniques makes it possible to see conditions to improve adventititous rooting. the advent of combined macro and microprop­ In Adventititous root formation in cuttings, agation systems which mass produce selected eds Davies, T.D., Haissig, B.E. and clones for intensive production forestry (John Sankhla, N. Dioscorides Press, Oregon, and Mason, 1987). A similar type of system is 248-273. already being used in horticulture to mass MacDONALD, B. (1986). Practical woody produce desirable cultivars of Rhododendron plant propagation for nursery growers. and other woody plant species. Batsford, London. (669 pp.) MASON, W.L. and GILL, J.G.S. (1986). Vege­ tative propagation of conifers as a means of REFERENCES intensifying wood production in Britain. BLACKWOOD, C.H. (1989). Large scale pro­ Forestry 59 (2), 155-172. duction of genetically improved Sitka MASON, W.L. and KEENLEYSIDE, J.C. spruce by stem cuttings. Forestry 62, (1988). Propagating Sitka spruce under (suppl.), 207-212. intermittent mist and other systems. DAVIES, T.D., HAISSIG, B.E. and SANKHLA, Combined Proceedings International Plant N. (eds) (1988). Adventitious root formation Propagation Society 38, 294-303. in cuttings. Dioscorides Press, Oregon. MASON, W.L. (1989). Vegetative propagation HARTMANN, H.T., KESTER, D.E., and of hybrid larch (Larix x eurolepis Henry) DAVIES, F.T. (1990). Plant propagation: using winter cuttings. Forestry 62, (suppl.), principles and practices. 5th edn. Prentice- 189-198. Hall, New Jersey, USA. MASON, W.L. (1992). Reducing the cost of HOLLINGSWORTH, M.K. and MASON, W.L. Sitka spruce cuttings. In Super Sitka for (1991). Vegetative propagation of aspen. the 90s. Forestry Commission Bulletin 103. Forestry Commission Research Information HMSO, London, 25^41. Note 200. Forestry Commission, Edin­ POTTER, C.J., NIXON, C.J. and GIBBS, J.N. burgh. (1990). The introduction of improved poplar JOBLING, J. (1990).Poplars for wood produc­ clones from Belgium. Forestry Commission tion and amenity. Forestry Commission Research Information Note 181. Forestry Bulletin 92. HMSO, London. Commission, Edinburgh. JOHN, A. and MASON, W.L. (1987). Vegeta­ WHITE, J.E.J. (1990).Propagation of lowland tive propagagtion of Sitka spruce. Pro­ willows by winter cuttings. Arboriculture ceedings of the Royal Society of Edinburgh Research Note 85/90/SILS. DoE Arbori- 93B, 197-203. cultural Advisory and Information Service, LANDIS, T.D., TINUS, R.W., McDONALD, Farnham, Surrey.

147 Chapter 11 Irrigation

J. R. Aldhous

Introduction 11.6 How much water to apply and how often. Application of water by irrigation to promote survival and growth in dry periods is simple In these latter sections, water use is in concept. However, in order to use water expressed in terms of ‘precipitation equiva­ effectively, it is desirable to have some under­ lent’, i.e. the amount of rainfall or water that standing of the physical processes that may be applied through irrigation, in terms of underlie current practice in the UK. These depth of water per unit area of land. are, unfortunately, complex, both in them­ selves, in their interaction and in their mea­ surement. There is no easy, universally 11.1 Energy and water demand applicable means of estimating the day-to-day water requirements of crops. The literature on 11.1.1 Solar energy the subject is voluminous, much of it devoted to attempts to identify ‘indicators’ that are readily measured and can be used to predict Evapotranspiration when and how much irrigation to apply. Solar energy provides the driving force, The transfer in 1990 of responsibility for directly or indirectly, for all water movement water supply, to public companies owned by from the earth’s surface to the atmosphere. shareholders, and at the same time the Studies in the early part of this century on increasingly stringent standards set for water crops in arid and semi-arid regions showed a quality within the European Community, have good relationship between crop yield and not yet had an obvious effect of availability or water transpired by the crop (Vaux and Pruit, cost of water for crop irrigation. However, such 1983); these formed the basis for the first sci­ effects cannot be ruled out for the future. entific approaches to irrigation practice. The sections following outline the more However, it was H. L. Penman who estab­ important theoretical and practical points lished and first developed the concept of affecting current irrigation practice. The first ‘potential evapotranspiration’ and provided a three sections focus on ‘potentials’, i.e. the ten­ basis in mathematical physics for relating sions or suction pressures that may develop in solar energy to water loss by evaporation from relation to plants and water. the soil and transpiration from plants. His prediction of ‘potential evapotranspiration’ 11.1 Energy and water demand. required estimates of temperature, vapour 11.2 Soil water. pressure, wind-run and sunshine-hour data, 11.3 Water tension in plants. but also included some assumed constants. The next three sections cover the main Since his first publication (Penman, 1948) a practical issues in managing irrigation. substantial number of variants or alternatives 11.4 Planning for irrigation. have been proposed (e.g. Monteith, 1965; 11.5 Irrigation equipment. Monteith and Unsworth, 1990). Some incorpo-

148 Plate 18. Rigipot containers. Plate 19. Rootrainers.

Plate 20. Japanese paper pots.

Plate 21. Oak seedlings growing in containers in a polyhouse. (R.L. Jinks) Plate 22. Rootrainers on carrier frames ready for removal by fork-lift to houses. In background, machinery for filling containers. (J.R. Aldhous)

Plate 23. Trays of Japanese paper pots being automatically sown by vacuum sower. (E9801)

Plate 24. Double span polytunnel with benches of rooting Sitka spruce cuttings; fixed overhead mist irrigation pipes. (E 8823) rated refinements to the physics underlying Soil surface reflectance the equation but made the calculation more A proportion of solar energy falling on ground difficult; others simplified it to make it easier and ground cover is reflected. Once the ground to use in practice, but introduced further is fully covered with uniform vegetation, this assumptions that restricted the general factor varies little. However, while exposed, applicability of the simplification. the colour of the soil surface affects the Penman assumed that all vegetation would amount of solar energy that is reflected, behave like a grass sward; however, it is now lighter colours being the better reflectors. In clear that the structure and in particular, the the nursery, the only real choice available to roughness (aerodynamic resistance) of the managers is in the colour of the seedbed grit. crop surface itself affects evapotranspiration Lighter colour grits have been shown to be so that different constants are required, for cooler at the soil surface than dark grits in hot example for grass and lucerne, and some quite weather, the difference often being critical to different assumptions are required for high seedling survival; see Chapter 6, Table 6.4. If forest because of the volume of water inter­ irrigation is required to maintain seedbed cepted by foliage. moisture and reduce surface temperatures Nevertheless, the estimation of crop evapo­ during hot weather, lighter colour grit is likely transpiration, modified to greater or lesser to be advantageous. extent for specific conditions, underlies many practical irrigation schedules (Batchelor, 1984; Doorenbos and Pruit, 1977; Penman, 11.1.2 Temperature 1986; Stewart, 1983). Air temperature records, mean, maximum and minimum, wet and dry bulb, are essential pre­ Percentage ground cover requisites for the calculation of evapotranspi­ The first calculations of evapotranspiration ration. assumed a full crop cover; modifications have subsequently been made so that ‘reduction fac­ An independent second approach to pre­ tors’ can be applied, to take account of incom­ dicting irrigation needs can be made based plete ground cover in the early stages of many solely on temperature and humidity. This crops. Even so, few agricultural or horticultural follows from the situation that at any given crops cover the ground as sparsely for so long in temperature, if the air is fully saturated the season as young conifers; evaporation from with water vapour and the leaf temperature the soil surface is relatively more important in is not higher than the air temperature, no forest nurseries than in crops that cover the further evaporation or transpiration can ground early in their development. take place, and that the drier the air, the While the soil surface is moist, evaporation greater the transpiration from a crop. rates from foliage and soil are similar. Transpiration can be estimated from the However, once the soil surface is dry, corre­ water vapour pressure potential, or vapour sponding to a ‘soil moisture deficit’ of about pressure deficit, i.e. the drying power, of the 12 mm, soil surface evaporation falls (see air around plant foliage. p. 151). After sowing and in the early stages of Provided the initial calibration has been seedling growth, there may be little or no done, plants’ water requirements at any time ground cover by vegetation; similarly, after can be estimated from the current air temper­ transplanting and sometimes after undercut­ ature and the vapour pressure deficit of the ting, there is nothing like a full ground cover air. These enable an estimate to be made of by the crop. Deciding the appropriate the foliage temperature for plants well sup­ allowance for such incomplete cover is central plied with water; comparison with the actual to rational water use. Estimated values for foliage temperature provides a basis for nursery crop types are given in Table 11.3. assessing water need (Idso, 1982, 1983).

149 11.2 Soil water Field Permanent c a p a c ity wilting point A number of systems for assessing and Available water preparing irrigation schedules have been ■____ based on the relationship between water in the soil and crop growth. They work on the assumption that if the soil is always reasonably moist, healthy plants will not suffer from lack of water. Monitored changes in soil moisture provide indirect esti­ mates of the current water balance, i.e. precipitation - evapotranspiration - drainage - runoff, and can be used either as an immediate basis for irrigation prescriptions or as a check on water balance sheet calculations from weather data and records of water applied. Assessment of soil water involves the con­ cepts of: Soil moisture tension (bars)

• Soil water tension/matric potential; A Readily available water (under low stress) • Soil water content B Residual available water (under high stress) - field capacity, C Water too tightly held in soil to be available to plants - permanent wilting point, - available water capacity, Figure 11.1 Relationship between soil moisture - soil saturation. content, soil moisture tension (matric potential), availability of soil water and soil texture. 11.2.1 Soil water tension/matric potential through the soil in response to differences in Water in a drained soil is held in films matric potential. enveloping soil particles. Such water is under For any given soil, there is a direct relation­ tension (or ‘matric potential’ or ‘matric suc­ ship between soil water tension (matric poten­ tion’). This is the result of the interaction tial) and soil water content (Figure 11.1). within the soil of: However, the relationship will only be the • gravitation, same for soils of very similar soil texture char­ • surface tension in water films enveloping acteristics. soil particles, and • suction forces, or potentials, arising from 11.2.2 Soil water content/soil moisture evaporation from the soil surface and tran­ content spiration from plant foliage. The amount of water in a soil at any time is most commonly expressed as a volume per­ These forces affect the whole of the soil centage of the volume of soil (volume/volume water and provide the potential for water to or v/v). Less frequently, it is expressed in move through the soil to replace evapotranspi­ terms of percentage by weight (w/w). ration losses. Consequently, soil water is under a tension which varies continuously, depending on the scale of water loss through evapotran­ Field capacity spiration, the extent this is replaced by This is defined as the amount of water incoming water from irrigation or natural rain­ remaining in a freely draining soil 48 h after fall and the rate at which water can move the soil has been saturated, e.g. by prolonged

150 heavy rain. Under these conditions, a ‘soil Table 11.1 Typical available water capacities of moisture tension’ or ‘matric potential’ of 10.05 some common soil textures in approximately bars develops. ‘Field capacity’ is however not a increasing order completely stable constant. On heavier soils, natural gravitational drainage is slow and can Available water capacity Soil texture continue for several weeks, so that 48 h esti­ Low: not more than 12.5% by volume Coarse sand mates of field capacity following saturation Loamy coarse sand include some short-term stored water which is Coarse sandy loam absent when the soil is slowly rewetted until the moisture tension equivalent to field Medium: >12.5 and <20% by volume Sand capacity is reached (Parkes et al., 1989). Loamy sand Fine sand Loamy fine sand Soil moisture deficit (SMD) Clay The SMD is the difference between the soil Clay loam Sandy loam water content at ‘field capacity’ and the soil Loam water content at any given time. It is usually expressed in terms of ‘precipitation equiva­ High: >20% by volume Very fine sand lent’ (see last paragraph of the introduction to Silt loam this chapter). Peaty soils In this list, available water capacities are reduced where Permanent wilting point (PWP) there is: high stone content; appreciable compaction; reduced PWP is the condition of the soil where healthy organic matter. plants can extract no more moisture from the soil; consequently they wilt and do not recover For full list, see MAFF Reference Book 138 (MAFF, 1981). overnight. PWP corresponds to a soil moisture tension/matric potential of approximately 20 able water capacity’ of a soil is available at a bars. As soil moisture tension increases matric tension of 1 bar or less. While such beyond 1 bar, plant growth may slow because water continues to be available, plants are of restrictions in water supply. See also sec­ under low moisture stress and are not checked tion 11.3.1 ‘Diurnal variation’. in growth. Such water is referred to subse­ quently in this Bulletin as ‘readily available soil water’. As moisture tensions exceed 1 bar, Availability water capacity (AWC) while moisture is available, the stress within The water available to plants is the difference the plant increases. in water content between the soil at ‘field Examples of estimates of available water and capacity’ and ‘permanent wilting point’. Soil readily available water for different soil depths texture determines the quantity of water are given in Table 11.2. It should be noted that within this range (see Table 11.1 and Fig. 11.1). for the extreme cases shown here, there are At one time it was believed that all the noticeable differences between the amounts of ‘available’ water in soil was equally available ‘readily available water’ and the residual avail­ to plants and that plants would grow at a able water, the coarsest texture soil having little steady rate as long as there was some ‘avail­ water left once all the readily available water able’ water. Re-examination of early data has been used. See also ‘droughtiness’ in the showed that in most cases this was not so and immediately following subsection. that growth was affected by the extent of Irrigation regimes based on assessment of water depletion (Stanhill, 1957). water depletion are often designed to replenish ‘readily available soil water’ when Readily available soil water the ‘available water capacity’ is calculated or For most soils, approximately half the ‘avail - is found by measurement to have fallen to

151 Table11.2 Water availability in surface soil down to 30 cm depth

Soil texture Available water Readily available soil water Residual available capacity per 10 cm (i.e. available at 0.0 5-1 bar matric potential) water per 10 cm depth of soil depth of soil In soil-depth per 10 cm depth of soil 10cm 20cm 30 cm

Loamy coarse sand 12 8 8 16 24 4 Sandy loam 16 10 10 20 30 6 Fine sandy loam 20 12 12 24 36 8

Units are mm precipitation equivalent per unit area.

50%, or measurements of 1 bar matric poten­ • low average rainfall at the time of year tial are being obtained. Prescriptions for irri­ water is most needed by crops, gation regimes based on readily available soil • growth of crops with large water require­ water are given in Table 11.3. ments, or varying combinations of all factors. The Droughtiness concept has been used for agricultural land as Droughtiness expresses the risk that readily the basis for land classification and for available soil water reserves are used up by assessing the worthwhileness of irrigation. the crop or lost by evaporation before they are It will be seen from Table 11.2 that the replaced by precipitation. Droughtiness may coarsest texture soil has the least ‘readily arise from: available soil water’ per unit depth, will run • small water storage capacity due to soil tex­ out of readily available soil water more ture, quickly and is therefore more ‘droughty’ than

Table 11.3 Forest nursery crop irrigation prescriptions, reduction factors for incomplete crop cover and acces­ sible soil depths for sandy soils

Reduction Crop Accessible Ground factor for Irrigation prescribed based on type soil depth cover partial calculation of soil moisture deficit (SMD) (cm) (%) crop cover using reduction factor

Newly sown seedbeds 5 0 0.5 If SMD >6 mm immediately after sowing, apply 6 mm, then 6 mm whenever SMD reaches 6 mm. After end of June, use mid-season regime.

Newly lined out seedlings 10 10-20 0.6 If SMD >10 mm immediately after lining out, apply 10 mm and repeat whenever SMD reaches 10 mm until 8 weeks after lining out, then use mid-season regime.

Newly undercut 8-10 20-100 0.5-1 If SMD >10 mm, 10 mm immediately after seedlings depending on density undercutting, and repeat whenever SMD of ground cover reaches 10 mm, until late in the season.

Mid-season 30 30-80 0.7 for 1st year 15 mm whenever SMD exceeds 15 mm. 0.9 for 2nd year

152 soils with greater readily available soil water face subsequently dries, a dense crust forms at capacities. the soil surface which slows the rate of water Irrigation regimes on the droughtier soils infiltration and, where no seedbed grit has need to be more frequent and less in quantity, been applied, may also inhibit seedling emer­ even though the same volume of water is gence. applied in the end. Applying relatively small amounts of irrigation at less than 7 day inter­ 11.2.3 Measurement of soil water vals is sometimes referred to as ‘high fre­ Water in the soil has been measured in terms quency irrigation’ (Hobbs and Krogman, of: 1978). It requires a mechanised system that • weight, can be moved round the nursery efficiently. • the tension under which it exists at any given time, Available water capacity and machine access • percentage of the soil volume. The disadvantage that is often associated with Weighing less droughty soils, is that such soils not only retain more water but are also slower to drain, Earliest measurements of soil moisture con­ more easily affected by compaction and may tents were by weighing, drying and reweigh­ not be so quickly available for machine access ing. The technique remains valid, provided the after periods of rain, especially in the winter. conditions for drying are standardised. The It should be noted that in Table 11.1 the AWC results however may overestimate the water of very fine sandy soils is higher than for available to plants. many loams and clays. Consequently, on soils Weighing is of most use when used to which though sandy, have a high proportion of assess the change in weight of a sample, with fine sand, a particularly close watch should be a view to restoring its original weight by kept for the development of cultivation pans watering, e.g. plants grown in special con­ and immediate steps taken to loosen any com­ tainers (lysimeters), or modules such as trays paction at the first opportunity. of seedlings in Japanese paper pots when growing in polytunnels. In this second situa­ tion, there is in fact little or no soil in the Soil saturation growing medium and it is the loss from the Soils are ‘saturated’ when all the available medium itself which is being monitored (Lane, pore spaces between soil particles are filled 1989). with water. As soil water drains under the force of gravity, the emptying pore spaces Measurement o f soil moisture tension / become filled with air until ‘field capacity’ is matric potential reached. Soil moisture tension can be measured by ten- siometers consisting of a porous ceramic con­ ‘Slaking’ tainer filled with water connected either While soil surface layers are saturated, and directly to a water-operated, or indirectly to a especially if the soil is being bombarded by piezo-electric, pressure gauge. The most up-to- heavy raindrops or large droplets from an irri­ date designs are less cumbersome than earlier gation system, there is a risk that soil parti­ models, with hydraulic circuits which auto­ cles will be loosened and moved; any soil matically vent any air entering the system. structure or aggregates left after cultivations They are used on a small scale in farms in the may collapse under the impact and ‘slake’, i.e. UK (MAFF, 1981); in the US, they control irri­ particles will slump into the larger air chan­ gation schedules in container-grown plants nels and block them. Where this happens, the (Burger and Paul, 1987; Lieth and Burger, infiltration rate drops; often when the soil sur­ 1989).

153 A portable tensiometer has been developed able to move in and out of tissues by osmosis, which by careful pushing at a shallow angle i.e. the property of water to pass through a into the soil and taking care not to change the semipermeable membrane from a solution of angle while doing so, can give an indication of low salt concentration to one of higher concen­ the water status in the surface layers of newly tration. Plants may also move water through germinating seedbeds and recently lined out cell tissues expending energy to do so. transplants. Consequently, some plant cells regularly Electrical resistance blocks made of porous develop positive pressures, e.g. to maintain materials have been widely tested as a means turgor, while within the main water-con- of estimating matric potential but have not ducting tissues, water may be under consider­ been sufficiently consistent in operation to able tension. come into general use (Duryea and Landis, High tensions (or potentials) within leaf tis­ 1984). sues may lead to closure of stomata on leaf surfaces and reduction of the rate of water loss. One consequence of such closure is that Estimation o f soil water content by foliage temperature rises to equal or exceed neutron probe that of the surrounding air. (As long as water Soil moisture content can be measured using is evaporating through transpiration, temper­ neutrons from a low grade radioactive source. atures should be a few degrees below that of Aluminium tubes are inserted into the soil the surrounding air.) A second consequence is wherever soil moisture is to be determined; that the gas exchange essential for photosyn­ the neutron source is lowered down each tube thesis is prevented. Stomatal closure is, how­ when a measurement is required. Neutrons ever, a very late response to moisture are reflected by hydrogen ions, the amount of shortage. neutron reflection recorded being directly pro­ portional to the water content of the soil. 11.3.1 Diurnal variation The system has to be calibrated for any Plants cannot avoid being exposed to a particular site and is mostly used as a check repeated diurnal cycle of changing atmos­ on the effectiveness of irrigation regimes pheric vapour pressure deficits, reflecting the based on evapotranspiration, rather than as temperature and humidity of air as it changes the primary basis for prescription. It is not through 24 h. On many days, this deficit suitable for measurements in the top 25 cm of reaches its maximum for a period from late soil. morning to mid-afternoon and falls to zero Proper precautions must be observed when overnight. handling the equipment; nevertheless, the Water tension in plants follows a similar technique is utilised commercially in the UK diurnal pattern, but with a time lag. In hot by specialist enterprises offering irrigation weather, water may be transpired at a greater prescription services (SAC, 1991). rate than can be supplied by the roots so that foliage wilts during warm afternoons. How­ ever, as long as there is water available in the 11.3 Water tension in plants soil and plants remain healthy, they will In the same way as moisture moves in the soil recover unharmed. This temporary wilting is in response to naturally occurring physical not a sign that the soil is at ‘permanent forces, water movement in plants is a wilting point’. response to tensions generated at the tran­ Currently, schemes for controlling irrigation spiring surfaces of plant tissue and resis­ schedules take no account of diurnal variation tances in the soil and stem water conducting except where there is a risk of damage to tissues. plants by high temperatures at the soil surface In addition, however, in plants, water is and irrigation is applied for its cooling effect.

154 11.3.2 Measurement of water tension in • long-term rainfall, temperature and wind, plants etc., for the site, both values (average and range) and distribution during the growing Pressure chamber or pressure ‘bomb’ season so as to estimate potential net water Water tension in leaves - normally referred to loss from the nursery (section 11.4.4); as ‘leaf water potential’, may be measured by • availability of water and the scale of provi­ placing detached leaves in a ‘pressure sion of sprinklers, pumps, reservoirs/bore­ chamber’ where pressure is applied up to the holes, pipework, etc. (section 11.4.5); point that water is forced out of exposed con­ • soil texture and structure, and the local ducting tissue, counteracting the tension topography (section 11.4.6); within the leaf (Ritchie and Hinckley, 1975). • the estimated profitability of investment in The technique can be used to test not only the irrigation (section 11.4.7). water status of plants in relation to irrigation, but also in relation to storage and handling shortly before despatch from the nursery. 11.4.1 Crop water requirements Water tension measurements on NW Irrigation is currently applied in forest nurs­ American conifers have been made in a eries to prevent or relieve plant moisture number of regions, particularly, New Zealand, stress: where the pressure chamber technique is now • in germinating seed immediately after considered fast, reliable and accurate (Cleary sowing, especially where the seed has been and Zaerr, 1980). treated by moist prechilling; In the UK, pressure bombs have been used • when seedlings are transplanted during the to assess effects of undercutting - the results growing season; given in Figure 8.1 were obtained by this • when seedlings are undercut during the method. However, it is not in routine use in growing season; nurseries. • during the growing season in periods of dry weather. Relative humidity at plant surfaces In each situation, how much water to apply Methods exist for assessing water tension in and when to apply is determined by esti­ plants by measuring the relative humidity at mating current evapotranspiration rates and the surface of plant leaves, or at the surface of soil moisture deficit, and relating these to the stem tissues from which the epidermis has particular requirements of the crop and soil at been removed. Currently, these techniques can the time, as described in section 11.6.1 below. be applied to horticultural crops but not yet to Irrigation may also be required: forest plants (McBumey and Costigan, 1982). • to ensure top dressings of fertiliser are washed into the upper layers of the soil; 11.4 Planning for irrigation • to assist the action of herbicides, where appropriate; When considering the possibility of installing • to reduce the risk of damage by unseasonal irrigation for open nursery ground, several frost; groups of factors have to be taken into • to cool the seedbed surface in periods of account: very hot weather to prevent heat damage. • crop water requirements in dry weather, forecast from plans for the scale of future For these operations, empirical prescriptions cropping; these should include forecasts of are applied, as described in section 11.4.3. aggregate and peak seasonal demand, and demands arising from other operations 11.4.2 Irrigation prescriptions, crop requiring water, e.g. application of fer­ cover and soil depth tilisers, frost protection (sections 11.4.1-3); Table 11.3 (p. 152) gives recommendations for

155 irrigation for various crop stages, values for ings can be washed into the soil using irriga­ the percentage of the ground covered by crops, tion. If the soil surface is damp, a minimum of and associated reduction factors to be used 7 mm of water should be applied for this pur­ when calculating the daily water balance. It pose; if dry, the minimum should be 15 mm. also gives the depth of soil to be considered, Fertiliser top-dressings can also be applied when calculating both the size of the water just before an irrigation is due, so that the reserves in the soil and the amount of irriga­ need for extra water is avoided. tion required for a particular type of crop. Soluble fertilisers may also be applied to Table 11.2 (p. 152) shows the amounts of crops through the irrigation water. The water readily available to crops for the range amount of additional irrigation water of soil textures and rooting depths commonest required is so small as not to affect long-term in forest nurseries. planning. The recommendations in these tables must be taken as guides only, the nursery manager Residual herbicides applied over seedbeds modifying them according to the actual state or lines of crop and soil as seems necessary. Over­ Where herbicides are applied which act watering must be avoided as any temporary through uptake by weed roots in the surface waterlogging could give rise to fungal damage. layers of the soil, a light application of irriga­ The reduction factor for seedbeds is based tion (5-7 mm) will ensure the herbicide is car­ on assumptions that the surface soil must be ried down to into the soil sufficiently to kept damp at all times, but that the surface become active. Such treatment is not neces­ cover of seedbed grit will materially reduce sary if there has been any significant rainfall the rate of water loss by surface evaporation since the herbicide was applied. Herbicide from the underlying soil. If seedbeds are should be deferred if a heavy application of shaded, surface evaporation will be further irrigation is imminent. reduced. It is assumed that netting protection Protection against frost during the against birds has no effect on moisture loss. growing season For newly lined out seedlings and for The protection achievable by irrigation against freshly undercut beds, the aim is to ensure unseasonal frost depends on two effects: that the soil immediately after the operation is well wetted and that for the first 2 weeks 1. the latent heat released when water freezes afterwards, daily water deficits are kept low. and During this period, the soil surface should 2. the conductivity of the soil as a heat source. remain damp. Where a range of reduction fac­ The aim is to keep the foliage of plants wetted, tors is given in Table 11.3, a value within the so that even though the air temperature is range should be selected based on the esti­ well below freezing, latent heat from the mated ground cover of the crop to be irrigated freezing water will prevent the foliage temper­ and the species, checking by the appearance of ature from falling to a level that plants are the crop that the factor chosen is not too low. physically damaged. If the soil at the same Particular attention should be paid to soil sur­ time is well wetted, it will act better as a face conditions for newly sown pre-treated or ‘storage heater’ and heat conductor than if stratified seed, especially if this had been well dry. chitted at the time of sowing. The most that a full canopy of foliage can retain before water runs off and soaks into the 11.4.3 Other uses of irrigation ground is the equivalent of about 2.5 mm of rain; most crops will be able to hold less than Washing in fertilisers this. Intermittent slow, light applications of Dry granular fertilisers applied as top-dress- irrigation with as fine a droplet as possible are

156 likely to be the most effective in keeping sive undercutting/wrenching regimes, the foliage surfaces wet. They should commence need for irrigation has to be determined at the when severe radiation frost is expected when time in relation to crop growth, timing of cut­ ground temperatures are just around freezing ting/wrenching and soil moisture. point, and continue until temperatures have risen above freezing point again. Plants may 11.4.4 Long-term climatic data become heavily encrusted with ice. Any conse­ The prescriptions given in Table 11.3 are of quent mechanical damage is likely to be less little use in long-term planning of water need, than frost damage if the plants are at a sus­ unless forecasts can be made of how often any ceptible stage of growth and the frost is given prescription is likely to be necessary. severe. For the United Kingdom, data from long-term records maintained by the Meteorological Temperature reduction Office are available, currently for the period Where seedbed surfaces get so hot in early 1960-1985. They can be applied to irrigation summer that seedlings are at risk of heat planning, through the ‘Met. Office Rainfall damage, mid-day irrigation can be applied to and Evaporation Calculation System’ or cool seedbeds as an alternative to shading. ‘MORECS’ (Gardner, 1983). Heat damage can be expected when surface temperatures exceed 35—40°C. The effect of Estimate of dry year water requirement irrigation is to reduce temperatures by up to The first requirement is an understanding of 10°C through the cooling effect of water evapo­ how much water is likely to be required in ration (Duryea and Landis, 1984). ‘dry’ years. There is no standard ‘dry’ year; Irrigation directly for temperature reduc­ variation in rainfall patterns and amounts can tion has not played a large part in irrigation only be viewed on the basis of ‘how often over practice in forest nurseries in the UK to date. the last 20 years would x, y or z mm of water have been required for crops not to have suf­ Hardening off and irrigation regimes fered severe moisture stress/poor germina­ tion/poor survival which irrigation could have Growth of several conifer species (e.g. Douglas overcome?’ fir, Abies concolor, and Pinus radiata) can be For agricultural crops, ‘model’ irrigation prolonged into the autumn by irrigation. In plans have been identified and graphs drawn New Zealand and NW United States, regimes which indicate for given values of rainfall and have been developed to allow the soil moisture crop water need, how often over a 10-year deficit to increase towards the end of the period, irrigation would be necessary to avoid growing season (Rook, 1973; Zaerr et al., crop water stress (Hogg, 1967; MAFF, 1981; 1981). The aim has been to encourage vig­ 1984 a, c). orous shoot growth early in the season and For forest nurseries, local calculations have gradually to increase moisture deficits in the to be made to establish the same principle; second half of the growing season. these are best done with the assistance of an There is evidence that plants respond to a agrometeorologist able to offer advice. See sec­ period of water stress by developing thicker, tion 11.6.3 below. Otherwise, calculations more waxy foliage cuticle, and that the extent must be based on tables of monthly average of suberisation (development of a water-resis­ evapotranspiration such as included in MAFF tant layer) in the roots reflects the available Booklet 2396, Daily calculation of irrigation soil water (Kramer and Bullock, 1966; Rook, need (MAFF, 1984b). 1973). In normal seasons, irrigation should not be continued on conventional seedbeds and lines Estimate of peak demand beyond the end of August. For beds on inten­ The second requirement is to identify the size

157 and timing of possible peak water demands, to Natural Heritage (Scotland) Act 1991. Control determine the capacity of the equipment, bore­ areas may be designated; anyone wishing to holes, reservoirs, etc., to supply that demand. abstract water for irrigation within a control This does not require additional climatic data; area has to obtain a annual licence from the calculations have to be made to show the rate Board. of water use in relation to alternative sources In England and Wales, applications to of water supply and methods of application. obtain water for irrigation have to be made to See also section 11.4.7 ‘Economic appraisal’. the National Rivers Authority. The Water Act, 1989, transferred powers to license water 11.4.5 Availability of water abstraction under the 1963 Water Resources Act from River Authorities to the National The availability of a water supply to meet Rivers Authority. In many areas, the National peak short-term demand, which is adequate Rivers Authority operates a regional office both quantitatively and qualitatively (espe­ from the same address as the previous Water cially in dry years) has to be investigated. Authority main office. Water is likely to come from local boreholes Licences in England and Wales stay in force or specially constructed reservoirs. Supplies unless surrendered or revoked. However, they from mains and from local rivers are often may be suspended temporarily in times of restricted by water authorities, just at the time severe regional drought if a ‘General Drought when plant stresses are building up. Where Order’ or ‘Emergency Drought Order’ has been such supplies are available, the user usually issued. Alternatively, conditions may be has to provide a reservoir at least capable of included in the licence requiring the mainte­ holding one day’s supply so that it can be nance of specified minimum flows of water, or recharged overnight. In other circumstances, minimum levels in boreholes or reservoirs. water may not be available in the dry summer Licences will also specify: months so that any reservoir has to be large enough to hold several weeks’ peak demand. • point of abstraction, • purpose of use, Water quality • maximum quantity that can be abstracted Water used for irrigation should if possible be in a given period, soft. Hard water used regularly can raise the • means of abstraction, pH of the soil sufficiently to depress the • basis of assessing the quantity used. growth of seedling conifers sensitive to soil reaction; if no other alternative is available, it Costs depend on local circumstances but may be necessary periodically to counter any are usually higher in the summer than in the pH rise by local acidification; see Chapter 3, winter. section 3.2.4 ‘Soil acidification’. It may turn out that water is only available A water analysis is required, not only to during the winter, in which case, construction determine pH but also to check for the pres­ of a reservoir for summer supplies may have ence of other dissolved salts, pesticide to be considered and a separate licence to residues, etc. impound sought. If granted, a combined licence to impound and extract is normally Legislation controlling abstraction of issued. water for irrigation There is separate legislation for Scotland and 11.4.6 Soil factors for England and Wales, regulating abstraction Soil factors influencing the scale of irrigation of water for irrigation. and the type of equipment suitable for the site In Scotland, River Purification Boards are include: responsible for controlling irrigation under the • available water capacity,

158 • water infiltration rate, such as undercutting and side-cutting break up any crust and thereby facilitate infiltration. • soil and site drainage, In practice, many forest nursery soils do • soil bearing capacity. develop crusts during the season; in planning, provision should be made using infiltration Available water capacity rates on soils where crusts have developed, so (see also section 11.2.2) as to have a ‘worst situation’ figure and avoid The available water capacity of soils encoun­ the risk of wasteful run-off. Irrigation equip­ tered in forest nurseries is likely to fall within ment should be specified that does not gen­ the range of values shown in Table 11.1. The erate large droplets, cause capping and reduce range is sufficient for it to be worthwhile to infiltration rates. have a proper assessment of available water capacity based on soil samples from the Soil and site drainage nursery site. The Soil survey field handbook The consequences have to be considered of (Hodgson, 1985) describes how this can be excessive wetness caused either by unexpect­ done. Alternatively, ADAS and similar advi­ edly heavy rainfall following shortly after irri­ sory services can undertake this (see section gation, or by malfunction of the irrigation 11.6.3). system. Normally, a nursery’s drainage system Essentially, the assessment measures the will be robust enough to cope with seasonal size of the water reservoir in the soil; the high intensity downpours and will not need larger this reservoir, the greater the chances any modification. However, if the soil already of rainfall replenishing soil water before a crit­ shows signs of local soil erosion in such circum­ ical deficit is reached, and the less the need stances, serious thought should be given to the for irrigation water. This would affect the size consequences of heavy rain, e.g. thunderstorm, of any reservoir necessary, but would not on recently irrigated soil. affect the possible maximum rate of daily application. Soil bearing capacity and cultural operations Water infiltration and soil structure Finer textured soils, e.g. loamy fine sands, The maximum rate at which water will enter when fully rewetted may not be able to bear soil depends on the size and number of stable tractors, etc., without damage. If operations air spaces at and below the soil surface, soil such as undercutting or lifting require soil to moisture content at the time, and how long be under a slight moisture deficit in order to water has been falling on the soil surface. get good traction and avoid soil compaction, Infiltration progressively falls with time to this could slightly reduce overall water reach an ‘equilibrium infiltration capacity’; requirements and necessitate particular this may take between 20 min and 2 h attention to good surface drainage. depending on the soil texture and soil density. Soil compaction can have a particularly marked effect in reducing infiltration capacity. 11.4.7 Economic appraisal The infiltration rate can also vary during a At this point, economic evaluations have to be season according to whether the soil has a made as to whether investment in irrigation is stable surface crumb structure, capable of justified. Judgements in particular have to be withstanding the impact of heavy rain and made as to whether to provide for a recurrence large droplets or has slaked and developed a of the worst drought that occurred in the last crust (see section 11.2.2, last paragraph), and 20 years, so that equipment and facilities will whether any cultural operation during the be under-used for most of the time, or whether season has compacted the soil. Operations provision is set at for example, to meet

159 requirements in 7 years out of 10, plants suf­ because they can be moved and set up by one fering some stress in the other 3 years but man and tractor (Plate 29). much less than if no irrigation were available. In view of the size of investment if large 11.5.1 Pump, mainline and laterals scale irrigation is in mind, it is important to Whatever the final means of distributing the consider a number of different possible combi­ water over the crop, the irrigation system nations of schedules, equipment and future must include: cropping plans before reaching a decision. • pump; ‘Sensitivity analysis’ should be used to esti­ • mainline; mate the effects of changing the various judge­ ments and working assumptions incorporated • laterals. in the initial proposals. While this may appear Other equipment, such as relief valves, filters, to involve repetitive calculations, it is the only etc., may be required according to local cir­ sure way to reach a clear understanding of the cumstance. best options. Pump The pump draws water from a reservoir, bore­ 11.5 Irrigation equipment hole or stream and is powered by electric motor or internal combustion engine. The There is a very wide range of irrigation equip­ pump must be of a capacity and design to sus­ ment available on the market in the United tain flow of water to meet peak demand, when Kingdom, developed for agricultural and horti­ the water reservoir or borehole levels are at cultural crops. Reference books listed at the their lowest and the water most likely to be end of the chapter provide detailed guidance dirty and contaminated with sand. on principles and practice in operating irriga­ tion equipment. If considering substantial If it appears that pressure at spraylines is investment in new equipment, professional insufficient, because of long pipe runs or other assistance should be sought for information on uncontrollable cause, the possibility of currently available equipment, calculations of installing a supplementary pump near the irri­ water need, pipe layout, etc., e.g. from local gator should be considered as an alternative to offices of ADAS in England and Wales, and increasing the capacity of the main pump and branches of the Scottish Agricultural College pipework, or risking inadequate water distrib­ in Scotland. Information on sources of advice, ution through low water pressure. etc., can also be obtained from the Irrigation A pressure relief valve and return pipe to Association, c/o National College of Agri­ the reservoir is desirable in order to maintain cultural Engineering, Silsoe, Bedfordshire, even pressure and sustained water flow under MK45 4DT. all operating conditions. For open-grown nursery stock in Britain, water has to be applied by some form of sprin­ Filters kler system. The two methods currently in use Filters may be necessary to reduce the are the oscillating sprayline, and the mobile amount of solids flowing through the system, rotating boom. arising from dirty water, borehole sand, corro­ The oscillating sprayline method works sion products in pipes and accumulated bacte­ well, involves relatively less capital outlay but rial slime, etc. requires a lot of manpower whenever the Wherever filters are installed in any pipes have to be moved. system, they must be cleaned out regularly, In recent years, mobile rotating boom otherwise they will reduce the flow of water sprinklers linked to hose reel and wire reel through the system. systems have come increasingly into use Filters are essential to protect any part of

160 the nursery where trickle irrigation is being determined by the cost and time required to used, e.g. container stock. move equipment.

Mainline pipework Laterals The mainline delivers water from the pump to Laterals deliver water from the main water the lateral distribution system. Often, this pipe layout to spraylines; laterals are usually line is permanent and is PVC pipe laid below portable, made of lightweight alloy, gal­ ground so as not to interfere with the passage vanised steel or plastic, so that they can easily of machinery. Where the pipe is 50 mm diam­ be moved. eter or less it should be at 0.5 m depth or They may be replaced by hoses where more; if more than 50 mm diameter, the pipe mobile hose reel systems are in use. should be 0.75 m deep, both to avoid being 11.5.2 Spraylines and sprinklers damaged by wheeled traffic and to escape the effects of severe frost. There are two main types of sprayline in use The main pipework layout can all be under­ in forest nurseries: ground; equally, there may be situations • fixed or oscillating spraylines, where a smaller permanent layout and one or • mobile rotary boom sprayers. more portable main spurs is more appropriate, While rotary sprinklers are widely used in especially where different main sections are agriculture, they normally give too large a likely to need irrigation in different years. droplet size for forest nursery requirements.

Sprayline/sprinkler droplet size is deter­ Pressure loss and friction mined by nozzle size and operating pressure. Pressure is greatest at pipework connections In forest nurseries, equipment should be nearest the pump; pipes must be of a grade selected and operated to avoid: sufficient to withstand these pressures. The • production of large droplets which would cost of pipes depends on their size and pres­ damage the soil surface; sure class; in deciding what is an acceptable • surface run-off as a result of too rapid or too pressure, the cost of pumping to overcome fric­ prolonged application of water. tion in the distribution system has to be bal­ anced against the cost of increasing pipe size. See also end of section 11.2.2, ‘Soil saturation’ and ‘Slaking1. • For a given pipe diameter and flow rate, Whenever possible, irrigation spraylines loss of pressure due to friction is propor­ should be laid out as near as possible on a con­ tional to the length of the pipe; tour, so that pressure at nozzles along the line • For a given size and type of pipe, the loss of are affected only by the friction pressure loss pressure due to friction is approximately in the pipe. proportional to the square of the flow rate. • For a given length of pipe and flow rate, the Oscillating and fixed spraylines pressure required is inversely proportional Oscillating and fixed spraylines have to be set to the fourth power of the pipe radius. For up by hand. They provide a fine spray applied example, doubling the pipe radius will slowly; oscillating sprayline droplets rarely reduce the pressure required sixteenfold. damage the soil surface. Manufacturers and suppliers can provide The advantage of fixed or oscillating spray­ graphs and tables showing friction losses for lines is that they can apply water relatively the pipes they supply. uniformly to rectangular sections of ground. At intervals along main pipe layouts and at Any rotary system, whether sprayline or the ends, connection points or hydrants are boom-mounted sprinkler does not cover the necessary. The number of these should be corners of sections without special provision or

161 waste of water. Where mobile rotary sprin­ have to be made according to actual perfor­ klers are used, corners of sections are only mance, possibly altering the speed of travel able to be watered if unproductive ground and the distance between parallel runs. Trial beyond the end of the section is also treated. and error, linked to observations of water dis­ tribution in temporary local gauges is the only Travelling spraylines way to gain experience of how to respond to Travelling spraylines are mounted on car­ windy conditions when irrigating. riages which slowly traverse the area to be sprayed (Plate 30). The equipment is propelled by a water-pow­ 11.6 How much water to apply ered turbine which turns a drum on to which and how often a guide cable winds. The cable is anchored at In operation, irrigation water has to be used the end of the area to be watered, and when as effectively as possible, because of the cost of the boom gets there, it turns itself off. The water and its application, and the need to con­ supply hose lies in the alley between beds and serve what in dry seasons may be a limited is dragged along as the machine moves up the section. resource. There is an appreciable volume of water in In the UK, schedules of irrigation in forest the booms and hoses; care has to be taken nurseries are controlled by water balance when draining the equipment before moving sheets. These require records of current rain­ it, to avoid local scour or erosion of beds by fall and irrigation applied, and may be based drainage water. on long-term climatic data alone, or the same data, updated to take account of recent Self-propelled rotary boom sprayers weather. Self-propelled rotary boom sprayers have recently been introduced into Forestry Com­ 11.6.1 Rainfall and irrigation records mission nurseries. The spray pattern from this To control the use of irrigation, it is essential equipment is of acceptably fine droplets, the to have a consistent record of rainfall mea­ equipment being set to apply the equivalent of sured using a properly sited standard rain 3-6 mm rainfall per pass. The equipment takes gauge. Information on siting and design can 2 hours to cover 100 m run; the boom is 19.5 m be obtained from the Observer’s handbook long and covers a swath 35 m wide. (Anon., 1982). Additional gauges should be available to be Irrigating in windy conditions placed wherever irrigation is in progress. The Sprayline performance is distorted even by amount of water applied can be estimated quite light winds (5 m s_1); in theory, to obtain from the rated capacity of nozzles, the dura­ uniform distribution of water, spraylines and tion of irrigation and the nominal area the line of travel of rotary boom sprinklers treated; however, some gauges should always need to be aligned with the wind direction. In be set out for every irrigation to check how practice, this is not possible as the layout of evenly water is being applied, how equipment seedbeds and lines determines the way irriga­ is performing in relation to its nominal tion equipment can be used. output, and what allowances should be made, In windy conditions, especially variable or for example, in windy weather. gusty winds, it is important to set out gauges to monitor the amount of water reaching the ground. 11.6.2 Balance sheets and irrigation Oscillating spraylines can be adjusted so prescriptions based on monthly that the arc of spraying can point into the average data wind. With rotary boom sprayers, adjustments Irrigation schedules in the UK can be based

162 on simple water ‘balance sheets’ using local starting point. The monthly figures are con­ monthly average climatic data as the basis for verted into an average daily water loss. estimating water loss. Average daily values The irrigation and rainfall figures are are calculated per month and adjusted for obtained from daily records kept on the crop cover, rainfall and irrigation to estimate nursery. soil moisture deficits. Irrigation is applied During the months when natural evapo­ whenever a threshold soil moisture deficit is transpiration is high, i.e. May-August, daily exceeded. deficits occur frequently and in spite of rain­ The main limitation of this method is that fall, soon lead to a sufficient cumulative deficit it cannot take into account short-term diver­ to justify irrigation. The amount to be applied gences from the monthly average estimates of should follow the recommendations in Table water loss. Consequently, in hot weather, 11.3 using the balance sheet ‘running deficit’ plants are subjected to extra moisture stress, multiplied by the appropriate ‘reduction while in cold spells, plants could be over­ factor’ from Table 11.3. This allows for incom­ watered, both incurring unnecessary expense plete crop cover typical of most forest nursery and risking leaching soil nutrients. crops, and is assumed to reduce the soil mois­ ture deficit to zero when the application is When to irrigate: calculation using a completed. Table 11.4 illustrates a typical balance sheet and long-term climatic data page maintained by this method. A running daily water balance sheet can be maintained by offsetting the daily estimated water loss against recorded daily rainfall and 11.6.3 Prescriptions based on long­ irrigation. term data adjusted for recent weather Values for estimated average monthly Contemporary electronic technology is cur­ water loss by evaporation and transpiration rently bringing down the cost of instrumenta­ can be obtained from reference books such as tion to measure local weather. It is also MAFF Booklet 2396 Daily calculation of irri­ providing the software both to enable such gation need (MAFF, 1984b). Monthly values measurements to be applied to calculations for the growing season for the most local refer­ such as estimating daily evapotranspiration ence points to the nursery are taken as the and also to provide irrigation prescriptions

Table 11.4 Example of an irrigation balance sheet (all figures in mm)

Location: South-east Oxfordshire Monthly average loss by evapotranspiration: 75 Daily average loss by evapotranspiration: 2.5

Daily average Rainfall in Reduction loss by evapo­ previous Running factor for Date transpiration 24 hours Irrigation deficit current crop Notes

- - - — 5.7 — (brought forward) 13.5 2.5 0.0 0.0 8.2 0.5 - 14.5 2.5 0.0 0.0 10.7 0.5 - 15.5 2.5 0.0 6.1 13.2/0.0 0.5 Seedbeds irrigated for 2 hours during day 16.5 2.5 0.0 0.0 2.5 0.5 - 17.5 2.5 1.8 0.0 3.3 0.5 - 18.5 2.5 5.6 0.0 0.0 0.5 - 19.5 2.5 0.0 0.0 2.7 0.5 - 20.5 2.5 1.1 0.0 4.1 0.5 -

163 which take account of the local recent The grower is then regularly given specific weather. Consequently, techniques previously advice as to how much water he should apply, restricted to research establishments (Norman when and to which crops. The service may and Campbell, 1983; Papadopol, 1984; Phene, arrange for periodic field visits to check actual 1989), are now commercially available. soil moisture content against what their pre­ dictions show. Any nursery manager using Commercially available irrigation this system should consider following the irri­ prescription services gation regimes given in Table 11.3. Commercial services to growers, offering weekly irrigation prescriptions for some agri­ 11.6.4 Empirical control cultural crops, include: Any balance sheet based on long-term aver­ • ADAS ‘Irriguide’ system. This, though ages can be overridden or adjusted if treat­ designed for arable farm crops, can be ments seem inappropriate, for example extended to give some guidance to forest because the weather is exceptionally hot or nursery managers - for current details cold or windy. apply to the local ADAS office. If a balance sheet cannot be kept at all, for • Scottish Agricultural any reason, the following empirical prescrip­ College (SAC); these offer services tion should be followed. • Hydro/Agri (fertiliser more oriented to • Germinating seedbeds should be irrigated manufacturers); farm crops in dry spells with one 10 mm application of • Irrigation Management especially potatoes water per week until germination appears Services, Silsoe College, and vegetables. complete, or more frequently if the surface Beds. ‘ of the soil under the grit cover appears to ADAS also offer a service, ‘Irriplan’, dry out before the next weekly watering is assessing whether it is worthwhile installing due. irrigation equipment; this is primarily • A similar prescription should be followed directed at farmers but can be modified for for newly lined out and recently undercut specified forest nursery irrigation regimes. seedlings. Commercial scheduling services require: • For established seedbeds and lines during • At the start of the season, details of: dry spells, a weekly application of 15 mm (a) the location (to be able to relate the site should suffice. to the national meteorological database), and, on a field by field basis, data on soil tex­ 11.6.5 Avoidance of over watering ture, available water capacity within the pro­ Care should be taken never to apply more file, and an indication of the slope of the site; water than would restore the soil to field (b) crops to be grown; capacity. (c) irrigation regime to be followed for the • There is a risk that a cap of water-satu­ crops to be treated; rated soil could allow a sudden temporary (d) the time taken to apply a given amount depletion of oxygen in the soil, thereby of irrigation with the equipment available. harming actively respiring roots and pro­ • Each week: viding opportunities for attack by fungal (a) rainfall and irrigation each day; pests. (b) date of any cultivation or similar oper­ • Irrigating excess water costs money! ation. • In addition to wasting water, it is probable When appropriate: that some soluble fertilisers will be lost by information of crop development and leaching. ground cover. There is also the risk that heavy rainfall

164 shortly before any fertiliser plus irrigation HODGSON, J.M. (1985). Soil survey field treatment, will saturate the soil; further water handbook. Technical Monograph 5. Soil will mainly run off or drain through, taking Survey, England & Wales, Harpenden. some of the recently added nutrients away in HOGG, W.H. (1967). Atlas of long-term irriga­ solution. A local 3-day weather forecast should tion needs for England and Wales. MAFF. always be obtained if fertilisers are to be IDSO, S.B. (1982). Non-water-stressed base­ applied in conjunction with irrigation. lines: a key to measuring and interpreting plant water stress. Agricultural Meteor­ ology 27, 59-70. REFERENCES AND FURTHER READING IDSO, S.B. (1983). Stomatal regulation of ANON. (1982). Observer’s handbook, 4th edtn. evaporation from well-watered plant Meteorological Office, Met.0.933. HMSO, canopies: a new synthesis. Agricultural London. Meteorology 29, 213-217. BATCHELOR, C.H. (1984). The accuracy of KAY, M. (1983). Sprinkler irrigation; equip­ evapotranspiration estimated with the FAO ment and practice. Batsford, London. modified Penman equation. Irrigation KRAMER, P.J. and BULLOCK, H.C. (1965). Science 5, 1-11. Seasonal variations in the proportions of BURGER, D.W. and PAUL, J.L. (1987). Soil suberized and unsuberized roots of trees in moisture measurements in containers with relation to the absorption of water. solid state electronic tensiometers. Hort- American Journal of Botany 53, 200-204. Science 22 (2), 309-310. LANE, P.B. (1989). Thetford nursery gantry BURMAN, R.D., CUENCA, R.H. and WEISS, for application of liquids to Corsican pine A. (1983). Techniques for estimating irriga­ grown in Japanese paper pots. Eastern tion water requirements. Advances in Region Work Study Report 129. Forestry Irrigation 2, 335-394. Commission, Edinburgh. CLEARY, B.D. and ZAERR, J.D. (1980). Pres­ LIETH, J.H. and BURGER, D.W. (1989). sure chamber techniques for monitoring Growth of chrysanthemum using an irriga­ and evaluating seedling water status. New tion system controlled by soil moisture ten­ Zealand Journal of Forest Science 10 (1), sion. Journal of the American Society for 133 et seq., 141. Horticultural Science 114 (3), 387-392. DOORENBOS, J. and PRUITT, N.O. (1977). MAFF (1980). Methods of short term irrigation Crop water requirements, irrigation and planning. Booklet 2118. HMSO, London. drainage. Paper 24 (2nd edtn). FAO, Rome. MAFF (1981). Irrigation. Reference Book 138. (144 pp.) HMSO, London. DURYEA, M.L. and LANDIS, T.D. (1984). MAFF (1984a). Irrigation; when and why. Forest nursery manual: production of bare­ Booklet 2067. MAFF, Alnwick. root seedlings. Nijhofl/Junk, The Hague. MAFF (1984b). Daily calculation of irrigation GARDNER, C.M.K. (1983). Evaluating the need. Booklet 2396. MAFF, Alnwick. success of MORECS, a Meteorological Office MAFF (1984c). Thinking irrigation; farm model in estimating soil moisture deficit. water supply. Leaflet 672. MAFF, Alnwick. Agricultural Meteorology 29, 269-284. MATHIESON, I. (1985). Scheduling by neu­ HIGGS, K.H. and JONES, H.G. (1988). Water tron probe. Horticulture Now, (Irrigation use in strawberries in SE England. Journal Review), 16-17. of HortScience 64 (2), 167-175. McBURNEY, T. and COSTIGAN, P.A. (1982). HOBBS, E.H. and KROGMAN, K.K. (1978). Measuring stem water potential of young Frequent light irrigation scheduling to plants with a stem hygrometer. Journal of improve efficiency of water use. Canadian Experimental Botany 33 (134), 426^431. Journal of Agricultural Engineering 20 (2), MONTEITH, J.L. (1965). Evaporation and 109-112. environment. In The state and movement of

165 water in living organisms, ed. G. E. Fogg. ecological research. Advances in Ecological Academic Press, New York, 205-234. Research 9, 165-254. MONTEITH, J.L. and UNSWORTH, M.H. ROOK, D.A. (1973). Conditioning P. radiata (1990). Principles of environmental physics. seedlings to transplanting, by restricted 2nd edtn. Edward Arnold, London. watering. New Zealand Journal of Forest NORMAN, J.M. and CAMPBELL, G. (1983). Science 3, 54-69. Application of a plant environment model to SAC (1991). Mechanisation - irrigation sched­ irrigation. Advances in Irrigation 2, uling. Brochure from Scottish Agricultural 155-188. Academic Press. Colleges, Perth, Scotland. PAPADOPOL, C. V. (1984). An integrated irri­ STANHILL, G. (1957). The effect of differ­ gation system for forest nurseries in ences in soil moisture status on plant Ontario. Paper 84-2619; Winter Meeting of growth; a review and analysis of soil mois­ American Society of Agricultural Engineers, ture regime experiments. Soil Science 84, Michigan. 205-214. PARKES, M.E., NAYSMITH, D.B. and STEWART, J.B. (1983). A discussion of the McDOWALL, M.A. (1989). Accounting for relationship between the principal forms of slow drainage and hysteresis in irrigation the combination equation for estimating scheduling. Irrigation Science 10, 127-140. crop evaporation. Agricultural Meteorology PENMAN, H.L. (1948). Natural evaporation 30,111-127. from open water, bare soil and grass. VAUX, H.J. and PRUIT, W.O. (1983). Crop- Proceedings of the Royal Society, London water production functions. Advances in (A), 193, 120-145. Irrigation 2. Academic Press. PENMAN, H.L. (1986). Scientific aspects of ZAERR, J.B., CLEARY, B.D. and JENK- irrigation. A Royal Society Discussion. The INSON, J.L. (1981). Scheduling irrigation Royal Society, London. to induce seedling dormancy. Proceedings of PHENE, C.J. (1989). Techniques for comput­ Intermountain Nurseryman’s Association erised irrigation management. Computers and Western Forest Nursery Association and Electronics in Agriculture 3. Elsevier Combined Meeting, August 12-14, 1980, Science Publishers. Bosie, Idaho. USDA Forest Service, Inter­ RITCHIE, G.A. and HINCKLEY, T.M. (1975). mountain and Range Experiment Station, The pressure chamber as an instrument for General Technical Report 109, 74-79.

166 Chapter 12 Nursery weed control

D. R. Williamson and J. L. Morgan

An effective programme to control weeds in staff, effective equipment and protection of the nursery is essential. Weeds the environment; • compete for water and nutrients • cleaning of equipment and safe disposal of • smother germinating seedlings, and residues after treatment. • their removal may physically disturb seedlings or small transplants. 12.1 Weed control over the whole The great success of crop husbandry in recent years is due to the combination of effec­ nursery tive weed control, a balanced supply of nutri­ There is no dormant season for many weed ents and a soil pH adjusted to suit the crops in species and some weeds can set fertile seed production. within a few weeks of germinating, completing The aim is to kill or remove weeds before four or five generations in a year (Aldhous, they are capable of reproducing or competing. 1961). To reduce the weed seed population, While the use of herbicides and pre-sowing managers must be prepared to control weeds partial soil sterilisation has removed much of at any time of year. The task is made easier if the tedium of hand-weeding, chemicals are not introductions of weed seed with incoming infallible in their effect, especially where plants or bulky organic manures, and spread applications are delayed by bad weather or of weeds from uncropped land can be pre­ the timing is misjudged. There must always vented. be a place for mechanical weeding and as last resort, hand weeding, where the alternative is 12.1.1 Sources of weed seeds a cover of freely seeding weeds. A clean nursery, more often than not, is one Weeds with plants and soil that is well managed and profitable. Unless nursery managers are very familiar Nevertheless, hand-weeding is expensive and with the source of possible plants coming into its effect short-lived; chemical weed control the nursery, it is impossible to be sure that has therefore been generally adopted stock coming in will not bring seeds of several throughout the forest nursery industry. weed species. The same applies to import of The use of herbicides and all other pesticides soil. In the past, and also very recently, weed- is governed by legislation under the Control of free nurseries established on former heath­ Pesticides Regulations and the Control of land or woodland, became weedy through Substances Hazardous to Health Regulations import of stock from weedy nurseries or soil (see Chapter 15, section 15.6.1 et seq.). full of weed seed. (There are examples too, of These regulations must be observed serious nursery pests also being brought in regarding: with imported stock.) While herbicides will • requirements set out on the product label; help minimise the build up of such imported • safe application, in terms of competent weeds, it is preferable to avoid the risk.

167 Fence lines and uncultivated land 12.2 Chemical control of weeds Fence lines, surrounds of buildings, roads and in nursery stock in open ground tracks are best kept bare of vegetation by reg­ ular cultivation or by the use of persistent residual weed-killers or by the frequent use of Caution contact and translocated herbicides. If this is Some of the materials described here have been impracticable or undesirable, an alternative is subject to small scale research trials and only to maintain a close cover of perennial vegeta­ limited subsequent commercial experience. Any material not previously used on a nursery should tion which will exclude other weeds and not be applied on a small scale in carefully observed give rise to unwanted seed or vegetative parts. trials before full scale use.

Organic manures and greencrops Recommendations are given as at December, Organic supplements are currently used only 1993. Checks should be made that these have not on a limited scale, usage being related to been superseded. locally available materials. Whenever such a All the herbicide ‘Products’ listed below appear as possibility exists, it is important to consider ‘Approved for Agricultural Use’ in MAFF Reference what weed seeds there may be in the material Book 500 Pesticides 1994 (MAFF, 1994). In this and to reject potential weed sources. context, forest nurseries are grouped with Where greencrops are grown, herbicides horticultural nurseries as part of ‘agriculture’. may not be required where the greencrop is to Nevertheless, listing in the reference book must not be ploughed in. However, selective herbicides be taken to imply that the labels of the products appropriate to the greencrop and weed may listed there carry full recommendations, covering need to be considered if there is a heavy weed forest nurseries. In many cases, this is not so and germination and the greencrop is thin. uses recommended are ‘off-label’. The use of such Alternatively, a non-persistent, non-selective products is covered by whatever ‘label’ herbicide may be desirable to kill the crop and arrangements are in force at any time. For 1994, any weeds, before ploughing in. the ‘off-label’ arrangements current at the start, continue in force until the end of the year. These allow products approved for use on any growing 12.1.2 Flexibility in control of weeds crop to be used on plants grown in forest nurseries. The following sections detail alternative In all cases, those uses of a herbicide which are not methods of weed control. While each is listed specified on the approved product label are at the separately, it is important to emphasise that user’s own risk; manufacturers cannot be held no one method is sufficient in itself to give a responsible for any adverse effect on crops or for satisfactory and economical control of weeds. A any failure to control weeds. Nevertheless, nursery manager wishing to keep his weeds employers and operators must always use the under control as cheaply and efficiently as pos­ product in accordance with the product label sible must be prepared to change from one recommendations in respect of safety of nursery technique to another when appropriate. staff and visitors to the nursery, and protection of Exclusive adherence to any one technique is the environment. liable to lead to a rapid build-up of one or more species of weed flora; see also section 12.2.3. 12.2.1 Definition of terms Two sets of terms require definition, relating to the crop and to spray distribution:

Stages of growth Pre-sowing: Before sowing of the crop has taken place.

168 Pre- Before the emergence of seedlings grouped according to how they enter and move emergence: of the crop; this can be before or within plants (Rice, 1986; BCPC, 1990). after the emergence of weed species. Contact and translocated herbicides Post- After seedlings of the sown crop These enter through foliage and stem sur­ emergence: have begun to emerge; this can be faces. Contact herbicides affect only the tis­ before or after the emergence of sues they touch (and therefore even, overall weed species. application is important); translocated herbi­ Active: When seedlings are actively cides rely on movement within the plant to growing and have not hardened susceptible parts (e.g. growing points and off, the period of active growth is where cell division is active). Where contact or from when buds begin to swell, translocated herbicides have been sprayed on through flushing and shoot elon­ to tall weeds close to growing crops using a gation and ripening, until winter shield to protect the crop, it should be remem­ resting buds have formed and bered that if the treated weeds move in the shoots are fully lignifled and hard­ wind, freshly applied herbicide can be trans­ ened. In addition, for deciduous ferred to crop plants. species, when foliage remaining on Most contact and translocated herbicides plants has not started to senesce. give better control if the target weed species is Dormant: After the shoots of seedlings or actively growing. transplants have ceased to elon­ gate and have hardened; terminal Soil-acting (residual) herbicides and side resting buds have formed Residual herbicides should be applied to soil in late summer/autumn but before which has a fine tilth and is free from clods. buds have started to swell and These herbicides require moisture in the soil elongate at the beginning of the to be activated and many (particularly those following season. For deciduous rapidly degraded by sunlight) need to be incor­ species, when in addition, the porated immediately after application by irri­ foliage has taken on autumn gation with 5-10 mm of water, or a similar colouring, or has fallen. amount of rainfall if the seedbed surface is not moist. The length of time residual herbicides Distribution of sprays in relation to the remain effective varies depending on the crop chemical in use, soil type and climate, particu­ Overall: The herbicide is applied over the larly rainfall, sunlight and temperature. whole weeding site (i.e. crop and Residual herbicides may achieve selectivity weed). through occupying only the top 2-3 cm of soil, Inter-row: The herbicide is applied to the being taken up by roots of germinating weeds weeds/ground between the rows of in that band of soil. Any crop roots in the transplants or between drills of same soil may also take up the weedkiller and seedlings. may be damaged; equally, any well-estab­ lished weeds with a substantial proportion of Directed: The herbicide is applied so that roots below the treated soil may resist the the spray is directed to hit a effects of weedkiller. Residual herbicides target pest or weed but avoid crop should therefore not be applied to ground with trees. well-established weeds among the crop plants; these weeds should be controlled either by 12.2.2 Mode of action of herbicides contact herbicide or mechanical means before Herbicides are often described or loosely a residual herbicide is applied.

169 Care should be taken that the ground is specific herbicides used in their nursery. The well compacted around the roots of newly following test is simple and informative: lined out stock, otherwise there is a risk of 1. Fill two seed trays with nursery soil. herbicide being carried down by heavy rain 2. Sow one tray with seed collected from per­ into their active rooting zone. Similarly, herbi­ sistent weeds from the nursery. cides should not be applied to freshly undercut or wrenched plants until the soil has settled. 3. Sow the remaining tray with seed collected from a wild source of the same weed (i.e. Influence of weather and soil on the use of that has never been sprayed). Label trays. herbicides 4. Allow seed to germinate and grow to the The efficacy of some herbicides may be influ­ stage where problems with control are enced by weather and soil conditions so that experienced. This may be immediately after the following precautions should be consid­ sowing. ered. 5. Place trays on the ground and apply the her­ bicide to be tested as a single pass. The • In very hot or dry conditions, the crop is sprayer should be calibrated to match the more likely to be under moisture stress and swathe width and forward speed for the trial. to be more susceptible to damage by the 6. If the wild seed source is killed and the herbicide; if a herbicide must be used, it should be applied towards the end of the nursery source unaffected then herbicide day, when it is cooler. resistance is likely. • Avoid applications when the weather is 7. If both seed sources are damaged to the very windy, because of the risk of drift. same extent then there is a need to examine (a) the choice of herbicides that are • Apply soil-acting herbicides when the soil is used in the nursery and (b) the method of moist and rain is expected, or when irriga­ application to explain the lack of efficacy of tion can be applied to ensure it is not left on nursery treatments. the soil surface where it may be lost through the effects of sunlight. 12.3 Recommended herbicides 12.2.3 Herbicide resistance Table 12.1 gives details of herbicides currently Nursery managers are strongly advised available that should be considered for control against using the same herbicide repeatedly of the various weeds commonly found in forest over a number of years on the same area of nurseries. This information has to be linked to ground, which otherwise may lead to: the type of crop (seedbeds or transplants), and • the development and/or spread of herbicide- its stage of growth, as outlined in the fol­ resistant strains of particular weed species, lowing sections. e.g. groundsel, willowherb and mayweed; Herbicides are listed and discussed under • the development of soil microflora which the name of their active ingredient (a.i.). can rapidly degrade the chemical active Where rates of application are given, these ingredient, thus reducing the effectiveness refer to the rate of product in litres or kilo­ of residual herbicides. grams per treated hectare (1 ha-1 or kg ha-1). N.B. See statement about ‘Products named It is therefore recommended that herbicides in the Bulletin’ in the Preface. are used in rotation, e.g. using alternatives regularly. 12.3.1 Seed bed pre-sowing treatments Identification o f herbicide-resistant weeds Growers with persistent weed species can Soil sterilisation assess whether these weeds are resistant to This usually takes place in late summer to

170 The availability of products always depends on the BEFORE ANY HERBICIDE overall demand in the agricultural and horticultural APPLICATION, READ THE LABEL. markets. Products over which there is some doubt IT CARRIES FULL INSTRUCTIONS FOR as to future availability are marked t- Products no USE AND THE PROTECTION OF THE longer manufactured but of which there may be OPERATOR AND THE ENVIRONMENT. stocks that can legally be used, are listed in Forestry Commission Technical Paper 3 (Williamson etal., 1993). Poisons Rules and can only be applied by licensed contractors. Products marked with an asterisk (*) in section 12.3 do not have a full 'label' approval; where there is Soil temperature should be at least 8°C at any doubt, enquiries should be made to the 15-20 cm depth. Treatment period 48-96 Forestry Authority, Research Division, at either the hours depending on temperature. Aerate soil Northern Research Station, Roslin, Midlothian, for 7-21 days before sowing. EH25 9SY, or Alice Holt Lodge, Wrecclesham, Farnham, Surrey, GU10 4LH, for up-to-date ‘Stale’ seedbeds information on the status of any product Treatment of ‘stale’ seedbeds is based on the recommended for ‘off-label’ use. principle that weed seeds buried in the soil only germinate when cultivation brings them early autumn of the year before sowing and very close to the soil surface. Provided there is controls many soil pests (nematodes, fungi) as sufficient time for seedbeds to be prepared well as weeds and weed seed. Sterilants will and for it to be sufficiently warm for seeds to usually improve the growth of trees as well. germinate before sowing, post-sowing competi­ With both soil sterilants, it is important to tion can be markedly reduced if the early flush aerate the soil and release all the sterilant of weeds is killed by spraying or very shallow residues prior to sowing. A recommended test cultivation before sowing. for the presence of residues prior to sowing is The technique is invalidated if the beds are to grow cress in sealed jars containing sam­ deeply cultivated, as this brings up another ples of sterilised soil. If the cress fails to grow, crop of weed seed. then further cultivation is required to release Rate per hectare the sterilant. Small Large or Dazomet weeds established Approved product Basamid; 98-99% a.i. weeds Rate 380-570 kg ha-1 depending soil type. Glufosinate-ammonium The high rate is used only on heavy soils. Approved product: Challenge; 180 gl-1 a.i. 3.01 5.01 Must be incorporated when soil temperature is at least 7°C. Should be incorporated by rota- Glyphosate vation and sealed in by rolling or polythene Approved product: sheeting. Wait at least 4 weeks before culti­ Roundup; vating soil to release any residual gas. If 360 gl- a.i. 1.51 4.01 dazomet is applied in the autumn it is normal Paraquat: approved product Gramoxone is to wait until the spring before releasing available and has been recommended previ­ residues. See Chapter 6, section 6.1.2. ously; current products above offer the same Methyl bromide efficacy of weed control while providing Contains 98% methyl bromide + 2% chloropi- greater operator safety. crin as a warning odourant tear gas. Rate 300- 500 kg ha-1. 12.3.2 Seedbed pre-emergence Subject to the 1982 Poisons Act and the 1972 Seeds of small seeded broadleaves and conifers

171 Table 12.1 Susceptibility of common forest nursery weeds to selective herbicides before weed emergence

Active iiingredients

:o .ti.s o E , a>(b "S' •E

Weeds

Annual meadow grass S MS MS S S s R s S s SSSS s s s Bitter cress, hairy S s s MR MS S S Black bindweed MS S MS S MS s MS MS S S S s s MS Black nightshade S MS MS R MS R MS R S MS S s s S Broadleaved dock s S s Chamomile spp. S MS MS S s SS s s Charlock S s MR S S s S MR R S s s Cleavers MR s R MR MS R MS S S s s s MR Common chickweed S s SSSS S s SSSSS s s S Common fumitory MS MS R MS R R S s SRSSS s s MS MS Common hemp nettle S S S S S MR S S S Common poppy SSS s SSSS s S Corn buttercup R S S s s Corn marigold S R SS s S SRS s S Dead nettle, red S MS S MS S MS S S S S S s s S Fat hen S S S MS MS S S s S MS S S S s s s S Field pansy MS S S MS S s R S MR MS MS S s MS Field penny cress S S R S S S S RR SS Forget-me-not, field S S S s SSSS s s S Groundsel SS R SSS s MS s S S S MS s RS Henbit dead nettle s S S s MS s S SSS s s S Knotgrass MR s S MS MS s s S s R MS MS S s s s R Mayweed S s R S MS MS s S s SSSS s s RS Mercury, annual S MS MS S Mustard S R SSS Orache, common MS S MS MS s S s SS s s MS Pale persicaria MS S MS MS S s S S Parsley-piert SS s S R S s S Pineapple weed S MS MS s s s S s s S Plantain S S Radish, wild s s R S s s s MR S s S Redshank MS s MR S MS MS s s s MS MS MS s s s MS Scarlet pimpernel S MS S s s s RR s R S Shepherd's purse S S R SSS s s s S MR SS s s MSS Small nettle SSSSSS s MS MS S S S s s s S Smooth sow thistle S S s S SSS s s S Sorrel, sheep’s MR s s s SS MS s Speedwells MS s SS s s s MS s S S SS s s s MS Spurrey, corn MS s s s S s MS S S s s MS Thale-cress S s Volunteer cereals MS S Volunteer oil seed rape s MR s S Willow herb MS s s MS MS S s R MS

Key: S - Susceptible MS - Moderately susceptible MR - Moderately resistant R - Resistant - Not tested

172 are normally sown on to the surface of raised BEFORE ANY HERBICIDE seedbeds and covered with 2-3 mm depth of APPLICATION, READ THE LABEL. grit. Pre-emergence herbicides are then IT CARRIES FULL INSTRUCTIONS FOR applied after sowing but before crop germina­ USE AND THE PROTECTION OF THE tion. Large seeded broadleaves such as oak, OPERATOR AND THE ENVIRONMENT. beech and sweet chestnut are usually drilled into seedbeds and then covered with at least 25 mm of soil. Such species are therefore usu­ sowing. Tolerated by coniferous species. Does ally more tolerant of pre-emergence herbicides. not control germinated weeds since it has no Chlorthal-dimethyl foliar activity. This product is rapidly broken Approved product: Dacthal W-75\ 750 gkg-1 a.i. down by sunlight and is therefore best applied Rate 6.0 kg ha-1. between November and March unless irri­ Controls a wide range of grass and broad­ gated into the soil with at least 25 mm of leaved weeds. Apply immediately after water. sowing. Tolerated by a large number of tree Simazine species but not pine. Does not control germi­ Approved product: Gesatop 50WP\ 500 gkg-1 nated weeds since it has no foliar activity. a.i. Rate 4.0 kg ha"1. Diphenamid t Treat only large seeded broadleaves species, Approved product: Enide 50W ; 500 gkg-1 a.i. i.e. oak, beech, and sweet chestnut which have Rate 8.0 kg ha-1. been drilled into seedbeds. Application should Should be applied immediately after sowing. be immediately after drilling. Does not gener­ Tolerated by a wide range of tree species; but ally control germinated weeds due to lack of birch, alder and occasionally larch are dam­ contact action. aged by pre-emergence application. Does not control germinated weeds since it has no con­ 12.3.3 Seedbed post-emergence tact action. Diphenamid t Diphenamid in mixture with chlorthal- Approved product: Enide 50W; 500 gkg-1 a.i. dimethyl Rate 8.0kgha_1. Approved products: Enide 50W*\ 500 gkg-1 a.i. Can be applied to all species post-emergence Rate 8.0 kg ha-1. including birch and alder. Apply when first Dacthal W-75; 750gkg_1 a.i. Rate 6.0kgha-1. true needles or leaves are fully extended. In mixture, these two products control a wider Stunting can occur if applied earlier. range of weeds and give greater persistence Subsequent applications can be made at 6- than diphenamid on its own. Apply immedi­ weekly intervals. ately after sowing. Propyzamide Glufosinate am m onium Approved products: Kerb 50V/* \ 500gkg-1 a.i. Approved product: Challenge-, 150gl_1 a.i. Rate 3.0kgha_1. Rate 3.01 ha-1. Kerb Flo*; 400gL1 a.i. Rate 3.75lha-1. This can be used with care to clean up Propyzamide is tolerated by all commonly seedbeds post-sowing provided crop seed has grown forest species and is particularly useful not started to germinate. Check that no seed on standover beds when applied at the end of radicles are present before deciding to spray. the first growing season. Apply October to Napropamide December (January north of a line from Approved product: Devrinol; 450 gL1 a.i. Aberystwyth to London). For crop safety rea­ Rate 2.21 ha-1. sons, propyzamide should not be used within 6 Controls a wide range of grass and months of an application of simazine or broadleaved weeds. Apply immediately after atrazine.

173 Simazine 12.3.5 Transplant lines and second year Approved product: Gesatop 50WP ; 500 gkg"1 undercut seedbeds a.i. Rate 2.0 kg ha-1. Only apply to second year seedbeds when Soil-acting herbicides with no or limited plants are greater than 5 cm tall. All conifer post-emergence activity on weeds species except Norway spruce may be treated. Residual herbicides are widely used in trans­ Do not treat within 2 weeks of undercutting, plant lines and second year undercut beds. In i.e. allow soil to settle around the roots of trees the case of transplants these are normally before treatment. applied immediately after lining out to ground which is free from weeds, and repeated as nec­ 12.3.4 Seedbed post-tree emergence: essary. When a precision sowing and under­ repeat low dose regime cutting regime is in operation, residual As a result of research, it now appears pos­ herbicides should be applied during the first sible to use a wider spectrum of herbicides at winter dormant period. Many of the residual low doses when applied at regular intervals herbicides listed do not control germinated after crop emergence to maintain weed-free weeds and therefore if good weed control is to conditions. be achieved they must be applied before weeds Apply the following herbicides in a repeat emerge. It is therefore important to adopt an low dose regime after an initial pre-emergence effective weed control regime on first year pre­ application. The first application should be cision sown seedbeds to ensure the ground is made as soon as trees have reached the first clean when the second year residual herbi­ true leaf/needle stage. Treatments should be cides are applied. Depending on the prevailing repeated at 6-weekly intervals. conditions, these can be applied any time from These treatments have been successfully when trees become dormant in the autumn to screened for three seasons over Sitka spruce, just before bud burst in the spring. When Japanese larch, common alder and birch. applying soil-acting herbicides to undercut stock application must only take place after Metamitron soil has settled following undercutting or Approved product: Goltix WG*; 700 gkg"1 a.i. wrenching. Soil disturbance must be kept to a Rate 1.7 kg ha"1. minimum when these operations are carried Limited information on tolerance of crop out. This is because of the risk of herbicides species. coming into direct contact with tree roots. Metazachlor The herbicides listed in this section either Approved product: Butisan S*\ 500 g l"1 a.i. have no foliar activity or only control weeds in Rate 1.251 ha-1. an early post-emergence stage. Limited information on tolerance of crop species. Decision chain when using soil-acting Napropamide herbicides Approved product: Devrinol*; 450 gl"1 a.i. 1. Where lining out is being considered, culti­ Rate 1.11 ha-1. vate to produce a fine, firm tilth. Limited information on tolerance of crop 2. Identify potential weed problems. species. 3. Match weed spectrum to a suitable herbi­ Propyzamide cide or mixture of herbicides. Approved products: Kerb 50W*; 500 gkg-1 a.i. 4. Consider the suitability of the herbicide for Rate 1.50 kg h a 1. the crop species and stage of growth. Kerb Flo*; 400gl"1 a.i. Rate 1.871 ha-1. 5. Apply the herbicide to soil which has a firm, Limited information on tolerance of crop fine tilth. Soil should be moist before appli­ species. cation; if not, herbicides should be incorpo­

174 rated with irrigation (5-10 mm of water) BEFORE ANY HERBICIDE immediately after application. APPLICATION, READ THE LABEL. Atrazine IT CARRIES FULL INSTRUCTIONS FOR Approved product: Gesaprim 500SC*\ 500gl-1 USE AND THE PROTECTION OF THE a.i. Rate 4.0111a"1. OPERATOR AND THE ENVIRONMENT. Use on conifer transplant lines. Normally applied in spring prior to flushing. Use half rate on sensitive species (e.g. Norway spruce, Metamitron larch and western hemlock). No control of tri- Approved product: Goltix WG*; 700 g kg-1 a.i. azine resistant weeds. Mobile in the soil and Rate 5kgha"1. can be washed into low lying areas causing Controls a wide range of grass and local overdosing. broadleaved weeds. Tolerated by a wide range Chlorthal-dimethyl of tree species. Approved product: Dacthal*', 750 gkg-1 a.i. Metazachlor Rate 6.0kgha'1. Approved product: Butisan S*; 500gl_1 a.i. Controls a wide range of grass and broad­ Rate 2.5lha"1. leaved weeds. Tolerated by a wide range of Controls a range of grass and broadleaved tree species. weeds. Tolerated by a wide range of tree Cyanazine species. Approved product: Fortrol*; 500 g l'1 a.i. Napropamide Rate 4.01 ha-1. Approved product: Devrinol; 450gkg'1 a.i. Controls a wide range of grass and broad­ Rate 9.0lha"1. leaved weeds. Tolerated by a wide range of Broken down by sunlight so best applied tree species, but damage can occur if trees November-March unless irrigated into the soil have started to flush or are in active growth. with at least 25 mm of water. Apply immedi­ Diphenamid f ately after lining out. Has proved satisfactory Approved product: Enide 50W; 500gkg"1 a.i. on most conifers, but only limited information Rate 10.0-12.0 kgha-1. is available for broadleaves. A wide range of tree species are tolerant. Does Napropamide in mixture with simazine not control germinated weeds. Repeat treat­ Approved product: Devrinol', 450gl"1 a.i. ments can be applied at 6-weekly intervals. Rate 3.5lha"1. Isoxaben Gesatop 500SC; SOOgl"1 a.i. Rate l.Olha-1. Approved product: Flexidor 125\ 125 gl"1 a.i. Crop tolerance as napropamide but care is Rate 0.251 ha"1. needed on simazine-sensitive tree species. Controls a wide range of grass and broad­ Oryzalin t leaved weeds but has no activity on grass Approved product: Surflan\ 480gl"1 a.i. weeds. Should not be used on areas that will Rate 4.5-6.01 h a 1. be used for seedbeds next season due to strong At the time of writing, product temporarily residual activity. Land must be mouldboard unavailable while the manufacturers gather ploughed at least 20 cm depth before the fol­ information to satisfy the Pesticide Safety lowing crop. requirements. Seek manufacturer’s advice on Lenacil approval status before use. Approved product: Venzar*\ 800 gkg"1 a.i. Controls a range of weed species. Tolerated Rate 2.2 kg ha-1. by a wide range of tree species. Controls a wide range of grass and broad­ Oxadiazon leaved weeds. Tolerated by a wide range of Approved product: Ronstar Liquid', 250gl_1 a.i. tree species. Rate 4.0 or 8.01 ha"1.

175 Rate depends on the weeds to be controlled. weeds at the appropriate stage of growth. As Only apply in late winter before buds start to weeds become larger, the choice of effective swell. Contact with young leaves and shoots herbicides diminishes; it is therefore impor­ must be avoided. This herbicide has almost tant to carry out a detailed inspection of the entirely soil activity but will control weeds nursery on a regular basis so that surviving very early post-emergence before the first true weeds can be controlled soon after emergence. leaf stage. Tolerated by most conifers (e.g. Atrazine spruces, pines and larches) but there is only Approved product: Gesaprim 500SC*; 500 gl"1 limited information on broadleaves. Tree tol­ a.i. Rate 4.01 ha-1. erance depends on the above instructions Use on conifer transplant lines. Normally being closely adhered to. applied in spring prior to flushing. Use half Pendimethalin rate on sensitive species (i.e. Norway spruce, Approved product: Stomp 400 SC*\ 400gI-1 larch and western hemlock). No control of tri- a.i. Rate 6.0lha"1. azine resistant weeds. Mobile in the soil and Controls a wider range of grass and can be washed into low lying areas causing broadleaved weeds. Tolerated by a wide range local overdosing. of tree species. Clopyralid Propyzamide Approved product: Dow Shield*-, 200gl_1 a.i. Approved products: Kerb 50W*-, 500gkg"1 a.i. Rate 0.51 ha-1. Rate 3'.0kgha_1. Controls a narrow weed spectrum very effec­ Kerb Flo*; 400 gl_1 a.i. Rate 3.751 ha-1. tively. Apply November to December (January: north Tolerated by a wide range of tree species of a line from Aberystwyth to London). Treat when they are dormant. Many tree species all common forest tree species. For crop safety have been successfully over sprayed during reasons propyzamide should not be used the growing season once the extremely tender within 6 months of an application of simazine early growth has hardened. Larch can exhibit or atrazine. In mild autumns application severe twisting of needles but eventually should be delayed until the weather has grows out of this transient damage. Douglas turned cold and wet. fir shows the same symptom to a lesser extent. Some broadleaved species exhibit tran­ Simazine sient damage as curling of margins of leaves, Approved product: Gesatop 500SC ; 500 gl"1 a.i. particularly alder and beech. Rate 2.0-4.01ha_1. Cyanazine All conifer transplant lines may be treated as Approved product: Fortrol*; 500 gI-1 a.i. well as all commonly planted deciduous species except ash. Does not control germi­ Rate 4.0lha"1. Controls a wide range of grass and nated or triazine-resistant weeds. Higher rate broadleaved weeds early post-emergence. is used on heavier soils. Soils must be moist and sufficiently compacted to prevent herbi­ Tolerated by a wide range of tree species, but cide washing down to the rooting zone of trees. damage can occur if trees have started to flush or are in active growth. Use half rate on sensitive species, e.g. larch. Fluazifop-P-butyl Herbicides with foliar activity Approved product: Fusilade 5*; 125gl"1 a.i. When the control of weeds after they have Rate 1.5-3-Olha"1 + Agral 0.1% of final spray emerged is the objective, herbicides with foliar volume. activity are usually required. It is vital to Only effective against grass weeds, but annual identify correctly the weed problem and select meadow grass, fescue spp. and all broadleaved a herbicide which will control the relevant weeds are resistant. When controlling annual

176 grasses (black-grass, barren (sterile) brome), BEFORE ANY HERBICIDE volunteer cereals and wild oats use the APPLICATION, READ THE LABEL. 1.5lha-1 rate. This will be effective from the 2 IT CARRIES FULL INSTRUCTIONS FOR true leaf stage (when there is sufficient foliage USE AND THE PROTECTION OF THE to take up the herbicide) to the fully tillered OPERATOR AND THE ENVIRONMENT. stage. Perennial and rhizomatous grasses should be treated at the 4 true leaf stage with 3.0lha-1. All forest trees can be treated. This Paraquat product is not approved for application Approved product Gramoxone is available and through hand-held equipment. has been recommended previously; current rec­ Metamitron ommendations offer the same efficacy of weed Approved product: Goltix WG*; 700gkg-1 a.i. control while providing greater operator safety. Rate 5.0 kg ha-1. Controls a wide range of grass and broad­ 12.3.6 Fallow leaved weeds but only at the cotyledon stage The fallow period in a forest nursery rotation post-emergence. Tolerated by a wide range of provides an opportunity for controlling deep tree species. rooted perennial weeds by a combination of Metazachlor cultivation and chemical control. Repeat appli­ Approved product: Butisan S; 500gl-1 a.i. cations may be necessary to achieve adequate Rate 2.5 lha-1. control. Controls a limited range of grass and broad­ Glufosinate ammonium leaved weeds early post-emergence. Tolerated Approved product: Challenge-, 150 gl-1 a.i. by a wide range of tree species, but pine can Rate 3.0-5.0lha-1. be damaged if treated when in active growth Only useful against non-rhizomatous weeds. before candles have hardened. Best used pre-planting to clean up flushes of Propyzamide germinating weeds after cultivation. Approved products: Kerb 50W; 500 gkg-1 a.i. Rate 3.0 kg ha-1. Glyphosate Kerb Flo; 400gl-1 a.i. Rate 3.751ha-1. Approved product: Roundup-, 360gl-1 a.i. Apply November to December (January: north of Rate 1.5-4.01 ha-1. a line from Aberystwyth to London). Controls a Repeat applications combined with intervening range of broadleaved weeds early post-emer- cultivation can be particularly useful against gence and a wide range of grasses up to an deep rooting weeds such as Equisetum spp. advanced stage of growth. Treat all common Sodium chlorate forest tree species. For safety reasons propyza­ Approved product: Atlacide soluble powder-, mide products should not be used within 6 580 gkg-1 a.i. Rate 375-500 kg ha-1. months of an application of simazine or atrazine. Should only be used in extreme circumstances The two herbicides listed below can be used as to control persistent weeds, e.g. Equisetum a directed spray avoiding all contact with the spp. At least 6 months should elapse between crop to control established weeds in trans­ treatment and sowing or lining out. A ‘cress plant lines. test’ should be carried out before any crop is Glufosinate a m m onium planted on the treated area. Approved product: Challenge; 150gl-1 a.i. Paraquat Rate 3.0-5.01 ha-1. Approved product Gramoxone is available and Glyphosate has been recommended previously; current rec­ Approved product: Roundup-, 360gl-1 a.i. ommendations offer the same efficacy of weed Rate 1.5-4.01 ha-1. control while providing greater operator safety.

177 12.4 Mechanical control of weeds 12.4.3 Ploughing and cultivating implements Implements which uproot or sever weeds are These are suitable for controlling weeds only in mainly used in transplant lines and on fallow fallow ground, and act by burying weeds in the ground. They can also be used between drills of drill-sown seedbeds but care must be taken case of ploughs or by soil disturbance and because of the delicate nature of the crop par­ uprooting weeds in the case of cultivators. If cul­ tivation using this type of machine is employed ticularly in the early stages of growth. The disturbance of soil through the use of on fallow ground, the ground should only be cul­ machines will have the effect of reducing the tivated to a depth of 10 cm, so that any cultiva­ tion pan that is formed during the season can be effectiveness of any residual herbicides which have been applied previously. broken by ploughing at the normal depth when the ground is prepared for cropping. The various types of implement are normally attached to a tractor-mounted tool bar so that several inter-row strips can be cultivated at one 12.4.4 Timing of cultivations pass. Machines are usually designed to treat The timing between cultivations will vary one nursery bed at a time but it is essential that depending on the type of weeds to be con­ the spacing between rows is constant. trolled, the type of cultivator being used and Implements for weed control can be grouped the prevailing climatic conditions. But cultiva­ into scarifiers, hoes and ploughs or cultivators. tion must be carried out frequently enough to prevent weeds from seeding. 12.4.1 Scarifying implements This type of implement can be divided up 12.4.5 Control of weeds by hand into two main groups. Those which have ver­ The oldest way of controlling weeds is to pull tical tines which run in groups of three or them individually by hand. Although effective, more between rows of plants, or those which it is generally the most expensive method. have wheel like rotating brushes which Through the use of herbicides and cultivation brush the weeds out of the ground between equipment, the amount of hand weeding has rows of plants. Both types of implements are been drastically reduced. Nevertheless, there most effective when used on light soils at are circumstances where weeds can only be intervals of 2-3 weeks; they are less effective controlled by hand; in the period soon after on heavy soils and cannot deal with estab­ the germination of the forest tree seedlings or lished weeds. when the weed is resistant to the herbicide or the crop is unable to tolerate a chemical which 12.4.2 Hoeing implements is effective against the weed species present. These implements slice the soil just below the Hand weeding is a slow job and it is impor­ surface, severing big weeds and uprooting tant to start weeding soon after the problem small ones. In addition to hoes with stationary weed species become visible. This allows the blades, there are machines where the blades weeds to be removed without damaging the rotate or reciprocate. If carelessly used, crop and the job can be completed before the mechanical hoes can damage roots and side weeds on the last piece of ground become too shoots of plants to a far greater extent than large, or shed seed. scarifiers. Fixed blade hoes are generally less satisfactory than rotary or reciprocating hoes as they tend to ridge up the soil at the base of plants, smothering lower foliage. Rotary or 12.5 Spraying equipment reciprocating hoe blades move much faster in The decision on the type of sprayer will depend relation to the soil, and leave the disturbed upon the size of the nursery and the size of the soil more or less in place. actual spraying operation. Wherever practical,

178 a tractor-mounted hydraulic boom sprayer Flat fan nozzles, which are available in a should be used in preference to knapsack range of spray angles, produce an elliptical sprayers as it has the advantage of greater spray pattern. In order to achieve an even depo­ output, more even distribution and of isolating sition over the swathe it is essential that the the operator from the pesticide. nozzles are set at an angle on the boom to avoid impact of spray from neighbouring nozzles, and 12.5.1 Tractor-mounted hydraulic that the boom height is correctly adjusted to boom sprayers take account of the spray angle of the nozzle to There is a large range of suitable sprayers give the correct overlapping of the spray. available. When making a choice, the fol­ ‘Even spray flat fan’ or floodjet nozzles pro­ lowing points should be considered: duce a rectangular pattern giving an even dis­ tribution across the swathe which is necessary • Tank size. Large enough to spray the max­ for knapsack sprayers being a single nozzle imum area without refill. applicator, and for inter-row spraying where • Boom. the spray from each nozzle must be confined (a) With facilities to adjust height. to the soil between crop rows. (b) Sufficient length to spray 3 or 5 beds. The size of the nozzle will depend upon the (c) Facility to shut off flow to boom sections required swathe width and application rate; the to permit spraying of single beds. manufacturer’s nozzle data literature should be (d) Pressure control system to achieve a consulted to help select the appropriate nozzle. constant volume flow to the nozzles. (e) Automatic pesticide mixer. 12.5.4 Spray pressures Pressure controls the flow through the nozzle, 12.5.2 Knapsack sprayers droplet size and to a limited degree the spray There are two types of knapsack sprayer, the angle and hence the swathe width of single pressurised which requires pumping up before nozzle applicators. Lowering the pressure will spraying and the semi-pressurised which reduce flow, increase droplet size and reduce requires pumping up while spraying proceeds. spray angle, increasing the pressure will have There is a wide selection of knapsacks available the opposite effect. in the suitable range of 10-15 litres capacity. Generally, larger droplets can be used for The knapsack should be fitted with a pres­ soil-acting herbicides than where foliage is to sure control system in order to maintain a be treated, because it is often critically impor­ constant flow through the nozzle when either tant to get an even, complete cover of spray on the pressure drops in the pressurised knap­ foliage. However, the smaller the droplet size, sack or fluctuates through the pumping action the greater the risk of drift; for that reason of semi-pressurised knapsack. droplets should be no smaller than is neces­ The lance should be fitted with a means of sary to give adequate cover. interchanging nozzles. The most appropriate operating pressure 12.5.3 Nozzles settings for the nozzles in use and the droplet size required can be obtained from data sheets Always read the product label to ascertain if supplied by the nozzle manufacturers. there are any specific recommendations. As there is a large range of types of nozzle 12.5.5 Calibration (BCPC, 1988), giving different distribution patterns, spray angles and flow rates, it is rec­ It is essential, in order to achieve even distri­ ommended that flat fan nozzles are fitted to bution of the pesticide, that the sprayer is the tractor-mounted boom sprayer and ‘even correctly calibrated each time it is used. The spray flat fan’ or floodjet nozzles fitted to the calibration procedure is: knapsack. • Read label for recommended volume of

179 application and spray quality (nozzle type REFERENCES and operating pressure). ALDHOUS, J.R. (1961). Experiments in hand- • Calculate sprayer ground-speed. Measure weeding conifer seedbeds in forest nurs­ the time in seconds to cover 100 m and cal­ eries. Weed Research L 59-67. culate km h_1 by the following formula: BCPC (1988). Nozzle selection handbook. British Crop Protection Council, London. Speed km Ir1 = ------BCPC (1990). Weed control handbook - Time (seconds) Principles, 8th edition. Eds Hance, R. J. • Measure nozzle spacing for boom sprayers and Holly, K., for British Weed Control or swathe width for knapsacks. Council. Blackwell Scientific Publications, • Calculate nozzle output by the following Oxford. formula: MAFF (1994). Pesticides 1994. Reference Book 500. HMSO, London. Nozzle output = RICE, R.P. (1986). Nursery and landscape Volume of application Speed Nozzle spacing* weed control manual. Thomson Publi­ (litres/hectare) (km/h) (m) cations, Fresno, USA. 600 WILLIAMSON, D.R., MASON, W.L., * For knapsack substitute swathe width. MORGAN, J.L. and CLAY, D.V. (1993). • Select nozzle from manufacturer’s data lit­ Forest nursery herbicides. Forestry Com­ erature. mission Technical Paper 3. Forestry Com­ mission, Edinburgh. • Measure the output from at least one nozzle from each boom section. If the nozzle output differs from that calculated, increase or decrease the pressure or change nozzles until the nozzle output equals the calcu­ lated nozzle output. Consult the British Crop Protection Council’s Nozzle selection handbook (BCPC, 1988) for further information on nozzle selection and calibration.

12.5.6 Cleaning the sprayers After spraying, the sprayer should be thor­ oughly washed down and cleaned inside in an approved manner. See Chapter 15, section 15.6.6 ‘Disposal of pesticide residues’.

12.5.7 General All operators of spraying equipment should be fully trained and hold the NPTC certificate. They should be supplied with and wear the necessary protective equipment. See Chapter 15, section 15.6.1.

180 Chapter 13 Protection against climatic damage, fungal diseases, insects and animal pests

R. G. Strouts, S. C. Gregory and S. G. Heritage

Although insect pests, fungal diseases, current legal requirements into account, con­ extremes of weather and various animals can tact the Forestry Authority Research Stations, from time to time cause devastating damage addresses in Appendix I. in forest nurseries, few types of damage occur Descriptions of many pests, diseases and frequently enough to justify the use of chem­ disorders are available in the published litera­ ical or other control measures as a matter of ture and are listed in the references at the end routine. Enough is known about the condi­ of this chapter (e.g. Bevan, 1987; Peace, 1962; tions that encourage certain types of damage, Phillips and Burdekin, 1992; Smith et al., for the nursery manager to be able to avoid 1988). them or, where this cannot be done, to reduce their likely severity. Chemical control mea­ sures can mitigate the worst effects of some 13.1 Climatic damage pests and diseases, and guard against conse­ quential secondary outbreaks. It is worth 13.1.1 Low temperature noting however that, serious though pests and Tree species, provenances and varieties differ diseases can be, the most frequent causes of greatly in susceptibility to low temperature injury to young plants are cultural malprac­ injury and, since the weather conditions that tices such as the misuse of chemicals, and lead to injury are equally variable, only gen­ extremes of weather. eral guidance can be given here and in the fol­ The current legislation governing the use of lowing sections. pesticides is outlined in Chapter 15, section Plants may be subjected to damagingly low 15.6. Few of the pesticides recommended in temperatures at any time of the year. this chapter have ‘on-label’ approval for use However, other than in exceptionally severe on forestry nursery stock; at the time of winters, most low temperature injury is writing, their use for the purposes described caused by autumn and spring frosts. The most in this chapter is permitted under arrange­ damaging frosts are usually those following ments that may at any time change. It is spells of unseasonably warm weather as this incumbent on the user to understand these may delay the onset of winter hardening or before using any fungicide or insecticide. The induce premature breaking of dormancy current arrangements may be reviewed at any (dehardening). The risks of frost injury should time, and this may result in the choice of be borne in mind when selecting nursery sites product or active ingredient being restricted and when planning the layout of existing (see also Chapter 12, section 12.1). For recom­ nurseries. During the life of a nursery, care mendations on insecticides and fungicides for must also be taken to ensure that no frost hol­ use on forest nursery stock which take the lows develop as a consequence of growth of

181 adjoining plantations, shelterbelts or hedges. Exceptionally, bark on older shoots and If these do grow up and prevent cold air from stems may be killed. The damage sustained draining away, one or more gaps must be cut can vary from localised lesions to substantial to let the air escape. These gaps should be dieback and occasionally the death of the about as wide as the barrier is high. See also whole plant. Chapter 14, section 14.2.5 and 14.3.5. Shoots and foliage injured by low tempera­ 13.1.3 Autumn or ‘early’ frosts tures are susceptible to secondary fungal inva­ By the time the first autumn frosts occur, most sion. This subject is dealt with in section forest tree species in the nursery have already 13.1.5. acquired a degree of frost hardiness. However, Plants can be protected against low temper­ some species and certain provenances of others ature injury by provision of overhead shelter continue to grow late and there is consequently or by spraying with water. In some nurseries a high risk of damage to them, especially in and with some very susceptible species, frost northern nurseries. Factors that delay hard­ protection using overhead shading or netting ening can increase the likelihood of injury in covers may be justified as a routine measure. normally frost-resistant plants. A spell of Otherwise, because of the variability of the unseasonably warm weather before the first British weather and its influence on hard­ frost is one such factor; others are early defoli­ ening and de-hardening processes, the deci­ ation by pests or diseases, and nutritional sion to give frost protection has to be taken status. locally on a daily basis. It is essential, there­ Autumn frost damage may lead to foliage fore, that the means of protection can be browning in conifers and death of unhardened installed at short notice. See Chapter 11, sec­ buds and shoots. Shoot injury commonly tion 11.4.3 for details of the use of irrigation to results in forking the following season. Species give local protection against unseasonable often damaged are Douglas fir and southerly overnight frosts. provenances of Sitka spruce. 13.1.2 Spring or ‘late’ frosts Most species used in British forestry are liable 13.1.4 Winter cold to be damaged by spring frosts from time to Winter cold can cause injury to a number of time but Scots pine, lodgepole pine, birch and species, especially if low temperatures alter­ most poplars are rarely frosted. Germinating nate with mild spells or are accompanied by conifers are also generally resistant. Newly strong winds. Western hemlock, western red lined out transplants usually break dormancy cedar, Douglas fir and Abies species are among later than plants left undisturbed and may those that can be damaged by such conditions. also be less at risk from spring frosts. Symptoms are variable but can include foliage Autumn sown hardwoods, especially beech discoloration and shoot dieback. and oak, often germinate before the last spring The browning of foliage that may follow frost and may sustain heavy losses unless pro­ strong, dry winds in cold winter and early tected by plastic shading or netting overhead spring weather is believed to be, in essence, shelter. drought damage. Plants may be unable to Death of buds, new shoots and leaves is the take up water from frozen or near-frozen soils commonest form of damage: the injured tissues and hence may be unable to replace rapid rapidly shrivel and turn brown or black. moisture loss in very cold weather. Affected plants usually recover by producing Low winter temperatures on their own can new shoots from surviving or adventitious injure less hardy species such as some buds, though plants which recover are often Nothofagus species. Exceptionally cold spells forked. If singled, the remaining shoot often have been known to kill the roots of Lawson resumes apical dominance. cypress in containers.

182 Although snow cover can insulate buried heavy losses of small 1-year-old seedlings, but plants effectively, freezing winds over the it is rare on well drained sandy soils. There is snow surface may injure exposed shoot tips. evidence that dense or drill-sown beds are less The exceptionally severe winters that lead likely to be damaged because blocks of plants to widespread injury are rare events and rou­ tend to lift and resettle as units. Autumn tine provision of shelters is probably not justi­ lined out stock is particularly vulnerable in fied in most situations. However, in northern the months immediately after transplanting. nurseries, species that regularly suffer slight If frost lift occurs, little can be done except injury may benefit from winter covers. to re-insert the seedlings when ground condi­ tions allow. In severe cases this is, however, 13.1.5 Secondary infection following often impracticable. low temperature injury Tissues killed by frost, or indeed by other abi­ 13.1.7 Heat and moisture stress otic agents, are subject to invasion by a As noted in Chapter 6, section 6.3.7, the tem­ variety of fungi. Some of these are oppor­ perature of the soil surface in periods of tunistic pathogens which can subsequently bright, hot sunlight varies according to the spread into previously undamaged tissues. colour and nature of the seedbed surface The most common and probably most dam­ material and can become high enough to aging such organism is Botrytis cinerea (grey injure the root collar of small, thin-barked mould) which is discussed separately in seedlings. Such damage has become less Section 13.2.2. It is a ubiquitous fungus and common, partly through use of light-coloured can invade frost-damaged tissues extremely grit for seedbed cover, and partly because of rapidly in the cool humid conditions that often the availability in many nurseries of irriga­ prevail in autumn and spring. tion, the use of which can cool seedbed sur­ Shoots injured by low temperatures may faces in hot weather. also be infected by Phacidium (Potebniamyces) Drought damage, although largely the coniferarum, formerly known as Phomopsis result of dry soil conditions, can be much pseudotsugae and dealt with under that name worsened by drying winds. Symptoms vary in older Forestry Commission publications as from reversible wilting, through the fading a cause of dieback in Douglas fir. P. conifer­ and death of foliage, to the withering and arum can invade more substantial woody dieback of shoots. Foliage browning usually shoots than is usually the case with Botrytis. commences at the margins of leaves or the It is a particular risk on Douglas fir but occa­ tips of needles. Irrigation, which will prevent sionally occurs on other conifers too. or mitigate drought damage, is discussed in Chapter 11, section 11.4. 13.1.6 Frost lift In glasshouses and polythene tunnels, where temperatures are more likely to reach Freezing in wet, heavy soils causes ice crystals damaging levels than in open ground, provi­ to form just below the soil surface. As freezing sion of adequate ventilation is vital. continues, these crystals grow, so that the sur­ Cloched seedlings may suffer severe heat face of the soil lifts or heaves. The soil surface and moisture stress from bright sunshine and carries with it shallow or weakly rooted drying winds should these follow quickly on seedlings, forcing them upwards; on thawing, the removal of the cloches. the fine soil particles fall back quickly, leaving the plants partly uprooted. Repeated freezing and thawing can eventually push plants out of 13.2 Protection against fungal the ground altogether. Small stones are brought to the soil surface in the same way. diseases On heavier soils, frost lift can bring about Although fungal damage can be locally severe

183 at times, few diseases warrant the expense Damping off and fungal root rots can be and labour of routine preventive treatment. very difficult to diagnose, even with laboratory Moreover, repeated use of certain types of facilities. In particular, they can be impossible fungicide in a limited area can lead to a build­ to separate from direct root injury by water­ up of resistant strains of pathogens. logging, a condition that itself greatly favours If repeated, damaging attacks of a disease attack by the primary and secondary root dis­ occur, check whether there is a local infection ease fungi that are often present at low levels source or an inappropriate cultural practice that in nursery soils. can be dealt with directly as a first response. Several seedling root pathogens can live in Nevertheless, should they be required, effective water and so, in addition to an association fungicidal treatments are available against sev­ with poor drainage, there is a risk of intro­ eral important nursery diseases. ducing them into nurseries and greenhouses via contaminated irrigation water. This danger can be avoided by the use of mains 13.2.1 Damping off and root rot water and is unlikely to arise if spring or arte­ Serious diseases of seedlings can be caused by sian water is used. Detailed information on several seed- or soil-borne fungi that attack the purification of suspect water supplies can young roots and stem bases. These pathogens be obtained from Ministry of Agriculture’s are mostly in the genera Fusarium, ADAS or, in Scotland, SOAFD advisers or Rhizoctonia, Phytophthora and Pythium, the from the the British Effluent and Water Asso­ last two being the most commonly identified ciation, 5 Castle Street, High Wycombe, in British forest nurseries. Buckinghamshire HP13 6RZ. Whatever the Fatal infections that occur in the first 3^4 water source, storage tanks must be kept cov­ weeks after germination have traditionally ered and clean. been referred to as ‘damping off but this is a Control of seedling root diseases is as diffi­ poorly defined term and may cover a variety cult a problem as their accurate diagnosis. If of symptoms. Germinants may be killed they are associated with poorly drained areas, before they emerge from the soil (‘pre-emer­ as is often the case, improvement of drainage gence damping off) or may brown and wither should be a priority. However, if root disease shortly after emergence, following death of is a recurrent and serious cause of loss in open their roots. Sometimes infection occurs at seed beds, pre-sowing partial soil sterilisation ground level, causing the seedling to fall over (Chapter 6, section 6.1.4) probably gives the while still green and still attached to the best chance of control. This treatment will (often live) root by the withered base of the also control nematodes (eelworms) which can hypocotyl (Strouts, 1981). cause very similar damage to that caused by In nursery beds and lines, root diseases can fungal root pathogens. Soil sterilisation affect scattered individuals but often, and cannot be guaranteed to provide long-term especially in seed beds, expanding patches of control of soil-borne disease since the treated infection develop. The centres of large patches beds can be re-invaded from surrounding may be devoid of seedlings where pre-emer­ untreated soil or from infection sources else­ gence deaths occurred. where in the nursery. Soil sterilisation will As plants increase in size, infection by not control seed-borne diseases. nursery root pathogens is less likely to have a In greenhouses, the use of properly ster­ fatal outcome though it may lead to stunting. ilised or soil-less compost and clean irrigation However, some root disease fungi, particularly water, together with the practice of good Phytophthora species, can continue killing greenhouse hygiene, should prevent the occur­ nursery stock up to transplant size and rence of root diseases. Although the use of sus­ beyond. Fungal root diseases of older plants pect rooting medium should be avoided, some are commonly known as ‘root rots’. soil-borne pathogens can be controlled by

184 incorporating fungicide into the rooting BEFORE ANY FUNGICIDE medium before sowing. APPLICATION, READ THE LABEL. It is not possible currently to control estab­ IT CARRIES FULL INSTRUCTIONS FOR lished outbreaks of root disease among USE AND THE PROTECTION OF THE seedlings; there is no fungicidal treatment of OPERATOR AND THE ENVIRONMENT. proven efficacy in British forest nurseries against any of this group of pathogens. Rate: 3.0 kg product in 1000 litres water applied at high volume (more than 13.2.2 Grey mould (Botrytis cinerea) 7001 ha'1). Grey mould is a common colonist of dead organic matter and will also readily invade Thiram: any 80% w/w wettable powder for­ dead or dying soft tissues on living plants. mulation. Under circumstances favourable to the Rate: 4.0 kg product in 1000 litres water fungus, it can then grow into living tissues applied at high volume (more than and greatly extend the original damage. 700 lha-1). Infected parts often become invested with a Benomyl: any 50% w/w wettable powder for­ sparse grey web of hyphal threads bearing mulation. See note below. pinhead-like clusters of spores at their free Rate: 1.1kg product in 1000 litres water ends, just visible to the naked eye. As plants applied at high volume (more than become woody with age, the disease becomes 700 lha-1). less important though occasionally the fungus Timing will kill the main stems of transplant-sized Seedbeds: apply immediately damage is seen conifers. The humid conditions which often then every 10 days until no mould is evi­ prevail inside dense stands of young plants dent. Following autumn frost damage, are conducive to Botrytis damage so over­ apply immediately, once only. stocking in seedbeds and greenhouses should Greenhouses: apply immediately damage is be avoided wherever possible. In greenhouses seen, again one week later, then every raising container stock, good air circulation 10-14 days until no mould is evident. should be maintained to promote the rapid drying of wet foliage (Anon., 1989). Note Plants that do become densely packed Avoid regular and frequent use of benomyl as should be better ventilated if this is possible, this could lead to the development of Botrytis inspected regularly and sprayed with a fungi­ strains which are resistant to this fungicide. cide at the first sign of the disease. In these circumstances, it is worth taking some trouble 13.2.3 Lophodermium needle cast of to ensure that the particularly susceptible pine (Lophodermium seditiosum) shaded foliage is treated. Infection can also occur on shoots and foliage The cause of this disease was formerly damaged by frost or chemicals (including fer­ thought to be Lophodermium pinastri and the tilisers). Nursery managers should be prepared disease is dealt with under that name in most to spray crops should such damage occur, espe­ older Forestry Commission publications. cially if this happens late in the season, when Infection usually takes place in late wet foliage is very slow to dry. summer or autumn on current needles but sometimes also on older needles. Pale spots appear on them and gradually enlarge and Fungicidal control o f grey mould darken. The black transverse bands or Materials ‘diaphragms’ on needles mentioned in earlier Captan: any 83% w/w wettable powder for­ literature are not a useful diagnostic feature. mulation. L. seditiosum fruit bodies are visible on

185 infected needles but are too much like those of the disease is a recurrent problem, such as other fungi to be useful in field recognition of those near older pine trees, which com­ the disease. Eventually the needles turn com­ monly harbour the fungus. pletely brown, often with a characteristic dull, • Spraying after symptoms appear will not mottled pinkish-brown coloration, and begin arrest the disease. to fall. This stage is normally reached in late • Avoid regular and frequent use of benomyl winter or spring and, in serious outbreaks, as this could lead to the development of whole beds or transplant lines may be almost Lophodermium strains resistant to this needle-less by spring. fungicide. The additional stress imposed by Lophodermium defoliation on plants that are lined out or planted in the forest in the 13.2.4 Meria needle cast of larch autumn or spring following infection, increases Meria occurs on European, hybrid and Jap­ the risk that the affected plants will fail to anese larches but is uncommon on Japanese establish. Severe infection can be fatal to 1- larch. Severe infections may be fatal to 1-year year seedlings, even without transplanting, seedlings or other small, weak plants. but older nursery stock usually recovers if Normally, however, infected plants recover, carefully lined out or left undisturbed. The cur­ though growth may be reduced. rent foliage of such plants should be protected Foliage infection takes place in spring and with a fungicide during summer and autumn symptoms may appear as early as May though against infection from the old, diseased needles frequently they do not become evident until which, by then, will usually have fallen. later in the summer. Infection generally occurs near the tip or in the middle of the Fungicidal control of Lophodermium needle and results in a yellow then brown patch. The needle browns and withers from Materials the tip down to the infected zone while the Maneb: any 80% w/w wettable powder formu­ base may remain green. lation. Typically, symptoms are first seen in the Rate: 2.8 kg product in 1000 litres water older needles at the base or in the middle of applied at high volume (more than current shoots but they then progress towards 700 lha-1). the shoot tip during the season. The needles Zineb: any 70% w/w wettable powder formu­ at the very tip of shoots sometimes remain lation. green however - a useful feature which may Rate: 4.2 kg product in 1000 litres of water help distinguish Meria from injury caused by applied at high volume (more than frost, where terminal needles are usually the 700 lha-1). most severely damaged. The fungus survives over winter on fallen Benomyl: any 50% w/w wettable powder for­ needles and on infected needles that remain mulation. See ‘Remarks’ below. attached to the plants. In consequence, severe Rate: 2.0 kg product in 1000 litres water applied infections can develop in plants spending a at high volume (more than 7001 ha-1). second year in the same beds or lines. Plants that show evidence of infection in one year Timing should be protected by spraying during the fol­ Once every 4 weeks, the first application in lowing year. Transplanting also reduces the mid July, the last in mid November. risk of reinfection by distancing plants from old infected foliage. Remarks The disease is only a serious problem in wet • Routine spraying of Scots and Corsican seasons or, as mentioned above, in stood-over pine may be necessary in nurseries where beds and lines. Although the greatest risk of

186 infection is associated with diseased nursery BEFORE ANY FUNGICIDE stock, older larch can probably also act as an APPLICATION, READ THE LABEL. infection source. The risk of attacks in nurseries IT CARRIES FULL INSTRUCTIONS FOR can therefore be further reduced by avoiding USE AND THE PROTECTION OF THE siting larch stock near larch plantations. OPERATOR AND THE ENVIRONMENT. Fungicidal control of Meria Materials Badly affected leaves may fail to expand Zineb: any 70% w/w wettable powder formu­ properly and become distorted. They may also lation. exhibit dead, brown patches and fall prema­ Rate: 4.1kg product in 1000 litres water turely. Infected shoots may wither or, if they applied at high volume (more than survive infection, may fail to harden normally 7001 ha"1). in autumn and so become liable to frost injury. Only young growing tissues are susceptible Sulphur: any 80% w/w wettable powder for­ to infection so that foliage produced late in the mulation. season, when spore production is usually at its Rate: 4.0 kg product in 1000 litres water height, can be heavily mildewed. This is fre­ applied at high volume (more than quently the case with lammas growth and 700 lha-1). foliage produced on plants reflushing after Timing insect defoliation. Severe attacks of mildew can kill young seedlings and cause stunting Apply every 2-3 weeks, the first application at and bushy growth in older plants. flushing, the last in early August. Treatment can be discontinued during settled periods of hot, dry weather but should be resumed if Fungicidal control of oak mildew weather changes. Materials Sulphur: any 80% w/w wettable powder for­ Remarks mulation. See ‘Remarks’ below. As explained above, infected plants which are Rate: 4.0 kg product in 1000 litres water to be stood over should be sprayed in the fol­ applied at high volume (more than lowing year. Otherwise, treatment is recom­ 700 lha-1). mended only in nurseries where attacks are regularly experienced. Dinocap: any 500 g l_1 emulsifiable concen­ trate. 13.2.5 Oak mildew (Microsphaera Rate: 0.5 litres product in 1000 litres water alphitoides) applied at high volume (more than Newly emerged leaves are infected in May by 700 lha-1). spores produced from buds in which the fungus Benomyl: any 50% w/w wettable powder for­ has overwintered. Pale brown spots appear, mulation. See ‘Remarks’ below. mostly on the undersides of leaves, and from Rate: 1.1kg product in 1000 litres water them the fungus spreads across the leaf as a applied at high volume (more than conspicuous white mycelium covered in a thick 7001 ha"1). powdering of white spores. These are dispersed by air to repeat the process of infection on more Timing leaves and shoots. As summer progresses, the Apply at first sign of mildew and every 2 production of spores, and hence infection, can weeks if mildew reappears. increase enormously. In contrast to many foliage diseases, oak mildew and related ‘pow­ Remarks dery mildews’ (such as that on hawthorn) • Some sulphur products may not be thrive in dry, warm weather. approved for use in greenhouses.

187 • Avoid frequent and regular use of benomyl Benomyl: any 50% w/w wettable powder for­ as this could lead to the development of mulation. mildew strains resistant to the fungicide. Rate: 1.0 kg product in 1000 litres water applied at high volume (more than 13.2.6 Keithia disease of western red 700 lha-1). cedar (Didymascella (formerly Keithia) thujina) Timing Typically, this disease kills scattered leaves. Apply at fortnightly intervals from late April However, severe infections can lead to shoot until early November. dieback or even death of whole plants. In spring, spores which have overwintered Remarks on Thuja foliage, germinate and infect scale These recommendations are based on leaves. Fruit bodies quickly develop on the French work carried out in the 1980s killed tissue and these, along with others (Boudier 1983, 1986). We are unaware of which may have overwintered on tissues any trials or observations made in this killed the previous year, release spores which country to confirm the efficacy of these infect newly developing leaves. treatments. Dead, infected scale leaves may carry up to three of the distinctive Keithia fruit bodies. 13.2.7 Moulds on plants in storage These are easily visible to the naked eye as The development of storage mould is generally round or oval, blister-like structures, about a reflection of inappropriate storage conditions 1.0 mm in diameter. They are dark brown or or faulty practice. By the time the problem is golden brown in colour and covered by a round discovered, it is usually too late for control lid which folds back in moist air to release the measures to be taken. Cold-store managers spores beneath. Old fruit bodies appear as should therefore pay strict attention to the black cavities. guidelines on plant storage given in Chapter The disease can cause heavy losses in 14, section 14.7.3. western red cedar plants from their second year until about their fifth year, when they acquire considerable resistance. Keithia can 13.3 Control of insects generally be avoided if plants are raised from seed in a nursery at least half a mile from any 13.3.1 Need for vigilance other western red cedars and if, in addition, each crop is completely cleared and the debris To achieve an adequate level of protection from burnt before the next crop is sown. Since this insect and other pests, it is important to is rarely practicable, plants may require examine plants starting from early May, when fungicidal protection. most insects become active and continuing Plants raised from cuttings have the throughout the summer. Particular attention reduced susceptibility of the more mature should be paid to the underside of leaves and stock plants. needles. When seen, appropriate measures should be taken to reduce infestations before Fungicidal control of Keithia they cause more than local damage. (see remarks below) Few insects cause damage on open-grown stock in the present-day nursery. However, Materials numbers of species may build up and cause Prochloraz: any 50% w/w wettable powder appreciable loss in a particular year. Table formulation. 13.1 lists those which have from time to time, Rate: 1.8 kg product in 1000 litres water applied caused such loss. In the table, moth larvae at high volume (more than 7001 ha-1). and beetles which as larvae or adults, damage

188 roots of nursery crops are listed first; spring- BEFORE ANY INSECTICIDE tails, a leaf miner and spinning mite follow APPLICATION, READ THE LABEL. and then, moths and beetles which feed on IT CARRIES FULL INSTRUCTIONS FOR foliage. Finally, eight aphids and two sucking USE AND THE PROTECTION OF THE insects are listed. Details of the appearance of OPERATOR AND THE ENVIRONMENT. the insect at the stage it is damaging are given, followed by symptoms of damage, the months of the year when damage is expected marketed by manufacturers is a legal require­ and the species damaged. ment and it is an offence to use non-approved Most insect outbreaks will require the use products or to use approved products in a of insecticides for their control, although manner that does not comply with the specific insect-pathogenic nematodes are being devel­ conditions of approval. Under these regula­ oped against some soil-borne pests. Nursery tions, new arrangements were introduced practice can, however, influence the frequency from January 1990 which allowed any pesti­ with which certain control measures have to cide provisionally or fully approved for use on be put into effect. To keep insects down, pos­ any growing crop to be used on forest nursery sible sites where numbers can build up must crops before final planting out. There are a be eliminated as far as possible. For example, number of restrictions attached to these beech should not be used as a hedge within arrangements, the most important, for the nurseries or as a surround, if beech seedlings forest nursery manager, is that insecticides are to be raised; (see Chapter 2, section 2.3.5). must not be used on protected crops, i.e. Weevils and some other species listed are grown in glasshouses, poly-tunnels or under likely to be more prevalent if coniferous plan­ cloches, unless the product label specifically tations immediately surround the nursery. allows such usage. It is essential that the Cutworm larvae, particularly those of the safety precautions, application rate and turnip moth, are susceptible to rainfall and do timing together with any other conditions for not thrive and cause extensive damage in very use that are described on the pesticide label or wet summers. Irrigation of nursery soils can accompanying leaflet are strictly observed. also be an effective counter-measure. A (See also Chapter 15, section 15.6.1). pheromone monitoring scheme for Agrotis The legislation allows a very wide range of segetum is now operated by MAFF. insecticides to be used in forest nurseries to Soil insects are generally much more trou­ suit the insect species and availability. blesome in bare-root nurseries where crops Agricultural chemical supply merchants stand for 2 years than in those where seedlings should be able to advise on the suitability of or transplants are usually lifted after 1 year. an insecticide against specific pests, or more However, the warmth provided by growing con­ specialist advice should be sought from: tainer stock under polythene can reduce insect The Entomologist or The Entomologist generation times considerably and therefore The Forestry The Forestry give rise to problems with soil-borne insects Authority Authority during one growing season, both in houses and Research Division Northern Research under cloches in open ground. Alice Holt Lodge Station Wrecclesham Roslin 13.3.2 Selection of insecticide Famham Surrey Midlothian The use of insecticides is controlled by The GU10 4LH EH25 9SY Food and Environment Protection Act 1985 (FEPA), the Control of Pesticides Regulations 13.3.3 Protecting transplants from 1986 (COPR) and the Control of Substances damage by Hylobius Hazardous to Health Regulations 1988 Young trees used for restocking felled conifer (COSHH). Approval of individual products sites are liable to be heavily damaged by

189 190 Table 13.1 Insect pests found in forest nurseries .1 13 2 o Q. Q)<0 o <0 C V) E U eij ^ O) ■■§ E s u■s g Q Q § -8 § Q & •t ^ ^ 'Si8 ! 1 s -c i Q | •1^ .O 0) t Q, ,t t - (o COr- (a "! c « oiE O COCO - r a: O egCO O)E 0 2 5) g> o?'O E I5 4 b O^ co Q) to t eg g>3 2 co eg O)O) 0) c H! c 0 O O0 0 E CO j

? | | ? c . ***. eg .0 S c ® to c O) O 0 CO ^ eg ^ 0 E COO) 0)

CO ^ I « 5 5 . P *D^ 'c jg ^■g CO L L CO •< <0 - O)*- o 4_r — — CO T— 4— < E 5 t O)S’ O 0 c - 5 ? a> t .c & J5 £ a) >>5 E ° b) 0 0 0 E . b O) £ £ 03 CO ® I "O © 0 i. ^ i. CD . Q a t n M s s i § E to 2 05 2 S o F® m E s > ®

O o CO £ 5 £ M c - 0 (0 0 - ■ c O c >> ciJ >> t r c eg CD2 Q 3 3 .Q 2 Q.0 O = O 0 O) O E . S O3 O 0

X co I O O 'I ■2 E C £ -g ■£J2 g .O r =tr &£ -2 o a? 0 0 O 0 C 0 O c CO — E o J= S F 5 " ° > ^ 2 1 "“ "“ 1 2 Q. 0 O s 2 . Q . . Q O O CO O Q. 1 0 o -oo > . COQi& < ff LL E tr

o . .co ~o *o (0 co o CO— O) ? J *0 8 0 c o.> 0 0 CM 0 0 O)O) *2o .32§ □ " E E .E 0 £ 0 0 E 0 >» S 2 0 . o 0 ■§ p ro £ 0 0 m I I 3 l _ 2 o>-2 3 2 0 -Q0 C i 0 s S ^ .E a> 5 • -£0 £ o P j= ..S’ o 'to to Q s I 0 v*— C0 co b) £ I I o Eg E to « ? ra fe ° S s. “ 0

e 0 3: -S =3 *3 •2 O — JZ *0 ■O "0 7 - > Z P*E 0 S 0 ‘c 0 c E 0 £ 0 CD5 O 5 > 0 0 0 £ 0 0 0 0 0 0 O E 3 0 0 . Q 0 . Q 0 > 3 C 0 O c O c 0 E 3 O) 3 0 E 0 c C 0 0 J0 "O 00 ■0 0 * "c 0 0 $ 5 0 0 0 b> 0 0 > 0 0 0 c >» 0 0 0 . Q 0 0 . > 0 0 0 > 0 C 0 . Q 0 0 0 0 *D 'I 0 0 0 0 0 ■D 0 _ O 0 0 > 0 E 5 2 ■2 2 € £ o •C C =* "D *0 I I >OI J ■g 19 i 0= 1 = i5 CO TT < ‘o LL (0 0 E _ >» c T c c 0 0 O 0 £ 0 _Q 0 O 0 O 0 0 0 0 c § £ 0 % "g ra 2-2 2 0 - o > 0 C CO 0 O ^0 □>5 ™ £ S S I = T = Cl®_ I 0 . a 0 0 o P E F 0 0 2 CO 0 l l O 0 _ 5

5 ra 5 § E 2 0 2 g O 0 CO Q. _: > “ 0 0 0 b 0 , - >» ■- T3 I CO —I ■o ■g-5 _>>(0 j- O E e o E E 0 C « 0 0 O0 0 0 £ = 0 >E £? 0 O)a) ® 2 o S 5 0 > \ — -i "S CD E E 0 0 a_ 0 a. a. ^ C_ 3 0 c CO 0 o a

£ § 0 0 ■o E 0 3 £ ^ ^ 0 0 0 0 0 I U)®I < 5 ^ 2 CJ)0 c 3 E .^ CO £3 ■M CO O cvj >r-C 0 o ■§ ^ 0 >N g S 0 C 0 0 0 £

O 3 ■= i3 TJ 5 5 0 0 0 O . 5 a. a ^ ■£^ 0 0 0 >*»0 0 I 0

Barypeithes Strawberry Small black weevil; 2-3 mm. Adults ring bark the stems May-June All species. araneiformis fruit weevil of young seedlings and ■ ■ Adult cause death. Very similar Barypeithes Short snouted Similar to above but with long to young cutworm damage, pellucidus weevil grey hairs; 2-3 mm. but earlier in the season. Type of pest: Root, stem and leaf feeder "o § E■§ *= . - q h ,£! a: a ca ca Di E a ca ca ® r- s E S 03 2 ' S 5 0 ■ "> -®b | € o to 0) eg £ c ■*—ca 3 > § S co O) ca O) 03 "o CDC 2 ca E ca CD ) j ca o qj o 0) 0) 0) E 0 -8 8 ca r 5 C o *C 0 ^ .0) ^ S. S. 0 ^ ^ O^3 <8 "8 "8 <8

o> ca E cas> 0)

o o> E co E § | 5 Z < *o 0 CO > > w = D E ■D -E P< o 05 £ £ CO 0 < Q- *o *3 co 5 Q_ £ 0 «- M- o = Eto = 8 E 1 - § E 8 0 3 a> _ 0 0 >*0 g o > 0 § C— C3 CO 2 J20 E E = ? > "O0 ^ c co O) 3 _co»_ 0 CQ. 0 0 3C co § CO 0 COis 0 > 0 CO o 0 0 0 5 ® °> a

0 -S -S 0 > co 0C 0 CO 0 0 o 0 Q. 0 0 C O)0 ca w w § -Q -Q E CO -E 9 *D | 1 O) £ z <0 0 0 in CO Q. '>0 U 0 E t 0 ^ _0 •C c £ ^ --= Q ) o 5 O 0 C C n to2 Q 0 CO8 J-

03 s i S a * c •■§ 8 J>l -c 5 a *a £ < ° * 3 5 5 3 , 'j j ■a £ *o *o E < 9 in O ” 1 . g . 3 S C3.CO 3 0 0 ST = o o O 0 O 0 o *“ to0 3 £ V E o E o 0 § 0 0 > 0 C S 0 aj ® c *- *- c o o 0 C Q_ > > ‘ c £ £ 0 0 m L_

8 5 "8 =iJ 11 o o E 3 O)n _Q O 0 S's Q m 0 1 I | f ■8 55 2 JS < g s ■O l CD g '§ 8 i -g 7 C o . § t « J co l * _c 3 — £ ■p r (3 (3 > r O) ■p j2 3 1 1 a3 a) S'? E > • • > E 0 o O) 0 °-o •== h -S c

_0 .co 0 Q_ 0

s 0 8 Q. c8 i_ - o H W < if ® if LL (3 "S CO < I -Q —I "§ f ° I Q. 3 a. ^ . 2 ° to o ® c 1 8 ? s CO CO G^ 0 O C 0 0 □ 0 § « c Q- i= ®-K C 2 w o u> « > S JC 0 ^ “ ™I 0 $ 3 3 *D W w D> 0 Q- I § i [I

0 m 0 0

s - g y Q- =s Uj * .c £ co c 1 <5 ^ -Q jo *D £ CO fl-B - -ft - 5 o f C 0 Q. s i 0 0 £ 0 E C "D « 28 5 I 0 0 Q. n o in O 3 w c o o Z 5 £Z 0) > 0 C

C 0 U) 3 2 0 C

CD 03 .E JZ c E 2 E 5 *00 W *“ 0 C 11 £ -D C 0 0 O)

6 5 a o

Oligonychus Conifer Adult and Very small semi-transparent All stages feed usually on May-Sept. Spruces Will also attack other conifers. ununguis spinning mite juvenile red and green mite (0.5-1 mm). underside of needles causing wilt and fall. Needles turn dingy yellow and threads of 191 silk are plentiful. o 0 *3 0 O P nj 0 E OJ CC

(0 *o (0 TJ CO U co 0 "D c TJ C ■O c ~o ■a cq o cq O cq o cq o 0 o 0w ^ 0 _ o O o o o q) G O cq »_ 5 p »_ 5 p k_ 5 p _ 5 0 »_ 5 0 0 0 Q_ 0 ~o Q © "2 Q. 0 "O a. 0 *o o 0 TJ >- Q. *3 o £ cq p £ cq p £ cq p £ cq o £ 0 r- 0) 0 Q_ o .c Q_ o -C Q_ o x: Q_ O -£= □_ O -C

0 sk 0 cq 2 0 I _L 7 .E Q. Q. K. o -Q < <

o> 0 0 0 0 "D 0 0) O o © > g S s> © ^ tn ~ TJ o 0 .E Z © — o Si c3 © w D) .Q © J=: 0 0 E ,c 0 S O) © 0 o — o o 7=i 0 c .« ° -© 0 T3 0 -o o> ^ c 1! “ 0 •i <0 cq © w s' ca © © 2 c s •9 o e l s 5 C & o © <“ « 0 © l - s 0) *_: ™ M •—C 0© 0 © §1 O .15 cq cq -- CO© £_ TJ £ 7 -Q £ © g c -o 0 E D © " i “ © 0 • cq ^_ u .E •= 0 ^ O)o 0 3 Q -c _i o CO o E S’ ® C O spinnings on needles.

E E (0 0 : E O TJ 0 0 o E 0 • 0 D) 0) cq cq m a. o w — cq O) a. -Q £ E C £ CNJ c o 0 JD a. . to S cq o $ 0 5 - 0 ^ 0 E E _c O *o J fl) ^ o -C w o g> S l l s> i ^ CO 0 0 O *o TJ-rn °_Q .0 C CO 0 E 0 0 © 0 c in 6) 8 *o o *- 0 Q. ° 0 — C\| cq -t- 5 a) in -C CO ra 73 0JZ . - q . ._ © 0 P 0 CO • •ti c ra cq j= £ & ts 0 s TJ •g1 S’ 0 0 0 0 © 0C '§ 0 5 5 £ W 5? r> CO c © X *i£ >» P 0 TJ 2 cq ~ £ . 0 0 Z. © 0 0 _Q - * o - g *o © ^ © P O)— — 0 _ U0 * t■ S S ' to © r r 0 = « ^ E ^ 5 .o“S £ 2? ra *? .i= © ■5 5 © x: 0 2 o S c 511 •t ? s> o> w . o> 5 Q- o s | I CO (0 b -* o | s « ft ■©4 I2 £ 1 - ■O = E ■s O TJ ^ c ra cq -a C © o © X) c O 0 TD —I 0 . Q >, cq= 51 O 0 5k 0 O 0 0 O) .c 7 0 cq 0 0 t O) & £ £ cq cq cq 0 0 O (0

S' O Q) c c o ■8 ^ tq O) E E E 0 C © 0 =§ ® o to t3 X3 C Di E » to ^ 1 o 7 c

2 Grey Larva Greenish larva, green head with Young larvae feed Aug.-Sept. All Commonest of several species 2 red-barred black-marked prothoracic plate; gregariously on shoot tips. conifers of tortricids which can transfer CO 0 a cq x: 0 a •2 £ cq O6 .to a 0 r- ® 3 -s S -2 c ^ n S E § : § I 0 0 S 5 (Q 8. 0 0 0 C 0} cq * 2 Argyrotaenia o s — I co O -o O -2 us 8 pulchellana

192 0) >» .2 o •Sc rao ra ra ra .c 03 0 3 O 5k 5k ra ra O’ £ 03 0) c 0 3 c o 03 . O 03 s 8 I | c (8 >>05 03 0 O 0 03 (0 O) 03 ^ 5 O O ■g ° 3 Q. 0)6 5 o2 0 ra 5 2 o O ec CL 5k I- a. *o E

tfi x ra' I-* O *0 3 O) 03 0 03 3 X3 2 .£ F *0 T3 03 ■Q ■Q o C m_ .E 0 0 C C 03 5k ra o 0 03 0 03 0 03 5k "O 3 ¥ C 03 3 s 5 0) 0 ^ 0 E 2 3 05 03 S g -g ra 0J C C 0 O 3 o O 5k C 03 *03 03 t : 03 Jfe ra o E 0 03 k . .■K 03 03 *o .o' 03 0 03 0) 5k 3 J Z g 0 0) o ra 03 c ° 9 T3 C ■o 03 'c o E P 3 o !c 0? 5 0 ■o 0 C o "O 03 03 0O c 0 ‘c 1 03 ~ 0 r 5 ra C <: 03 TJ 0) ra c X3 C o 03 0) 3 0> C 0 0 03 _±: ““ ~o 03 O S ° C o X g -o 0) < 03 _ w •| E 03 O " « 2k 03 5 ■o 0 0 X) ra 03 & ® 8 o 8 g 0 E o CQ 03 ^ ra !2 x £ I ™ O 0 *0 0 o Q -c —I 0) —I 03 03 i= m ® CO w O X3 5k LL 0 JtZ o _03 X ra 03 5 k c 03 X 0.-0 ■ c c c 0 5 £ O) 0 0 o 0 l l eg O) c E « ‘ 0 0 c Z <° *5 in • CM 03 ■£ 03 of o r ^ c\j X . . 03 0 2 5 - 03 03 'E ra co o r .9 o .«= c S 03 O) O **“ .2 0 o 5 .2 ra '> §-■0 : ra 03 *o n 03 0 D) 8 O CL3 $ § " * # t c r a k . £ o 03 ZT: O o X X W o -2 E -2 P O CD 03 E E 0 C -C • * 5 O 3 c o *0 ‘I f- 0 5 .s: v_0 ra w° u 8 -S _o 0 E I _ 5k CM 03 ^3 C 0 CM 5k ^ 0 5 ra E 0 ra 3 £ 8 O O) Q. w TJ o £ c» o X) 1 03 LT 0 U) rac O o C x> 5 0 ra Ui 0 £ 3 0 T3 ra *0 ra S *""! "o —03 |E -g -o *o €! 03 0 CL o zt: jc: c ra $ t | 03 > _“ 3 co 03 C x : 0 3 03 E CL o 0 o o X s ® o E ra O ra ra 03 -Q 03 03 o. c ■9- c1 §, o O ■o o -1- n 03 • - ra g 03 w ^ E ra X) X3 ‘c ra .2 — "O b -a | ^ w 03 *o > 0 0 03 !2 c m "O E l | c ra & JZ X 0 £ T3 C JZ 0 b T3 C 0 ra£t k_ 03 ra ra c 03 Q. •o Q § -S Q -8 < in 5 —I 03* _i 'II O) —i ra ® 5 —i ra > raQ. (5 £ § .C ■o TJ *5 8* c c C O) ra ra x: X ra x O 2 03 ra ^ ra ±5 Q. Q. ~ CL o E O) C* 3 3 £ E 3 E cq ra ra T3 T3 ra 5k Q 03 —i ra < _i <5 c^ C <3 c>* 0 5 O T3 ra o 3 X -I g 0 Q. ■§ -c ra O) *K- 1 c ra .c 5 0 0 5K CL 0 *3 S 03 O g - € 0 5 = *o 5k "O c 0 Q* 5 ^ ? X 0 0 (Q ,CS> (a£ 2 £ 0 P ra a l rara 2 Q. ,*S 03 o Q> Uj c S i XI Q- 03 X 03 _i 03 cq ra ra (3 C L3 kJ .03 V) ra cs Q> c •c Q. SP .o o H*. ;g .ra ■9l ^ E ra 0) O r a .ra 2 ^ 3 .c Q> .c 03 8 a .8 - * 5 - 6 fo E? E £ ® ra ra y r3 -5 S i § 6 5j < ra O a. Uj nj CO ca.

193 194

Type of pest: Shoot and leaf suckers continued cn —oo o l— CO co *= a I— ,c *§ ts ■S'S c P S I I § ■§ § Q , g e t • co Q 03 o © CO G 0) 0 E 0 u E c B tolu O .c 03 O)^ nj ^ E 0) ■§ 6 6 ■§ E co O) 0) CD l o c S=;O <0 s>§ £ • CO TO CD 03 E I T I » -a b © co s O) 8 8* o CO co 2>E X 5 co CO - r © q> £ C CD CO y c ® CO O C 3 H -C E ■&■= £ C C _£= -£= S 1M jg -ri O D C 5 X - 5 c0 i 1 = c ^ < 3 . Q ±S 2 cd52 ° r -o “ 8 1 Q_ (0 1 “ O § 8 5 co c g § -o o f f 3 CO S' 5 • *9 CO £ 03 > CO iS c c iS C | w o X b r O c _ CO o o c (0 CD o n B. X3 Q. ) E o) 5 o JOo O o 03 i9 w **— X) c c E c fc 8 c ^ < 3 CD£ CO ■si _Q CO CO 0 c 0 0 0 0 -Q 0 p .«o 0 O 0 0 3 CO co jz CO 03 CO03 a P XI c _ CO CO 0 0 C CD 0 0 O O . Q o * P LL XJ O 0 0 O O 0 U) c tfi 0 0 0 0 2 Q) .2 7 -g 3 ll T3 S > Z J 0 CO P _ CO D " ® < ~0 f > f CO 1 o C 1 O - t CO © 2 2 03 O © © > !>. — J=© 0 CO * *0 >* 03 = c ^ < 3 a. ±s 2 2 c © 2 > 03 O f .co 45 CD 0 _ 0 Q_ CO CO 2 0 © c o 5 1 C 0 C = S c 0 -5 8 © 0) COC 0 L C 0 % 0 CD 0 *D0 O _C CO g. -g s a 5 0 o s> 3 — O & £ * p o - r

I >, XI O-O E 3 1 i g S 0 0 E Z> O B 0

O sz 7 _>, ® r o ■ co — 5 T3 5 < 't~.© Q CVJ -Q P p 5 8 3 = 1 1 ® W £ C < 3 0 : O _C JD JO jk 0* 3 0 o 5 0 E0 2 > © 5? a) r a O o O 3 CO 3 o c co -C C © © 3 C (f) © C C . Q 03 E o > E E « g O P 0 5 CO 3 0 O £ CO 0 O CO 3 o P ^ - r 0 0 . Q

E

b_ 8 £ 2 O -D ■5 * c > co•*- | -Q w 3 O 0 L I to £P *o J 1 C 0 C 0 0 -C C c ^ < 3 x> O) I S'S (0 O) E 1 1 v o ^ O _ 0 l 0 CL l 0 3.™ © © c "0 © 0 O CO 3 o C c W) 0 0 £ .C « « 8 & © p c o o CO Q. c 0 3 § o 3 0 c CD ©-Q 3 % . Q

»_ ° ° O . CO o E CD 0

75 S m n JS § I _>» ■“ X) 3 o * 0 < c 1 8 5 c 0 0 0 L O , q " CO CL 3 - 0 3 E XL c ! X3 3 7 X3 m < O C 3 c 0 $ Q c ) O V) 0 •ft"o Q.XJ 0 0 § 0 X * > % 0 O 0 . Q i 3 0 c ) O 0 tfi CO B O 3 o a S' p) SL0

© $ XJ B 0 © »- C 3 0 0 JZ *0 CO 0 . Q c ! 0 tfi O 0 3 0 0 . c 0 E E 0 , > c >% E O 0 . Q 0

. XJ o i » 0 0 o t r 0 E 0 CO tfi 0 E 0 0 c c 0 0 >» 0

Fagocyba Beech Nymph Yellow/brown, elongate. 3-4 mm. Adult jumps like a flea. May-July Beech cruenta leafhopper and adult Sucks sap from leaves like an aphid causing them to go chestnut brown. Hylobius abietis (the large pine weevil). These BEFORE ANY INSECTICIDE insects feed on the plant stem from the root APPLICATION, READ THE LABEL. collar upwards which they can completely IT CARRIES FULL INSTRUCTIONS FOR girdle and cause plant death. Fifty per cent of USE AND THE PROTECTION OF THE plants may be expected to be lost on average, OPERATOR AND THE ENVIRONMENT. although mortality levels vary unpredictably from site to site and often from year to year within a forest. The most effective method of young trees against Hylobius abietis and protecting plants is to treat them before Hylastes species and Research Information planting with an insecticide. Note 177 Application leaflet on the use of It is recommended that the application of ‘Permit’ and ‘Permasect’ for pre-planting treat­ insecticides to planting stock before planting ment of young trees against Hylobius abietis should be carried out at centralised treatment and Hylastes spp. These publications, and centres with purpose-built changing and amendments issued at regular intervals, also washing facilities. These offer the opportunity give the current position regarding approvals for higher standards of safe working practice, for use under COPR and are available from including handling of insecticide concentrates Publications Section, The Forestry Authority, and safe disposal of empty containers. Research Division, Alice Holt Lodge, The efficacy of the treatment also benefits Wrecclesham, Farnham, Surrey, GU10 4LH. from centralised facilities because closer supervision can ensure that the correct con­ 13.4 Protection of seedbeds centration of chemical is maintained. Where plants are dipped, the provision of covered against birds heeling in areas enables the insecticide Birds have been known to eat all the seed deposit to dry on the plant stem regardless of sown on seedbeds. The loss in one area of adverse weather. Such facilities may best be almost 40 kg of pine seed due to feeding by located at nurseries or plant storage and dis­ small birds has been recorded. Such severe tribution centres. damage is exceptional but in most nurseries Dipping the tops and upper root systems of there is some feeding, mostly by greenfinches, bare-rooted plants in a high concentration of chaffinches and sparrows. Linnets, skylarks, an insecticide product diluted with water pro­ crossbills and pigeons can also do severe vides protection for the growing season for damage. Birds do most harm to sowings of spring planted plants. The main advantage is species with large seeds such as Corsican its simplicity, with no reliance on high tech­ pine, Pinus strobus and P. peuce and some nology. Containerised plants such as those hardwoods. Species like western hemlock are grown in Japanese paper pots are best treated seldom troubled. by spraying them in their trays. The insecti­ Capercaillie have extensively damaged pine cide may be applied using a knapsack sprayer in Scottish nurseries by feeding on young or using a moving spray-boom system. growing shoots. As with the control of nursery pests, the use Pheasants may feed on oak, beech or sweet of insecticides against Hylobius is controlled chestnut seed if sown in the autumn. by FEPA, COPR and COSHH. Limited ‘off- The only certain counter-measure to birds label’ approval has been given for the use of feeding on seed is a complete physical barrier permethrin to dip plants before planting and of netting over the seedbeds. Bird scarers of this remains valid until 31 July 1995. Details flashing metal, strings of cartridges or carbide of the techniques and the necessary protective bangers may be effective for a few days but clothing are contained in the Forestry the birds get used to them and subsequently Commission Research Information Note 185 ignore them. There are no seed dressings that Approved methods for insecticidal protection of can currently be recommended.

195 13.4.1 Netting against birds prevent mice from climbing over. Joins in the netting must be made mouse-proof. Traps A suitable physical barrier may be made using should be set within the fence to catch any 2.0 cm polythene netting laid across seedbeds mice already inside. immediately after sowing and supported on flattened hoops of No. 8 or No. 10 galvanised wire. The hoops should not project more than 13.6 Damage by other animals 15 cm above the seedbed at the highest point, so that a tractor can be used to apply a pre­ If freedom from rabbit damage is to be guar­ emergence spray through the netting. Short anteed, a rabbit fence is virtually essential. lengths of wire bent over at one end should be See Forestry Commission Bulletin 102, espe­ used to pin down the edges of the netting in cially Figure 1 (Pepper, 1992). contact with the soil so that birds do not get Hares and deer occasionally get into nurs­ under it. The netting must also not be allowed eries. Hares are rarely more than a nuisance, to droop in the middle; otherwise birds will but if deer, present in the locality, are regular peck through it. visitors, a deer fence should be put up around Properly erected, such a barrier should the nursery. The cheapest form of deer fence keep birds away completely. The netting must is a 1 m width of broad mesh netting erected be put over beds as soon as possible after above a standard rabbit fence, to give a total sowing and may have to remain for 6-9 weeks height of 1.8 m. after sowing. It may be taken away once the Dogs, foxes and badgers occasionally get seedlings have started to produce the first into a nursery and dig holes but the damage true leaves. they do is insignificant. Although polythene netting is relatively Moles are seldom troublesome in a nursery easy to put over beds, it is quite expensive, but where they do occur they should be both in capital outlay and in the labour of trapped. A licence is required before strych­ handling it. Polythene netting is nevertheless nine can be used to poison moles. both easier to handle and cheaper to buy than light gauge galvanised netting. Also, the zinc REFERENCES AND FURTHER READING used in galvanised netting can render the soil ANON. (1989). Breakthrough in grey mould toxic to nursery plants; this risk is serious wherever netting remains in position for sev­ problem. Information Forestry 16 (3), 1. eral months, especially where air is heavily Pacific Forest Centre, Victoria BC, Canada. polluted. On ground where galvanised netting BCPC (1983). Pest and disease control hand­ is left rolled up for any length of time, plants book, 4th edtn. BCPC Publication, London. may subsequently fail to grow. BEVAN, D. (1987). Forest insects. Forestry Commission Handbook 1. HMSO, London. BOUDIER, B. (1983). Didymascella thujina, 13.5 Protection of seedbeds principal ennemi du Thuja dans l’ouest de la France. Phytoma, Defense des cultures, against mice November 1983, 51-54. If mice are thought to be damaging seed, traps BOUDIER, B. (1986). Essai de mise au point should be set. If the damage is too severe to be de methode de lutte contre Didymascella controlled by trapping or if the seed is particu­ thujina. Internal paper, Ministere de larly valuable, a temporary mouse-proof fence l’Agriculture, 14200 Herouville Saint-Clair, may be erected round the seedbeds concerned. France. (4 ppj The fence should be of 'A" mesh galvanised COOPER, J.L (1994). The viruses diseases of netting. It need be no more than 60 cm wide, trees and shrubs. NERC Institute of with 10 cm buried in the ground and the top Virology and Environmental Microbiology. 8 cm curled over away from the seedbeds to HMSO, London.

196 CORDELL, C.E., ANDERSON, R.L., HOF- PEPPER, H.W. (1992). Forest fencing. FARD, W.H., LANDIS, T.D., SMITH, R.S. Forestry Commission Bulletin 102. HMSO, and TOKO, H.V. (1989). Forest nursery London. pests. US Department of Agriculture, PHILLIPS, D.H. and BURDEKIN, D.A. (1992). Forest Service, Handbook 680. Diseases of forest and ornamental trees, 2nd OVERHULSER, D.L. and KANASKIE, A. edtn. Macmillan, Basingstoke. (1989). Lygus bugs. In Forest nursery pests, SMITH, I.M., DUNEZ, J., LELLIOTT, R.A., ed. Cordell, C E. et al., Agricultural Hand­ PHILLIPS, D.H. and ARCHER, S.A. (eds.) book 680. USDA Forest service, Wash­ (1988). European handbook of plant dis­ ington DC. eases. Blackwell Scientific Publications, PEACE, T.R. (1962). Pathology of trees and Oxford. shrubs with special reference to Great STROUTS, R.G. (1981). Phytophthora diseases Britain. Clarendon Press, Oxford. of trees and shrubs. Arboricultural Leaflet 8. HMSO, London.

197 Chapter 14 Lifting, storage, handling and despatch

H. M. McKay, J. R. Aldhous and W . L. Mason

Introduction confirming orders arises out of concern to avoid planting loss and possibly acrimony over The final and most critical stage in nursery the responsibility for such losses. It must be management involves the lifting of plants remembered that replacing failed planting from a nursery and their delivery to a cus­ stock is expensive and involves additional tomer in as good a condition as possible. This establishment costs because of slower growth stage is made up of a complex chain of opera­ and greater weeding. tions which can include lifting, storage, grading, insecticide treatment, packing, despatch, receipt, temporary storage and planting. The first part of this chain is the 14.1 Integrated procedures responsibility of the nursery management and It cannot be stressed strongly enough that, if the second is that of the customer. Customers customers are to establish their plants suc­ will consider a nursery to be successful if the cessfully, there must be a close understanding plants are delivered on time, if these conform with the nursery manager. The nursery man­ to previously agreed size specification, and, ager must know the customer’s needs and the most importantly, if they find that the plants latter must understand the nature of the inte­ survive well and grow vigorously after grated chain between lifting and delivery of planting. For success to be achieved, the plants. Careful handling of plants at all stages nursery management must always recognise is necessary if plants are to survive and grow. the importance of two concepts: Equally, the best quality plants cannot be expected to survive without good establish­ • there must be careful control of each opera­ ment practice. tion from lifting until delivery and subse­ While individual operations are discussed quent planting; separately in this chapter, in practice, much • the plants must be in the best physical and thought must be given as to how best to inte­ physiological condition to withstand the grate use of machinery, storage facilities, period between lifting and planting. available time and manpower in relation to Foresters have often found that newly stock, soils, weather and customers’ require­ planted young trees either fail to survive or ments so that risk of damage to plants is min­ grow weakly in the first year. Some of these imised. losses can be due to the conditions at time of The aim is to ensure that plants are in first or immediately after planting. However, some class physiological condition at the time of are the result of plants from the nursery being planting, and can quickly regenerate roots either of poor physical quality (see standards before seasonal changes in day-length and in Chapter 1, section 1.5.2), or in poor condi­ temperature stimulate plants to break bud tion as a result of the damage sustained and commence shoot growth. It must always during lifting, storage and handling. The prac­ be remembered that plants with damaged root tice of purchasers asking for samples before systems will struggle to survive after planting.

198 Additional options Essential Insecticide Opportunity to cull and/or sequence Storage treatments grade and/or count

Figure 14.1 Stages in plant handling and despatch.

Figure 14.1 illustrates in outline, the sequence 14.2 Causes of damage and loss of operations that has to be followed. The essence of the manager’s task is to flesh it out by of plant quality putting in numbers of plants, dates of delivery, nursery production capacity, rate of work of men The concept of plant ‘quality’ expresses its cur­ rent ability to grow well, as soon as seasonal and machines, and at the same time decide how much to allow for delays due to severe and cultural conditions allow. ‘Quality’ in this winter weather and similar contingencies. sense, combines ‘physiological’ and ‘physical’ condition. The detrimental effect of damage or loss of quality at any stage between lifting and 14.1.1 Work-study investigations planting is cumulative (Tabbush, 1988); by analogy, plants may be thought of as col­ Two Forestry Commission Work Study teams lecting penalty points at any stage, their final have studied plant handling in the nursery performance reflecting their aggregate penalty and methods of despatch from nursery to point score. See also section 14.4.3 (electrolyte forest. They showed how effective use can be leakage). Unfortunately, there is nothing that made of cages for moving plants within the can be done to restore quality once plants nursery, with pallets and boxes offering reli­ have deteriorated, other than planting them able physical protection against crushing and out as carefully as possible on a well-prepared mechanical shock while in transit from site in the hope that they may recover and nursery to forest. grow. If deterioration has gone too far, then it Studies also looked at how the planter will be better to start again with good quality needed to carry plants before planting, consid­ plants. Any concern about the quality of ering whether anything should be done in the plants should be communicated to the nursery nursery to assist his work, rather than treat as soon as possible after receipt. nursery work and forest planting as unrelated The aim in lifting, storage, handling and operations (Dauncey et al., 1988, 1989; Scott, despatch is to ensure that plants are in as 1987a, b). good a condition as possible when received for

199 planting. This aim implicitly recognises that unless the store is designed to maintain a very plant quality can deteriorate, often very high humidity. Where plants are stored in quickly, through poorly timed or executed bags, the bags must be completely sealed to operations, which can influence quality in a prevent the escape of moist air. Even small number of ways as described below. slits in bags have resulted in plant deaths through desiccation in directly refrigerated 14.2.1 Root loss during lifting, culling cold stores. Shoots are unlikely to be damaged by desic­ and grading cation between lifting and planting. However, Plants which have grown well in the open exposure to drying winds may lower the nursery and are of suitable size and condition plant’s water content directly; mild drying for planting in the forest, can have root sys­ conditions may also indirectly induce stomatal tems which are 30 cm or more in depth and closure and hence reduce photosynthesis. with 60 cm or more lateral spread. Inevitably, in lifting such stock, root systems are dam­ 14.2.3 Deterioration during cold and aged through breakage of the longer roots, canopy storage many root tips are lost and symbioses broken Plants can be damaged by mould growth if between plants and mycorrhiza-forming fungi. they have been stored with wet foliage. In Systematic undercutting and wrenching will such cases the damage is usually obvious, but reduce the depth of rooting and therefore reduce in many cases the plants appear to be in good the worst damage that occurs at lifting. health. Deterioration in cold storage has been However, it is difficult not to damage roots even inferred in many instances of large-scale when lifting well-conditioned undercut plants. planting failure (Mason and McKay, 1989). See section 14.5. When plants are being sepa­ Plant survival after cold storage is closely rated and handled during culling and grading, related to the quality of the fine root system woody roots may be torn off and fine roots as assessed by electrolyte leakage (see 14.4.3) detached unless care is taken. even though the foliage appears in good condi­ tion (McKay and Mason, 1991). The following 14.2.2 Desiccation mechanism may explain deterioration of Fine roots of all forest tree species are very tissue in storage. During autumn and winter, sensitive to desiccation so bare root plants in compounds build up in living cells to protect particular must be protected from drying con­ the cell membranes from winter damage. ditions. Hermann (1967), for example, These compounds and the energy required for recorded damage to Douglas fir seedlings with their transformations cannot be produced in washed roots after only one minute’s exposure the dark, cold conditions of the cold stores. to desiccating conditions in a growth chamber. Adequate levels of protective compounds and Desiccation also appears to predispose plants energy must therefore be present in the plants to rough handling damage (Tabbush, 1986). In at the time of storage to maintain the cells in experiments at Wykeham, Yorkshire, survival good condition until they are planted out. of Sitka spruce was significantly reduced by Deterioration of the root system mostly 70 minutes exposure to windy conditions in occurs during storage in early winter or late March, and Douglas fir was even more suscep­ spring when the root system is not fully dor­ tible (Tabbush, 1987a). mant. It is generally true that nursery stock is The effect of loss of moisture in fine roots is best stored between mid-December and mid- not reversed by rewetting. Roots which retain January but there are major differences a covering of nursery soil dry out more slowly between species, provenances and plant types but too much nursery soil can provide a source in the length and timing of safe lifting ‘win­ of fungal infection during storage. dows’ (see Table 14.4). Lifting times must be The risk of drying during storage is high modified from year to year depending on the

200 condition of the plants and the condition of the Table 14.1 Root growth potential (number of new nursery. roots after 14 days) and percentage loss at the end Deterioration of the root system is also of the first growing season, following heating, drying caused if plants are stored for too long (see and rough handling before planting 14.7). The maximum safe storage period depends on the initial plant quality, the Sitka spruce Douglas fir species, the provenance and the plant type. Pre-planting Root growth Loss Root growth Loss Desiccation may damage plants in direct treatment potential % potential % cold stores if bags are tom. Desiccation is also a hazard to plants throughout humi-cold No heating 11.5 16 0.25 19 stores, if the stores do not operate close to sat­ Heating 8.4 22 0.48 17 uration (Sharp and Mason, 1992), and to plants adjacent to doors if vehicles are contin­ No drying 19.6 5 0.45 11 Drying 0.3 34 0.28 24 uously moving in and out. Loss of quality during canopy storage is No rough handling 16.8 9 0.68 12 also due to deterioration of the root system Rough handling 3.1 30 0.05 23 rather than the shoot. No maltreatment 37.1 2 0.5 8 14.2.4 Rough handling All maltreatments 0 54 0.01 35

Bad handling can adversely affect plant perfor­ Data from ‘factorial design’ experiment (Tabbush, 1986). mance. While nursery managers have con­ 0 0 O X X stantly been exhorted to handle plants with Heating Drying Rough handling care, it is only during the last decade that fig­ ures have been available showing how plant performance can deteriorate if handled badly. a substance, possibly abscisic acid, that is For example, Tabbush (1986) subjected Sitka transported to the leaves causing the stomata spruce and Douglas fir to a bad handling treat­ to close (Coutts, 1980). ment in which plants were dropped onto a con­ The effects of different forms of rough han­ crete floor (Table 14.1). Bad handling in dling are being investigated; it is possible that combination with overheating and drying small jolts induce stomatal closure, moderate treatments, which in themselves had detri­ jolts may also rupture cell membranes while mental effects, was particularly damaging severe jolts may break woody roots and frac­ raising mortality from 2 to 54% for Sitka ture the water columns within the plants. The spruce and from 8 to 35% for Douglas fir. shocks which plants normally receive under There is some evidence that the reduction in operational conditions between lifting and height growth is more closely related to the planting are currently being investigated. maximum force experienced by the plants than to the mean or total force (McKay et al., 1993). 14.2.5 Frosting There is usually no obvious physical Roots are much less frost tolerant than shoots damage visible following rough handling. (Pellett, 1971) but soil temperatures rarely However there is evidence that physiological reach damaging levels. However, frost toler­ changes take place as a result of mechanical ance of the root system has become increas­ damage to roots which may cause the large ingly important with the advent of container reduction in root growth observed by Tabbush production where roots do not have the benefit (1988). of a massive soil volume to act as a buffer Low levels of physical handling or pressure against sudden drops in temperature. on the root system can also cause stomatal clo­ Container plants overwintered outside, espe­ sure. Water-stressed or mechanically dam­ cially if stored off the ground to maintain air- aged root systems appear to be able to produce pruning of the roots, and bare root plants

201 stored in bags in the open may be exposed to temperature until they have received this damaging temperatures. chilling requirement. Thus, plants are not nor­ mally damaged by short unseasonal warm 14.2.6 Overheating spells during winter. Temperatures between 0 Temperatures above 40°C can damage both and +5°C are the most effective in bringing roots and shoots (Levitt, 1980; Tabbush, about the physiological changes involved in 1987b). Such temperatures have been recorded loss of bud dormancy (van den Driessche, inside clear polythene bags left in full sunshine 1975). As the number of chilling hours experi­ for several hours. The introduction of coex­ enced by plants accumulates, buds take fewer truded black and white bags has reduced this days to burst. When the chilling requirement risk of direct damage through overheating. has been fully satisfied, seedlings take only However, temperatures exceeding 20°C have 10-12 days in a warm glasshouse for their been recorded within black and white bags left leading bud to open. Plants can be described in full sunlight in March. These temperatures as ‘quiescent’ when their chilling requirement are unlikely to have any direct damaging has been met, but the environmental condi­ effects but may, through hastening bud-break tions are not favourable to growth. and other growth processes, lower plants’ gen­ The concept of ‘chilling requirement’ is rele­ eral resistance to stress. Therefore all plants in vant to the timing of plant lifting and storage. bags should be stored in shade. Ritchie (1986) found that stock of local seed Heating may also result from bacterial and origins deteriorated least when plants were plant respiration in the absence of a good cir­ cold stored before their chilling requirements culation of air. This may happen with densely for the winter had been fully met. Storage at packed loads of plants in transit late in the temperatures of typical plant cold stores and planting season or with plants left in uninsu­ for the appropriate period enabled any out­ lated vehicles for 36 hours or more, especially standing chilling requirement to be met before if the vehicle body is warmed when standing the plants left the store. Over a number of in the sun. years, Ritchie (1984 b) has established for Any buildings used as temporary stores Douglas fir the number of chill hours required also must be well ventilated. in relation to storage practice; chill hours have been used to identify safe lifting windows in Western USA. However, where species (e.g. 14.3 Factors affecting the over­ larches) are raised in climates markedly dif­ winter physiological condition of ferent from those of the plants’ seed origin, bud pre-chill requirements and bud dormancy plants may not be a reliable guide to plants’ overall end-of-winter condition. 14.3.1 Dormancy status and stress tolerance Shoot frost hardiness Two physiological measures, bud dormancy In typical winters, shoot frost hardiness and shoot frost hardiness, have been linked to increases rapidly in November, levelling out the plants’ overwinter condition to the extent during December and January. Dehardening that they are often loosely thought to indicate in spring is less predictable and varies from the dormancy status of the plant as a whole. year to year depending on the air tempera­ ture. Shoot frost hardiness (Colombo and Bud dormancy Hickie, 1987 and Faulconer, 1988) has been Woody plants have become adapted to the used in the USA and Canada to identify times winter environment of their origin and they of cold storage. In practice, the decision is require a certain amount of chilling over based on the degree of damage caused at the winter. Shoots will not respond to rises in selected temperature, e.g. -10°C, rather than

202 the exact temperature causing damage to 50% growth slows. There may be further flushes of of the shoots. growth during summer when temperature and Bud dormancy and shoot frost hardiness soil moisture allow. In the autumn, active root tests yield information on these particular growth continues well after bud set but slows aspects of the plants’ overwinter condition. down gradually during autumn and winter to However, assessments of the ability of plants reach a minimum by mid-December. The to withstand the stresses to which they are length of the following inactive period when inevitably exposed between lifting and roots are neither dividing nor expanding planting are more useful to the nursery man­ varies with the winter conditions, the species ager. In general, plant tissues are most easily and to a limited extent the plant type. damaged when they are growing rapidly and However, since roots are more easily damaged least sensitive when they are least active than shoots, it is important to realise that the (Coutts and Nicoll, 1990; Ritchie, 1986). Since period of root inactivity is much shorter than roots are more easily damaged than shoots, the period of shoot inactivity. the physiological tests most relevant to nursery staff assess the stress tolerance and 14.3.3 Environmental factors activity of the root system rather than shoot influencing plant activity dormancy status. The conditions inducing shoot dormancy seem to be related to climatic factors operating in 14.3.2 Seasonal patterns in plant activity the area of plants’ natural distributions. In The time of bud set is dependent on the some species which have evolved in areas nor­ species and provenance but it can be manipu­ mally receiving rain throughout the year, the lated by undercutting and nutrition. The main trigger is day length but in other species periods of shoot extension are obvious but most notably Douglas fir, summer droughts cells in the buds continue to divide for several are the main factors inducing dormancy. months after the overwintering buds have Shoots develop frost hardiness in two formed (McKay and Mason, 1991). During stages (Greer et al., 1989). The first occurs autumn and early winter, the rate of cell divi­ after the day length has shortened to a critical sion decreases but cells may continue dividing level (Cannell and Sheppard, 1982). In until mid-December before stopping for a few Britain, this is in October for Queen Charlotte months. The external appearance of shoots Islands Sitka spruce. Hardening is most rapid changes during this period of decreasing cell during November and is in response to low air division; stem colour darkens and shoots temperatures. Maximum shoot frost hardiness become stiffer. Cell division begins again in is reached by mid-December. Later, shoots April as the buds start to swell. deharden quickly when air temperatures rise The cycles of activity are less obvious below leading to bud break and it is well known that ground but the roots too have periods of cell thereafter new foliage is particularly suscep­ division and cell expansion. The cycles of tible to frost damage. activity in the root system are not easy to pre­ The factors influencing activity and frost dict for they depend on the amount of energy hardiness of roots are less clearly understood. available, and the environmental conditions, In autumn and winter when shoot expansion especially soil temperature and moisture. has ceased, undercutting has stopped and Generally the energy requirement for shoot soils are moist, temperature and day length growth takes precedence over the requirement are the main controlling factors. Both for root growth, therefore root growth tends to daylength and temperature affect root elonga­ occur between periods of active shoot growth. tion but over the range of soil temperatures In general, there is a flush of root cell division normally experienced by forest nursery sites, and expansion in spring just before bud burst. temperature has the greatest effect. Root frost During the time of greatest shoot growth, root hardiness in some species appears to be

203 Table 14.2 The relative tolerance of Sitka spruce of particularly of Douglas fir, great care must be Queen Charlotte Islands provenance (QSS), Douglas taken to prevent root drying. fir (DF), Japanese larch (JL), Scots pine (SP), Sitka spruce of Oregon provenance (RSS) and Alaskan Storage tolerance origin (ASS) to desiccation, cold storage, rough han­ Of the species studied, Sitka spruce was the dling and frost most tolerant to cold storage. For example, the root system showed no deterioration when Desiccation Cold storage Rough handling Frost stored in January of the mild 1988-89 winter

QSS 8 8 8 8 for 5 months. Douglas fir (Darrington, Wash­ DF 1 1 6 1 ington origin) was extremely sensitive that JL 6 6 8 7 year to storage at +1°C. In the more ‘typical’ SP 7 6 8 3 winter of 1990-91, Douglas fir could tolerate RSS 7 5 8 6 storage with minimal damage for only one ASS 5 9 9 9 month when stored at the optimal time. 0 = very intolerant; 10 = very tolerant. Japanese larch resembles Sitka spruce during the early winter but the tolerance of its root system to storage decreases several months induced by shortening daylength (Smit-Spinks earlier in the spring. The tolerance of Sitka et al., 1985) but in other species temperature spruce provenances increases with increasing is more important (Lindstrom and Nystrom, latitude (McKay, 1993). 1987; McKay, 1994). Deterioration during canopy storage has not been studied so intensively but the limited 14.3.4 Species and provenance results indicate that Sitka spruce is more tol­ differences in tolerance of stresses erant than Douglas fir. The results of experiments carried out Survival after cold storage was more closely between 1988 and 1991 to study the relative correlated to the condition of the root than the tolerance of some of the main commercial shoot. Shoots of Douglas fir are more tolerant of conifers to standard experimental stresses are cold storage than are Sitka spruce yet their summarised in Table 14.2. Stock types are roots are less tolerant than those of Sitka ranked on a scale of 0 to 10 according to the spruce. Therefore the appearance of Douglas fir electrolyte leakage from the fine roots after foliage after storage is a poor guide to the plants stresses applied at intervals from October to overall health status (McKay and Mason, 1991). April. These results agree with the earlier findings of Tabbush (1986, 1987a and 1988) Rough handling tolerance who compared Queen Charlotte Islands Sitka Species and provenances did not differ greatly spruce and Douglas fir on the basis of root in their ability to withstand a ‘moderate’ rough growth potential. handling treatment of five drops from 1 m. However there are clear seasonal patterns in Desiccation tolerance sensitivity to these standard experimental Douglas fir was the most sensitive and Queen rough handling treatments. In general, all Charlotte Islands Sitka spruce the most tol­ species studied were most tolerant between erant to an experimental drying treatment of mid-December and mid-March. Care must 5 hours exposure to air circulating at 15°C therefore be taken when handling freshly lifted (unpublished data). There were clear seasonal plants outwith these months to minimise the patterns in these species’ tolerance to the physical jolts given to the plants. standard drying treatment. In general, roots were at their most tolerant from mid- Frost hardiness December until March. These results empha­ There are major species differences in the sise that, during late autumn planting frost hardiness of both shoots and roots.

204 Overwinter shoots of Japanese larch and unfavourable even though undercut plants, in Sitka spruce of Queen Charlotte Islands origin very dry years, may be smaller. are similar in the degree of frost they can tol­ The nutrient status of planting stock affects erate; Douglas fir is much less frost tolerant. many aspects of the physiological quality of For example, even in a mild winter, Sitka stock some of which are important to the plants spruce and Japanese larch required a temper­ at the stages from lifting to planting (van den ature of -28°C for 3 hours to kill half of the Driessche, 1991). For example, potassium shoots whereas a temperature of -15°C killed increases drought resistance by improving half of the shoots of Douglas fir. The shoot stomatal function and by increasing the toler­ frost hardiness of Sitka spruce provenances ance of the protoplasm to water shortage. The increased with latitude. beneficial effect of increasing K on protoplasmic During the winter of 1990-91, in a series of drought tolerance is likely to be of greater rele­ experiments, Douglas fir roots could tolerate a vance to stock between lifting and planting 3 hour exposure to only -4°C and showed than the effect on stomatal function since the almost no ability to increase frost tolerance roots will lose water more rapidly than the between October and March (McKay, 1994). shoot whenever plants are exposed during the Scots pine roots were slightly more tolerant handling chain. The effect of nitrogen depends than those of Douglas fir. Sitka spruce, even of on the time of its application. Summer and Oregon provenance, and Japanese larch early autumn applications can delay bud set or became increasingly tolerant of low root tem­ stimulate lammas growth delaying the develop­ peratures. By late January, Queen Charlotte ment of shoot frost hardiness, whereas late Islands Sitka spruce and Japanese larch roots season applications have little effect or a slight could withstand a 3 hour exposure to -15°C beneficial effect on shoot frost hardiness. and -11°C respectively. Sitka spruce and Unfortunately there is little information Japanese larch became less frost tolerant available on the interaction of nutrition and during mid-January to April when they were aspects of the physiological condition of the tolerant of — 6°C. These results lead to the rec­ root system which are relevant between lifting ommendation that Douglas fir and Scots pine and handling. The remainder of this section is must be protected from severe or prolonged therefore informed speculation. Since nutri­ frosts at all times during winter. During ents, in particular N and P, stimulate root October and from April onwards all stock growth, nutrient applications particularly late should be given some protection against frost. season applications might be expected to decrease the general tolerance of the root 14.3.5 Preconditioning system to stresses such as long-term storage, Plant quality may be altered by ‘precondi­ rough handling and desiccation. N supply is tioning’ in the nursery, especially in the known to affect the root to shoot ratio; high second half of the growing season preceding levels have a greater positive effect on shoot lifting and despatch. Transplanting is the growth than root growth resulting in an commonest form of physical preconditioning; overall reduction in R:S ratio and might be physical and physiological preconditioning expected to reduce overall survival. However may also be achieved by intensive undercut­ N applications after bud set should increase ting and side-cutting regimes. root growth and provide adequate N reserves Undercutting followed by regular wrenching for rapid root growth after outplanting. causes repeated branching in the upper root system giving a higher proportion of fine root. Undercutting and wrenching also induce phys­ 14.4 Plant attributes influencing iological changes which usually enable survival undercut plants to establish themselves more readily where soil or climate factors are The most important characteristic of plants

205 immediately after planting is the physiological 14.4.2 Root growth potential status of their stomata. If these close, the Early survival after planting in the forest is plant can no longer maintain a high flow of dependent on the plants’ water status and the photosynthate to the shoots and roots. Many ability of the root system to supply adequate species, e.g. Douglas fir, are dependent on water. If a plant can produce abundant new newly formed photosynthate to produce new roots quickly, it will rapidly establish root con­ roots whereas other species, e.g. Sitka spruce, tact with the surrounding soil, thereby can use stored energy to produce new roots increasing water and nutrient uptake. There (Philipson, 1988); even so root growth is have been many attempts to assess the ability greater if newly formed photosynthate is of plants to produce new roots after planting. available. Therefore, if the stomata close in Stone (1955) examined the root develop­ response to water deficits or physical shocks, ment of plants after 60 days in favourable photosynthesis will be curtailed and root greenhouse conditions and then grew them on growth reduced or inhibited. After planting in for a further 120 days. Many subsequent mod­ the forest, uptake of water from the site to ifications of this type of test are reviewed by permit photosynthesis will depend on the Sutton (1990). Generally root growth potential ability of the existing root system to provide (RGP) is now measured over 2 weeks. The water to the plant. number of new roots produced is a guide to Ideally nursery stock should have sufficient the condition of the plants. If abundant roots water to allow photosynthesis immediately are produced by a sample of plants, they are after planting (needle water potential should likely to survive and grow well after normal be <20 bars). If not, they should have ade­ planting (see Burdett, 1979). However, the quate live fine root in relation to the shoot to opposite is not always true', some batches of quickly overcome water-deficits, thus forming plants showing up poorly in RGP tests do have plants with a positive cycle of photosynthesis, a low survival potential but others survive new root growth and adequate water uptake. well. This reduces the value of the test to the At worst, provided stored carbohydrate can be nursery manager. used for root growth, plants must have ade­ The standard Forestry Commission quate stored carbohydrate and a sufficiently Research Division test is to place 15-20 plants large existing root system to support wide­ per batch individually in root observation spread new root growth. boxes - a 45 cm length of plastic roof gut­ tering, filled with moist peat to within 5 cm of 14.4.1 Assessing physiological quality one end (the top). The root system of each Many methods have been used to measure plant is spread over the peat with the root various aspects of the physiological quality of collar 5 cm below the level of the peat and held plants. These were reviewed by Ritchie firmly in place by a clear acetate sheet taped (1984a). Tests developed between 1984 and to the sides and other end of the gutter. If the 1989 include variable chlorophyll fluores­ roots are so muddy that new root growth will cence, stress-induced volatile emissions, not be seen easily, the roots must be washed mitotic index, electrolyte leakage from gently. Air pockets around the root system shoots, triphenyl tetrazolium chloride, days should be minimised. The root boxes are stood to bud break and the phytogram (Hawkins on end in a rack for support and stacked and Binder, 1990). The two tests described in against one another with the clear face angled the following section, root growth potential slightly downwards. This minimises the light and root electrolyte leakage, have proved striking the roots and encourages the roots to useful in recent experiments carried out by grow against the face. Forestry Commission research staff as Plants are grown in controlled environment indices of early survival and growth in forest rooms for 14 days at 20°C, the optimum for experiments. root growth of Sitka spruce, a relative

206 humidity of 75%, a light level of Roots (or shoots) are washed in tap water 350—450 pmol rrr2 s-1 and a day length of 16 h. and rinsed in de-ionized water. Root samples of Plants are watered twice daily but no nutri­ 100-500 mg fresh weight are taken from the ents are supplied. After 14 days the number of fine roots (<2mm diameter) approximately new white roots >lcm in length produced by 8 cm from the root collar. Shoot samples are each plant is recorded. For Sitka spruce, the taken from the ends of lateral shoots by critical value below which survival is unlikely, removing the terminal bud and cutting the is ten new white roots per plant (Tabbush, next 2 cm length of shoot. The test material is 1988). The results should be evaluated in two added to distilled or de-ionized water and left ways. Firstly, the mean RGP for the 15-20 for 24 h at room temperature. The concentra­ replicates is compared with the critical level; tion of ions in solution is measured with a con­ secondly, the proportion of plants with a RGP ductivity probe. The samples are killed by falling above and below the critical value is boiling for 10 min. When cool, a second conduc­ calculated. tivity measurement is made for each sample. If RGP tests cannot be carried out in a con­ The represents the maximum possible leakage. trolled environment room, it is possible to get The 24 h reading is expressed as a proportion of comparative results in a glasshouse or artifi­ the maximum possible value. Normally 10-15 cially-lit room. However, since the amounts of replicates are needed to characterise a batch of root growth vary with temperature, light plants. Fuller details are given in Forestry levels and daylength (Sutton, 1990), these Commission Research Information Note 210 values can only be used safely to compare (McKay, 1991). A commercial plant quality plants tested at the same time. testing service has been developed using such tests; further details are available from the 14.4.3 Fine root electrolyte leakage Forestry Authority’s Northern Research All living cells contain charged ions (elec­ Station (address in Appendix I). trolytes) surrounded by a cell membrane. When healthy tissue is placed in water free of ions a small proportion of the cell contents, including 14.5 Lifting charged ions, will leak out. However, if the cell When plants are lifted violently, bark may be membranes are damaged the leakage rate is stripped from roots or stem. Damage during greater. This leakage can be easily measured lifting can be minimised if care is taken to ease and used as an expression of root condition. To plants out of the ground as gently as possible, so date, the technique has been used by Forestry that as much as possible of the fine fibre and Commission research staff mainly to assess short branched roots plus root tips are retained. damage after cold storage and frosting. Root This will enhance the chances of good survival electrolyte leakage has also been used success­ in nursery lines or in the forest. Roots exceeding fully to measure damage after desiccation, 15-18 cm should normally be trimmed back to rough handling and overheating. In some cases, that length, or other length selected to suit the such as cold storage damage, root electrolyte following planting operation. leakage was more closely correlated than RGP Plants may be lifted by hand or by machine. to survival. While the technique requires fur­ As soon as possible after lifting, the plants ther testing, it shows great promise as an indi­ must be protected from moisture loss. cator of plant quality and has the further Exposure even for a few minutes under advantage that the test can be completed in 2 strongly drying conditions can reduce survival days. It is hoped that the assessment of elec­ of plants (Tabbush, 1988) and makes them trolyte leakage, could provide a useful guide to more vulnerable to subsequent damage. the overall deterioration in plants, corre­ sponding to the ‘penalty points’ concept men­ 14.5.1 Hand-lifting tioned in paragraph 14.2 above. When lifting by hand, the beds should always

207 be worked from an outside edge. A garden fork Plants are loosened by the passage of the shoe or spade should be inserted vertically to the under the row, are gripped between two soft- full depth of the blade and the handle pressed faced endless rubber belts mounted at an down until it is at an angle of 45° from the angle to the soil surface, which lift them com­ vertical. This movement is repeated until the pletely from the ground. They then pass over a soil is loose, when the tops of as many plants series of adjustable root shakers to remove in the loosened ground as can be grasped com­ soil. When released at the end of the lifting fortably should be lifted, gently shaking the belts, the plants can: soil from the roots while lifting. The soil • fall to the ground for subsequent hand- should never be removed by swinging roots sorting and packing; or against a foot since this will reduce RGP (see • be collected from the belt and packed into Deans et al., 1990). plastic bags held on a carousel - an oper­ 14.5.2 Mechanical lifting ator on the machine packs bags and another walking alongside the lifter, Several types of machines are available which removes full bags and replaces them with are designed to loosen plants in the soil and lift empty ones; or them. They fall into three groups; the ‘line • be packed into boxes or pallet-based con­ lifters’, such as the ‘Famo’ which can lift stock tainers carried on the lifter. Operators fill suitable for forest planting; ‘lifting bars’ which and remove boxes (Plate 32). loosen plants in the bed, but do not lift them, and ‘bed harvesters’ which lift a whole bed of How plants are handled from that point plants at a single pass. The first type enable depends on the requirements for grading and large numbers of plants to be lifted completely storage of the plants. in a short time but require substantial sup­ Where plants are delivered into boxes or porting equipment and organisation. Bed bags, these are carried on the forklift or on the looseners may cover ground even more quickly, trailer of a supporting tractor which follows but depending on the exact nature of the the lifter. If necessary, lifting can proceed equipment and the stock being treated, may uninterrupted using a second supporting leave the plants still protected by the nursery tractor to take the place of the first while that soil where they grew, so that lifting can be one takes away filled boxes to the grading completed manually at a slower rate. Bed har­ shed or plant store, and returns with an vesters are expensive machines with conveyor empty one. belts to lift plants to a grading table and/or In operation, the ‘Famo’ lifts plants with packing line. There were none being used in very little damage except when the share hits British nurseries at the end of 1993 although a large stone; the sudden deflection may cause they can be found elsewhere in Europe. stripped roots on the plants coming out of the ground at that instant. This damage can be ‘Famo’ lifting excessive on stony sections; on such ground The ‘Famo’ lifter (Plates 31 and 32) can lift other methods of lifting should be used. There lines of plants at the rate of up to 200 000 can also be problems when using this type of plants per day and is suited to the larger nurs­ single-row lifter with undercut plants. eries with substantial breaks of single species. Successful operation of the machines depends It can be adapted to work in rows down to upon the soil being firm enough to support the 12 cm apart. There is no restriction of plant plants when the shoe passes through the bed. spacing in the row as the lifting mechanism is If the soil has been loosened by intensive based on two continuous converging belts. undercutting and/or wrenching and has not The lifter is attached to the three-point been reconsolidated by rain, the plants may linkage of the tractor, with the lifting shoe off­ fall over before being gripped by the rubber set to the right of the rear tractor wheel. belts.

208 The tractor carrying the ‘Famo’ and the commercial nursery and subjected to different tractor transporting plants pass over the types of handling damage after lifting. ground many times, seriously risking soil com­ Machine lifting using a ‘Famo’ appears less paction as a result. The soils must be carefully detrimental than the use of a lifting bar and examined later for signs of compaction; if hand-lifting. The results also show the dam­ found, subsoiling must be undertaken as soon aging effects of dropping plants or removing as the soil is dry enough and tractors are the soil by knocking roots against a boot. available.

Lifting bars 14.6 Culling, grading and Specially designed lifting bars (Plate 34) counting which loosen soil and so assist lifting continue to be widely used, both for single lines and for On lifting plants, the first priority must be to ensure that, during any subsequent pro­ beds. The most suitable bars are those on which the angle can be adjusted to lift the soil cessing, they are handled gently, are kept cool to a greater or lesser extent; they are set so and are not allowed to dry to any extent. Their condition will deteriorate every time they are that the soil is loosened sufficiently to free the roots but not so much that the soil is turned handled and roots are exposed to the air. Grading should therefore be kept to the essen­ over and the plants buried, or plants are left tial minimum. above the soil with roots exposed. Bars may incorporate an agitator to assist loosening. Before despatch or preparation for lining The setting of the bar may have to be adjusted out, plants must be culled, i.e. separated into from time to time in relation to the worka­ those of a quality acceptable for use, and bility of the soil. Once the soil has been loos­ rejects, including all diseased plants, together ened, plants are lifted out by hand. The soil with those that are too small at the root collar, may settle back round the roots if more than a have inadequate roots, or multiple leaders or couple of days separate mechanical loosening have been damaged during lifting. Rejects, or and lifting, especially if heavy or prolonged culls, should be destroyed. See Chapter 1, sec­ rain follows loosening. tion 1.5 for quality standards. The require­ ments for plants to be described as ‘EEC If properly supervised, machine lifting is Standard’ are given in Appendix IV. nearly as safe as careful hand-lifting in main­ Acceptable plants may be further graded by taining root system quality. Table 14.3 gives height into two or more size classes. the results of a RGP test carried out on Sitka In commercial nurseries, plants are usually spruce transplants of the same age and origin sold and priced by height grades and careful that were lifted in three different ways on one grading is essential to obtain the best com­

Table 14.3RGP of Sitka spruce transplants given different lifting or handling treatments [results expressed as a percentage of highest value]

Treatment Careful Famo Lifting bar Careful Careful hand lifting lifting and and knocked and dropped with fork hand lifting against boot

RGP 100 80 60 38 28

Results are the average of 10 plants per treatment. RGP tested over 21 days in a greenhouse. Plants were in 35-45 cm height category.

209 mercial advantage. Height grades always insecticide treatment (p. 189), observing the cover a range of heights and the average size requirements of current Pesticide Regulations of a batch of plants should correspond with (see Chapter 15, section 15.6). the middle value of a stated height range. In estate nurseries raising plants for use on the same estate, grading of stock after culling 14.7 Storage is necessary only if plants are so variable in Traditionally, plants should be lifted while size that some will need an additional year’s dormant, packed, immediately despatched to weeding in the forest compared with bigger the forest and planted without any delay at plants. any time. Unfortunately, this is seldom practi­ The practice of loosening beds and cable for any but small lots of plants and for removing plants in the various grades only as some, e.g. larch, there may be benefits in required is quite widespread, but the first retaining fully dormant plants lifted during plants removed are likely to lose more roots in November-February in store at 1°C and the process than if all the plants are lifted planting in early spring (McKay and Howes, together. Correspondingly the plants which 1994). are last to be removed run the risk of being Plants are regularly stored: left with roots exposed through the removal of • outdoors in the nursery, heeled in; neighbouring plants. Where hand-lifting and individual working • in unheated well ventilated sheds; is practised, plants can be counted and graded • in insulated cold stores; on the nursery as lifting proceeds. • at the planting site. In nurseries where lifting is mechanised Whatever the location, it is essential that con­ and plants are brought ungraded into store, ditions are suitable for the plants. Poor grading can be done under cover provided storage practice is a major cause of post­ there is adequate light and shelter. This has planting failure in Britain (Mason and the advantage that work may proceed during McKay, 1989; Sharpe and Mason, 1992). wet weather and in the early mornings when the ground is still frosty. Ideally, grading and 14.7.1 Outdoor storage packing should be done as near as possible to the plant store. Outdoor storage in nursery heeling areas or In the many mechanised nurseries, con­ sheughs was formerly widely used for storing veyor belts are used either to deliver unsorted plants. Although it has largely been replaced plants to staff who remove particular grades, by indoor storage in sheds or cold stores, it still or to remove sorted plants placed on the belt has a place for small numbers of plants for by staff drawing from boxes of unsorted short periods of time (i.e. 7-14 days). Plants are plants. also regularly stored outdoors in co-extruded After grading and counting, plants may be polythene bags under the shade of plantation tied in bundles, or if polythene bags or boxes canopy or elsewhere out of direct sunlight. are being used, sufficient plants may be put in The object of outdoor storage is to have a bag or box to fill it comfortably so that plants readily available for despatch or for plants remain in place without being tied in lining out while keeping them cool and stop­ bundles. ping them from drying out. Where it is necessary to apply an insecti­ cide before stock is planted in the forest, and Heeling in the grower requires this treatment to be Plants may be ‘heeled in’ or ‘sheughed’, loose applied in the nursery rather than in the or in counted bundles. A trench with a sloping forest, plans for counting, grading and storing back is dug and the plants laid in it thinly so plants may have to be modified to incorporate that their roots are completely in the trench

210 and most of the tops are out. As soon as the • plants are going to be planted in the forest plants are in, loose soil is put back over the or lined out in the nursery so late in the roots and lightly firmed down. There must growing season that if left in situ, they will never be so many plants in any part of the have started to break bud before they are trench that the root systems of plants, moved, or whether loose or bundled, are in buried air • surplus seedlings are to be stored until mid­ pockets and out of contact with the soil. summer for lining out, or If it is anticipated that orders for plants • ground has to be cleared and prepared for will come in very frosty weather, straw should the coming season’s seedbeds and lines. be spread thickly over the plants to prevent soil being frozen to them. It is important to Cold storage facilities are essential if plants prevent conifers being frozen in a sheugh in are to be held dormant for any length of time. cold, sunny weather when shoots can be Over the last decade, cold stores have come severely damaged by ‘winter’ desiccation. more widely into use and are available in Time must always be allowed for plants to many large and medium-sized nurseries. thaw if they have been stored at temperatures Their dimensions have caused previous plant below freezing. See also section 14.7.4. storage methods to be reviewed so as to make the best use of the height of stores and the Canopy storage opportunities for efficient mechanical han­ dling of plants. Pallet and stacking box sys­ Plants should not normally be stored in co­ tems are coming into greater use as a extruded bags under a plantation canopy consequence (Dauncey et al., 1989). See Plates (‘canopy storage’) for more than 14 days. The 35 and 36. risk is that the bags heat up in response to changes in ambient temperature and the car­ 14.7.3 Storage in polythene bags bohydrate reserves within the plants are depleted by respiration. Moulding of foliage Polythene bags have been in use for storage can also be a problem under these conditions. and movement of forest plants in the United While canopy storage may be unavoidable Kingdom for over 30 years. The reason for under certain conditions (e.g. if a cold spell storing plants in polythene is to prevent the occurs at the planting site immediately after roots from drying out by loss of moisture to the plants have been delivered), its use should be outside air. kept to an absolute minimum. When plants are stored in bags under canopy storage, the Recent developments necks of the bags must be turned down to pre­ There have been three developments in the vent rainwater running down into the bags last decade affecting their use. and flooding the root systems. Firstly, transparent bags have been replaced by ‘co-extruded’ bags where the inner 14.7.2 Storage under cover surface is black and the outer surface white opaque polythene (Tabbush, 1987b). They Plants may have to be kept in a cold store or have two advantages over the clear bags; the unheated, well ventilated shed, until required where: more important is that co-extruded bags are better able to protect plants from overheating • so large a number of orders for plants is if subject to direct sunlight. Trials in the mid- expected that they cannot all be met 1980s showed that the foliage of plants promptly, unless plants can be lifted and exposed to direct sunlight in clear polythene stored before the orders arrive, or bags reached almost 50°C within 3 h. By con­ • plants are likely to be required at times trast, the foliage temperature of plants in co- when the nursery ground is frozen or too extruded bags did not exceed 22°C (Tabbush, wet for lifting to proceed, or 1987b). The other advantage is that the white

211 surface can carry printing - e.g. a reminder mally saprophytic in the soil have however ‘Forest trees - handle gently’. spread as a white mould starting from the The second development has been a greater roots or near the root collar. This has devel­ attention to ‘storage + handling + transport + oped when plants have been in store for too planting1 as an integrated system, so as to long, or when they were packed in too wet a ensure the best performance of every newly condition, or where soil has come into contact planted tree. This is linked with the increase with foliage. Plants in bags in which such in the number of plants being used for white mould has started to show itself should replanting on clear-felled forest sites and the be removed from the bag as soon as possible need for insecticide treatment for such plants. and planted or lined out, or heeled-in in a The key point in an integrated handling shady spot. system is that the protection provided by poly­ Where large consignments of plants are to thene bags in conserving moisture in plants be despatched, counting and checking is sim­ must be retained. However, it is not clear plified if all bags have the same number of whether this will be in the form of: plants of a given species in them. • co-extruded bags transferred in open It is essential at all times to know the iden­ skeletal crates; tity of the contents of bags. They should be • a light co-extruded liner within a transit marked clearly and unambiguously, for box, the liner and contents being trans­ example with permanent felt tip marker pens. ferred to a planting bag on site; or With every batch of bags delivered, there • whether some other system achieving the should be a form giving the customer a record of the complete history of the plants listing same end will evolve. age, when the plants were lifted, how long The third development is a much greater they were stored, other treatments, etc. See understanding of the consequences of bad also section 14.9.3 on ‘Labelling’ at the end of handling and storage of plants, and their this chapter. interaction with dormancy and plant quality. Bag sizes Storage conditions Bags are readily obtained to order in sizes Plants may be stored safely for long periods in suited to the stock grown in the nursery. They co-extruded bags provided the recommenda­ must be of a large enough size to hold plants tions below are strictly observed. Bags should without crushing and the shoots should not be tightly sealed to ensure there is no loss of come out of the top of the bag. moisture through the neck of the bag. The Where bags are to fit inside boxes, gusseted polythene ensures that the roots do not dry bags may fit more easily; where bags full of out and that plants reach the planting site in plants are to be stored in the open, they as moist condition as when they were lifted. should be long enough for the top of the bag to Plants stored in polythene bags have been be tied and turned over to prevent rain water found extremely convenient to handle. collecting in the neck of the bag, seeping into However, convenience must not lead to care­ the bag and causing waterlogging of plants. lessness and abuse. Bags must not be dropped, thrown or otherwise handled roughly. While Summary of recommendations for the use deterioration is not obvious, plants’ ability to of black and white co-extruded polythene survive and grow after rough handling is bags for the storage and movement of markedly reduced. See section 14.2.4 above nursery stock and Table 14.1. There have been no cases of Botrytis (grey • Plants should be lifted and placed in poly­ mould) spreading from infected to other plants thene bags as quickly as possible. If there is inside polythene bags. Fungi that are nor­ likely to be any delay, roots must be pre-

212 Plate 25. Sitka spruce cutting material. (38037)

Plate 26. Sitka spruce rooted cuttings. (E8824)

Plate 27. Single span polytunnels with netting shading, for production of 1st cycle cutting material of genetically improved strains. (E8820)

Plate 28. One-year-old Sitka spruce seedlings in 2-litre pots at wide spacing. These plants are expected to reach 1.5 m or more by the end of their second growing season from sowing. (E8818) Plate 29. Briggs Rotorainer rotating sprayline. (39383)

Plate 30. Briggs rainomatic irrigation equipment, showing self-winding hose and reel on carriage. (A1986)

Plate 31. Famo lifter. (40609) vented from drying out by covering with • Full bags may be stored either in a cold damp straw. store or, as a short-term measure, in a cool • The surface of needles or leaves of plants well-ventilated shed or under the canopy of should be dry when being put into poly­ a plantation. thene bags. Plants lifted and packed with • Where plants in bags have to be stored for wet foliage are liable to rot. Packing with any length of time, bags should be packed dry foliage is especially important for not more than two layers deep, and prefer­ Douglas fir, western hemlock, western red ably in one layer on pallets or shelves. Bags cedar and Lawson cypress. Deciduous must not be stacked several layers deep for species should not be stored until the leaves more than a few hours, otherwise heating have fallen since dead leaves can act as a may occur. Whenever bags are stored, it source of moulds. must be in such a way that air can get to at • Plants should be packed with shoots in the least one side of each bag. same direction. • When plants are to be stored for more than • Plants must not be packed in layers with a week in one place, bags should be the roots of one layer pressing on the tips of arranged so that the plants are more or less shoots of plants in a lower layer. It may be upright. For shorter periods, e.g. when in found more convenient to tie plants into transit, this does not matter. bundles before packing, especially where • Full bags must be kept out of direct sun­ many small plants are being packed in a light at all times. This is especially impor­ large bag. Generally, however, it is prefer­ tant in March and April. able not to tie into bundles. • Plants must not be packed too tightly. Duration of storage in polythene bags • Plants must be fully enclosed inside the Table 14.4 gives the maximum recommended bags. safe storage periods and lifting ‘windows’ for • The thickness of material used for bags the common forest species, when polythene should depend on whether they will be bags are used. These dates are for guidance reused. Bags intended for the movement of and need to be adjusted for season, nursery plants freshly treated with insecticide location and the provenance being used. The against post-planting beetle/weevil attack key point with broadleaves is to ensure that should be used only once. they are stored after the leaves have fallen and before the buds or roots start to move • Check for punctures or tears as these seri­ again in the spring. ously diminish the efficiency of bags. One or Normally, plants should remain fully two small punctures will have little effect enclosed in their bags until required, unless on plants stored for short periods (up to 14 the safe storage period has been exceeded, or days). However, plants to be stored for more plants have been damaged in transit, when than 3—4 weeks should be put into undam­ they must be removed and examined for dete­ aged bags. All badly punctured or torn bags rioration. There is no objection to opening should be destroyed. bags for a short while to determine the condi­ • Bags should be tightly closed at the neck tion or quality of plants. If plants have to be with a string or wire tie. Adhesive or cellu­ kept towards the end of the recommended safe lose tape does not stick to damp or dirty storage period, regular inspection is well bags, while rubber bands quickly perish. worthwhile, especially if the weather is warm • When tying, bags should be gently squeezed or if there is any doubt that the storage condi­ to expel excess air. Tops should be turned tions are adequate. over to prevent rainwater entering bags if Plants starting to flush while in polythene stored outside. bags must be removed and heeled-in.

213 Table 14.4Lifting dates and storage periods for plants to be cold stored in polythene bags

Optimum Normal Maximum Species Lifting window lifting time storage storage period period (months) (months)

Sitka spruce (QCI or similar provenances) late November - mid March January Up to 3 5

Sitka spruce December - February January Up to 3 4 (Washington and Oregon provenances)

Sitka spruce (Alaskan provenance) mid November - late March mid December Up to 4 5

Larches December - mid January mid December Up to 3 5

Scots and lodgepole pines December - early March January Up to 3 5

Corsican pine December - February January Up to 3 4

Douglas fir mid December - early February January Up to 2 2

Norway spruce December - early March January Up to 3 4

Other conifers (Abies, Tsuga, etc.) December - early March January Up to 3 4

Broadleaves December - February January Up to 3 5

The lifting window is defined as the period between the first and last dates for lifting in a normal winter. Lifting should be delayed in a mild autumn. In a mild winter, do not exceed the normal storage period. The maximum storage period is possible when plants are lifted at the optimum time. 14.7.4 Cold storage of plants Plants held in store should remain dormant In Britain, cold storage of forest plants came and keep a high RGP well beyond the time in into general practice in the mid 1960s and spring when freshly lifted stock has actively over the years has found an increasing role in developing buds. Trees that have been well plant handling. It is estimated that 30^40% of stored can be despatched from the cold store plants planted in British forestry each year against late orders with a higher survival are cold stored for a short period. potential than if stock had just been lifted. Cold stores* offer nursery and forest man­ Serious deterioration can occur if plants are agers great flexibility. Once plants have put into store before they become fully dor­ become fully ‘storable’ in late autumn, they mant in the autumn or after dormancy has may be lifted when soil conditions are suitable broken in the spring (Plates 35 and 36). and labour is available. Subsequently plants may be culled and graded and returned to Type of store store for despatch to the forest when ordered. Most cold stores are directly refrigerated, i.e. the cooling unit and fan are within the storage * Strictly, plants require ‘cool’ stores, operating at 0° to chamber. Any water lost from plants or any­ +2°C or ‘freezer’ stores operating at -2° to 0°C. The cold thing else in the store condenses and freezes stores used for deep freezing meat and other foodstuffs as ice on the cooling coils, slowly desiccating are not suitable for plants since they operate at tempera­ tures of around -15°C. References to cold stores in this any unprotected stored material. Plants in Bulletin refer either to cool or freezer stores unless other­ such stores must be held in sealed waterproof wise specified. containers, i.e. polythene bags. The storage

214 temperature can be just above or just below fied stores should have an antechamber with 0°C. Stores should operate within 1°C of the heavy polythene skirts outside the chamber selected temperature. It is undesirable for the door, to act as a partial airlock between the thermostat to be set at 0°C as this causes the moist air of the chamber and the drier air of coolers to undergo potentially damaging the surrounding building. repeated thawing/freezing cycles. For general storage, stores should be set to Size of store operate at 1° to 2°C. However, provided plants When planning a cold store, three factors need are fully storable, long-term storage is prob­ to be considered when deciding upon the size ably safer at -2°C in directly refrigerated of storage facility required. These are the size stores. When operating at that setting, stores of the unit in which the plants are to be held should not be used to store seed while it is (bags or pallet), the space necessary for access undergoing moist prechilling. If plants are (e.g. are forklifts being used) and the volume stored at -2°C, provision must be made for required for good air circulation. them to thaw out before being handled, other­ wise branches and roots may be tom off as Storage principles and management frozen plants are separated. This will nor­ Useful discussion of the management of cold mally require up to 48 h interim storage in a stores can be found in Bartsch and Blanpied cool, well ventilated shed. (1984), Guyer (1991), Hardenburg et al. Two alternative store designs reduce the (1986). The following are some principles that risk of desiccation, so that plants can safely be should be remembered at all times. left unprotected in them for a period of time. • Successful storage depends upon the main­ In ‘humified’ stores, cold air is blown through tenance of the desired air humidity and a water cascade, or fine mist is sprayed regu­ temperature and ensuring good air circula­ larly, the resultant cold moist air being ducted tion throughout the store. to all parts of the chamber. However, the storage temperature is always above 0°C. • Air humidity should be maintained in all Indirect cold stores may also be built ‘jack­ types of stores by hanging a curtain of eted’; i.e. with the cooling air circulating in a heavy polythene strips on the inside of the wall cavity fully enclosing the store. Jacketed chamber door to act as a seal when the door stores are the most expensive of the three is open. In humidified stores this should be types of store. supplemented by an antechamber as out­ The main advantage of ‘humified’ or ‘jack­ lined above. eted’ cold stores is that plants can be stored • A stable air temperature is essential, par­ bare-rooted without the need for polythene ticularly where plants are being stored in bags. This is an attraction to the nursery man­ polythene bags. Fluctuating temperatures ager who can lift plants straight from the will result in condensation on the inside of nursery to the cold store chamber without the bag and this can result in moulds devel­ needing to bag them first. The plants can then oping on the plants. be extracted from the chamber as required, • It should be recognised that there are up to graded and bagged for despatch to the five potential sources of heat in a cold store. planting sites. These are: the heat generated by outside The danger with such stores is that plants conditions; the heat of plants that are being will continue to lose moisture from the roots brought in fresh from the field at a temper­ unless >95% relative humidity is maintained ature above that of the store; the heat gen­ (Sharpe and Mason, 1992). Loss of humidity is erated by the respiration of the living a particular danger when the doors of the plants in the store; the heat that comes in chamber are opened while plants are moved from outside each time the door is opened; into or out of store. For this reason, humidi­ and the heat generated by people and

215 equipment in the store (e.g. lights, Following a power failure, the refrigerating machinery, forklifts, etc.). The refrigeration unit should be switched off and only switched system must be designed to cope with these on again when full power has been restored. sources of heat. Any material being brought Electric motors driving compressors in the into store should ideally be cooled to the refrigeration unit can be seriously damaged if temperature of the store within 24 h of run on fluctuating low voltage (e.g. when the arrival. Checks should be made to see room lights flicker and do not deliver full whether the refrigeration equipment can light). achieve this under the most testing condi­ tions; i.e. on a warm day when a large Monitoring cold stores number of warm plants are being brought It is vital that cold stores are properly moni­ in, the door is frequently open, etc. tored for both air temperature and relative • There should be adequate air circulation on humidity. Twenty-four hour recording instru­ all sides of the plant material so that there ments should be used wherever possible in is no danger of heat build-up through respi­ case there is some malfunction out of working ration. hours. Spot checks should also be made in dif­ • The floor should be smooth so that it can be ferent parts of the store to check that no ‘hot­ kept clean. spots’ occur. • At the end of the season, the storage chamber and all ancillary equipment (e.g. crates, pallets) should be cleaned and disin­ 14.8 Insecticide treatment fected. Nursery stock planted on forest land where a conifer crop has recently been clear felled, Associated facilities may be in serious risk of attack from the pine Provision should be made for a grading shed weevil (Hylobius abietis) or black pine beetles or working area close to the cold store. Ideally, (Hylastes spp.); such plants may require treat­ this should be situated within the same ment with an insecticide before being planted. building, so that plants are not exposed to the Treatments need to be applied after lifting open air. There must be good access to stores and before planting, to protect stem and root and loading areas for tractors and lorries. collar tissues that after planting may be up to 2-3 cm below the soil surface. Stems and Hire of stores foliage should also be treated for at least While most of the bigger nurseries have cold 12-15 cm above the root collar. Plants may stores, in many parts of the country, it is pos­ remain susceptible to insect attack for 2 years sible to hire fruit or vegetable stores, the agri­ after planting; consequently, insecticide treat­ cultural/horticultural usage complementing ments are required which are persistent and the requirements of the forest nursery man­ which will require the minimum of ‘topping ager. It is important that these stores should up’ treatment after planting. be operated at the temperatures appropriate Because even persistent insecticides to forest nursery stock. become less effective with the passage of time, treatments should be applied as shortly before Power failure and plants in cold stores planting as practicable. Some forest managers Plants can tolerate several days in store treat stock on receipt from the nursery; how­ without power if plants have previously been ever, the techniques for treatment and the cooled to the normal storage temperature. safety precautions for those treating plants Access to a store should be minimised to avoid have become so demanding that many forest unnecessary warming. The store should have an managers prefer plants to have been treated alarm system to indicate a possible malfunction. in the nursery shortly before despatch.

216 14.8.1 Dipping electric field to create numerous small, highly Dipping is the principal technique for charged droplets in an enclosed treatment applying insecticides against pine weevil and chamber. These droplets are attracted to the pine beetles. See Chapter 13, section 13.3.3 for nearest earthing point and spread themselves information on approvals for insecticides to be evenly across its surfaces, including under used for this purpose. surfaces. Nozzles and feedbelts are so arranged that plants carried on the belts into Technique for dipping the spraying chamber act as earthing points in such a way that droplets cover plant stem Currently approved techniques for dipping and foliage around and up to 10-15 cm above require plants to be held mechanically while the root collar. they are being dipped; they should not be held The Forestry Commission has developed a manually. version of this technique for use on transplants There are two methods of gripping plants shortly before they are planted in the forest. using frames; one where the plants are in This is fully described by Scott et al. (1990). bundles, and one where they are spread thinly between two boards (Lane, 1990; Anon., Location of Electrodyn units 1990). With both gripping frames, roots can be While the units can be placed anywhere, protected from drying by covering with poly­ because they involve an appreciable capital thene bags or sheeting. outlay, it is important for them to be fully Plants in frames are held, shoots down, utilised; location in forest nurseries is the roots up, and immersed gently in the insecti­ most logical place for them. cide for a few seconds. The frames are then put on racks where surplus insecticide can Outline of method of operation drain off; they may be moved to other racking Plants are used which are ready for despatch for the insecticide to become thoroughly dry on to the forest, i.e. any grading has already been the foliage and stem. The drainage and drying done. They are placed on a conveyor belt con­ racks must be so arranged that any insecticide sisting of a series of moving support wires, the dripping off is collected and stored until it can positioning and correct spacing of plants on be safely disposed of. the belt being crucial for uniform treatment. When the foliage is dry, plants should be They then pass into an enclosed but venti­ put into bags for despatch. The period lated chamber where the plants are sprayed between treatment and planting in the forest with permethrin at a pre-set rate determined should be minimised; this will require close co­ by the insecticide container nozzles. Treated ordination between nursery manager, haulier plants should carry a minimum deposit of and customer. 0.4. pgmm-2 - a similar dosage to that A substantial quantity of contaminated soil obtained when plants are dipped. sludge will accumulate in dipping tanks and The solvent used as carrier, cyclohexanone, has to be removed periodically. Also, the is extremely volatile and vaporises before the unused insecticide remaining after all plants plants leave the spraying chamber; conse­ have been treated will also have to be dis­ quently, plants are sufficiently dry for them to posed of safely. See Chapter 15, section 15.6.6. be packed immediately from the end of the conveyor belt. 14.8.2 Electrodyn spraying The whole set-up is approximately 5 m long The ‘Electrodyn’ sprayer system was devel­ and 1 m wide. The main limitation on installa­ oped initially to treat tropical crops growing in tion is that the spraying chamber must be con­ open ground and using hand-held equipment. nected by an efficient ventilation system to Specially formulated oil-based pesticides are outside air in order to keep operators’ expo­ passed from nozzles through a high voltage sure to the solvent within acceptable limits.

217 One advantage of the system over dipping any doubt at all as how long plants will be in is that there is virtually no waste liquid insec­ transit, plants should be put into bags or lined ticide and very little contaminated soil and boxes to reduce the risk of desiccation and plant material to be disposed of. travel shock. Disadvantages are the relatively high cost Plants should always be packed so that of the system and the need to observe strict they are unable to move freely within the box safety procedures over ventilation. or bag. However, they must not be packed in so tightly that force has to be applied to com­ press the plants to get them in the bag or to 14.9 Packing and despatch close the box. The nursery manager having to organise the In the past straw and damp moss were used sending of plants from his nursery to a forest to reduce moisture loss and to cushion plants planting site may often find himself in a from shock while in transit. Use of polythene dilemma. On the one hand, his customers may bags should prevent moisture loss, while bags prefer small deliveries at short intervals; on and boxes can assist in minimising impact the other hand, the most economical means of shock. Nevertheless, the concept of using transporting plants is usually a lorry load at a these more traditional materials, especially time. Loads of this size normally take a few straw, to cushion plants remains valid. Straw days to assemble. At the forest, though some should always be remembered as a space filler plants may be put in immediately after if a lot of plants do not properly fill the con­ delivery, some may have to wait a couple of tainer and a smaller suitable container is not weeks before being planted. available. The unpredictability of periods of snow and severe frost add to the complexity of manage­ 14.9.2 Methods of despatch ment but in this instance provide the basis for Virtually all plants are currently despatched favouring early lifting and storage. by van or lorry. Rail played an important part The risks to plants in such situations can formerly, but the network is so reduced that it be reduced to a minimum only by good storage is rare for services such as ‘Red Star’ to be a facilities and by close contact between the relevant choice, and then, only when small nursery manager and the forester receiving numbers of plants are involved. the plants - adjusting the programmes of lifting and despatch on the one hand and Refrigerated trailers planting on the other. Certain larger nurseries are equipped with A nursery manager should encourage his refrigerated articulated trailers, fitted with customers to give him 2 months’ notice of shelving. In such trailers, plants can safely be when plants are required, and a name and moved long distances within minimum risk. telephone number so that any last minute With careful planning and co-ordination change in arrangements can be agreed. There between the nursery manager and foresters should also be an agreed delivery point. receiving the plants, large consignments of plants can be delivered in batches over a 14.9.1 Methods of packing period rather than in one load. Where the planting site is near the nursery and speedy nursery-to-planting site delivery of Box systems plants by van can be arranged, no special In many nurseries, stacking boxes are used, packing is necessary, other than careful either by themselves or on pallets, depending on stacking on the vehicle. See 14.9.2 below. the method employed for loading. These enable However, if the distance is more than a very articulated trailers to be hired as required from few miles, and there is any risk of drying or local haulage contractors (Plate 37).

218 Several systems involving the use of boxes plants. Such arrangements are not recom­ have been under development recently. mended if plants have to travel more than a Details of those in use in Forestry Commission very few miles. nurseries are given in Table 14.5. All plants sent without polythene protec­ tion must be covered for the whole of the Other methods journey with a well tied down tarpaulin, so Consignments of plants can be moved short that the least possible amount of wind gets in distances without specially fitted lorries or and dries the plants. Transparent polythene trailers. However, greater care has to be taken sheets should not be used in place of tarpau­ in ensuring the load can travel safely. Plants lins. The tarpaulin should be of a light opaque should not be despatched in loads more than colour so that it does not absorb or transmit two layers of bags deep. Single layers are excessive sunlight, resulting in the heating-up preferable. If necessary, some secure staging of the plants. or shelving must be installed. If the body of the lorry or trailer is fully If plants are being sent without protection closed, it must be ventilated to prevent over­ from boxes or polythene bags, they should be heating in sunny periods. arranged in cones or ‘bee-hives’, with roots of all plants in the cone to the middle, shoots 14.9.3 Labelling pointing out, and wet moss in the middle Consignments of plants must always be around the roots. The stack should taper labelled so that there is no doubt as to the upwards with the centre filled with upright identity of every part. Where plants within

Table 14.5 Boxes in use for packing and despatch of plants

Box type 'Wykeham' ‘Collar pallets' ‘Socrates' C1471

Box dimensions Length 570 1200 040 (external) Width 366 1000 400 (external) Height 320 250 350 per module*

Material Polypropylene Wood White reflective HD polythene

Pallet required for bulk movement Yes No (Integral) Yes 0 0 0 x 1000

Boxes per pallet 12 on 0 0 0 x 1200 9(12) 20 on 1000x 1000

Packing within boxes Standard bags Standard bags Polythene liners

Boxes returnable Yes Yes Yes

Storage when not in use Nesting (75%) Collapsible Nesting (50%)

Maximum stacking height using 12 boxes 5 pallets 16 boxes strapped pallets

* Can be built up to 1250 mm models. Data from Dauncey etal. (1900).

219 the Forest Reproductive Material Regulations and to group them in bunches of 25 plants or are included, appropriately coloured labels thereabouts. These bunches are wrapped with should be used. plastic or polythene film placed round the Bags that contain plants treated with insec­ plugs to prevent moisture loss. The plants are ticide before planting, must also be clearly dis­ then placed in standard black-and-white bags tinguishable, the marking indicating the (see 14.7.3 above) and handled in the same chemical used. way as bare-root stock. Plants treated in this Where two or more lots of any species are way have been cold stored for 3-4 months included in a consignment, e.g. of different with no effect upon subsequent survival and ages or of different origins, there must be growth. some positive way of identifying the different Containerised plants should be handled at lots that is capable of withstanding the haz­ all times with the same care and attention as ards of lost or torn tags, etc. This is best bare-root plants. Particular attention should achieved by including tags inside packages, be paid to the moisture content of the plugs. and in addition, having some indelible distin­ They should not have been allowed to dry out guishing mark on the outside of each bag, box, before being brought in for grading and/or etc., so that they do not need to be opened to despatch. This can be a particular danger if establish what they contain. containerised plants are being used to extend Accompanying each consignment, there the planting season into warm conditions in should be duplicate copies of a despatch note, May and June. Under such circumstances it listing all items in the consignment; one to will be sensible to water the plants before remain with the recipient, the other to return despatch and if they appear dry at any time to the sender as proof of delivery. A third copy between delivery and planting. may be necessary if the carrier has to submit documentary proof of delivery to support his invoice for carriage. REFERENCES ANON. (1990). Proposed dipping system for 14.10 Handling of plants raised bare root transplants. Departmental report; in containers 17.10.90. Forestry Commission, Wykeham Nursery, Sawdon, Scarborough. Containerised plants can be transported one BARTSCH, J.A. and BLANPIED, G.D. (1984). of two ways. The first is for the plants to be Refrigeration and controlled atmosphere delivered to the planting site in the container storage for horticultural crops. NRAES in which they were grown and to be extracted Bulletin 22, Cornell University, USA. at the last possible minute. This system is BURDETT, A.N. (1979). New methods for most effective when the container is not measuring root growth capacity: their value returnable (e.g. Japanese paper pots). It can in assessing lodgepole pine stock quality. also be used with returnable trays of con­ Canadian Journal of Forest Research 9, tainers (e.g. Rigipots), but more supervision 63-67. and care is required to collect up the container CANNELL, M.G.R. and SHEPPARD, L.J. sets after use and return them to the nursery. (1982). Seasonal changes in the frost hardi­ Delivering plants in the containers means ness of provenances of Picea sitchensis in that thought needs to be given to methods of Scotland. Forestry 63, 9-27. handling between nursery and customer COLOMBO, S.J. and HICKIE, D.F. (1987). A which may involve various forms of palletisa­ one-day test for determining frost hardiness tion and shelving (Stjernberg, 1989). using the electrical conductivity technique. An alternative approach is to extract the Forest Research Note 45. Ministry of plants from their containers at the nursery Natural Resources, Ontario.

220 COUTTS, M.P. (1980). Control of water loss of fruits, vegetables, florist and nursery by actively growing Sitka spruce seedlings stocks. USDA-ARS Agricultural Handbook after transplanting. Journal of Experi­ 66. US Government Printing Office, Wash­ mental Botany 31, 1587-1597. ington. COUTTS, M.P. and NICOLL, B.C. (1990). HAWKINS, C.D.B., and BINDER, W.D. (1990). Waterlogging tolerance of roots of Sitka State of the art seedling stock quality tests spruce clones and of strands from Thele­ based on seedling physiology. In Target phora terrestris mycorrhizas. Canadian Seedling Symposium. Proceedings of the Journal of Forest Research 20, 1894-1899. Combined Meeting of the Western Forest DAUNCEY, A.J., SOBOTA, C.M., and Nursery Associations, Roseburg, Oregon, eds JAMES, D.H. (1988). Packaging and trans­ R. Rose, S. J. Campbell and T. D. Landis. port of transplants. Wales Work Study 91-121. Team, Report 123. Forestry Commission, HERMANN, R.K. (1967). Seasonal variation Edinburgh. in sensitivity of Douglas fir seedlings to DAUNCEY, A.J., SOBOTA, C.M., and JONES, exposure of roots. Forest Science 13, D. H. (1989). Integrated handling, packaging 140-149. and delivery of forest transplants; Delamere LANE, P.B. (1990). Small scale dipping system nursery. Wales Work Study Team, Report for bare root transplants. Work Study 131. Forestry Commission, Edinburgh. Branch Report (Eastern Region Team) 21/90. DEANS, J.D., LUNDBERG, C., CANNELL, Forestry Commission, Edinburgh. M.G.R., MURRAY, M.B. and SHEPPARD, LEVITT, J. (1980). Responses of plants to envi­ L.J. (1990a). Root system fibrosity of Sitka ronmental stresses. 2nd edn. Academic spruce transplants: relationship with root Press, London, 347-391. growth potential. Forestry 63 (1), 1-7. LINDSTROM, A. and NYSTROM, C. (1987). DEANS, J.D., LUNDBERG, C., TABBUSH, Seasonal variation in root hardiness of con­ P.M., CANNELL, M.G.R., SHEPPARD, L.J. tainer-grown Scots pine, Norway spruce, and MURRAY, M.B. (1990b). The influence and lodgepole pine seedlings. Canadian of desiccation, rough handling and cold Journal of Forest Research 17, 787-793. storage on the quality and establishment of MASON, W.L. and McKAY, H.M. (1989). Sitka spruce planting stock. Forestry 63 (2), Evaluating the quality of Sitka spruce 129-141. planting stock before and after cold storage. FAULCONER, J.R. (1988). Using frost hardi­ Combined Proceedings International Plant ness as an indicator of seedling condition. Propagators Society 39, 234-242. In Proceedings, Combined Meeting of the McKAY, H.M. (1991). Electrolyte leakage: a Western Forest Nursery Associations, rapid index of plant vitality. Research Vernon, British Columbia. USDA Forest Information Note 210. Forestry Commis­ Service, Rocky Mountain Forest and Range sion, Edinburgh. Experiment Station, General Technical McKAY, H.M. (1993). Deterioration of fine tree Report RM 167, 89-95. roots during cold storage in two contrasting GREER, D.H., STANLEY, G.J., and WAR­ winters. Forestry Commission Technical RINGTON, I.J. (1989). Photoperiod control Paper 2. Forestry Commission, Edinburgh. of the initial phase of frost hardiness devel­ McKAY, H.M. (1994). Frost hardiness and opment in Pinus contorta. Plant Cell and cold-storage tolerance of the root system of Environment 12, 661-668. Picea sitchensis, Pseudotsuga menziesii, GUYER, D.E. (1991). Design basics for bare­ Larix kaempferi and Pinus sylvestris bare­ root storage. American Nurseryman 172 (9), root seedlings. Scandinavian Journal of 115-127. Forest Research (in press). HARDENBURG, R.E., WATADA, A.E. and McKAY, H.M. and HOWES, R.E.J. (1994). WANG, C.Y. (1986). The commercial storage Lifting times for larch establishment.

221 Forestry Commission Research Information SHARPE, A.L. and MASON, W.L. (1992). Note 244. Forestry Commission, Some methods of cold storage can seriously Edinburgh. affect root growth potential and root mois­ McKAY, H.M. and MASON, W.L. (1991). ture content and subsequent forest perfor­ Physiological indicators of tolerance to cold mance of Sitka spruce and Douglas fir storage in Sitka spruce and Douglas fir transplants. Forestry 65, 463-472. seedlings. Canadian Journal of Forest SMIT-SPINKS, B., SWANSON, B.T. and Research 21, 890-901. MARKHART, A.H. III. (1985). The effect of McKAY, H.M., GARDINER, B.A., MASON, photoperiod and thermoperiod on cold accli­ W.L., NELSON, D.G. and matisation and growth of Pinus sylvestris. HOLLINGSWORTH, M.K. (1993). The Canadian Journal of Forest Research 15, gravitational forces generated by dropping 453^460. plants and the response of Sitka spruce STJERNBERG, E.I. (1989). A review of con­ seedlings to dropping. Canadian Journal of tainerised seedling transportation methods. Forest Research 23, 2443-2451. Forest Engineering Research Institute of PELLETT, H. (1971). Comparison of cold har­ Canada, Technical Report TR-05. diness levels of root and stem tissue. STONE, E.C. (1955). Poor survival and the Canadian Journal of Plant Science 51, physiological condition of planting stock. 193-195. Forest Science 1, 90-94. PHILIPSON, J. (1988). Root growth in Sitka SUTTON, R.F. (1990). Root growth capacity in spruce and Douglas-fir transplants: depen­ coniferous forest trees. HortScience 25, dence on the shoot and stored carbohy­ 259-266. drates. Tree Physiology 4, 104-108. TABBUSH, P.M. (1986). Rough handling, soil RITCHIE, G.A. (1984a). Assessing seedling temperature and root development in out- quality. In Forest nursery manual: produc­ planted Sitka spruce and Douglas fir. tion of bareroot seedlings, eds M. L. Duryea Canadian Journal of Forest Research 16, and D. T. Landis. Martinus Nijhoff/Dr W. 1385-1388. Junk, The Hague, 243-259. TABBUSH, P.M. (1987a). Effect of desiccation RITCHIE, G.A. (1984b). Effect of freezer on water status and forest performance of storage on bud dormancy release in bare-rooted Sitka spruce and Douglas fir Douglas fir seedlings. Canadian Journal of transplants. Forestry 60, 31^43. Forest Research 14, 186—190. TABBUSH, P.M. (1987b). The use of co- RITCHIE, G.A. (1986). Relationships among extruded polythene bags for handling bare- bud dormancy status, cold hardiness, and rooted planting stock. Forestry Commission stress resistance in 2+0 Douglas fir. New Research Information Note 110/87/SILN. Forests Y, 29-42. Forestry Commission, Edinburgh. SCOTT, J.C. (1987a). Installation of a trans­ TABBUSH, P.M. (1988). Silvicultural princi­ plant handling system at Newton nursery. ples for upland restocking. Forestry Com­ Northern Work Study Team, Report 104. mission Bulletin 76. HMSO, London. Forestry Commission, Edinburgh. VAN DEN DRIESSCHE, R. (1975). Flushing SCOTT, J.C. (1987b). Plant handling. response of Douglas fir buds to chilling and Northern Work Study Team, Report 105. to different air temperatures after chilling. Forestry Commission, Edinburgh. British Columbia Forest Service Research SCOTT, J.C., WYATT, F. and LANE, P. Note 71. (1990). The ‘Electrodyn’ sprayer conveyor. VAN DEN DRIESSCHE, R. (1991). Effects of Northern Region Work Study Team, Report nutrients on stock performance in the 109. Forestry Commission, Edinburgh. forest. In Mineral nutrition of conifer seedlings, ed. R. van den Driessche. CRC Press, Florida, 229-260.

222 Chapter 15 Legislation and the nursery manager

J. R. Aldhous

In contemporary business, forest nursery This chapter also includes a section on the managers have to work within a continually OECD ‘Scheme for the Control of Forest changing legislative framework. Reproductive Material in International Trade’ Sections in this chapter outline current (OECD, 1974). While the scheme has no statu­ legislation affecting technical operations in tory force, it is so similar in operation to the the nursery, but not company law, accounting arrangements under the Forest Reproductive or business taxation, etc. The guidance that is Material Regulations that they are most given must not be regarded as a complete or appropriately described in this chapter (sec­ authoritative statement of the law; where this tion 15.4). is required, a professional legal adviser should be consulted. Whenever contemplating action in response 15.1 Forest Reproductive to any legislation mentioned here, always Material Regulations check whether there have been any more The Forest Reproductive Material Regulat­ recent amendments to legislation that may ions, 1977 (SI 1977/891; SI 1977/1264) are affect what you need to do. part of the framework of consumer protection In the following sections where current legislation in the UK; they are intended to statutes and associated regulations are men­ ensure that anyone establishing a plantation tioned, it should be taken for granted that any of young trees for forestry purposes is supplied relatively recent legislation has revoked and with healthy planting stock genuinely of the largely re-enacted earlier legislation. In the provenance or origin chosen by the planter. section on the Forest Reproductive Material They are administered by the Forestry Regulations, some older, now obsolete, regula­ Commission as the authority designated tions are described; for most other topics, the under the legislation (Forestry Commission, earlier revoked legislation is not mentioned. 1987). ‘Forestry purposes’ is not defined in the Where appropriate, full references to legis­ regulations, but in practice is taken as any lation are given: use of trees that qualifies for a forestry • Acts of Parliament are shown giving their planting grant. title, year of enactment and their chapter As part of its statutory obligation to ensure number in the statute book for the year, e.g. compliance with the FRM regulations, the Plant Varieties and Seeds Act, 1964 (1964, Forestry Commission has appointed staff who c.14). inspect the records and growing stock of firms • Statutory Instruments or Sis, the subordi­ trading in seed and plants falling within the nate legislation through which powers cre­ scope of Forest Reproductive Material (FRM) ated in Acts of Parliament are exercised, Regulations. are given their name, year of making, and The specific terms of the regulations incor­ reference number, e.g. Forest Reproductive porate the requirements of EEC legislation, Material Regulations, 1977 (SI 1977/891). and in particular, Council Directive No.

223 66/404/EEC as amended (EEC, 1966; 1969; Pinus contorta omitted. However, the EC 1975), and Council Directive No. 71/161/EEC directive is currently under revision (1994), as amended (EEC, 1971; 1974). and it is possible that the list of species will The regulations were enacted first in 1973 be extended because of the addition to the and amended in 1974. community of southern European states sub­ The 1977 Forest Reproductive Material sequent to when the FRM directives were Regulations (SI 1977/891) revoke (in Section first drawn up. (20)) and largely re-enact the 1973 and 1974 The forest tree species in the 1961 Seed FRM Regulations. The concepts of ‘select’ and Regulations were deleted under Section (2) of ‘tested’ forest reproductive material are intro­ the 1973 FRM regulations, thereby removing duced, there is a section on seed testing at the from statutory control all tree species previ­ Official Seed Testing Station, and minor modi­ ously in the 1961 Seeds Regulations list not fications are made to the previous regulations. covered by these Regulations. The list of species affected is not altered. The revocation in 1977 of the 1973 Regu­ The species covered by these Regulations lations does not reactivate that part of the are listed in Table 15.1. Because of their 1961 Seed Regulations from which forest tree ‘European’ link, they include species of forest species had been removed, because the whole importance in Western Europe as a whole, of the 1961 Seeds Regulations were revoked in rather than just the United Kingdom; e.g. 1974 under SI 1974/897 (Fodder Plant Seeds species such as Abies alba are included and Regulations).

Table15.1 Species to which the Forest Reproductive Material Regulations (1977) apply

Common name Botanical name Synonym

Seed or forest reproductive material raised from seed

Silver fir Abies alba Mill. Abies pectinata DC.

Beech Fagus syivatica L.

European larch Larix decidua Mill.

Japanese larch Larix leptolepis (Sieb. & Zucc.) Gord.

Norway spruce Picea abies Karst. Picea excelsa Link.

Sitka spruce Picea sitchensis Trautv. & Mey. Picea menziesii Carr.

Austrian and Corsican pine Pinus nigra Arn. Pinus laricio Poir.

Scots pine Pinus sylvestris L.

Weymouth pine Pinus strobus L.

Douglas fir Pseudotsuga taxifolia (Poir.) Britt. Pseudotsuga douglasii Carr. Pseudotsuga menziesii (Mirb.) Franco.

Red oak Quercus borealis Michx. Quercus rubra Du Roi

Pedunculate oak Quercus pedunculata Ehrh. Quercus robur L.

Sessile oak Quercus sessiliflora Sal. Quercus petraea Liebl.

Forest reproductive material raised from registered clonal stock by vegetative propagation

Poplar varieties Populus CVS.

224 Forest Reproductive Material 15.1.2 Categories of seed or plants (Amendment) Regulations, 1973 (SI under the Forest Reproductive Material 1973/1108), and 1974 (SI 1974/877) (FRM) Regulations These, respectively, set maximum lot sizes There are two categories of seed or plants of from which a sample should be taken for offi­ FRM species according to whether they are cial seed test and made minor changes to the from reproductive material which is ‘Tested’ criteria for transplant stock to meet ‘EEC or ‘Selected’. Standards’. Although not defined formally except through ‘derogation’ (section 15.1.6), there is 15.1.1 Definitions of terms also a ‘default’ category for seed or plants The Forest Reproductive Material Regulations which are neither tested nor selected. define certain terms, the more important of Criteria for ‘tested’ and ‘selected’ are fully these being summarised in Table 15.2. described in Schedules 2 and 3 of the 1977 FRM Regulations. The essential features are set out below. Table 15.2 Brief definitions of selected terms from the Forest Reproductive Material Regulations, 1977 15.1.3 Tested forest reproductive material Basic material - for seed sources, stands of trees and seed orchards; ‘Tested’ material must be superior to the local - for vegetatively propagated material, clones and mixtures standard in characteristics important for the of clones. species, both in economic and statistical terms. Normally, volume production is the Certificate of provenance first criterion; however, stem form, timber - certificate issued by the authority designated by national governments, describing the provenance of seed or plants. quality and disease resistance may each be a supplementary or primary criterion, according Forest reproductive material (FRM) to circumstance. - seed, cones and parts of plants intended for the Because of its definition, ‘tested’ can only be production of plants; also, young plants raised from seed applied to the tested product of a stand or or from parts of plants, natural seedlings and setts. seed orchard, or to vegetatively propagated Indigenous (synonym native) material. - believed not to have been introduced by human agency. Tested poplar clones Origin - place in which an indigenous stand of trees is growing, or Poplar has been propagated vegetatively for the place from which a non-indigenous stand was many decades, many individual clones having originally introduced. been specifically tested for resistance to bacte­ rial canker (Jobling, 1990; Peace, 1962; Provenance Phillips and Burdekin, 1992). ‘Tested’ clones - place in which any stand of trees, whether indigenous or non-indigenous, is growing. of poplar have shown sufficient resistance for them to be recommended for large scale use on Selected reproductive material appropriate sites. In 1989, a small number of - forest reproductive material derived from basic material the more promising, but incompletely tested approved for registration as ‘selected’ under the FRM poplar clones were accepted for use in Great Regulations. Britain under the FRM Regulations (Potter et Tested reproductive material al., 1990). A full list of the currently accepted - forest reproductive material derived from basic material clones of poplar is given in Table 10.2 in approved for registration as ‘tested’ under the FRM Chapter 10, section 10.1.1. Regulations.

Full definitions are set out in Section 2(2) of the Regulations. Seed from ‘approved’ seed orchards (FRM Regs, 1977) Because of developments resulting from tree

225 breeding and improvement programmes in Forest stands accepted as meeting the cri­ many countries, seed is available from seed teria for ‘selected reproductive material’ and orchards where the ability of the parent trees to entered in the national register are commonly produce superior progeny has been well estab­ referred to as ‘registered seed stands’. lished, but where the performance of the product of the seed orchard (i.e. from mass collection of 15.1.6 Unregistered seed or plants open pollinated seed) has not been separately tested. For the immediate future in Great Derogation Britain, this superior seed will be available from While preference should always be given to Forestry Commission seed orchards under the ‘selected’ or ‘tested’ stock of preferred origins, description ‘approved’ and should be considered seed crop failures and limited production at least as the equivalent o f‘tested’ seed. capacity result from time to time in shortages Seed orchard seed from orchards for which of selected or tested stock of the preferred tests are not yet complete, is described as ‘not source. Provision exists, in these circum­ tested’, but is the equivalent at least of stances, for authorising the collection of seed ‘selected’ seed (i.e. seed from registered seed ‘meeting less stringent requirements than stands). those laid down in the European Commission From 1990, the identity of seed from (EC) Directive’. Such authorisation - often ‘approved’ and ‘not tested’ seed orchards carry referred to as ‘derogation’ - is given by the EC the suffix ‘A’ (not ‘T’), and ‘NT’ respectively. in Brussels, following representations from See also Chapter 5, section 5.2.1 on identity each member state’s Forest Authority. The numbering of seed and plants. Forestry Commission, as Forest Authority, is responsible for collating forecasts of shortages 15.1.4 Selected forest reproductive of seed and plants by seed merchants and material forest nursery managers, and making repre­ sentations to the EC at Brussels on their behalf. ‘Derogation’ covers the initial collec­ Seed tion or import of unregistered seed and the ‘Selected’ seed is collected from registered subsequent raising of planting stock from it. stands identified as showing good form and The Forestry Commission makes enquiries above average volume production. The stand annually before submitting a list of requests must be big enough for there to be adequate for ‘derogation’ for the UK. Currently (1994), interpollination; also, it must be sufficiently this takes place in April to take effect from the separated from other stands to avoid serious following November. risk of cross-pollination with poorer quality In recent years, the interval of time trees. between forwarding the request and formal EC approval has seldom been less than 2 15.1.5 Register of seed and propagating months. material A procedure also exists, though it has Before any source of seed or propagating rarely been used, for considering ‘out of time’ material can be accepted as ‘tested/approved’ requests for ‘derogation’, arising out of unfore­ or ‘selected’, it has to be scrutinised for its seen circumstances. suitability as described in Chapter 5 of the Seed manual for forest trees (Gordon, 1992). Collection of unregistered seed from small Candidate seed stands are inspected and if stands suitable are entered in the ‘National Register There are no requirements for seed collection of Basic Material’. This register also contains from unregistered stands, apart from identi­ details of seed orchards and of registered fying the source accurately; however, collec­ stoolbeds of poplar clones. tors looking at small groups of trees as

226 possible seed sources should be aware that Table 15.1 for forestry purposes, must insist there are dangers of inbreeding if the number that for all the seed or plants of these species of trees is small, especially if it is possible that which they receive, they get the documents the parent trees themselves may have origi­ required under the FRM regulations. The doc­ nated from a very small number of trees, e.g. a uments are summarised in subsection 15.2.1. clump of trees in an ornamental landscape. This includes plants bought in and sold imme­ To maintain the broad genetic base of any diately to cover orders which the nursery seed source, a similar amount of seed should cannot meet from its own stock. They must be collected from a minimum of 40 or more also despatch stock to customers with the cor­ seed-bearing trees at any one time. rect certification. If a nursery manager collects seed of any Further information species covered by the FRM regulations, or All enquiries about any aspect of authorisa­ takes cuttings from poplar stoolbeds, there are tion to use unregistered seed of species cov­ additional procedures to observe, outlined in ered by the Forest Reproductive Material section 15.3. Regulations, should be addressed to the Records must be retained of all certificates Forestry Authority, 231 Corstorphine Road, and licences received or issued involving basic Edinburgh, EH12 7AT (Tel. 031-334-0303). material covered by the FRM Regulations. The Forestry Commission currently requires 15.1.7 European Community standards these to be kept for a minimum of 7 years. for seed and plants In addition to defining the quality of the seed Field and stock records source of plants in terms of origin and poten­ Nursery managers must be able to control and tial performance, the EC directive and the record the progress of each lot of stock associated UK legislation also provides for throughout its life in the nursery. This should standards of physical quality. include recording the position of stock as it is laid out on the ground, and means to ensure Seed standards that if any label marking seedbeds, transplant Seed of the species listed under the FRM regu­ lines or stock in propagating houses is inad­ lations has to be marketed as ‘EEC Standard’. vertently dislodged or wantonly vandalised, In practice, the requirements of the standard stock can be correctly identified. This require­ seed test itself, together with a supplementary ment is especially important when a nursery test for seed purity, allow any seed with a is carrying, for example ‘selected’ and ‘unreg­ valid UK or ISTA (International Seed Testing istered’ stock of the same species, or two or Association) seed test certificate and meeting more provenances, for example, of native the EC seed purity requirements, to be cate­ Scots pine. gorised as o f‘EEC Standard’. See also Chapter 5, section 5.6. Poplars It is especially important that there are reli­ Plant standards able field maps of stoolbeds and plant lines, The requirements that plants must meet, if and that there is a rigorous discipline imposed they are to be marketed as ‘EEC Standard’, at the time of taking cuttings, to deal only are listed in Appendix IV - EEC Plant with one variety at a time and to remove all Standards, and discussed in Chapter 1, section stray or left-over woody material. Poplar 1.5.2 along with other aspects of plant quality. clones are notorious for the difficulty in distin­ guishing closely related varieties, even when 15.1.8 Documentation in full leaf; when only setts or cuttings are Nursery managers dealing in species listed in available, it is often quite impossible. Control

227 procedures should include the rigorous exami­ Part II Further particulars to be furnished in the case of seed nation during the growing season of poplar 1. Number of Test Certificate (if any). rooted cuttings and transplants, any apparent 2. The description 'EEC Standard', or, where the seed does not comply with the conditions laid down in Part III of ‘rogues’ being destroyed. Schedule 7, and is authorised for marketing under regulation 11 (2), a statement that it does not so comply. 3. Percentage of purity. 15.2 Seed and plant sales 4. Percentage of germination. 5. Number per kilogramme of live seeds. 6. Number per kilogramme of seeds capable of 15.2.1 Receipt and supply of seed or germinating. plants within the United Kingdom 7. Weight of 1000 pure seeds in grammes. 8. Year in which the seed shall have ripened. Material received 9. If the seed has been kept in cold storage, a statement to that effect. Nursery managers should receive from any supplier, for all seed lots, and for all lots of Part III Particulars to be furnished in the case of young plants which will, or may possibly be used for plants and parts of plants sold or delivered under the forestry purposes, a ‘Supplier’s Certificate’ description ‘EEC Standard' 1. The description 'EEC Standard'. containing information shown in Table 15.3. 2. EEC classification number, in the case of the genus Populus. Table 15.3 Particulars required in a Supplier’s 3. Location of nursery in which the young plants were raised during their last growing season. Certificate 4. Age, in the case of parts of plants of the genus Populus which have had more than one growing season. Part I Particulars to be furnished in every case 5. The size of the young plants. 1. The number of the Master Certificate, if any, or the number, if any, of any certificate of provenance or clonal identity and the name of the country issuing it. 2. Type of material, whether seed, cones, parts of plants or The Supplier’s Certificate is an important young plants. document as it constitutes a legal warranty 3. Quantity of material being marketed. 4. Botanical name: the species and, where applicable, sub­ from the seed supplier to the nursery manager, species, variety, clone. and from the nursery manager to his customer 5. In the case of selected reproductive material or tested that the origin and other details given are as reproductive material, its category. described. 6. In the case of selected reproductive material, its region The Supplier’s Certificate should differ in of provenance. 7. In the case of tested reproductive material, its basic colour, according to the category of plants or material. seed: 8. In the case of forest reproductive material, which, Certificate although not derived from officially approved basic material, has been authorised for marketing in Category colour accordance with regulation 11 (2), its place of ‘tested’, blue provenance and the altitude of that place. 9. Its origin. approved UK seed orchards pink 10. (a) in the case of seedlings, the length of time the ‘selected’ green seedlings have been in the seed bed, and also, unregistered usually white (b) in the case of transplants, the length of time they have existed as seedlings and as transplants, There is no prescribed design for Supplier’s respectively, and the number of times transplanted. Certificates. The certificate format used by the 11. If the forest reproductive material although not derived Forestry Commission when supplying seed or from officially approved basic material is authorised for marketing in accordance with regulation 11 (2), a plants to the private sector is given in the statement to that effect. Forestry Commission booklet describing the 12. If derived from seed orchards a statement that the regulations (Forestry Commission, 1987). reproductive material is so derived. However while these are widely copied, the use 13. Name and address of the supplier. of that particular format is not obligatory. Other

228 Plate 32. Famo lifter with supporting tractor collecting plants into open-mesh crates before transfer to cold store. (E8880)

Plate 33. Grading transplants on a carousel. (38110)

Plate 34. Multi-roui plant lifter with secondary vibrating tines to loosen soil. (J.R. Aldhous) Plate 35. Open-mesh crates of newly lifted plants being moved in cold store prior to grading and packing. (E8885)

Plate 36. Plants in store, showing crates in tiers of four crates strapped to pallets, and stacked three pallets high. (39390)

Plate 37. Articulated trailer used for long­ distance delivery of plants from nursery to planting site. (40615) approaches are acceptable, in particular, certifi­ nursery manager some idea of the quality of cates linking with invoices or other elements of seed when calculating sowing densities. the essential paperwork arising from sale of seed or plants, or certificates linked in with 15.2.2 Imports of plants and seed computer-based stock control and sales docu­ Imports of plants and seed are controlled not mentation. Providing information of the correct only by the Forest Reproductive Material coloured paper can be achieved by photocopying Regulations but also by plant health legisla­ computer output on coloured paper, retaining tion (see this chapter, section 15.5). the original as a file copy. Table 15.4 summarises the documents that a nursery manager should require, when Seed and plants despatched importing any species covered by the FRM The seller of seed, cuttings or plants should regulations. give the buyer a supplier’s certificate within 14 days of the sale or delivery, whichever is later. 15.2.3 Exports of plants and seed Seed which is sold must in addition have a current Seed Test Certificate (Chapter 5, sec­ Exports to EC member states tion 5.6.6). However, where seed such as beech Consignments of ‘selected’ or ‘tested’ forest and oak have to be despatched for immediate reproductive material exported to destinations sowing and seed testing may take 3-8 weeks, within the boundaries of member states of the the supplier’s certificate and seed test certifi­ European Community, must be accompanied cate must be sent to the buyer as soon as by: available. An interim certificate is often • An ‘Official Certificate of Provenance’ - this issued, based on a ‘quick’ test to give the is obtainable on application to the Forestry

Table 15.4 Documents required when importing plants or seed covered by the Forest Reproductive Material Regulations*

Situation Certificate Import Licence to Phytosanitary Plant Seed test of of licence from market from certificate health certificate exporter provenance Forestry Forestry from pass- from from exporterf Commissionf Commission exporter p o rtf exporter

Plants imported into the UK Based in EC, plants from registered EC source Yes No No No Yes No

Based in EC, plants not from registered EC source Yes No Yes No Yes No

Not based in EC Yes Yes Yes Yes No No

Seed imported into the UK Based in EC, seed from registered EC source Yes No No No No Yes

Based in EC, seed not from registered EC source Yes No Yes No No Yes

Not based in EC Yes Yes Yes No No Yes

* Table based on Fig. 6, Forestry Commission, Explanatory Booklet, 1987; The Forest Reproductive Material Regulations, 1977. (Forestry Commission, 1907). t Or equivalent e.g. under OECD scheme, t A requirement under Plant Health legislation.

229 Authority, 231 Corstorphine Road, Nursery managers and seed suppliers may Edinburgh, EH12 7AT. wish to use the voluntary arrangements under • A Supplier’s Certificate - this should be the OECD certification scheme described in completed by the nursery manager whose section 15.4 of this chapter. stock is being exported. • (a) If seed is being exported, a current 15.3 Seed stand registration and Seed Test Certificate from an approved official seed testing station. seed collection (b) If plants are being exported, a plant Arranging and controlling seed collection has health passport issued by the nursery the advantage for the nursery manager that manager after a nursery inspection by as the collector, he can be in no doubt as to the the Ministry of Agriculture (MAFF) in provenance of the seed gathered. At the same England and Wales, and the Scottish time, he has to be sure that he has the skills Office Agriculture and Fisheries and facilities to clean, dry and store the seed Department (SOAFD) in Scotland. safely, so that it is in first class condition when it comes to sowing. N.B. Plant passports may need to certify that Full details of practical procedures for seed the plants and nursery ground in which they crop forecasting, seed collection and pro­ were grown are free from specific harmful cessing are given in Forestry Commission pests and diseases. The issue of such certifi­ Bulletin 59 Seed manual for ornamental trees cates therefore depends on the outcome of and shrubs (Gordon and Rowe, 1982) and in inspection of plants and soil tests, by a local Forestry Commission Bulletin 83 Seed MAFF or SOAFD inspector. Certain tests may manual for forest trees (Gordon, 1992). have to have been done in the growing season The following paragraphs summarise, for preceding export; nursery managers should species covered by the Forest Reproductive seek plant health inspectors’ advice before Material Regulations, the main points where accepting export orders. practice and legislation interact. For species not covered by these regulations, certain steps Exports to countries not members of the are not obligatory; nevertheless, anyone European Community and exports ofnon- organising seed collection is recommended to FR M species to E C member states use the sequence of operation as a check list, Regulations vary widely from country to especially if an OECD seed certificate (section country so that the exact requirements of any 15.4) is to be sought. country should be found, before any arrange­ Commercial seed collectors come within the ments for export are finalised. scope of the Health and Safety at Work etc. Act, 1974, and associated regulations; see sec­ 15.2.4 Species not covered by the tion 15.8.1. Forest Reproductive Material Regulations 15.3.1 Status of stand and access to Nursery managers are not obliged to receive seed crop or send ‘supplier’s certificates’, nor to obtain current ‘seed test certificates’ for plants and Status of stand seed not covered by Forest Reproductive Contact must be made with the owner or his Material Regulations. agent, or for Forestry Commission woodland, Nevertheless, planters are covered by con­ the local Forest District Manager, firstly, to sumer protection legislation, in respect of the confirm who is able to give permission for description and quality of seed and plants sup­ access to a potential seed crop and where plied. See this chapter, section 15.8.2. appropriate to agree provisional terms for col­

230 lection, and secondly, to find out whether the • priority and relationship with other con­ stand is registered as a ‘selected’ seed source. tractors in the woods, especially harvesting If not registered, the owner, agent or manager contractors, pesticide contractors and other should be asked whether any unsuccessful seed collectors; application for registration has been made in • relationship with shooting tenant and the past, whether an application is currently gamekeeping staff; being processed, and whether any ‘unregis­ tered’ collection has been made in recent • third party insurance requirements ade­ quate for collectors in the circumstances of years. the permission. If appropriate, check terms of current cover under Employers Application for registration (Compulsory Insurance) legislation If it is necessary to apply, or re-apply for reg­ istration, a request for a Form FRP1 15.3.2 Collection of unregistered seed ‘Application for seed stand registration’ should be sent to the Forestry Authority, Tree If a seed collection organiser wishes to collect Improvement Branch, Northern Research from a stand of a species covered by the FRM Station, Roslin, Midlothian, EH25 9SY. regulations but the stand is not acceptable for The completed FRP1, giving details of registration, then, in addition to the notifica­ species, approximate age of stand, elevation, tions necessary for registered seed, the seed col­ variety, origin, total stand area and area in lection organiser must apply for and obtain which seed may be collected, as far as these specific authority to collect unregistered seed are known, should be returned to the Forestry from the stand in prospect before any commer­ Commission following instructions with the cial collection starts. This may be applied for by form. The request should be accompanied by: the owner, seed collection organiser, nursery manager or seed merchant, from the Forestry • a map on 1:10000 scale showing the loca­ Authority, 231 Corstorphine Road, Edinburgh, tion of the stand and access from a public EH12 7AT. road; If the Forestry Authority considers that • the name and address of the owner and, if there are ample supplies of registered appropriate, the woodland agent or man­ ‘selected’ seed of the same region of prove­ ager; and nance/origin, readily available on the market, • the appropriate non-returnable fee, as authorisation to collect unregistered seed may advised with the application form. Note be refused. See also section 15.1.6. that a higher fee is required for inspections after certain dates. 15.3.3 Notification of intention to collect A seed collection organiser may apply for a Seed collection organisers are required to stand to be registered, if he has the owner’s inform the local Forestry Authority office in permission. The decision on whether the stand writing not less than 28 days beforehand of: has been accepted for registration will be noti­ • seed source. fied to the owner or the agent responsible for • proposed starting and finishing dates of col­ managing the woodland, with a copy to the lection. applicant, if appropriate. Registration, in itself, Addresses of current Forestry Authority confers no special rights on the applicant. offices are given in Appendix I. During collection, it is essential to ensure Terms of entry that individual collectors stay within the The seed collection organiser should establish boundaries of the seed stand as notified. with the owner/agent: Once the collection has been completed, the • dates and times of access for seed collecting; collection organiser is required to notify the

231 local Forestry Authority office of the total Forestry Authority office not later than the amount of cones, fruit or seed collected, and if beginning of May of the season the cuttings applicable, the amount of seed extracted. were inserted. If the Forestry Authority is satisfied with the information given by the collector, Unrooted setts; unrooted cuttings together with any reports that may have been Applications to the Conservator should be made by their inspectors, the collection organ­ made not later than the beginning of May pre­ iser will receive for the amount of marketable ceding the winter when unrooted setts or cut­ seed or fruit declared: tings will be taken. • if the stand is registered, a 'Master Certificate of Provenance’; • if the stand is not registered, a ‘Certificate 15.4 OECD scheme for the of Provenance’; control of reproductive material • if seed has been collected under ‘deroga­ moving in international trade tion’, a licence to market. This international voluntary scheme run Without one or other certificate, the seed col­ under the auspices of the Organisation for lected cannot legally be marketed anywhere Economic Co-operation and Development within the European Community. (OECD), originated in 1967 and foreshadowed the European Community Forest Repro­ 15.3.4 Poplars - registration and ductive Material Directives. After the latter certification came into force, the OECD scheme was amended so that definitions and requirements Stoolbed registration in common were identical, including notifica­ Procedure for registering poplar stoolbeds is tion to the national Forest Authorities of pro­ the same as for potential seed stands. A posals to collect seed, and to have records request + local details + fee must be sent to available for inspection (OECD, 1974). the Forestry Authority who will arrange for the stoolbeds to be inspected (see section 15.4.1 Status in the United Kingdom 15.3.1). The scheme was formally adopted in Great A valid inspection of poplar stoolbeds can Britain in 1984, the Forestry Commission only be made when they are established, and being the designated authority. then only after young leaves on developing The Forestry Commission in 1982 had pre­ shoots are fully expanded, as these are the viously issued a booklet about the scheme, means of checking the identity of the variety. reproducing details of the Method of Applications should be made therefore, not Operation, Regions of Provenance, Approved later than the beginning of May preceding the Basic Material, etc., published in 1974 by the first proposed marketing season. OECD (Forestry Commission, 1982). In practice, the scheme is used principally 15.3.5 Certification of poplar forestry for seed imports and exports. OECD certifi­ planting stock cates are accepted where unregistered seed is being imported from outside the European Rooted cuttings Community. (See Table 15.4 - Documents Application for a ‘Master certificate of prove­ required when importing seed.) nance’ should be made for each year’s inser­ The Forestry Authority maintains a reg­ tion of cuttings from registered stoolbeds, or of ister of selected stands of species not covered cuttings raised from plants themselves raised by the Forest Reproductive Material from cuttings from registered stoolbeds. Regulations, but which come within the scope Applications should be made to the local of the OECD scheme. For the UK, the same

232 regions of provenance apply as for the FRM the UK, such seed can be collected and seed collections. sold as ‘source identified’ seed, provided Currently, seed imported from Canada, the Forestry Authority has been given USA, Hungary, Romania, Japan and the formal and timely notice of the proposal Scandinavian countries are imported under to collect. OECD certificates. (b) ‘Seed from untested seed orchards’. The other member countries are: Australia, Apart from hybrid larch, this category Austria, Belgium, France, Holland, Ireland is of limited relevance to the UK; and Italy. Germany is an associate member; species for which seed orchards have Spain and Turkey are believed to be applying been established and which might be for membership. planted on any scale in Britain are cov­ ered by FRM rules. Future developments • There is no requirement in the OECD The OECD scheme is likely to be revised at scheme for seed to be tested prior to mar­ some future date, to keep it in step with the keting. EC scheme, taking into account changes in • In addition to maintaining registers of tree breeding practice and the development of selected seed stands, the Forestry Author­ vegetative propagation of stock raised in tree ity is obliged to register seed collectors, improvement programmes (Faulkner, 1987). seed extractories and seed stores where any For further details about the operation of the OECD-certified seed is being stored and OECD scheme in Great Britain, contact the nurseries where OECD-certified plants are Forestry Authority, 231 Corstorphine Road, being raised. Edinburgh, EH 12 7AT.

15.4.2 Comparison between the OECD 15.5 Plant and seed health and EEC schemes Following the creation of the European The most important differences between the Community ‘Single Market’, previous arrange­ OECD and EEC schemes are: ments for plant health inspections at customs • While the EEC scheme applies to a posts at national borders have been with­ restricted list of species when traded drawn. In their place, a scheme has been between and within EC member states, the introduced whereby plants for which any OECD scheme is open for any country to health risk of potential significance within the apply to join and does not set limits on the European Community has been identified, are species that may be included. inspected at the nursery where they are being grown (The Plant Health (Great Britain) • Within any country which has set up the Order 1993, SI 1993/1320). If no evidence of a scheme, observance of the OECD scheme is relevant pest or disease is found, the nursery voluntary. Seed suppliers and nursery man­ manager is authorised to issue a ‘plant pass­ agers may apply to enter the scheme when port.’ they see the need. However, neither the For plants raised in any nursery within the OECD nor the EEC scheme operates retro­ European Community, plant passport require­ spectively. ments relate to specific organisms on named • Under the OECD scheme there are four cat­ genera. Only where plants are being imported egories of seed instead of the two under the from elsewhere than European Community EEC. The additional categories are: countries is there any requirement for a phy- (a) ‘Source identified’. This applies to tosanitary certificate of freedom from pests unregistered sources of seed of species and disease. not covered by the FRM regulations. In Certain parts of the EC have been identi­

233 fied as being free of particular pests and dis­ vi. the botanical name of the plants; eases present elsewhere in the EC. These vii. the quantity of plants; have been designated as ‘Protected Zones’ in viii. if plants were obtained from another order to maintain that status. nursery, the letters RP, and a code The Plant Health and Seed Inspectorate number in place of the registration (PHSI) of the Ministry of Agriculture (MAFF), number of the original producer; or the Scottish Office Agriculture and ix. if plants were raised outside the EC, the Fisheries Department (SOAFD), is responsible name of the country where they were for implementing the new plant health rules raised; in respect of young plants in forest nurseries. More detailed information should be sought x. if plants can validly be moved into or from their local offices. within a ‘protected zone’, the letters ZP, and the codes for the relevant zones. The Forestry Commission, Plant Health Branch, is responsible for plant health mat­ If a delivery note is used for this additional ters affecting forests and woodland, wood and information, it must also include items i-v wood products. Enquiries should be addressed above. to: Plant Health Branch, Forestry Com­ mission, 231 Corstorphine Road, Edinburgh, 15.5.2 Plant passports for forestry EH12 7AT (Forestry Commission, 1992). planting stock A plant passport is needed whenever plants of 15.5.1 Plant passports genera listed as possible carriers of pest or dis­ A plant passport is a label or combination of ease are moved, sold or otherwise disposed of to label and delivery note prepared by the another nursery manager or grower, whether nursery manager arranging despatch of within the UK or the European Community plants. (EC). For any plants requiring passports, a label Woodland tree and shrub genera requiring a must be attached to the plants or to the plant passport whenever plants are moved include: packaging. This label must state: Crataegus, Malus, Prunus, Sorbus /except S. intermedia), Pyrus, Cotoneaster, i. the heading ‘EEC Plant Passport’; Pyracantha, Chaenomeles, Cydonia, etc. ii. the EEC member state code for the These are potential host species for fireblight country where the nursery issuing the and/or other pests and diseases of fruit trees passport is located, e.g. UK; and associated ornamental varieties. iii. a code letter or letters indicating the offi­ Additionally, passports are required for all cial body with which the nursery is regis­ rooted conifers over 3 m tall, because of pos­ tered, e.g. EW, S, NI; sible conifer bark beetle infestation. iv. the registration number of the nursery Northern Ireland and the Isle of Man have issuing the passport; been designated as ‘protected zones’ within v. a serial number, week number, batch the UK for several potential pests. Conse­ number or other number which unam­ quently, additional requirements have to be biguously identifies that consignment. met in order to allow plants to be moved into these areas: Items ii, iii and iv should run together, ii and iii being separated with a 7 ’, e.g. i. plants of species potentially susceptible to UK/S 1234. fireblight must have been raised in a Additional information must either be nursery in a ‘fireblight-free zone’; included on the passport label or must be ii poplars have to be free from Hypoxylon entered on a document (delivery note) travel­ mammatum; ling with the plants. iii. conifer genera have to be free from six

234 specific pests according to genus, as listed have to be met to enable a ‘Phytosanitary in the regulations. Certificate’ to be issued. In most circumstances, passports will be A fee is charged for issue of a Phytosanitary required for all movements of plants of: Certificate. Abies, Larix, Picea, Pinus, Pseudotsuga, Tsuga, Castanea, Platanus, Populus, 15.5.5 Registration for plant health Quercus. For plant passports to be able to be issued, However, small producers who are solely sup­ nurseries must be registered and a ‘respon­ plying local purchasers with stock for wood­ sible person’ nominated. land planting may be exempted from having New nurseries expecting to be involved in to register and issue passports. Nursery man­ anything more than the most local trade agers who consider they fall into this category should ensure that they are registered with should check with their local PHSI or SOAFD PHSI or SOAFD. Where the PHSI address is office. not known, the nearest office of MAFF will be Plant passports are not required for conven­ able to give details. tionally raised: Registered nurseries will be inspected regu­ Acer (except A. saccharum), Aesculus, larly for two aspects of their business. Betula, Carpinus, Corylus, Fagus, Growing plants of genera requiring passports Fraxinus, Juglans, Nothofagus, etc. will be inspected for their health; also the office system of recording stock movements There are no requirements for passports for will be reviewed so as to satisfy the inspector tree seed or fruits of any genus, except for that plants can be traced back to their origi­ Prunus fruits coming from outside the EC. nating nursery should the need arise. These may require a phytosanitary certificate in respect of potential fruit crop pests. A charge is not made for initial registration; however, for inspections of nursery stock and 15.5.3 Plants imported from outside the records, charges are made. In England and European Community Wales, these are (in 1993) on a ‘time spent’ basis. In Scotland, the charge is related to Schedules 3 and 4 of the Plant Health (GB) nursery area. Order (SI 1993/1320) detail restrictions and Details of arrangements for issuing pass­ some complete bans on all the more important ports and the procedure for passporting plants conifer genera and some broadleaved genera, which are bought in and sold on are supplied especially Quercus, Ulmus and Castanea. to nursery managers, once their nurseries For other genera, imported stock from non- have been registered. EC countries has to meet the same require­ ments as for stock from EC countries, except that a phytosanitary certificate is required 15.5.6 Legislation for plant health instead of a plant passport. UK legislation is based on the requirements of There are special rules for imported the amended European Community Council ‘bonsai’ trees. Directive on Plant Health, 77/93/EEC (EEC, 1977), and Commission Directive 92/90/EEC, 15.5.4 Export outside the European 92/98/EEC and 92/105/EEC (EEC, 1992 a,b,c). Community The principal enabling legislation is the Where plants may be exported outside the Plant Health (Great Britain) Order, 1993 (SI European Community, the Plant Health and 1993/1320). SI 1993/256 extends provisions to Seed Inspectorate or SOAFD should be Northern Ireland, while SI 1993/1641, /1642 approached as soon as the possibility is and /2344 schedule the fees for inspections for known, in order to find out what requirements passports and phytosanitary certificates.

235 15.6 Current pesticide legislation Pesticides register-, this contains details of additions and amendments to the annual Current pesticide legislation is directed issues of MAFF Reference Book 500 (i.e. the towards the safe and effective usage of pesti­ current year’s issue of Pesticides 1994), cides in the UK, giving particular emphasis on including ‘off-label’ approvals and with­ protection of the consumer (where edible crops drawals. The British Crop Protection are being treated), protection of the person Council produce a regularly updated sum­ applying the pesticide and protection of the mary of products and their uses (Ivens, environment. 1994); also, the horticultural nursery trade Forest nurseries for the purposes of this press usually carries editorial comment and legislation are grouped with other parts of the feature articles on the more important horticultural industry, and not with forestry. changes during the year. Two sets of ‘Regulations’ currently define Nursery managers should be aware of two the requirements for the legal use of pesti­ other codes: cides in forest tree and other horticultural • COSHH in fumigation operations: COSHH nurseries, whether stock is raised in open Regulations, 1988. Approved code of prac­ ground or in plastic greenhouses, tunnels, etc., tice (HSC, 1988), relevant should it be nec­ these are: essary to fumigate greenhouses or • The Control of Pesticides Regulations, 1986 polytunnels. (SI 1986/1510), made under the Food and • The safe use of pesticides for non-agricul- Environment Protection Act, 1985. tural purposes: Approved code of practice NB: forest and ornamental tree nurseries (HSC, 1991a). The coverage of this code are included as part of horticulture for the includes conventional forestry operations purposes of these regulations. but not forest nursery operations. • The Control of Substances Hazardous to For other relevant publications, see the Health Regulations, 1988 (SI 1988/1657), list at the end of the chapter. made under the Health and Safety at Work Act, 1974. 15.6.1 Essential operational needs These regulations are complex and are supple­ Four essential legal requirements have to be mented by various codes of practice and guid­ met: ance notes which amplify the requirements of 1. Pesticides used for any aspect of pest control the legislation. The most important are: in forest nurseries MUST be approved for • Pesticides: Code of practice for the safe use horticultural use on the crop needing treat­ of pesticides on farms and holdings, pre­ ment. Alternatively, there must be an pared jointly by MAFF and HSC and pub­ exemption in force for the crop or species in lished in 1990 (MAFF/HSC, 1990); question. • Storage of approved pesticides: Guidance for For a period after the introduction of the new farmers and other professional users. regulations, forest tree nursery managers Guidance Note CS19 (HSE, 1988). were able, under a temporary exemption for non-edible crops, to use products for which • MAFF Reference Book 500, ‘Pesticides 1994’ there was not a specific approval, subject to (MAFF, 1994), or its equivalent for the cur­ certain conditions. These arrangement are rent year. This lists all the products described briefly in Annex C ‘Off-Label approved under the Control of Pesticides Arrangements’; pp. xli-xliv of MAFF Regulations. Reference Book 500 (MAFF, 1994). While it A copy of each of the above should be available is probable that these arrangements will con­ in the nursery office. tinue for the short term, it is important to Periodically during the year, MAFF issue a have ready access to the current edition of

236 MAFF Reference Book 500 and to check, in ‘National Proficiency Test Council’, to those each new edition as it comes out, that no who pass the relevant tests. changes have been introduced which may Pesticide operations for the purposes of cer­ restrict what has up to that time been good tification of competence are grouped into practice. eleven ‘modules’. All operators requiring 2. All staff involved in the use of pesticides certification must obtain a certificate for must be competent to undertake the work the ‘Foundation Module’ and, in addition, required of them. certificates for those modules directly rele­ It is the responsibility of employers and self- vant to their work. Full details are set out employed individuals, to organise training, in the ‘Pesticide Application Test Schedule’ testing and practice to achieve and maintain available from the National Proficiency competence, and to ensure that their Test Council, 10th Street, National Agri­ employees obtain any necessary certificates. cultural Centre, Stoneleigh, Kenilworth, Initial training can be provided by courses Warwickshire, CV8 2IG. at agricultural or horticultural colleges. In Scotland, details are also available from: Information on what is available locally can Scottish Association of Young Farmers’ be obtained from the Agricultural Training Clubs, Young Farmers’ Centre, Newbridge, Board or local agricultural advisers (ADAS) Ingleston, Edinburgh, EH28 8NE. in England or Wales, or in branches of the 4. The ‘employer’ must make an ‘assessment’ Scottish Agricultural College. under the Control of Substances Hazardous Subsequent up-dating training may be to Health (COSHH) Regulations (Reg. 6) available from colleges; if instruction on and must take all reasonable steps to pre­ new techniques and products is not avail­ vent or to control exposure of employees to able within travelling distance, individuals hazards from pesticides and other haz­ will have to rely on information from manu­ ardous substances. facturers leaflets, advisory leaflets, visits Employees or their representatives should from advisers, etc. be informed of the results of the assess­ 3. Certain classes of individuals must have a ment, and in particular, they should be pro­ relevant ‘Certificate of Competence’ issued or vided with details of the assessment authorised by the ‘National Proficiency Test relating to any operation which they are Council’ (NPTC) or by the ‘Scottish Asso­ required to carry out. ciation of Young Farmers’ Clubs’ (SAYFC). Alternatively, they must work under the 15.6.2 Control of Substances Hazardous direct and personal supervision of a certifi­ to Health (COSHH) assessment cate holder. The classes of individual requiring ‘Certi­ COSHH Regulations 6, 7 and 8 and the associ­ ficates of Competence’ are: ated Approved code of practice issued by the Health and Safety Commission (HSC, 1993) • those born after 31st December 1964; amplify requirement (4) above. • anyone applying pesticides as a commer­ The Health and Safety Executive have also cial service, i.e. as a contractor; issued a guide to COSHH assessments (HSE, • anyone having to supervise any indi­ 1993); this is in more general terms than the vidual who should hold a certificate but code of practice. Ideally, the two documents does not. should be considered together. ‘Personal supervision’ should be taken as The ‘hazardous substances’ to be considered ‘working within sight and sound of the include all such materials on the nursery supervisor’. premises, e.g. petroleum based fuel oils, and The ‘Certificates of Competence’ for pesti­ are not restricted to pesticides. cide users are issued by or on behalf of the Nursery managers and others responsible

237 for the safe use of pesticides in forest nurs­ • the terms of current approvals for the pesti­ eries can adequately meet their obligations in cides in mind; respect of COSHH assessments and pesti­ • other hazardous substances listed; cides, in a four stage procedure, given below. This relies on the substantial programme of • relevant codes of practice; and testing before any pesticide is marketed, and • the particular environment of the nursery. the care that is paid to the wording of the approved product labels. Installing up-to-date practice • Survey of current and expected future needs; assembly of all relevant information. The next stage is to do whatever had been shown to be necessary to up-date the capa­ • Identification of proper course of action. bility to use pesticides etc. effectively and • Installation of up-to-date practices, based safely in the nursery, whether in terms of staff on the above point. training, improved storage facilities or appli­ • Checks just before use, that there have cation procedures, or other action. been no material changes in circumstances, requiring corresponding changes in proce­ Check just before use dures. The final stage is always to check whether any special local circumstance or conditions on the Survey day should cause the previously planned The first stage is to list all the pesticides and treatments to be modified because of any other substances hazardous to health, in the changed risk. This stage should be repeated current and future production programme of before every pesticide application. the nursery. This list should include possible While the first three stages should nor­ pesticides and other substances (e.g. fuels and mally be carried out as a recorded, formal pro­ lubricants) that might reasonably be needed, cedure and should be formally reviewed as well as those for which there is a clear regularly (e.g. annually), the final stage need. should be on-going, relating specifically to For the materials thus identified, details site, crop, pest and occasion. It is an essential must be obtained, e.g. from product labels, part of the assessment process. However, it manufacturer’s recommendations, of the best should involve a modest expenditure of time current techniques for applying them. or work, if the preceding stages have been For some products, there may not be an completed conscientiously. See also section exactly relevant recommendation on the 15.8.1. product label. In these circumstances, other sources of information should be sought - e.g. 15.6.3 Sources of information Forestry Commission recommendations, checking with the body making the recommen­ The approved label of pesticide product consti­ dation, that such ‘off-label’ uses are currently tutes the principal source of information on permissible. which to base the initial assessment of the hazards associated with individual pesticide Proper course of action products. Decisions on what operations during the Government Departments that may be able coming 12 months should be provided for, to provide additional information include: must take into account: • The Forestry Commission, 231 Corstor- • the existing staff, facilities and practices phine Road, Edinburgh, EH 12 7AT. (trained operators, equipment, store, waste • MAFF, Pesticides Safety Directorate, Roth- disposal, records, procedures for emergen­ amsted, Harpenden, Hertfordshire, AL5 cies, etc); 2SS or local ADAS offices.

238 • Health and Safety Executive, Pesticides will create some wastes. However, the aim of Registration Section, Health Policy management should be to keep the wastes to Division, Magdalen House, Bootle, an absolute minimum. For example, when get­ Merseyside, L20 3QZ or local HSE offices. ting to the end of a container of concentrate, it should become a matter of routine to wash out Manufacturers’ data sheets should be avail­ the container and use the washings to dilute able on request, under provisions of the 1987 the concentrate before making up the spray Consumer Protection Act. solution to its final dilution. In this way, you British Crop Protection Council publica­ finish up with clean containers without any tions include: washing waste. • The current UK pesticide guide (Ivens, 1994); The MAFF/HSC Code of practice for the safe • Weed control handbook (Holly and Hance, use of pesticides on farms and holdings details 1990); alternative acceptable methods of disposing of • Pest and disease control handbook (Scopes pesticide wastes. One or other of these and Staples, 1989). methods should always be followed. Equipment can be installed in a forest nursery for treating insecticide and other 15.6.4 Keeping up-to-date residues, so that the bulk of the liquid can New products, new uses for existing products safely be returned to the ground and pesticide and tightening environmental standards concentrate in solid form disposed of through result in a continual stream of changes in the an approved waste disposal contractor. list of ‘approved products’ or ‘approved uses’ Under the Environment Protection Act, for existing products. Nursery managers must 1990 the Department of the Environment, therefore ensure that they have up-to-date Scottish Office and Welsh Office have jointly information on the status of any pesticide produced a Code of practice on waste manage­ product they intend to use. ments (DoE, 1991). This refers to ‘controlled The information in this Bulletin was up-to- waste’. Waste from agricultural premises is date at the time of publication. There is no not ‘controlled waste’; as long as forest nurs­ guarantee that limitations may not have been eries continue to be considered as a part of imposed subsequently on any product listed, agriculture and horticulture, wastes from nor that manufacturers will continue to them are covered under 1985 Food and market products here recommended for use, Environment Act legislation rather than nor that codes of practice may not have been under the 1990 Environment Protection Act. changed.

15.6.5 Storage of pesticides 15.7 Seed and plant breeding As far as possible, the minimum amount of pesticides should be stored. 15.7.1 Seeds Act and Seeds Regulations There are now clear guidelines in the HSE Guidance Note CS19 Storage of approved pes­ Plant Varieties and Seeds Act, 1964 (1964, ticides for farmers and other professional users c.14) (HSE, 1988). These distinguish between small This act empowers ministers to regulate seed scale storage using cabinets or vaults and and plant description, testing and trading, larger stores. Nursery managers have to set and provides that particulars of seed or plants up an effective storage system, meeting the supplied under this statute, constitute a requirements of these guidelines. written warranty from the supplier. It also introduced the concept of ‘plant 15.6.6 Disposal of pesticide wastes breeders’ rights; see section 15.7.2. The purchase and use of pesticides inevitably The Forest Reproductive Material Regu­

239 lations draw their authority substantively National List or which have been in a from this Act. It also repealed the 1920 Seeds Common Catalogue for 2 years. These regula­ Act. tions bring the National Lists into line with requirements of EC directives on Commor. European Communities Act, 1972 Catalogues. (1972, c.68) This Act, in Schedule 4 D 5, Seeds and Other Seeds (Regulation, Licensing and Propagating Material, includes several provi­ Enforcement) Regulations, 1985 (SI sions affecting the 1964 Plant Varieties and 1985/980); amended SI 1987/1098) Seeds Act: These prescribe that no person shall carry on • para 5(1) adds a new section (16A) to the a seed business, or sample seed of any sort to 1964 Act to cover marketing; which Regulations under the Plant Varieties • para 5(4) adds vegetative propagating and Seeds Act, 1964 apply, unless registered. material and silvicultural planting mate­ However, ‘silvicultural propagating oi rial; planting material’ is specifically exempted. (Otherwise, seed merchants dealing in forest • para 5(4) also authorises the Forestry tree seed would be included, as the FRM regu­ Commission to set up and fund an ‘Official lations are made under that Act.) Seed Testing Station’ (where previously, it had been a ‘private’ seed testing station). Seeds (Fees) Regulations Fodder Plant Seed Regulations, 1974 These set fees for seed testing, etc., for seed (SI 1974/897) categories defined in specific agricultural crop Among other provisions, these Regulations seed regulations, e.g. SI 1985/975, /976, 1911, revoked the 1961 Seeds Regulations, both for /978, 1919. The fees are revised frequently; England and Wales, and for Scotland, in their enquiries have to be made when needed, to entirety (Section (2) and Schedule 1). find the most up-to-date SI. These are the first of several consecutively numbered regulations which cover various 15.7.2 Plant breeders’ rights groups of agricultural and horticultural seeds. Sections 1-15 of the Plant Varieties and Seeds Together and with the FRM Regulations, they Act 1964 establish ‘plant breeders’ rights’. replace most of the requirements of the 1961 Their definition and the means of establishing Seeds Regulations. them are set out in various regulations which have been subject to frequent amendment and Seeds (National List o f Plant Varieties) renewal between the commencement of the Regulations, 1982 (SI 1982/844; Act and the present time. Only the most amended, SI 1985/1529; SI 1989/1314) recent versions of the regulations and schemes These regulations provide for: are listed below. This Act implements the 1961 ‘International • a Plant Varieties and Seeds Gazette where Convention for the Protection of New Varieties additions to the National List of Plant of Plants’. A revision of this Convention was Varieties may be printed; agreed in 1991, the UK having been a signatory • establishment of reference collections of both to this and the original Convention plant material; (UPOV, 1991); amending legislation will be • conditions for submission of applications required but may not emerge until 1994 or and for the results of trials providing sup­ later, as the EC is also introducing a porting evidence. ‘Regulation’ based on the text of the convention. Marketing of agricultural crop seed is The amendments do not materially alter those restricted to species and varieties on the parts of the convention relevant to forest trees.

240 Plant Varieties Act, 1983 (1983, c.17) including specifically, varieties of Cupressus, This is a short Act; it extends the period of Thuja, Taxus, Tsuga and other species, for cut plant breeders’ rights by 5 years, and adds foliage. Varieties registered are currently into the list of varieties protected under the restricted to ornamentals. legislation, ‘rootstocks of forest and orna­ mental trees’. 15.8 Other legislation Plant Breeders’ Rights Regulations, 1978 (SI 1978/294, amended by SI 1985/1092) 15.8.1 Health and safety These revoke and re-enact earlier regulations; Health and Safety at Work etc. Act, 1974 they set out procedures for applying for a (HASAWA) grant of plant breeders’ rights and associated licences, selection of varietal names, register Legislation to ensure the health and safety of of plant varieties; schedules detail quantities employees has its roots in the 19th century of seed and specification for samples sub­ and certain provisions remaining in force are mitted with an application. of long standing, e.g. the Employment of Fees, controlled by regulation, are required Women, Young Persons and Children Act, to cover an initial application, and separately 1920 (1920, c.65), the Factories Act, 1964 subsequently, for testing and for annual (1964, c.34) and more recently, the Health and renewal of registration. Safety at Work etc. Act, 1974 (1974, c.37). Of these, the last is the one having most general 15.7.3 Schemes effect on nursery operations. Under the Regulations, ‘schemes’ may be pro­ The Health and Safety at Work Act, essen­ mulgated in respect of specified groups of tially added to the earlier legislation. Its plants, listing the species/varieties covered major innovation was to extend the scope of and the duration of rights. Regulations and health and safety legislation to all persons at schemes currently in force relating to plant work - employers, self-employed and breeders’ rights cover a vast range of agricul­ employees, and to the safety of the general tural and horticultural varieties. Two are public who may be affected by work activities. applicable to forestry genera. Earlier legislation on health or safety has been amended to enable it to be enforced Trees, Climbers and Woody Plants through Health and Safety regulations. Scheme, 1969 (SI 1969/1024, amended by The Control of Substances Hazardous to SI 1971/1093 and SI 1985/1091) Health (COSHH) Regulations, 1988 (SI This covers broadleaved ornamental trees and 1988/1657) described in section 15.6 in the shrubs under the Plant Breeders’ Rights context of use of pesticides, derive their Regulations, not only as growing plants but authority from HASAWA, 1974. may include varieties grown for blooms, The Health and Safety Executive Library foliage or stems. and Information Services annually issue a list Willow and poplar are also included under of currently available Health and Safety the scheme. The first registrations of willow Commission and Health and Safety Executive biomass varieties were made in 1993. No leaflets, booklets, etc. Further information is other varieties of either genus, whether available from: HSE Information Centre, timber producing or ornamental, have been Broad Lane, Sheffield, S3 7HQ. registered (Aldhous, 1992). Access to information on hazardous Conifers and Taxads Scheme, 1969 substances (SI 1969/1025) As from 1 March 1988, manufacturers and Similarly, this covers all conifers and taxads, suppliers of ‘articles’ and ‘substances’ are

241 obliged under an amendment to the HASAWA Self-employed people must be able to treat introduced through the Consumer Protection minor injuries themselves. Act 1987 (1987, c.43), The regulations supersede the Agriculture • to consider reasonably foreseeable risks (First Aid) Regulations, 1957 (SI 1957/940). during handling, maintenance and storage, Other legislation affecting health and as well as use, safety in forest nurseries • to provide safety information to customers, Agriculture (Power take-off) Regulations, 1957 • also to take account of non-domestic (SI 1957/1386). premises other than work-places to which Agriculture (Field Machinery) Regulations, they supply substances. 1962 (SI 1962/1472). Manufacturers consequently now supply on Classification, Packaging and Labelling of request, ‘data sheets’ for many of, if not all Dangerous Substances Regulations, 1984 (SI their products affected by this legislation. 1984/1244, amended by SI 1986/1922 & SI 1988/766). The Reporting o f Injuries, Diseases and See also HSE Guidance Note PM15 (HSE, Dangerous Occurrences Regulations, 1985 1978) in relation to stacking of pallets such as (SI 1985/2023) (RIDDOR) in plant stores, and HSE booklet HS(R)4 on Made under HASAWA, these regulations offices (HSE, 1989). came into force in 1986 (HSE, 1992). Employers, or anyone who is self-employed or 15.8.2 Consumer protection in control of work premises must: While the following notes are set out in gen­ • immediately notify (normally by telephone) eral terms, they are directly applicable to nursery stock bought or sold. their local HSE office or local authority environmental health department, if Trades Descriptions Act, 1968 (1968, c.29) anyone dies or is seriously injured in an This Act prohibits misdescriptions of goods and accident in connection with their business services in the course of trade. ‘Description’ or there is a dangerous occurrence (e.g. an includes: quantity, size, fitness for purpose, overturned tractor); physical characteristics, testing and the results • report to the appropriate authority within 7 thereof. The description must not be mis­ days if anyone is off work for more than 3 leading, nor must it mislead in respect of price. days as a result of an accident at work, or if For there to be an offence under the Act, the a death, serious injury or dangerous occur­ description must be false to a ‘material degree’. rence has been notified by phone, or if a Descriptions or marks made as a require­ doctor has certified a specific occupational ment of the 1964 Plant Varieties and Seeds disease (HSE, 1992). Act are excluded. However, regulations such as the Forest Reproductive Material Regu­ Health and Safety (First Aid) Regulations, lations under the 1964 Act, themselves 1981 (SI 1981/917) require sellers or suppliers to provide certifi­ These regulations are now covered by an cates giving specified information about seed Approved code of practice issued by the Health or plants; in so doing, the suppliers give their and Safety Commission (HSC, 1991b). The warranty that the information in such certifi­ regulations place a general responsibility on cates is correct (Plant Varieties and Seeds Act, all employers: Section 17 (1), and FRM Regulations). • to make ‘adequate and appropriate’ provi­ sion for first aid treatment of accidents or Supply of goods illness occurring at work; • Supply of Goods (Implied Terms) Act, 1973 • to notify employees of these arrangements. (1973, c.13)

242 • Consumer Credit Act, 1974 (1974, c.39) In England, Wales and Northern Ireland, • Unfair Contract Terms Act, 1977 (1977, these terms are implied in every transfer of goods for private use or consumption. In c.50) Scotland, they are for most transactions, but • Supply of Goods and Services Act, 1982 there are no statutory implied terms, for (1982, c.29) example, where the supply is part of a con­ These Acts include provisions, covering tract for ‘work and materials’. Such transac­ implied terms of trading for a wide range of tions are, instead, covered by common law. transactions. For normal retail sales to cus­ tomers, the implied terms of trade are set out 15.8.3 Employment in statutory form; customers cannot be deprived of them by exclusions clauses. These are that goods must: Employment protection • correspond with the description The principal statutory relationships between employer and employee, regarding terms and • be of merchantable quality conditions of employment, are laid down in: • be fit for the purpose. • Employment Protection (Consolidation) Act, The first of the above requirements is self- 1978, as amended by the Employment Act, explanatory. 1982. The second, however, involves an element • Employment Protection Act, 1975 as of judgement. ‘To be of merchantable quality, amended by the Employment Protection goods must be as fit for the purpose as it is (Handling of Redundancies) Variation reasonable to expect, having regard to any Order, 1979. description applied to them, the price and all • Transfer of Undertakings (Protection of the other relevant circumstances’ (DTI, 1988). Employment) Regulations, 1981 (SI 1981/ A customer has no right to reject goods on 1794) as amended by the Transfer of grounds of ‘not being of merchantable quality’ Undertakings (Protection of Employment) if the defects complained about were brought (Amendment) Regulations, 1987 (SI 1987/ to his attention before a sale. Also, if a cus­ 442). tomer examines goods before buying them, this right does not apply to defects that should • Wages Act, 1986. have been seen during that examination. The Department of Employment has pub­ The separate right, ‘fitness for purpose’ lished a series of explanatory leaflets on covers the situation when a customer says aspects of this legislation, a full list of which that goods are wanted for a particular pur­ can be obtained from any Job Centre. pose, which may not be one for which the goods are usually supplied. If the trader Contract of employment explicitly supplies goods to meet those Under current legislation, a contract of employ­ requirements, they must be reasonably fit for ment exists as soon as an employee proves his the purpose specified. If the trader is not con­ or her acceptance of an employer’s terms and fident that the goods will meet the customer’s conditions of employment by starting work; particular requirements, he must make it both employer and employee are bound by the clear that the customer cannot rely on his skill terms offered and agreed. Often, the contract is or judgement in this respect. not written down. Where goods were supplied in breach of Under the Employment Protection (Con­ these implied terms, customers have a right to solidation) Act, 1978, within 13 weeks of an a refund. They may also be entitled to compen­ employee starting work, the employer should sation if they suffer loss because goods failed to give the employee a written statement con­ meet the implied terms of trade (DTI, 1988). taining certain important terms of employ­

243 ment, with an additional note, mainly on dis­ Environment, Scottish Office, Welsh Office ciplinary and grievance procedures. HMSO, London. The statement can be used as important DTI (1988). A trader’s guide. Law relating tc evidence as to the terms and conditions in an the supply of goods and services. Depart unwritten contract. ment of Trade and Industry. DTI/PUB 022. A written contract of employment will nor­ EEC (1966). Council Directive No. 66/404/EEC mally refer to all the terms that have been on the marketing of forest reproductive agreed (D.Empl., 1987a). material. Official Journal of the European Communities, C125, 11.7.1966, p.2326. Wages EEC (1969). Council Directive No. 69/64/EEC, Most employees have a statutory right to amending Directive No. 66/404/EEC receive individually, from their employers, a Official Journal of the European Com­ written pay statement when or before they are munities, L 48, 26.2.1969, p.12. paid their wage or salary including details of EEC (1971). Council Directive No. 71/161/ EEC deductions for income tax and National on external quality standards for forest Insurance contributions (D.Empl., 1987b; 1988). reproductive material marketed within the community. Official Journal of the European Employment protection - self-employed Communities, L 87, 17.4.71, p.14. and part-time workers EEC (1974). Council Directive No. 74/13/EEC, amending Directive No. 71/161/EEC, on the The provisions of the Employment Protection external quality standards for forest repro­ Act do not cover independent contractors or ductive material marketed within the com­ freelance agents. munity. Official Journal of the European Staff working part-time or on short con­ Communities, L 15, 18.1.74, p.12. tracts, especially those who have a fixed term EEC (1975). Council Directive No. 75/445/ contract for less than 3 months but who have EEC, amending Directive No. 66/404/EEC actually worked for more than this period, on the marketing of forest reproductive have to have their entitlements under this leg­ materials. Official Journal of the European islation determined individually. Communities, L 196, 26.7.75, p. 14. EEC (1977). Council Directive No. 77/93/EEC REFERENCES AND FURTHER READING on regulating plant health in relation to ALDHOUS, J.R. (1992).Plant breeders’ rights. potential threats from imported pests and A review of their applicability to poplar and diseases. Official Journal of the European willow. (Unpublished report.) Communities, L 26, 31.1.77, p.20—54. D.Empl. (1987a). Written statement of main EEC (1992a). Commission Directive 92/90/ terms and conditions of employment (under EEC of 3 November, 1992 establishing the Employment Protection (Consolidation) obligations to which producers and Act, 1982). Booklet 1, Employment Legis­ importers of plants, plant products .... lation (PL700), 2nd revision. Department of details for their registration. Official Employment, London. Journal of the European Communities, D.Empl. (1987b). Itemized pay statements. L344, 26.11.92, p.38. Booklet 8, Employment Legislation (PL704). EEC (1992b). Commission Directive 92/98/ Department of Employment, London. EEC of November, 1992. Plants, Plant D.Empl. (1988). The law on the payment of Products .... which must be subject to a wages and deductions: a guide to Part 1 of Plant Health Inspection .... Official Journal the Wages Act, 1986. Booklet PL810. of the European Communities, L352, Department of Employment, London. 2.12.92, p. 1-5. DoE (1991). Waste management - The duty of EEC (1992c). Commission Directive 92/105/ care - A code of practice. Department of the EEC of 3 December, 1992 establishing a

244 degree of standardisation for plant pass­ guidance. Approved code of practice. ports .... and detailing procedures for their Revised 1991. HMSO, London. replacement. Official Journal of the HSC (1993). Control of substances hazardous European Communities, L4, 8.1.93, p.22. to health (General ACoP) .... Approved codes FAULKNER, R. (1987). Suggested and required of practice. COP 29, 4th edtn., Health & changes to the OECD ‘Scheme for Control of Safety Commission. HMSO, London. Forest Reproductive Material in International HSE (1978). Safety in the use of timber pallets. Trade’. Paper to IUFRO Working Group WP HSE Guidance Note PM15. S2.02.21. Forestry Commission (Northern HSE (1988). Storage of approved pesticides - Research Station), Edinburgh. Guidance for farmers and other professional FORESTRY COMMISSION (1982). Organi­ users. Health & Safety Executive Guidance sation for Economic Development and Co­ Note CS 19. HMSO, London. operation (OECD): Scheme for the Control HSE (1989). A guide to the Offices, Shops and of Forest Reproductive Material Moving in Railway Premises Act, 1963. Health and International Trade. Forestry Commission, Safety Executive. Health and Safety series Edinburgh. booklet HS(R)4. HMSO, London. FORESTRY COMMISSION (1987). Explan­ HSE (1992). Reporting under RIDDOR. atory booklet (1987); The Forest Repro­ Health & Safety Executive Leaflet, HSE ductive Material Regulations, 1977. 24. HMSO, London. Forestry Commission, Edinburgh. HSE (1993). COSHH assessments. A step-by- FORESTRY COMMISSION (1992). Plant step guide to assessment and the skills health and the Single Market. Explanatory needed for it. Health & Safety Executive, Booklet PH7, 2nd edition. Forestry HSG 97. HMSO, London. Commission, Edinburgh. IVENS, G.W. (1994). The UK pesticide guide FRM Regs. (1977). Forest Reproductive 1994. CAB International & British Crop Material Regulations, 1977. Statutory Protection Council, Famham, Surrey. Instrument 1977, No 891, as amended by JOBLING, J. (1990).Poplars for wood produc­ Statutory Instrument 1977, No 1264. tion and amenity. Forestry Commission HMSO, London. Bulletin 92. HMSO, London. GORDON, A.G. (1992). Seed manual for forest MAFF (1994). Pesticides 1994: Pesticides trees. Forestry Commission Bulletin 83. approved under the Control of Pesticides HMSO, London. Regulations, 1986. Reference Book 500. GORDON, A.G. and ROWE, D.C.F. (1982). HMSO, London. Seed manual for ornamental trees and MAFF/HSC (1990). Pesticides: code of practice shrubs. Forestry Commission Bulletin 59. for the safe use of pesticides on farms and HMSO, London. holdings. HMSO, London. HANCE, R.J. and HOLLY, K. (1990).Weed con­ OECD (1974). OECD scheme for the control of trol handbook. 8th edtn. Blackwell, Oxford. forest reproductive material moving in HSC (1988). Control of substances hazardous international trade. OECD Directorate for to health in fumigation operations: COSHH Agriculture and Food, Paris. regulations, 1988. Approved code of prac­ PEACE, T.R. (1962). Populus. In Pathology of tice. COP 30, Health & Safety Commission. trees and shrubs. Oxford University Press, HMSO, London. Oxford. HSC (1991a). The safe use of pesticides for PHILLIPS, D.H. and BURDEKIN, D.A. non-agricultural purposes: Approved code of (1992). Diseases of forest and ornamental practice. Health & Safety Commission. trees, 2nd edtn. Macmillan Press, London. HMSO, London. POTTER, C.J., NIXON, C.J. and GIBBS, J.N. HSC (1991b). First aid at work. Health and (1990). The introduction of improved poplar Safety (First-aid) Regulations, 1981, and clones from Belgium. Forestry Commission

245 Research Information Note 181. Forestry 19, 1991. Plant Varieties Protection Gazette Commission, Edinburgh. and Newsletter 63, 9-28. UPOV 438 (E). SCOPES, N. and STAPLES, L. (1989). Pest Geneva. and disease control handbook, 3rd edtn. WILLIAMSON, D.R., MASON, W.L., British Crop Protection Council, Bracknell. MORGAN, J.L. and CLAY, D.V. (1993) UPOV (1991). International convention for the Forest nursery herbicides. Forestry Com protection of new varieties of plants of mission Technical Paper 3. Forestry Com December 2, 1961 as revised .... on March mission, Edinburgh.

246 Appendix I

(a) The Forestry Authority - list of addresses

England Kent and East Sussex Conservancy National office Furnace Lane The Forestry Authority Lamberhurst Great Eastern House Tunbridge Wells Tenison Road Kent Cambridge TN3 8LE CB12DU Northumberland and Durham Conservancy Redford Conservancy offices Hamsterley Cumbria and Lancashire Conservancy Bishop Auckland Peil Wyke Co Durham Bassenthwaite Lake DL13 3NL Cockermouth Cumbria Thames and Chiltems Conservancy CA13 9YG The Old Bam Upper Wingbury Farm East Anglia Conservancy Wingrave Santon Downham Aylesbury Brandon Buckinghamshire Suffolk HP224RF IP27 OTJ West Country Conservancy East Midlands Conservancy The Castle Willingham Road Mamhead Market Rasen Exeter Lincolnshire Devon LN83RQ EX6 8HD

Greater Yorkshire Conservancy West Midlands Conservancy Wheldrake Lane Rydal House Crockey Hill Colton Road York Rugeley Y O l4SG Staffordshire WS15 3HF Hampshire and West Downs Conservancy Alice Holt Wye and Avon Conservancy Wrecclesham Bank House Famham Bank Street Surrey Coleford GU10 4LF Gloucestershire GL16 8BA

247 Scotland Wales National office National office The Forestry Authority The Forestry Authority Portcullis House North Road 21 India Street Aberystwyth Glasgow Dyfed G2 4PL SY23 2EF

Conservancy offices Conservancy offices Dumfries and Galloway Conservancy Mid Wales Conservancy 134 High Street The Gwalia Lockerbie Llandrindod Wells Dumfriesshire Powys DG11 2BX LD16AA

Grampian Conservancy North Wales Conservancy Ordiquhill Clawdd Newydd Portsoy Road Ruthin Huntly Clwyd AB54 4SJ LL15 2NL

Highland Conservancy South Wales Conservancy Hill Street Cantref Court Dingwall Brecon Road Ross-shire Abergavenny IV15 9JP Gwent NP7 7AX Lothian and Borders Conservancy North Wheatlands Mill Forest Research Stations Wheatlands Road The Forestry Authority Galashiels Research Division TD12HQ Alice Holt Lodge Wrecclesham Perth Conservancy Famham 10 York Place Surrey Perth GU10 4LH PH2 8EP The Forestry Authority Strathclyde Conservancy Research Division 21 India Street Northern Research Station Glasgow Roslin G2 4PL Midlothian EH25 9SY

248 (b) Laboratories undertaking soil analysis

England & Wales ADAS Laboratories Woodthome Wergs Road Tettenhall W olverhampton Staffs WV6 8TQ (Tel: 01902 754190)

Scotland Macaulay Land Use Research Institute Craigiebuckler A berdeen AB9 2QJ i.Tel: 01224 318611)

249 Appendix II

Glossary

Acid equivalent The amount of active ingredient parts of plants), or stock so pro (a.e.) of a pesticide in a product, duced. expressed in terms of parent Clonal orchard See ‘Seed orchard,' acid. Contact Of pesticide, having effect by Active ingredient That part of a pesticide formu­ coming into direct contact with (a.i.) lation from which its toxicity to pest or target species. pests is obtained. Controlled The artificial or permitted nat­ Approved product A pesticide which has been pollination ural transfer of pollen from a approved for use under the known source to a receptive Control of Pesticides Regu­ flower, all other pollen being lations, 1986. excluded. Additive Of a pesticide, a non-toxic mate­ Cultivar Plant variety, resulting from rial added to a formulation to breeding, and/or selection and/ improve its performance in any or cultivation; conventionally way. denoted by species name, fol­ Adjuvant Of a pesticide, a non-toxic mate­ lowed by ‘cv’ and cultivar name. rial added to a formulation to Dominant The tallest, largest-crowned enhance its toxicity towards (trees) trees in closed canopy wood pests. land. Basic material In relation to forest reproduc­ Family For vegetatively propagated tive material (under Forest stock, the progeny of a single (a) produced by sexual means, Reproductive open-pollinated (f) parent or of stands of trees and seed Material a single cross between two indi­ orchards; Regulations) viduals. (b) produced by vegetative means, clones and mixtures Flushing The commencement of growth of clones. of a plant above ground in the spring; characterised by Bulked family Of vegetatively propagated swelling and bursting of buds. mixtures stock, seed or plants of families mixed in specific proportions. Formulation (of The process of preparing a pes­ pesticide) ticide for commercial sale and Certificate of Certificate issued by the use either neat or after dilution. provenance authority appointed by national The material resulting from the governments, describing the above process. provenance of seed or plants. Types of formulation include: Chlorosis, Loss of green colour in plant Emulsifiable concentrate. A chlorotic foliage. concentrated solution of pesti­ Clone A population of genetically cide and an emulsifier in an identical plants produced vege­ organic solvent, forming an tatively from one original emulsion when mixed with seedling, (and may include water.

250 Granules. A free-flowing dry swathes overlap to obtain an preparation of pesticide, ready even spray distribution. for use. The diameter size range Even fan. Spray droplets are of the granules is often speci­ emitted so that the whole width fied. of the spray swathe is treated at Liquid. A concentrated solution the same rate. of pesticide which mixes readily Hollow cone. Spray droplets with water. from a stationary nozzle form a Suspension concentrate. A ring pattern. From a moving stable suspension of a solid pes­ nozzle, the edges of the treated ticide in a fluid, intended for swathe receive a higher dose dilution before use. than the centre. Wettable powder. Pesticide in a Solid cone. Spray droplets are powder so formulated that it distributed over the whole of will form a suspension when the sprayed area, the centre of a mixed with water. treated swathe usually receiving more than the edges. Forest Seed, cones and parts of plants reproductive intended for the production of Anvil flood. Spray droplets are emitted in a wide fan formed by material plants; young plants raised from seed or from parts of a stream of pesticide striking a plants. smooth surface (the anvil). Variable. A nozzle in which the Frit Of trace elements (required in distribution of spray can be very small amounts for healthy adjusted from a narrow jet to a plant growth), a very finely wide cone pattern. ground glassy material con­ taining specified proportions of Open Pollination by natural agencies, the named elements. pollination e.g. wind, insects, and without man’s intervention. Genetic qualities Qualities derived from the inherited characteristics of an Origin Place in which an indigenous individual tree. Cf. ‘Phenotypic stand of trees is growing, or the qualities’. place from which a non-indige­ nous stand was originally intro­ Genetically Possessing qualities derived duced. improved from inherited characteristics, which qualities are superior to Ortet The original plant from which the average for a population as all members of a clone derive. a whole. Persistence The length of time a pesticide Indigenous Of a stand of trees, native to the remains active where applied or locality. where it moves to (e.g. into soil or into plant tissues). Native Not known to have been intro­ duced by human agency. Pest Any unwanted organism. In the context of pesticide usage, Nozzle types Nozzles for liquid pesticide includes species which may have application are described by the deliberately been cultivated but spray patterns produced: subsequently Eire to be killed (e.g. Fan. Spray droplets are emitted greencrop before ploughing in). in a fan shape. Except for ‘Even fan’ jets (see below), the quan­ Pesticide A generic term covering herbi­ tity of spray from a fan jet is cides, insecticides, fungicides, greatest in the centre of the etc. The use of ‘pesticide’ in the sprayed swathe; such jets restricted sense of ‘insecticide’ is should be spaced so that not recommended.

251 Phenotypic Qualities resulting from the Resistant In respect of pesticide use, plan I qualities response of trees to the local site or pest unaffected or undam­ and environment. aged by exposure to a pesticide applied at the prescribed rate. Polycross Seed from flowers subject to either supplemental or con­ Root pruning The cutting of roots of plant trolled pollination with a pollen which have been lifted from the mixture of known composition. ground. See ‘Undercutting’. Prill Of fertiliser, granules formed by Seed orchards A plantation of selected clone cooling in a current of air, such or progenies which is isolated, or that the granules are more or laid out to avoid or reduce polli less spherical in shape and of a nation from outside sources, an" relatively small range of diam­ managed so as to produce fro eters. quent, abundant and easily har vested seed crops. Product Of a pesticide, a commercially available formulation of a pesti­ Selected Forest reproductive material cide. The specific uses of the (reproductive (FRM) derived from basic mate product set out on the product material) rial approved for registration label have to be approved under under the FRM Regulations. Control of Pesticides Regulations. Selective Of pesticides, killing or dam­ Provenance The place in which any stand of aging pests, leaving the crop trees, whether indigenous or plant undamaged, or killing cer­ non-indigenous, is growing. tain groups of pests but nor Seed collected from such stands. others. Ramet An individual member of a clone Self Of plant propagation, a plant or derived through one or more family resulting from the polli­ cycles of vegetative propagation nation of the female flowers from the original ortet. with pollen from male flowers on the same parent. Selfed fam­ Region of For a species, sub-species or ilies usually have poor growth provenance variety, the area or group of compared with families derived areas subject to similar ecolog­ from crosses between different ical conditions, in which are parents. found stands showing similar phenotypic or genetic character­ Shatter Of plants showing deficiency istics; for a seed orchard, the symptoms, formation of a green region of provenance of the tuft of foliage at the end of material used for the establish­ shoots, with an area of bare ment of that seed orchard. branches below due to loss of older foliage. Registered Seed, or plants raised from seed, from stands or seed Sheughing A synonym for heeling in. orchards registered under the Sibs Offspring of the same parents, Forest Reproductive Material but from separate fertilisations. Regulations. Full sibs have both parents in Reproductive See ‘Forest reproductive mate­ common; half-sibs have one material rial’, ‘Selected reproductive parent in common. (Abbrevi­ material’ and ‘Tested reproduc­ ation for sibling, the unabbrevi­ tive material’. ated word virtually never being used in this context.) Residual pesticide One which remains active in the soil for a period after it has been Side-cutting The severance of roots of plants applied. growing in beds or lines by

252 passing a vertical blade or disc plants which were lined out between rows of plants. See also after 1 year and were undercut 'Undercutting’. in the second year in the tans- plant lines. Supplemental The artificial transfer of pollen from a known source to recep­ Undercutting The severance of tap-roots and tive flowers of a known seed other roots of plants in seedbeds parent, without the complete or lines, by passing a horizontal exclusion of all other pollen. sharp blade through the soil at a pre-determined depth. See also Systemic Of pesticides, entering the plant ‘Root pruning’ and ‘Wrenching’. and persisting there. While so remaining, may be taken up by Vegetative Increase in number of plants by pests feeding on or invading the propagation rooting cuttings, grafting, bud plant. ding, micropropagation from tissue culture, etc. Undercut plants Plants which have been subject to undercutting. Where plants Wrenching The disturbance of plants in have been undercut as a delib­ seedbeds or lines, by raising erate cultural operation, ‘u’ may them a few centimetres and be incorporated in the abbrevi­ allowing them to drop back. ated description of the age, e.g. Wrenching may be carried out lu l for 2-year-old plants which by horizontal blade drawn by a have been undercut in the tractor, or by hand tools, e.g. seedbed; 1+ lu l for 3-year-old garden fork.

253 Appendix III

Common and botanical names of forest trees

Common name Botanical name Synonym

Silver fir Abies alba Mill. Abies pectinata D.C. Grecian fir Abies cephalonica Loud. Colorado white fir Abies concolor ( Gord.) Hildebrand Grand fir Abies grandis Lind. Californian red fir Abies magnifica A. Murray Caucasian fir Abies nordmanniana (Steven) Spach. Noble fir Abies procera Rehder Abies nobilis Lind.

Sycamore Acer pseudoplatanus L. Norway maple Acer platanoides L.

Horse chestnut Aesculus hippocastanum L.

Italian alder Alnus cordifolia Ten Alnus cordata Desf. Common alder Alnus glutinosa Gaertn. Grey alder Alnus incana Moench Red alder Alnus rubra Bong. Alnus oregona Nuttall

Silver birch Betula pendula Roth. Betula verrucosa Ehrh. White birch Betula pubescens Ehrh.

Sweet chestnut Castanea sativa Mill. Lawson cypress Chamaecyparis lawsoniana (A. Murr.) Parlatore. Leyland cypress x Cupressocyparis leylandii Dallim. Monterey cypress Cupressus macrocarpa Hartw. Mediterranean cypress Cupressus sempervirens L.

Gums Eucalyptus spp.

Beech Fagus sylvatica L. Ash Fraxinus excelsior L.

European larch Larix decidua Mill. Larix europaea D.C. Japanese larch Larix leptolepis (Sieb. & Zucc.) Gord. Larix kaem pferi Carr.

Hybrid larch Larix x eurolepis A. Henry

Southern beech Rauli Nothofagus obliqua Bl. Roble Nothofagus procera Oerst. Nothofagus nervosa (Phil.) Dim. & Mil.

Norway spruce Picea abies Karst. Picea excelsa Link. Serbian spruce Picea omorica Purkyne Oriental spruce Picea orientalis Link. Sitka spruce Picea sitchensis (Bong.) Carr. Picea menziesii Carr.

Arrola pine Pinus cembra L.

254 Common name Botanical name Synonym

Lodgepole pine Pinus contorta Dougl. Aleppo pine Pinus halepensis Mill. Bosnian pine Pinus leucodermis Ant. Pinus heldreichei v. leucodermis Ant. Mountain pine Pinus mugo v. uncinata Ramond Austrian and Corsican pine Pinus nigra Arn. Pinus laricio Poir. Monterey pine Pinus radiata D. Don Pinus insignis Dougl. Maritime pine Pinus pinaster Aiton Pinus maritima Poiret Stone or umbrella pine Pinus pinea L. Weymouth pine Pinus strobus L. Scots pine Pinus sylvestris L.

Poplar varieties Populus cvs (See Table 15.1).

Wild cherry, gean Prunus avium L. Bird cherry Prunus padus L.

Douglas fir Pseudotsuga taxifolia (Lamb.) Britt. Pseudotsuga douglasii Carr. Pseudotsuga menziesii (Mirb.) Franco.

Red oak Quercus borealis Michx. Quercus rubra Du Roi Turkey oak Quercus cerris L. Pedunculate oak Quercus pedunculata Ehrh. Quercus robur L. Sessile oak Quercus sessiliflora Sal. Quercus petraea Liebl.

Western red cedar Thuja plicata D. Don

Small-leaved lime Tilia cordata Mill. Tilia parvifolia Ehrh. Common lime Tilia x europea L. Tilia vulgaris Hayne Broad-leaved lime Tilia platyphyllos Scop. Tilia grandifolia Ehrh.

Western hemlock Tsuga heterophylla (Raf.) Sargent

Wych elm Ulmus glabra Huds.

Species shown in bold italic are included in the Forest Reproductive Material Regulations.

255 Appendix IV

EEC Standards for nursery stock

Standards are set for stock to be described as of 4. Forest species other than Populus: ‘EEC Standard’, both in respect of ‘parts of plants’ General characteristics and health i.e. setts and cuttings, and rooted plants. Part of plants shall not be considered to be of These standards are reproduced in schedules 5 fair marketable quality if: and 6 of the Forest Reproductive Material (Amendment) Regulations, 1977 (SI 1977/1264). (a) they have abnormalities of form or insuffi cient vigour; Conditions which parts of plants must (b) they have not been severed by a clean cut; satisfy (c) their age or size makes them unsuitable for 1. Lots shall include at least 95% of parts of plants propagation purposes; of fair marketable quality. id) they are partially or totally dried out or show 2. Fair marketable quality shall be determined by injury other than wounds incurred in the taking reference to the criteria relating to general char­ of cuttings; acteristics, health and, where appropriate, size, (e) they are affected by necroses or are damaged set out in the two following paragraphs. by harmful organisms; 3. Populus species: (/) they have any other defects which reduce (1) General characteristics and health their value for reproductive purposes. Parts of plants shall not be considered to be of fair marketable quality if: NOTE: All these criteria shall be considered in (a) the wood is unripe; relation to the species or clones in question. (b) the wood is more than two seasons old; (c) they have abnormalities of form, such as forking, branching or excessive bending; Conditions which young plants must id.) they have less than two well-formed buds; satisfy (e) they have not been severed with a clean cut; if) they are partly or totally dried out, injured or 1. Lots shall include at least 95% of young plants of have the bark detached from the wood; fair marketable quality. (g) they are affected by necroses or damage caused by harmful organisms; 2. Fair marketable quality shall be determined by (h) they have any other defects which reduce reference to the criteria relating to general char­ their value for reproductive purposes; acteristics, health, age and size, set out in para­ graphs 3 and 4 below. except that paragraphs (a), (b), (c) and (d) shall not apply to root cuttings and soft wood 3. General characteristics and health. cuttings. (2) Minimum dimensions of parts of the plants An asterisk in the following table shows for each of the Aigeiros section, other than root cut­ genus and species in question the defects which tings and soft wood cuttings: prevent young plants from being classified as of (а) - minimum length: 20 cm; fair marketable quality. All these criteria shall (б) - minimum top diameter: be considered in relation to the species or clone 8 mm for those described as Class 1/EEC in question and to the suitability of the repro­ 10 mm for those described as Class 2/EEC. ductive material for forestry purposes.

256 tn Defects which prevent young plants from §* ;Q 42 being classed as of fair marketable quality nj ft § 5 to o cp 03 tfl CD Q) I s -5 £ .c Q) ^ oi § ^ CL c 0. 43 iS o £

(a) young plants with unhealed wounds - except cutting wounds where excess leaders * have been removed * * * * - except other such wounds incurred in the taking of cuttings ** * * - except branch wounds ... * * * * * * * lb) young plants partially or totally dried out * * * * (c) stem showing considerable bending **** id) multiple stem ... * * ie) stem with several leaders * (f) stem and branches incompletely ripened *(1) *

(1) Except where the young plants were taken from the nursery during the first growing season. (2) Not applicable to clones of Populus deltoides angulata. (3) Not applicable to Populus plants butt trimmed in the nursery. (4) Not applicable to sets. (5) Not applicable to Quercus borealis.

4. Age and size A. Species other than Populus (a) Criteria of age and size of young plants shall not apply to young plants which have not been trans­ planted. (b) Minimum standards for age and size are listed in the table below:

Normal young plants Stocky young plants Minimum Minimum Maximum diameter of Maximum diameter of age 1 Height2 root collar age 1 Height2 root collar (years) (cm) (mm) (years) (cm) (mm)

Abies alba 4 10-15 4 4 10-15 4 5 15-25 5 4 15-20 5 5 25-35 5 5 20-25 6 5 35-45 6 5 25-35 7 5 45-60 8 5 35—40 8 - 60 and over 10 - 40 and over 10

Larix 2 20-35 4 3 35-50 5 4 50-65 6

257 Normal young plants Stocky young plants Minimum Minimum Maximum diameter of Maximum diameter of age 1 Height2 root collar age 1 Height2 root collar (years) (cm) (mm) (years) (cm) (mm)

65-80 7 80-90 8 90 and over 10

Picea abies 15-25 4 15-20 4 25-40 5 20-30 5 40-55 6 30-40 6 55-65 7 40-50 6 65-80 9 50-60 9 80 and over 10 60 and over 10

Picea sitchensis 20-30 4 30-50 5 50-65 6 65-75 8 75-85 9 85 and over 10

Pinus sylvestris 6-15 6-10 15-25 10-20 25-35 20-30 35-45 30-40 45-55 40-50 50 and over

Pinus nigra 6-15 6-10 (forma austriaca) 15-25 10-20 25-35 20-30 35-45 30-40 45-55 40-50 50 and over

Pinus nigra 5-10 10-15 (other than forma 10-20 15-30 austriaca) 20-30 30-40 30-40 40-50 40-50 50 and over 50 and over

Pinus strobus 6-10 3 10-20 4 20-30 5 30-40 6 40-50 7 50-60 8 60 and over 10

Pseudotsuga taxifolia 20-25 20-25 25-30 25-35 30-40 35—40 40-50 40-45 50-60 45-55

258 Normal young plants Stocky young plants Minimum Minimum Maximum diameter of Maximum diameter of age 1 Height2 root collar age 1 Height2 root collar (years) (cm) (mm) (years) (cm) (mm)

4 60-70 8 4 55-65 8 4 70-80 9 4 65-70 9 4 80-100 12 - 70 and over 12 - 100 and over 14

Fagus sylvatica, 2 15-25 4 Quercus 3 25-40 5 4 40-55 6 4 55-70 7 5 70-85 9 - 85 and over 11

Notes: 1 Age: Age is expressed in complete years. Each growing season or part thereof shall count as a complete year. The growing season shall be considered as having begun: - in the case of plants with a terminal shoot not yet containing a dormant terminal bud, when this shoot is not less than one quarter of the length of the previous year’s shoot. - in the case of young plants with a shorter terminal shoot, when this shoot contains a dormant bud. 2 Height: Height shall be measured to within plus or minus 1 cm in the case of young plants not exceeding 30 cm in height, and to within plus or minus 2.5 cm in the case of young plants exceeding 30 cm in height.

B. Populus (a) Age of young plants. The maximum age shall be four years for the stem and, where appropriate, five years for the root. (b) Size standards shall apply only to Populus plants of the Aigeiros section, and shall be as set out in the following table:

Point of EEC Height (m) Age diameter Classification Diameter measurement Number (mm) minimum maximum

0 + 1 0.50 m N1a 6 to 8 1.00 1.50 N1b more than 8 but not more than 10 1.00 1.75 N1c more than 10 but not more than 12 1.00 2.00 N1d more than 12 but not more than 15 1.00 2.25 N1e more than 15 but not more than 20 1.00 2.50 N1f 20 1.00 - more than 1 year 1 m N2 more than 8 but not more than 10 1.75 2.50 N3 more than 10 but not more than 15 1.75 3.00 N4 more than 15 but not more than 20 1.75 3.50 N5 more than 20 but not more than 25 2.25 4.00 N6 more than 25 but not more than 30 2.25 4.75 N7 more than 30 but not more than 40 2.75 5.75 N8 more than 40 but not more than 50 2.75 6.75 N9 50 4.00 -

259 Appendix V

Conversion factors

Length 1 centimetre = 0.3937 inches 1 foot = 0.3048 metres 1 inch = 2.540 centimetres 1 metre = 3.281 feet = 1.094 yards 1 yard = 0.9144 metres

Area 1 acre = 0.4047 hectares (4840 sq. yards) 1 hectare = 2.471 acres 1 square foot = 0.0929 sq. metres 1 square metre = 10.76 sq. feet = 1.196 sq. yards 1 square yard = 0.8361 sq. metres

Weight 1 gram = 0.03527 ounces 1 hundredweight (cwt) = 50.80 kilograms 1 kilogram = 2.205 lb 1 ounce = 28.35 grams 1 pound (lb) = 0.4536 kg 1 ton (long) (2240 lbs) = 1.016 metric tonnes 1 metric tonne = 0.9842 (long) tons

Volume 1 gallon (Imperial) = 4.546 litres 1 litre = 0.2200 gallons

Weight per unit area 1 cwt per acre = 125.5 kg per hectare 1 kg per hectare = 0.8922 lb per acre 1 pound (lb) per acre = 1.121 kg per hectare 1 metric tonne per hectare = 0.3983 tons per acre = 7.966 cwt per acre 1 ton (long) per acre = 2.511 metric tonnes per hectare

Volume per unit area 1 gallon per acre = 11.23 litres per hectare 1 litre per hectare = 0.08902 gallons per acre

260 Index

Abies spp., fertiliser damage 97 Benomyl, Botrytis 185 winter cold injury 182 Lophodermium 186 Abstraction of water 158 oak mildew 187 Access 16, 216 Keithia 188 Acidification of soil 31 Birds 87, 195 Acidity, see pH netting 130 Acoms, storage 71 seedbed protection 93, 130 ADAS Regional Soil Laboratories 32 Bishop weed (Equisetum) 177 Agrotis (cutworm) 189, 190 Bone meal 42 Age of plants 10 Boron 37, Table 4.7 Air pruning, container plants 125 organic matter 59 Alder, Frankia inoculation 107 Botrytis 99, 185 N-fixation 107 frost damaged plants 183, 185 seed sowing density 90 polythene bags 212 Alicep 172 rooting cuttings 142 Alleys between seedbeds 19, 84 Bracken-hopwaste compost 61, Table 4.10 Ammonium nitrate 31, 41, 45, Table 4.2 Breaking in a new nursery 20 Ammonium sulphate 41 Broadcast sowing 91 fertiliser Table 4.2 Broiler house litter 62 soil acidification 31 Bud hardening 203 Analysis, foliage 56 Buffer capacity 29 soil 10, 32, 40 Buildings chemical/pesticides store 18 tissue 56 cold store 214 Animal damage 196 office/staff rooms 18 Annual meadow grass Table 12.1 Bulky organic manures 61,97 Aphids 20, 189, Table 13.1 incorporation in seedbeds 84 ‘Approved’ effect on seedling yield 59 pesticide products 156 weeds 62, 167 seed 66, 225 Butisan 174 seed orchards 66, 225 Ash (Fraxinus spp.), soil pH 29 Calcium, nutrient deficiency 37 Aspect 16 Calibration of sprayers for pesticide application 179 Aspen 139 Captan, Botrytis 185 Assessment under COSHH 237 Cation exchange capacity 39, 59 Atlacide 177 organic matter 58 Atrazine 172, 175 Cell-grown plants 122 Autumn lining out and frost lift 183 Certificates Autumn sowing and frost risk 182 competence (pesticides) 237 Available water capacity 27, 151, 158 provenance, certificate/master certificate of 229 seed, test/interim test certificate 229 Balance of nutrients 37, 56 supplier’s certificate 228 Balsam poplar, see Poplar Challenge 171 Bark chips 61 Chalk 30 Bark, for container media 127 Chlorbufam 172 for rooting media 141 Chloridazon 172 Base saturation 39 Chlorthal dimethyl 173 Basic slag 30 Cloches 94, 183 Beech, aphis and hedges 20, 189 bird damage 94 mice 93 Clopyralid 176 seed storage, long-term 71 C/N ratios, organic matter supplements 59 short-term 72 Codes of practice sowing 92, 95 first aid at work 242 Benching, container plants 125 safe use of pesticides, non-agricultural 236

261 safe use of pesticides on farms and holdings 236, 239 Damping off 184 storage of approved pesticides 236, 239 Date of sowing 88 waste management 239 Day length 132, 203 Co-extruded polythene bags 211 Dazomet 85, 171 Cold storage 18, 214 Deficiency symptoms, see Nutrient deficiencies plants in 214 Density of sowing Tables 6.1, 6.2 Compaction, seedbed for sowing 86 Derogation 226 soil and impeded drainage 13, 27, 209 Desiccation 200, 215 Composts, application to beds or lines 60, 84 Despatch of plants 218 bracken/hopwaste Table 4.10 Diammonium phosphate 42 effect on seedling yield 59 Didymascella thujina 188 nutrient content Table 4.10 Dinocap, oak mildew 187 Compound fertilisers 42, Table 4.3 Diphenamid 173 rates Table 4.4 Dipping of plants 217 timing of application 47 Directed pesticide application 176 Conditioning of plants, see Hardening off Disposal of pesticide waste 239 Consolidation of seedbeds 86 Dolomite (dolomitic limestone) 30, 42, 127, test for 86 Tables 3.1, 4.2 Contact herbicides 169 Dormancy, bare-root nursery stock 99, 181, 200, Container production 76, 122 202, 214 sites for 23 container plants 132 size/spacing of containers 123 herbicide use and plants 169 systems 122 weeds 171 Dormancy of seeds 74, 79 Contracts of employment 243 breaking dormancy 79 Control of Pesticides Regulations, 1986 tests for 75 (COPR Regs.) 167, 189, 236 Douglas fir, Certificates of competence 180, 237 dormancy 203 Control of Substances Hazardous to Health ffost susceptibility 182, 203 Regulations, 1988 (COSHH Regs.) 236 mycorrhizal fungi 106 assessments 237 Potebnyamyces (Phomopsis) damage 183 Controlled-release fertilisers, see Slow release response to undercutting Table 8.3 fertilisers sowing density for undercutting Table 8.1 Copper, deficiency 127 Drainage 13 sewage sludge 62 containers 125 soil organic matter 59 irrigation 159 Costs of formation of nursery 23 Drought damage to plants 183 Couch grass control 177 Droughtiness 152 Counting plants for despatch 199, 209 Drying out of plants 200, 204 Crates for moving plants 192, Table 14.5 Crop % ground cover and irrigation 149, Table 11.3 Ecopots 122 Crop water requirements 155, Table 11.3 Ectomycorrhizas 104 Cuffing boards 92 EEC directives, reproductive materials 7, 136, 223 Culling 209 plant health 233, 235 Cultivation, compaction/pan 87, 153, 178 EEC standards, nursery stock 227, 256 depth, fallow land 178 seed 227 seedbeds 86 Electricity supply 16 seedbed area 84, 86 Electrolyte leakage 10, 207 transplant area 97 Electrodyn treatment 217 Cut test 75 Elevation, nursery site 13 Cuttings, poplar 137 Endomycorrhizas 106 preparation 137 Enide 50 W 173 type and time of collection (conifer) 140 Epsom salts 42, Table 4.2 willow 139 Equisetum 177 Cutworm 189 Essential nutrients 37 Cyanazine 176 Evaporative cooling container plants 124, 130 Dacthal 173 irrigation 124, 155, 157 Damage to plants, lifting 199 Evapotranspiration 148 possible causes 9, 20 Exposure 16

262 Fagus, see Beech Grey mould, see Botrytis Fallow area, nursery planning 3 Grey poplar, propagation 138 Farmyard manure 62, Table 4.10 Grit cover, particle size 92, 130 Fencing 23, 168 pH and fizz test 92 FEPA (Food and Environment Protection Act) 236 seedbed cover 93 Fertiliser scorch 38, 45, 86, 97 seedbed temperature 93 Fertilisers 38, 41, 95 Ground cover % and irrigation 149 hardening off/preconditioning 203, 205 Ground mineral phosphate 41, 46, Table 4.2 incorporation in new site 22 Groundsel, resistance to herbicides 170 irrigation to wash in 156 Growing medium, container plants 125 materials available Tables 4.2, 4.3 nutrient status 132 newly rooted cuttings 138 placement 86 Hand work, seedbed preparation 85 rates of application 45, Table 4.3 lifting 207 undercut stock Table 8.5 transplanting 101 top dressings 47, Table 4.5 weed control 178 timing of applications 47, 86, 97 Handling of plants 99, 198 Field capacity 151 Hard yellows, Mg deficiency 53 Field survival factors 78, 88 see also, K deficiency 52 First aid 19, 242 Hardening off, bare-rooted stock 9, 182, 203 First crops in new nurseries 23 container plants 124, 132 Flat fan nozzles, weed control 179 irrigation 157 Floating mulches 94 Hardwood (winter) cuttings, bird damage 94 poplar 136 undercut 1st year stock 120 conifer 140 Flood jet nozzles (herbicides) 179 HASAWA, Health and Safety at Flowering and seed development 66 Work Act, 1974, 236, 241 Fogging for vegetative propagation 140 Control of Substances Hazardous to Foliage analysis 56 Health 236,241 Food and Environment Protection Act, 1985 189 first aid 242 Forest Reproductive Material Regulations 223 Reporting of Injuries, Diseases & Dangerous seed tests 72 Occurrences 242 species Table 15.1 Heat damage 124, 130, 183, 202 tested poplar clones Table 10.2 seedbed grit 93, Table 6.4 Frankia and N-fixation 107 see also Evaporative cooling Freedom from weeds 15 Heathland nurseries 13 Frit of micronutrients 127, Glossary Frost 96, 181, 201, 203 Hedges 19 container plants 132, 133, 201 Heeling in 210 irrigation to avoid 158 Herbicide-resistant weeds 170 potassium nutrition 49, 205 Herbicides 168 Frost hardiness 181, 202, 203 Hoeing 178 Frost hollows 16, 181 Holding areas for container plants 125 Frost lift 98, 183 Hop-waste 61, 84 Fumigation, see Partial soil sterilisation effect on seedling yield 59 Fusarium 184 effect on soil structure 58 nutrient content Table 4.10 Galvanised netting Table 4.7 Horticultural Trades’ Association (HTA) 6 Germination, survival factor 88 Humidified plant stores 215 tests 72, 74 Humus 26 Gesaprim 175 organic matter decomposition 58 Gesatop 173, 176 Hybrid larch, vegetative propagation 69, 139 Glufosinate ammonium 171, 177 Hygiene, adjoining plantations 185 Glyphosate 171, 177 container houses 124 GMP 42, 46 cuttings 142 Grading 9, 97, 99, 209, 216 hedges 19 Gramoxone 171, 177 pesticide-resistant weeds 15, 170 Greencrops 60, 97 weed seed 167 breakdown in soil 60 Hylastes spp. 190, 216 effect on soil aggregates Table 4.9 Hylobius abietis 189, 216

263 IBDU 44 reporting of injuries, disease & dangerous Import of plants and seed 229 occurrences 242 ‘Improved’ seed 7, 66, 69 seed regulations 70, 239 Infiltration capacity 159 trades descriptions 242 Inoculation of seedbeds with mycorrhizal fungi 106 Legumes and N-fixation 109 of alder with Frankia 108 Levelling ground 22 Inorganic fertilisers 41 Licences, irrigation 158 application before sowing 86 Lifting 98, 198, 200, 207 before transplanting 97 Lime (mineral) and limestone 22, 127 conditioning for lifting 205 liming rates 30, Table 3.1 hardening off 204 soil analysis 34, Table 3.1 Insect pests 188, Table 13.1 seedbed grit 30, 93 Insecticides 189 soil pH 29 against Hylastes and Hylobius 189, 216 Lining out 97 Insurance, employers’ liability 231 ground preparation 97, Tables 4.4, 4.5 Integrated procedures for plant handling 198 fertilisers 97 Interim seed test report 75 herbicide application 174 Inter-row herbicide application 176 summer 100 Investment appraisal 2, 155, 159 Liquid fertilisers 41, 45, 47, 124, 128, 131, 148 Iron, lime-induced chlorosis 127, Table 4.7 Long-term storage of seedlings 213, Table 14.4 Iron-pan 15 Lophodermium 185 Irrigation 96, 148, 183 Low temperature damage 181, 201 balance sheets 162, Table 11.4 see also Frost cloches and floating mulches 95 Lupins, greencrop 61 commercial prescription services 163 Luxury uptake of nutrients 38 container production 124 Lysimeters 153 control by weight change 131 empirical control 124 Macaulay Land Use Research Institute 32 risk of contaminated water 184 Magnesian limestone 30, 42, 46, Table 3.1 undercut seedbeds 114, 117 Magnesium 42 vegetative propagation 140 ammonium phosphate 101 Irriguide 164 container production 128 Irriplan 164 deficiency symptoms 53 Isoxaben 175 Epsom salts Table 4.2 fertiliser 42, Table 4.2 Jacketed plant stores 215 soil analysis 32, Table 3.4 Japanese paper pots (JPPs) 122 Maneb 186 Manganese 37, Table 4.3 K, see Potassium and Inorganic fertilisers Marginal nutrient concentration Table 4.8 Keithia disease 188 Markets 2, 17 Kerb 174 Matric potential 150, 153 Kieserite 42, 46, Table 4.2 Mechanical control of weeds 177 Meria needle cast of larch 186 Labelling 5 Mess room for staff 19 Labour force 7 Metamitron 175, 177 Larch, Meria needle cast disease 186 Metazachlor 175, 177 response to undercutting 116 Mg, see Magnesium vegetative propagation 139 Mice 87, 93, 130, 196 Lawson cypress, winter injury 182 Micronutrients 37, 44, 56, Tables 4.7, 4.8 Layout of nursery 17 Micropropagation 146 Leaf water potential 155 Mist propagation, conifer cuttings 140 Legislation, abstraction of water 158 poplar root cuttings 138 consumer protection 242 softwood cuttings 137 employment protection 243 Moisture content of seed 71, 78 forest reproductive material 223 Moisture stress (plant) 183 health and safety at work 167 desiccation and dormancy 200, 202 pesticides 236 Moles 196 plant breeders’ rights 240 Molybdenum 37, Table 4.3 plant health 235 Monammonium phosphate 42, Table 4.2

264 MORECS (Meteorological Office Rainfall and avoidance of weeds 61, 62 Evaporation Calculation system) 157 optimum levels 60 Multicut production 112, 120, 205 stages of decomposition 58 Multispan polythene tunnel houses 123 Orthodox seed 71 Muriate of potash 42, Table 4.2 Oscillating sprayline irrigation 161 Mushroom compost 62 Osmocote 128, Table 4.3 Mustard, greencrop 60 Overall pesticide sprays 169 Mycorrhizas 104 Overheating 202 Overwatering 164 National Proficiency Test Council (NPTC) 237 Oxadiazon 175 National Rivers Authority 158 Nematode control 85, 171, 184 P, see Phosphorus Netting against birds 88 Packing and despatch 218 Neutron probe 196 Pallets 219 Nickel, in sewage sludge 62 Pans, see Iron pan and Compaction Nitrogen 41, 51, Table 4.2 Paraquat 171, 177 container plants 127 Partial soil sterilisation 85 liquid feed 128 avoidance of root disease 184 deficiency symptoms 51 Paterson lining out board 101 fertiliser 41, 45, Table 4.2 Peat, source of soil organic matter 62 hardening off 128, 205 for production systems, conifer cuttings 141 pH 31 containers 126 rates of application 51, Table 4.4 vegetative propagation 138 top dressings 96, Tables 4.5, 8.5 Penman equation 148 undercut stock 118 Perlite, container production 126 vegetative propagation 141 vegetative propagation 141 Nitrogen fixation, legumes 109 Permanent wilting point 151, 154 non-legumes 107 Permethrin 217 NK fertiliser 42, Table 4.3 Pesticides, approved products 156, 168, 181, 236 rates 46 legislation 167,236 timing 47, 205 register 236,239 Nodules, alder inoculation 108 stores 236 N-fixation 107 waste 167,239 Nothofagus, winter cold 182 Pests 181 Nozzles, weed control sprays 179 pH 29 Nursery plans and records 3 changing soil pH 29 shape and size 2, 17 container media 127 site requirements 2, 17 water supply 140, 158 Nutrient, availability 37, 40 Phosphate, see Phosphorus balance 37, 56 Phosphorus 41 container plants 127, 129 container plants 127 undercut stock 117 liquid feed 128 concentration, container plants 128 deficiency symptoms 52 deficiencies 50 fertilisers Table 4.2 marginal concentrations Table 4.8 rates Tables 4.4, 8.5 removal 39, Table 4.1 fixation 39,42 status and hardening off 49 organic matter 59 targets 37 soil analysis 33, Table 3.2 Photoperiod control, container plants 132 Oak, mice 94 Physiology and plant handling 9, 203, 206 mildew 187 Phytophthora 184 seed storage 72 Phytosanitary certificates, export of plants 229 sowing 92, 95 imported plants, Forest Reproductive Oats, greencrop 61 Material 229, Table 15.4 OECD scheme for reproductive material 232 plant health requirements 233 Off-label and on-label pesticides 168, 236 Pine weevil 189, 216 weedkillers 168 Pinus radiata 100 fungicides and insecticides 186, 189, 217 Placed fertiliser 86 Organic matter in soil 14, 26, 39, 58 Planning nursery production 3, 198

265 Plant breeders’ rights 240 Red lead 87 Plant health legislation 233 Registered seed 67,226 Plant lifting equipment 208 Registered seed stands 68,226 Plant passports 229,233 Residual herbicides 169 Plant storage 19, 198 Respiration and plant overheating 202 cold stores 214 Rhizina inflata 21 outdoor 210 Rhizobium and N-fixation 107, 109 polythene bags 211 Rhizoctonia 184 undercover 211 RIDDOR 242 Plough pans 14,28,84,87,209 Rigipots 123 Ploughs/ploughing 84,97 River Purification Board 158 weed control 178 Rock phosphate 42, Table 4.2 Poa annua 97, Table 12.1 Rolling seedbeds 92 Polyester fabric floating mulch 94 Ronstar 175 Polythene bags for plant storage 99, 211 Root collar diameter size standards 7, 123 Polythene sheet floating mulch 94 Root cuttings 136, 139 Polythene tunnel houses, container plants 124 Root growth potential 10, 107,206 vegetative propagation 140 Rootrainers 123 Poplar, certification of planting stock 232 Root response to undercutting 113 FRM requirements 136,225 Root rot 184 list of marketed clones Table 10.2 Root seasonal activity 203 soil pH 29 Rooting powder, vegetative propagation 138, 141 stoolbed registration 136,232 Rotary boom irrigators 161 vegetative propagation 136 Rough handling 201,204 Pore space 27, 126 Roundup 171 Post-emergence herbicide application 169 Rye grass, greencrop 61 Potassium 42, 44, Table 4.2 container plants 127 Safety statement 237 deficiency symptoms 52 Samples of plants 6, 198 fertiliser rates of application 53, Sampling, foliage analysis 57 Tables 3.3,4.4,4.5,8.5 soil analysis 35 time of application 47 Sawdust as a source of organic matter 59, Table 4.10 frost 49,205 Scarifiers 178 hardening off 49,205 Scots pine, native seed sources 67 liquid feeds 45, 128 Lophodermium 185 soil analysis 32, Table 3.3 Seed 66 Prechilling of seed 79 date of sowing 80 Precision sowing for undercutting 76,114 density of sowing 89 Preconditioning 205 dormancy 74,79 Pre-emergence herbicides 169 treatment for breaking 79 Pressure chamber (‘bomb’) 131, 155 tests for 75 Pre-treatment of seed 71,76,79,87, Table 5.6 preparation for sowing 87 container sowings 129 pre-treatment 76 Previous land use, new nursery site 13 sowing, conventional 91 Prilled fertiliser 41 for container plant production 129 Prochloraz 188 for undercut stock 114 Propyzamide 173, 174, 176 Seed collection 71,230 Prunus, phytosanitary certificate 235 intention to collect 230 Purity of seed 72,116 unregistered seed 226 Pythium 184 Seed dressings 87 Seed health legislation 233 Quality of plants 6,7, 10, 199,227 Seed Identity numbers 68 Quercus, see Oak Forestry Commission system 68 native Scots pine 69 Rabbits 196 Seed orchards 66 Rainfall 162 Seed origin 66 new nursery site 13 Seed provenance 68 Readily available soil water 150, 151, Tables 11.1, 11.2 Seed stands 230 Recalcitrant seed 71 registration 67,230

266 Seed storage 18, 71, 87 measurement 153 Seed test certificate 76 tension 150 Seed testing 72 Soil workability 13, 159 advisory tests 78 Solar energy & water demand 148 quality 76, 129 Source-identified seed 233 sampling for testing 72, Table 5.2 Sowing 88 Seedbeds 84 broadcast 91 area planning 2 containers 129 cultivation 84 date 88 inoculation with mycorrhizal fungi 106 density 88, Table 6.1 sowing 91, 114 precision 118 throwing up 85 undercut stock 114 top dressing 96 Spacing, container grown plants 129 width 84 cuttings 137, 138 Selected forest reproductive material 224 transplants 98 registered seed stands 68, 226 Spray equipment, cleaning 180 Semi-hardwood cuttings 140 container houses 124 Sets, poplar 136 weed control 178 willow 139 Spray pressure, pesticide applications 179 Sewage sludge 59 Sprinklers (irrigation) 161 nutrient content Table 4.10 Standards, plants 8, 227, 256 Shading 131, 138, 140, 202 EEC, seeds 227 Sheughing 210 plants 227 Shoot:root ratio 9 Stock plants for cuttings 137, 138, 139, 141 Shoot water potential 113, Figure 8.1 Stocktaking 5 Side cutting of roots 117 Stoolbeds, establishment (poplar) 137 Simazine 173, 176 registration under FRM regs 232 Sitka spruce, frost susceptibility 205 Stomatal closure 206 response to undercutting 117, Table 8.3 Storage of plants 98, 198, 210 Slaking (loss of soil structure) 153, 159 cold stores 214 Slope of ground/drainage 16 outdoor 202,210 Slow-release fertiliser 41, 45 polythene bags 202, 211 container plants 127 Storage of pesticides 236, 239 rates 45, Table 4.4 Stratification of seed 80 timing 47 Stratified seed, sowing 91 Sodium chlorate 177 Straw as a packing material 218 Softwood (summer) cuttings, poplar 137 Stumping, poplar rooted cuttings 137 conifers 140 plant type’ 11 Soil, acidity, see Soil pH Sturdiness as measure of plant quality 8 -acting herbicides 169 Styroblocks 123 analysis 14, 32, 40 Subsoiling 22 compaction 13, 27, 86, 209 Sulphate of potash 42 density 27 Sulphur, container plants 128 depth, nursery site 13 Meria 187 fertility 38 as a nutrient 37, 54 moisture (see also Soil water) 149, 151, 153 oak mildew 187 organic matter 58 soil acidification 32 pH 29 Superphosphate 4.2, Table 4.2 sampling 35 lupins 61 saturation 153 Supervision 17 structure 25, 27 Supplier’s certificate 228 greencrops 60 Sweet chestnut 92, 94, 173 seedbed preparation 86 slaking 153 Temperature, container plant production 124, 130 surface reflectance 149 high temperature, irrigation 93, 157, 183 texture 14, 25 (overheating) plant handling 202, 203, 211 water 150 low temperature 181 availability 27 See also Frost content 151 vegetative propagation 140

267 Temperature records 149 conifers 139 Tensiometers 153 plant type 11 Tested’ forest reproductive material 224 seed source identity 69 poplar clones Table 10.2 Ventilation, polythene container houses 124 seed orchards 225 Vermiculite, container plant medium 126 Tetrazolium test 76 vegetative propagation medium 138 Texture, soil 14, 25 Viability tests 72, 75 Thelephora terrestris, mycorrhizas 105 Thiophanate methyl 144 Waste from pesticides 239 Thiram 185 Water availability 126, 154 Tile drains 15 Water infiltration capacity 159 Tilth 86 Water balance sheet 163 Timing of cultivation for weed control 178 Water ‘potentials’ 153 fertiliser application 86 leaf 154 Tin, in sewage sludge 62 matric 150 Tissue analysis 56 vapour pressure 149 Tissue culture 146 Water pressure, irrigation 158, 161 Top dressings 42 Water quality 37 rates 51, Tables 3.3, 4.5 Water requirements 50, 52 seedbeds 96 vegetative propagation 138, 140 timing 47,51 Water release curve, rooting medium 131 Toxicity, greencrops 58 Water stress, plant handling 200 heavy metals 62 irrigation 150, 154 Trace elements, see Micronutrients undercutting 113 Translocated herbicides 169 Waterlogging and seedling damage 164, 184 Transplant areas, nursery planning 3 Weaning 142 Transplanting, see Lining out Weather and herbicide application 170 Triple’ superphosphate 42, Table 4.2 Weather data, day to day 148 Types of plant 10 long-term 157 Weed control 15, 85, 102, 124, 167 Undercut stock 112, 205 Weed resistance to herbicides 15, 170 equipment 119 Western hemlock, winter cold injury 182 yiu'/z production 112, 119 Western red cedar, hedges 20 multicut production 112, 205, 208 Keithia disease 188 nutrients 117 winter cold damage 182 plant quality 113 Willows, vegetative propagation 139 root response 113, 205 Willowherb 170 timing 116 Windbreaks 19 weed control 116 Winter chilling 201 Unregistered seed/plants 226 Winter cold 182 Unrooted sets, certification 232 container protection 133 Untested seed orchards 70, 226 Woodland nurseries 13 seed from EEC species 226 Wrenching 112 OECD species 233 Urea 41, 45, Table 4.2 Zinc 37 Urea formaldehyde 44 sewage sludge 62 toxicity 196, Table 4.7 Vapour pressure deficit 149, 154 Zineb, Lophodermium 186 Vegetative propagation 23, 66 Meria 187

Printed in the United Kingdom for HMSO Dd 0294485 C28 8/94 552 12521

268

HMSO publications are available from: HMSO Publications Centre (Mail, fax and telephone orders only) PO Box 276, London, SW8 5DT Telephone orders 071-873 9090 General enquiries 071-873 0011 (queuing system in operation for both numbers) Fax orders 071-873 8200 HMSO Bookshops 49 High Holborn, London, WC1V 6HB (counter service only) 071-8730011 Fax 071-831 1326 258 Broad Street, Birmingham, B1 2HE 021-643 3740 Fax 021-643 6510 33 Wine Street, Bristol, BS1 2BQ 0272 264306 Fax 0272 294515 9-21 Princess Street, Manchester, M60 BAS 061-834 7201 Fax 061-833 0634 16 Arthur Street, Belfast, BT1 4GD 0232 238451 Fax 0232 235401 71 Lothian Road, Edinburgh, EH3 9AZ 031-228 4181 Fax 031-229 2734 9780117103238 HMSO's Accredited Agents (see Yellow Pages) and through good booksellers

£25 net