SOIL GROUPS OF NEW ZEALAND
PART 7
YELLOW-GREY EARTHS
Edited by J.G. Bruce
NEW ZEALAND SOCIETY OF SOIL SCIENCE 1984 Bibliographic reference: PREFACE Bruce, J.G. (Ed.) 1984: Soil Groups of New Zealand. Part 7, Yellow-grey earths. New Zealand Society of Soil Science, Lower Hutt, New Zealand. 123 p. Yellow-grey earths. their intergrades and associated soils represent some 11.5% of the area of soils in New Zealand and occupy a large proportion of the country's flat and rolling land, particularly in the South Island. They are important agri culturally as they are used for mixed arable farming, cereal cropping and prime lamb production. in addition to wool. In some locations they arc used for dair ying and in more recent years for the expanding viticultural industry. Typing: Tessa Roach Draughting: M.J. Smith Yellow-grey carths have been (and still arc) somewhat of an enigma to soil scientists from both New Zealand and abroad. They do not rest easily in their taxonomic position in the New Zealand Genetic Classification where they are placed betwixt the brown-grey earths and the yellow-brown carths or perhaps more pertinently in that somewhat ill-defined no-mans-land - the seasonally dry districts where rainfall ranges between approximately 500 mm and I OOO mm. This uncertainity is at least partly because they are the only soil group in New Zealand which includes both intergrades and associated soils in the general sur vey legends. Of the 2.89 M ha assigned to the group as a whole, just over 57% ( 1.66 M ha) arc included as yellow-grey earths -the remaining 1.23 M ha of these soils are ascribed to intergrades and associated soils. This volume has been compiled from both published and unpublished information. Authors This present volume of Soil Groups of New Zealand includes a lot of current must be consulted before papers are cited in other thinking on various aspects of the yellow-grey earths and will perhaps throw publications. some further light on their genesis and development. While talking recently to Dr A.E. Hewitt. who has the invidious task of revising the New Zealand Soil Classification. he mentioned that when he had sorted out a suitable definition and classification for the yellow-grey earths this would be a major step in for mulating a new New Zealand Soil Classification. As this volume finally comes to press. I would like to thank all contributors for their articles - many of the contributors have prepared articles for the pre vious six volumes in the series - and the request usually comes at a time when pressures arc greatest. For convenience the date of receipt of articles has also been added. I wish also to thank Dr R.J. Furkert. N.Z. Soil Bureau for his help in the final preparation of this volume.
J.G. Bruce N.Z. Soil Bureau DSIR Gore February 1984
P.D. l-IASSELBERU, GOVERNMENT PRINTER, WELLINGTON. NEW ZEALAND-1984 CONTENTS
page 1. DEFINITION AND CLASSIFICATION Yellow-grey earths - definition and classification J.D. Cowie ...... 7 The FAO-Unesco classification R.B. .\filler ...... 8 Soil Taxonomy applied to yellow-grey earths, intergrades and associated soils J. G. Bruce ...... 10 Classification in the Federal Republic of Germany J.A. Pollok ...... 13 2. DISTRIBUTION AND DESCRIPTION Distribution and description of yellow-grey earths in Manawatu and Wanganui Regions T. G. Shepherd ...... 15 The influence of climate on the distribution of yellow-grey earths and other soil groups in Hawke's Bay E. Gr(tfiths ...... 20 Distribution and description of yellow-grey earths in the Wairarapa K. W. Vincent ...... 24 Distribution of yellow-grey earths in the Wellington region J.G. Bruce (Ed) ...... 26 Distribution and description of yellow-grey earths in Nelson-Marlborough J.B. Camphell ...... 28 Distribution of yellow-grey earths and associated soils in Canterbury and the Upper Waitaki Basin T.H. Webb. £.J.B. Cutler ...... 33 Distribution and description of yellow-grey carths in North Otago F.G. Beecrofi ...... 35 Distribution and description of yellow-grey earths in Central Otago F.G.Beecroft ...... 38 Distribution and description of yellow-grey earths in South Otago FG. Beecroft ...... 44 Yellow-grey earths of Southland and West Otago J.G. Bruce ...... 46 3. PEDOLOGY AND MORPHOLOGY The parent materials of yellow-grey earths and related and associated soils E.J.B. Cutler ...... 52 Central yellow-grey earths H.S. Gibbs ...... 56 Southern yellow-grey earths J.G. Bruce ...... 57 Micromorphology of yellow-grey earths B.C. Barratt ...... 59 An hypothesis on the formation of yellow-grey carths R.L. Parfitt, J.D.G. Milne ...... 65 4. CHEMISTRY Survey chemistry of yellow-grey earths L. C. Blakemore ...... 66 The magnesium status of yellow-grey earths R. Lee ...... 71 The potassium status of yellow-grey earths R. Lee ...... 73 Development of variable charge properties in Tokomaru silt loam .!.A. Pollok ...... 76 5. PHYSICAL CHEMISTRY Secondary iron oxides in yellow-grey earths C. W. Childs ...... 79 Mineralogy of some yellow-grey earths in Otago I. NITION AN CLASSIFICATION YELLOW-GREY EARTHS - DEFINITION AND CLASSIFICATION J.D. Cowie, Soil Bureau, D.SJ.R., Lower Hutt (Received !\larch 1982) INTRODUCTION I. A pale coloured, compact and weak structural subsoil with low porosities - colours are gener Yellow-grey earths were first recognised as a dis ally 2.5Y or 5Y hues, and bulk densities are tinctive group of soils during soil surveys in above 1.45 g/cm3• Hawke's Bay in the late I 930's. They were origi nally given the name of 'New Group' but this was 2. A fragipan or related massive horizon normally later changed to yellow-grey loams (Grange 1945: occurs at depths below about 45 cm from the Pohlen et al. 194 7). At first they were thought to surface. This horizon is traversed by grey ver be podzolised because of the presence of a sandy tical or reticulate grey veins which are referred textured pale-coloured subsurface horizon, but ana to as gammations. lyses of these soils showed them to be only weakly 3. Percentage base saturations are generally to moderately leached. They were also recognised moderate to high and either stay steady or in the Wairarapa and Manawatu district and, in the increase with depth. This is in contrast to the North Island, were defined as soils occurring under yellow-brown earths where percentage base satu relatively low rainfalls (890-1150 mm) with a sum rations decrease with depth. mer dry season (N.Z. Soil Bureau 1954). Typically subsoils are yellowish grey in colour. compact. and 4. Calcium to magnesium ratios decrease with have a blocky rather than nut structure. Generally depth from a figure of 2 to I in the upper A they have a fragipan or genetically similar massive horizon to 1.1 or less in the lower B and C. horizon at depths below 25 to 60 cm from the sur 5. Organic matter is medium to low in the A hori face. This horizon has a gammate or reticulate pat zon and drops sharply in the B horizon to very tern of grey veins. Subsoils are usually heavier than low values ( < 1.0% C). topsoils and clay illuviation is present to varying degrees. In the wetter areas subsoils arc glcyed and 6. Low phosphate fixations and low Tamm iron have olive grey colours and common to abundant and aluminium values. yellowish brown mottles and concretions. Further testing of these and other criteria are At this stage yellow-grey earths were not recog required for a more mutually exclusive definition. nised in the South Island. similar soils being included as Lowland Tussock Soils and in part, as Highland Tussock Soils (Grange I 946). These were soils from loess or loess-like sediments occurring CLASSIFICATION in lower rainfall areas (635-1150 mm) and formed under low tussock grassland vegetation. Subsoils In the legend of the 1948 Soil Map of New were 'creamy yellow' in colour and compacted into Zealand, the yellow-grey earths were subdivided a 'clay pan' at 45 cm or more below the surface. primarily on the basis of degree of gammation into weakly, moderately and strongly gammate. The In the 1948 Soil Map of New Zealand (Taylor degree of gammation was implied to have strong 1948). the similarities of these soils with the North genetic implications and this has been confirmed Island yellow-grey loams were recognised and a by Bruce ( 1972). who has shown that in the South zonal group of yellow-grey earths was created to land region gammation is related to rainfall and the include all these soils of sub-humid to humid areas moisture status of the soil. In dry subhygrous situ with their distinctive morphology. ations, close to the brown-grey earth boundary, gammate patterns are faint. They become more distinct in dryhygrous zone and in the intergrades to yellow-brown carths and then become much less DEFINITIONS distinct or absent in the vcllow-brown earths. Maximum gleying occurred, in the yellow-grey A strict definition of the yellow-grey earths as a earths intergrading to yellow-brown earths. group is difficult to formulate and at this stage only general properties can be given. Common features Further subdivisions of these gammate subgroups are: was based on the degree of leaching and gleying and 8 9 then on the type of mclanisation. i.e. whether tus sub-group to the yellow-brown carths was recog BAY cemented by silica so that dry fragments do not sock or forest melanised. nised. However, with the lack of any definitive cri teria for the group, and the differing concepts slake during prolonged soaking in water or in The yellow-grey earths of Hawke's Bay were hydrochloric acid. In the General Survey of the Soils of the South amongst pedologists as to the central concept of the classed in the Soil Association Lo 35-2bc, fragipan Island (N .Z. Soil Bureau l 968a). the yellow-grey group, there has been the danger that most soils phase. This means: Duripans vary in the degree of cementation by earths were subdivided into 3 subgroups based on arc placed as intergradcs and the zonal group is very silica and in addition they commonly contain moisture status and degree of gammation as follows: limited. 1. It is an Association in which Orthic Luvisols accessory cements, mainly iron oxides and calcium This was recognised by Bruce (pcrs. comm.) who (Lo) are dominant; carbonate. As a result, duripans vary in appear l. dry subhygrous sub-gammate yellow-grey carths ance, but all of them have a very firm or extremely proposed that, with consideration of the basal form, free from mottling 2. It is No. 35 of the Lo Associations which has firm moist consistency, and they are always brittle all soils could be placed in either one group or the Eutric Cambisols as associated soils; 2. subhygrous gammate yellow-grey earths with other and that soils preYiously regarded as inter even after prolonged wetting. weakly to moderately developed mottling grades could be accommodated as subdivisions at 3. It is of texture class 2 (1 is coarse, 2 is medium, The soils of Hawke's Bay in the Lo 35 Associa the appropriate category by nominating the dis 3 is fine); 3. dry hygrous gammatc to net gammate yellow tion are central yellow-grey earths with clay-illuvial tinctive properties or processes operating. Pro grey earths with moderately to strongly 4. It is of slope classes b and c (a is fiat to undu B horizons (N.Z. Soil Bureau ! 968b). The asso cesses or properties which he considered important ciated stony soils are put in a Dystric Cambisol developed mottling. lating, b is rolling to hilly, c is steep to were degree of glcying, degree of development of mountainous); association, Bd 49-2abc, and the area to the south In this way the increase in degree of gammation the fragic horizon; and development and type of and east with intergrades to yellow-brown earths and of gleying with increased rainfall was gammate colour patterns. Degree of leaching and 5. It contains a fragipan. are put in another Lo Association (Lo 61-2/3c) with recognised. clay illuviation would be other criteria. Luvisols are soils with argillic horizons and % Acrisols (low % base saturation equivalents of Luvisols) and Dystric Cambisols. In the soil legends on the maps accompanying base saturations higher than 50 in some part of the Soils of New Zealand (N.Z. Soil Bureau 1968b) profile. They come second to last in the key after these criteria were not used; instead a primary sub CONCLUSION all other soils with argillic horizons, or indeed MANAWATU almost any other diagnostic horizons, have been division was made into: In the Manawatu the yellow-grey earths with There is a need to test criteria for a mutually removed. The Orthic Lul'isols are the Luvisols that arc left after all other possible subgroups (Plinthic, clay-illuvial B horizons are placed in the Gleyic (A) with weakly developed B horizon exclusive definition of the yellow-grey carths that Luvisol association Lg 22-2a which has no asso will avoid the necessity of the use of intcrgrades. Gleyic, Albic, Vertie, Calcic, Ferric, and Chromic) (B) with structural B horizon have been keyed out. ciated soils but has inclusions of Dystric Cambisols Key criteria arc likely to be colour and compaction (e.g. Kiwitea soils). To the north the associated (C) with clay illuvial B horizon of the B horizon; presence of a fragipan and gam Cambisols follow Luvisols and come at the end steepland soils and the intcrgradcs to yellow-brown mation; trends in base.saturation and Ca/Mg ratios of the key. They mostly have only cambic B hori earths go into an extensive Dystric Cambisol asso The recognition and separation of soils with with depth; and P retention and Tamm Fe and Al argillic B horizons was a worthwhile step forward zons. Coming right at the end they tend to be some ciation including Eutric Cambisols and Andosols values. Subdivision of the group can be based on thing of a ragbag to pick up any soils that have not (Bd 47-2c) that extends up through inland Taranaki. as this has proved a useful criteria to separate dis properties or processes. such as type and develop tinctive soils and show relationships. been fitted in elsewhere. The Eutric Cambisols have ment of gammation; fragipan development and % base saturations higher than 50 and key out at In all these classifications an intergrade group or degree of leaching, glcying and clay illuviation. the end of the Cambisols after Gelic. Gleyic. Ver WAIRARAPA tie, Calcic, Humic, Ferralic, Dvstric. and Chromic The yellow-grey earths with clay-illuvial B hori subgroups have been removed: zons in the Wairarapa. occurring on the rolling and The fragipan phase marks soils which have the hilly land to the east of the plains, are placed in Lo upper level of the fragipan occurring within 100 cm 62-2bc, an association also including Orthic Acri THE F AO-UNESCO CLASSIFICATION of the surface. A fragipan is a loamy (uncommonly sols and Gleyic Luvisols. The related steepland soils a sandy) subsurface horizon which has a high bulk of eastern Wairarapa are included in a large area of dominantly Dystric Cambisols but with some R.B. Miller*, Head Office, D.S.I.R., Wellington density relative to the horizons above it; is hard or very hard and seemingly cemented when dry; is Eutric Cambisols and inclusions (less than 15%) of (Received December 1981) weakly to moderately brittle when moist; when Orthic Luvisols (Bd 50-2c). The pattern is not very pressure is applied peds or clods tend to rupture different from that of Hawke's Bay. suddenly rather than to undergo slow deformation. Unesco 1974, 1978). it was soon clear that in yellow Dry fragments slake or fracture when placed in MARLBOROUGH grcy earth areas the detailed information needed to water. ln New we have traditionally recog- make the classification decisions was not available. Only small areas in Marlborough have yellow nised yellow-grey earths as being_ soils that_ looked The decisions were made using the data available A fragipan is low in organic matter, slowly or grey earths with clay-illuvial B horizons, most of like the Timaru silt loam. Puttmg them mto an plus the experience of pedologists who had worked very slowly permeable and often shows bleached the yellow-grey earths have weakly developed or international soil arrangement has been rather more in the various regions. The results no doubt leave fracture planes that are faces of coarse or very coarse structural B horizons. On the 1:5 OOO OOO map these difficult. This is essentially because they have sev much room for improvement but all-in-all seem to polyhedrons or prisms. Clayskins may occur as are put together with associated steepland soils and eral key properties that fall near boundaries - toi;> give a reasonable general impression of the soil patches or discontinuous streaks both on the faces stony soils into association Be 97-2bc, fragipan soils near the mollic/hum1c/umbnc-ochnc cover. and in the interiors of the prisms. A fragipan com phase, in which Eutric Cambisols are associated boundary, subsoils near the argillic-cambic boi._md monly, but not necessarily, underlies a B horizon. with Haplic Phaeozems and Orthic Luvisols. The ary, and % base saturations near the Ult1sol It may be from 15 cm to 200 cm thick with com Haplic Phaeozems are soils with mollic A horizons, monly an / Acrisol-AlfisoljLuvisol boundary. abrupt or clear upper boundary, while but without argillic horizons. DISTRIBUTION the lower boundary is mostly gradual or diffuse. Yellow-grey carths occur mainly in seven areas Some of the Hawke's Bay soils today would be CANTERBURY-NORTH OTAGO classed as duripan phase rather than fragipan phase. SOIL MAP OF THE WORLD of New Zealand: Hawkc's Bay. Manawatu, Wa1- The yellow-grey earths of this region are very rarapa, Marlborough, Canterbury, North Otago, The duripan phase marks soils in which the upper extensive. They mostly fall into the subgroup with In preparing the 1:5 OOO OOO soil map of New Central Otago-Waitaki. and South Otago-Southland. level of a duripan occurs within I 00 cm of the sur structural B horizons and associated stony soils and Zealand for the Soil Map of the World (FAO- face. A duripan is a subsurface horizon that is related stcepland soils. Much smaller areas of soils 10 11 with clay-illuvial B horizons are found in rather SOUTH OTAGO-SOUTHLAND Table 1 _ Soil T.axonomy nomcn.claturc to subgroup level in which yellow-grey earths. intergrades and rainfall areas to the south. In the I :5 OOO OOO The yellow-grey earths with clay-i!luvial B hori associated soils probably qualify. Recommended additions arc shown in parentheses map they are shown in four associations: Dys~ric zons of South Otago have been mapped as fragipan Cambisols (Bd 3-2a, stony phase) on the plams; phases of Gleyic Acrisols. Ag l 3-2b, with Dystric Order Suborder Great group Subgroup Cambisols (Be 98-2bc, fragipan phase) (which Cambisols in association. In Southland the asso some Luvisols) in North Canterbury; ciation is Ag l 4-2ab. fragi pan phase in which both Udults Hapludults Aquic: Ochrcptic: possibly Typic Acrisols (Ag l 2-2b, fragipan phase) (which Ultisols Dystric and Humic Cambisols and Dystric Fluvi Alfisols Aqualfs Fragiaqualfs Typic: Aerie some Cambisols and Phaeozems) mainly Ochraqualfs sols are in association. Typic: possibly Aaic in South Canterbury; and Gleyic Luvisols (Lg 38- Ustalfs (Fragiustalfs) (To be developed: possibly Typic. Aquic and Udic) fragipan phase) (which includes some Acrisols) Durustalfs Not defined. (Typic) possibly more Hapluslalfs l ldic: possibly more in North Otago. l ldalfs Fragi udal I~ Ochrcptic: Aqueptic (with modilicalio11): possibly Typic and Aquic lnceptisols Aqucpts F ragiaq ucpts Typic: Aerie: possibly Humic CENTRAL Haplaqucpts possibly Typic: Aerie: Humic FUTURE REVISION Ochrepts Fragiochrcpts Typic: Aquic:+(llstic) Yellow-grey earths with weakly developed B Durochrcpts (Ustic) and related steepland soils, are extensive It is hoped that the more rigorous definitions that Ustochrcpts Udic:+(Pctrofcrric) in the areas of Canterbury and Otago. Most Eutrochrcpts Dystric will emerge from studies for this volume will make are taken into Eutric Cambisols (Be l-2abc) which Dystrochrepts Typic: possibly Aquic and others future designations more reliable. areas of soils have some areas of lith ic phase. The remainder arc Umbrepts Fragiumbrcpts possible more accurate. and transfers of technology more Haplumbrcpts Typic: possibly Lithic a mixture of Luvisols and Cambisols in Associa useful. tion Lo 63-1/2bc. *Retired. present address 3a Crofton Road. Ngaio. Wellington ULTISOLS Typic Fragiaqualf - Marton Generally soils with an argillic horizon, with or without a fragipan, and having a base saturation Aerie Fragiaqualf - Tokomaru (by sum of cations) < 35% at 1.25 m below the top and Typic Ochraqualf - Ohakea; with Aerie of the argillic horizon or 75 cm below the upper subgroups also a possibility. boundary of a fragipan if one is present. Yellow-grey carths qualifying as Ustalfs at pres Some yellow-grey earths mapped in parts of ent belong to two great groups - Durustalfs (Ustalfs Southland (Kaweku soils of the Waimea Plains) with a duripan); and Haplustalfs (the simplest form TO YELLOW-GREY EARTHS, appear to have these requirements. They appear to of Ustalfs). Durustalfs have not had subgroups be polygenetic soils with a compacted and strongly AND ASSOCIATED SOILS developed but the Matapiro soils from Hawke's Bay leached clay illuvial subsolum. At suborder level probably represent the central concept of the great on moisture they are Udults, and at great group group and would be Typic. J.G. Bruce, Soil Bureau, D.SJ.R., Gore level Hapludults, the simplest form of Udults, as (Received May 1982) the compacted horizon does not meet the require Whether they have a fragipan or not, other ments of a fragipan. As the argillic horizon is thin, yellow-grey earths (without a duripan) qualify as the Ochreptic subgroup is favoured, however both Haplustalfs. An example without a fragipan is Tima Unpublished notes on 'Proposed Changes in Soil INTRODUCTION Typic and Aquic subgroups may also occur. (Ota?o). It is probable that the secondary lime Taxonomy Definitions to Accommodate New requirement ('f) would put these soils in the Udic Mapua (Nelson). an intergrade between yellow Zealand Soils' by the late Dr Guy Smith. as well subgroup. For U stalfs with a fragipan a new great Soils classified in the New Zealand genetic clas as 'Soil Taxonomy Memoranda' - a continuing col grey and yellow-brown earths, also meets the group of Fragiustalfs is needed and for which sification as yellow-grey carths arc a zonal group requirements of a Hapludult and qualifies for the lection of articles on taxonomy by various authors subgroups would need to be developed. Such a great which have developed under a rainfall of between initiated by Soil Bureau in 1978 - have been freely Aquic subgroup. group would probably head the key. Claremont 500 mm and about I I 00 mm (ustic to udic used in preparing this article and arc here (South Canterbury) would be an example of a approximately) on a variety of parent materials of acknowledged. which loess predominates. They have few diagnos ALFISOLS Fragiustalf. Table l lists orders. suborders, great groups. tic morphological properties that unite them as a Generally soils with an argillic horizon. with or Udalfs with a fragipan - Fragiudalfs - are rep subgroups of Soil Taxonomy in which yellow-grey group, from the presence of a fragipan which without a fragipan, and having base saturation (by resented by yellow-grey earths from Hawke's Bay earths, intergradcs and associated soils probably may occur in loess soils. When Soil Taxonomy (Soil sum of cations) > 35% at 1.25 m below the top of to Southland. They could occur in a number of occur. Recommended additions arc in parentheses. Staff 1975) is applied to these soils (includ the argillic horizon or at 75 cm below the upper subgroups, t~e most likely of which are Aqueptic, ing for the purpose of this article. intcrgrades and Possible lithic subgroups. apart from one. are not boundary of a fragipan if one is present. and Ochrept1c and (possibly) Typic and Aquic. associated yellow-brown shallow and stony soils). indicated. However for soils with epipedons darker than the Suborders of Alfisols are based on moisture the number of great groups and derived subgroups Typic subgroup, the Aqucptic definition should regime and yellow-grey earths are included in three is large. A number of changes to Soil Tax include 'with or without d' to accommodate soils onomy appear to he nL·ccssary. and rl'iale largely - Aqualfs, Ustalfs, and Udalfs. like Otamauri (Hawke's Bay). Other Fragiudalfs to the occurrence of fragipans in an ustic moisture SOIL ORDERS At least two great groups of Aqualfs are repre include Godley (Banks Peninsula); and Pukemutu regime which are not known to occur in the United sented by these soils and they occur largely in the (Southland). It follows that Hapludults may also be States. Modification of some definitions also Most yellow-grey earths key out into two lowly placed soil orders - Alfisols and lnccptisols - though lower part of the North Island. Thev are the Fra represented by other yellow-grey earths that have appears necessary. a few qualify earlier as Ultisols. giaqualfs and Ochraqualfs with the following no fragipan in the strict limitations of Soil subgroups: Taxonomy. 12 13 INCEPTISOLS Dystrochrepts include soils such as intergrades between yellow-grey and yellow-brown earths which CLASSIFICATION IN THE FEDERAL REPllBLIC OF GERMANY Suborders intd which yellow-grey earths and have a fragipan or fragic features which do not associated soils ·may be classified include Aquepts, qualify as fragipans in the strict sense of Soil Tax Ochrepts, and Umbrepts. onomy. Many of the associated yellow-brown shal J.A. Pollok, Department of Soil Science, Massey Unin·rsity, Palmcrston North For Aquepts the predominant great group is Fra low and stony soils also qualify as Dystrochrepts. (lkn~iv~d lh·n~mhl•r 1981) giaquepts which are fairly widespread in the South Arthurton and Oreti soils (Southland) are examples Island. Examples are Waimumu (Southland), a of these soils qualifying in the Typic subgroup. Typic Fragiaquept and Otokia (Otago). an Aerie Other subgroups are also likely to occur. Soil classification in the Federal Republic of So far as the yellow-grey earths of Otago and Germany is based essentially on the ideas of Mtick Fragiaquept. Humic Fragiaquepts may also occur, Umbrepts, the simplest form of Inceptisols, do Southland arc concerned, it is clear from the profile but it is likely that they would be of minor extent enhausen (1962; 1975) and the Arbcitsgemeinschaft descriptions given in Bruce ( l 973b), Bruce et al. not have many yellow-grey earth representatives. Bodenkunde (Soil Science Working Party) (1971 ). and confined largely to localised poorly drained Fragiumbrepts are a possibility but as far as is (1981), and Leslie (1980), for the Waikoikoi, Wai depressions. known none have been recognised as yet. During two visits to the Federal Republic in 1964 mumu and Otokia soil series. that the pseudogley and 1974. the author did not encounter anv soils ing process is operative in these soils as well. Again Haplaquepts - the simplest form of Aquepts - Haplumbrepts are represented by a soil sepa it is a question of the degree of development. In should be considered for yellow-grey carths not with the massive fragipan that is characteri~tic of rated in the Hokonui set (Southland) and which New Zealand yellow-grey earths. The explanation Bruce et al. (1981) the Waikoikoi and Waimumu having a fragipan. Wakanui soils (Canterbury) may qualifies for the Typic subgroup. but Lithic series have been classified in terms of Soil Tax qualify for this great group. probably lies in the fact that the classical loess of subgroups may also occur. Germany (whence the name locss actually springs) onomy. The same is true for the catena of soils Ochrepts - this suborder has a number of great is calcareous and fragipans do not normally form embracing the Otokia series in Leslie (1980). The groups in which yellow-grey earths may be classi in calcareous loesses. Chernozems or Pararend soils key out as follows: fied. In addition to deep loess soils, it includes the zinas are much more likelv to be encountered. Waikoikoi series Typic Fragiochrept thinner soils developed on other kinds of parent Indeed for the purposes of .studying certain New Waimumu series material, as well as many yellow-brown shallow and Typic Fragiochrept Zealand and German soils formed from loess (Pol planar intcrftuvc Aerie Fragiaquept stony soils associated with yellow-grey earths. CONCLUSIONS lok 1975), the author was hard put to find any non convex backslope Typic Fragiochrept calcareous loess as parent material for the German Southern yellow-grey earths developed on loess Otokia catena In general, yellow-grey earths occur in two types soils that were required for comparative purposes. are mostly in Typic or Aquic subgroups of Fragi rectilinear midslopc Aquic Fragiochrept of great group, either those with fragipans or the The best that could be done was to locate some dc ochrepts. However a number of Typic Fragi concave toeslope Aerie Fragiaquept simplest great group representing the suborder. The calcified loess, which is not quite the same thing. ochrepts occur in an ustic moisture regime and it exceptions are the Durustalfs in which duripans Thus, if the reference is consulted. one will dis The soils classed as Aerie Fragiaquepts would appears necessary to have an Ustic subgroup, and occur, and great groups of Ochrepts where. in addi cover that whereas the New Zealand yellow-grey come within the category of strongly developed to add to the definition of Typic Fragiochrepts 'd tion to soils with duripans, higher base status soils earths have magnificent fragipans, the German soils Pseudogleys. Those classed as Typic Fragiochrepts - have an udic or perudic moisture regime'. Thus without fragipans (Ustochrepts and Eutrochrepts) placed opposite them do not. Instead they possess would fall into the category of moderately Ustic Fragiochrepts would be like Typic Fragi qualify. very impressive Bt or Btg (argillic) horizons. That developed Pseudogleys, while the Aquic Fragi ochrepts except for 'd' with or without 'c'. ochrept would occupy an intermediate position. A number of additions to Soil Taxonomy appear is because once the loess has been decalcified, it is Timaru (South Canterbury) is an example o~ a to be necessary to accommodate some yellow-grey possible for clay migration to take place from the All the soils considered so far would fall within upper to the lower part of the profile. Ustic Fragiochrept. Waikoikoi and Knapdale soils earths and associated soils. the European soil type (Bodentyp) of Pseudogleys. (Southland) are examples of Typic and Aquic Fra However, what fragipans and argillic horizons They would mostly be typical. or normal, subtypes giochrepts respectively. I. A new great group of Ustalfs - Fragiustalfs - have in common in humid temperate climates is and the degree of development. moderate or strong, Durochrepts - Ochrcpts with a duripan - are for Ustalfs with a fragipan. At present such soils their capacity to impede the passage of rain water would be accommodated at the level of varieties known from Hawke's Bay and at present qualify in qualify as Haplustalfs. Subgroups need to be down through the profile. The net result is that within the subtype. Any modifications, such as for the Typic subgroup. However, they occur in an ustic developed. Based on the subgroups of Haplus water is perched above the horizon of low perme example those induced by cultivation or erosion, moisture regime, and as Typic Durochrepts have a talfs, subgroups of Fragiustalfs would, in addi ability. It is at this point that the German classi would be taken out as subvarieties. In addition, xeric moisture regime, an Ustic subgroup appears tion to Typic, be likely to include Aquic and fication identifies the soils as Pscudoglcys (Pollok under the heading of form (Bodcnloca((orm) specific necessary. Udic. 1978). The Marton and Tokomaru soil series at the reference may be made to texture and parent 'wet end' of New Zealand yellow-grey carths fall material, e.g. silt loam derived from Otiran loess! Yellow-grey earths probably qualifying in the 2. Definition of Typic Durustalfs and possibly very clearly int? this category. so much so that they Ustochrept great group include Wanaka (Otago) development of other subgroups. As to higher categories, the Pseudogleys are would be classified as Typ1schc Psc11doglcyc. stark grouped first into the class of internally damned which fits the definition of the Udic subgroup (lack ent1rickelt (strongly developed, typical Pscudog 3. Modification of the definition of Aqueptic Fra up, wet soils (Staunasscboden) and then into the of secondary lime). leys). This would conform to my own understand giudalfs to allow for soils with epipedons darker division of terrestrial soils ( Tcrrestrische Boden), In addition, the definition of the Typic subgroup than the Typic subgroup. ing of these soils. The active scat of present-day soil essentially after the manner of Kubiena ( 1953). of Ustochrepts should have a petroferric exclusion, formation lies above the fragipan of the Tokomaru 4. An Ustic subgroup of Fragiochrepts for soils series, or the argillic horizon of the Marton series. It becomes clear that the Bodentyp stands at the to allow for a Petroferric subgroup to accommo that at present qualify as Typic Fragiochrepts but date soils such as Steward (Canterbury). The predominant process is that of pseudogleying. heart (Mittelpunkt) of the German soil classifica have an ustic moisture regime. and soil amelioration is primarily dependent upon tion system. It is the basic expression of the soil Eutrochrepts are unlikely to have many yellow 5. An Ustic subgroup of Durochrcpts for soils that the removal of excess, seasonally-perched water. building process (Mtickenhausen 1975). grey earth representatives. They would be similar at present qualify as Typic Durochrepts but have As one moves through the regions of Hawke's There remains the problem of intergrades to Ustrochrepts but have an udic moisture regime an ustic moisture regime. and would probably qualify in the Dystric subgroup Bay. Wairarapa and mid-Canterburv, where rain between yellow-grey earths and other soil groups. on the lack of carhon;tll's within a depth of I m of 6. A Pl'lrofcrril· suhgrnup of 1 lslochrcpts to fall is diminishing and summer dro~ght increasing Bruce (I 973b) classes the Arthurton soil series as the surface. Meyer soil~ (South Canterbury) may accommodate -.oils that have a pctroll:rric con relative to the Manawatu. one finds the process of an intergrade between a yellow-grey earth and a qualify as Dystric Eutrochrcpts. tact within I m of the surface. pseudogleying less strongly expressed. The classical yellow-brown earth. Such Chergangsformen are soil series of Matapiro, Wharekaka and Timaru readily accommodated in the German system at the would fall into the class of moderately developed sub-type level. Many New Zealand yellow-brown Pseudogleys. earths can be accommodated within the Bodentyp of Bra1111crdc. It then becomes a question of whether 14 15 the Arthurton is more like a yellow-grey earth than grey earths should it need to. The fragipan falls 2. DISTRIBUTION AND DESCRIPTION a yellow-brown earth or vice versa. If the forme~, within the concept of the Sohle (sole, floor), an the soil is referred to as a Brawzcrdc-Pscudog!cy, 1f impervious horizon that perches water. The the latter, as a Pseudoglc.r-Braunerde. The Boden emphasis is then placed onthe pseudogleying pro typ that the soil is closest to comes at the end. One cesses at work in the soil above the sole, as the soil is reminded very forcibly at this point of the con moisture regime fluctuates seasonally. The marks cept of sub-groups in Soil Taxonomy. of such processes may be readily seen in the field in the form of mottlings and ironstone concretions. In conclusion, the German Bodcnsystcmatik is The resultant soil is a Pscudogley. DISTRIBUTION AND DESCRIPTION OF YELLOW-GREY EARTHS IN well able to accommodate the New Zealand yellow- MANAWATU AND WANGANUI REGIONS T.G. Shepherd, Soil Bureau, D.S.I.R., Palmerston North (Received December 1982) The yellow-grey earths of the Manawatu-Wanga Campbell 1977, 1979; Cowie & Rijkse 1977; Rijkse nui Regions are classed as gleyed central ycllow 1977; Cowie 1978) given in Table 1. grey earths in the Soil Map of New Zealand (Taylor 1948) and occur in a characteristically subhumid climate with a seasonal dry season. receiving from Table 1 Yellow-grey earths of the Manawatu 800 to 1140 mm of rainfall annually. They arc con Wanganui Region - soil sets and series sidered to be moister than the yellow-grey carths in other parts of the country. partly because of the Sets Series slightly higher rainfalL and partly because of the heavier textures and impermeable pan in the sub N.Z. Soil Bureau (l 954) (Recent work) soil causing perched glcying conditions. Tokomaru -==---- Tok11rangi The soils occur on the flat to undulating uplifted Tokmnaru Pleistocene marine and river terraces and on the Milson Milson rolling and hilly land formed by the incision of Marton Marton rivers and gullies across the terrace surfaces. Halcom be Halrnmbc Ohakca Ohakca The yellow-grey earths are formed predomi nantly from quartzo-feldspathic loess derived from floodplains including those extending off the pres ent shoreline during Pleistoccne cold climates, and possibly from coastal sand dunes as well. Inter !he y~llow-grey earths of the Manawatu-Wanga mittent additions of tephric loess and/or airfall nu1 ~eg1ons are similar in colour, structure and tephra of both rhyolitic and andcsitic origin have consistence to many yellow-grey earths elsewhere contributed to the parent material (Ficldes & in New Zealand, but differ in having more abun Weatherhead 1968, Wallace & Neall 1982). The dant gleying with fine Fe-Mn nodules in the lower sequence of loess deposits and terrace surfaces A horiz~n, and in the higher clay content, lesser occurring throughout the region have been compact10n, and greater fragmentation of the fra described in detail by Fleming (1953), Te Punga gipan. They are characterised by dark greyish brown (1953), Cowie (l 964b) and Milne ( 1973). However, to dark grey sandy loam to clay loam topsails with only the upper two loess deposits, the Ohakea and a weakly to moderately developed structure. The the Rata loess, and particularly the younger Ohakca subsoils have a gleyed olive grey to olive, firm, locss, have contributed to the parent material or sandy loam to clay argillic B horizon with many to the present day soil. The Ohakea locss is charac abundant yellowish brown and strong brown mot terised in part by the presence of the 20 OOO year tles and many black nodules. A zone of compaction old Aokautere Ash marker bed (Cowie I 964b) which (frag1pan) often occurs in the upper part of the occurs two-thirds of the way down the deposit. The parent material and has a high bulk density (typi main period of accumulation of the Ohakea loess ~ally aro_und 1.7-1.9 g/cm') and hence a low poros is believed to have been during the aggradational ity. Honzontal and particularly vertical pale grey phase of the Ohakea Terrace, a period which began and rust coloured grey veining gives rise to a gam about 25 OOO yrs ago and ended about 12 OOO yrs matc p~ttem bel?w the B horizon. While the pro ago (Milne 1973). Differences in the rates of accu cesses involved 111 the formation of fragipans are mulation and texture of the Ohakea loess due to by no means well understood. compaction brought the increasing distance from the source of the loess a_bout _by seasonal wetting and drying orienting par have produced differences in the soils. ticles mto t~e closest possible arrangement, and by the expansion and contraction of swelling mica Yellow-grey earths of the Manawatu-Wanganui ceous clays is proposed by Fieldes (1958) and region were initially mapped as five sets bv N.Z. Arbuckle (in Blakemore 1958). Steinhardt et al. Soil Bureau (1954) in the General Survev ·of the ( 1982) also noted that NaoH in comparison with Soils of North Island. More recent work has sub CBD (sodium citrate-bicarbonate-dithionate) divided these five sets into six series (Wilde 1976: extracted 10 to 40 times as much silica from the 16 17 fragipan horizon of two soils from North America, landscape a gently undulating appearance. The soils occur in limited areas to the north-east of Palm olive grey clay loam Cxg horizon with many yel loess overlying sandstone and siltstone. and suggested that silica played an important ro~e lowish brown mottles, moderately developed coarse as a binding agent in holding the frag1pan matnx erston North, west and north-west of Feilding, and While soil profiles are variable they may show on the eastern side of the Pohangina River in the prismatic structure and pale grey vertical veins. This together. horizon may or may not meet the criteria of a fra 18-20 cm of a friable dark greyish brown fine sandy vicinity of Awahou South. Profiles of Milson silt loam Ah horizon with a few subrounded greywacke The Tokorangi series is formed from very coarse gipan. The underlying Cg horizon is a massive light loam are poorly and imperfectly drained and have stones, over 10-14 cm of a firm light yellowish wind-blown sand deposited on the intermediate and grey to grey clay with many strong brown mottles a 15-20 cm friable dark greyish brown silt loam Ah brown or light olive brown fine sandy loam with high terraces immediately bordering the eastern horizon with a moderately developed granular and many black concretions. bank of the Rangitikei River in Manawatu County. many yellowish brown mottles with some grey structure and few yellowish brown mottles, over 12- While Marton silt loam is the predominant soil The series occurs also on the western side of the wacke gravels, over 23-30 cm of a compact light 15 cm of a firm light olive grey silt loam Ag hori type, Marton black silt loam is mapped by Wilde olive grey clay loam Bgt horizon with many yel- Rangitikei River between Bulls zon with a weakly developed nut structure and ~nd Pou:vha~aura (1976) in Waitotara County and Marton clay loam . lowish brown mottles, few faint clay cutans on ped and along the Turakina River m the v1_cm1ty of manv reddish brown mottles and fine black nod is reported to occur in the vicinity of Denlair Road faces and many greywacke gravels. This passes into Otairi. Profiles are moderately well dramcd and ules: over 15-18 cm of a firm white or pale olive in Wanganui County by Campbell (1977a). The a compact olive grey silt loam or sandy clay loam have a 17-23 cm friable very dark greyish brown fine sandy clay loam Bg horizon with a weakly finer textured Marton soils may have formed from Cwg horizon with many yellowish brown mottles, sandy loam Ah horizon with a weak very fine nut developed nut structure and abundant yellowish a finer textured loess or from greater weathering many greywacke stones, and weakly developed ver structure over a 30-34 cm friable greyish brown clay brown and brownish yellow mottles and few fine resulting from a slow rate of accumulation of loess. tical grey veining. The Halcombe soil may also loam Bgt horizon with common yellowish brow~ black nodules: over 23-45 cm of a \'Cry firm olive Campbell (1977a) also reported that a number of mottles, many brown clay cutans and common soft clay loam Btg horizon with a weak prismatic struc grade with depth into a loose light olive brown variants of the Marton silt loam occur where the dark brown Fe/Mn nodules, over a 15-20 cm fri ture and many yellowish brown mottles and coarse sand C horizon which may exhibit hard loess cover is thin. ening along near horizontal veins by the deposition able yellowish brown sandy loam Bg horizon w_ith moderately developed clay coatings on ped faces. of iron oxides. many olive grey and brown mottles, over loose ohve This overlies 22-28 cm of a firm pale olive silt loam The Marton soil is distinguishable from Toko sand with few olive grey mottles. Cxg horizon with a massiw to coarse prismatic maru and Milson soils by its heavier textured sub The Ohakea series are imperfectly to poorly The Tokomaru series is formed from the thick structure and many strong brown and light grey soil, the greater development of clay cutans in the drained soils occurring on the lower terraces and mottles, and few fine black nodules. The horizon loess deposit on the intermediate and high terraces subsoil, the blocky structure of the subsoil, the less represent the youngest of the yellow-grey earths of also has prominent grey vertical veins which pene bordering the eastern banks of the Rangitikei and well developed fragipan, the intermittent occur the region. They are formed from wind-blown loess trate into 8-15 cm of a fine pumiccous sand layer Manawatu Rivers. The texture of the loess ranges rence and shallow depth of the Aokautere Ash from the rivers and/or fine textured colluvium from a silt loam to a fine sandy loam in those areas below (Aokautere Ash). This in turn overlies 45 to (average depth of 45 cm within the solum), and the washed from higher terraces or hills. The fine tex 60 cm of firm light grey to grey sandy clay loam immediately adjacent to the sand country north of presence of a greater proportion of interstratified tured parent material is thickest near the back of Glen Oroua. Profiles arc imperfectly to poorly Cg horizon with many yellowish brown mottles and clay and halloysite and less illite and vermiculite the terrace and thins out towards the edge where drained and have a 16-24 cm friable dark greyish many fine black nodules. in the clay fraction, as shown by Pollok (1975). the underlying gravels come to the surface and give rise to Ashhurst silt loam and its stony phase, which brown silt loam Ah horizon with a weak to moder Milson silt loam differs from Tokomaru silt loam The Halcombe series occurs on the rolling to are classed as associated yellow-brown shallow and ately developed nut structure and many dark red in that it is developed from a thinner locss column, moderately steep and moderately steep to steep stony soils related to yellow-grey earths. The tex dish brown and yellowish brown mottles along root contains a greater percentage of clay in the subsoil, slopes that form the sides of valleys dissecting the ture of the colluvium differs from place to place channels, over l 0-20 cm of a friable to firm greyish and shows more profile dcYClopment. The Milson terrace land. The dissection of the terraces has and the texture of the soil ranges from peaty loam brown silt loam ABg horizon with a moderately soil also occurs on a lower, less incised terrace sur exposed successive layers of loess, old weathered developed nut structure. many medium strong face than that on which the Tokomaru soil is in the depressions to sandy loam and clay loam, clays, gravels, sands, and mudstone and the soil although the Ohakea silt loam is the predominant brown and yellowish red mottles and few to many developed. profiles are very varied according to their position soil type. It occurs on the south-eastern side of the fine hard iron/manganese nodules, over 36-48 cm on the slope. of a compact light brownish grey and light olive Marton soils occur on the high terrace surfaces Manawatu River in Kairanga County and is grey clay loam Btg horizon with abundant strong on the north-western side of the major rivers where Halcombe hill soils and Halcombe steepland soils mapped as far south as Tokomaru by Gibbs (1957) brown mottles, many olive grey clay cutans, and a the locss has thinned still further and the texture occur between the Manawatu Gorge and Tiritea in Horowhenua County. Ohakea silt loam occurs moderately developed coarse blocky and prismatic has become finer. The landscape is more finely dis Road on the south-eastern side of the Manawatu on both the western and eastern sides of the Pohan structure. This horizon rests on 65-80 cm of a very sected with deeper valleys than in areas of Milson River. They are moderately well to imperfectly gina River in Pohangina County and is mapped in compact light grey or light olive grey sandy clay silt loam, giving it a rolling topography. The Mar drained and are formed from sandstone, conglom and around Ohakea and west of Feilding in Man loam Cxg horizon (fragipan) with a very coarse ton soils are the most widespread of the yellow-grey erate, and loess. Halcombe soils are also reported awatu County. The soils occur also in scattered prismatic structure and many to abundant strong earths in the Manawatu-Wanganui region and occur as far south as Tokomaru in Horowhenua County pockets in the lower half of both Rangitikei and brown and yellowish brown mottles. Soil-filled as far north as Kai-iwi ( 15 km west of Wanganui) where they are mapped by Gibbs (1957) as the Hal Wanganui Counties and are restricted mainly to the cracks form prominent vertical grey veins 2-4 cm and as far south as Whakaronga (4 km north-east combe silt loam soil set. Halcombe fine sandy loam Kai-iwi Valley in Waitotara County. of Palmerston North). occurs west of Pohangina in Pohangina County on wide and 15-40 cm apart and may reach depths of Ohakea silt loam profiles may have 20-25 cm of easy rolling to rolling terrace scarps and is derived 250 cm or more. The fragipan overlies 60-80 cm Marton silt loam is poorly drained and has a 20- a friable dark greyish brown silt loam Ah horizon from loess, sandstone, and greywacke gravels. Hal of a compact light olive grey and pale olive fine 23 cm friable dark greyish brown silt loam Ah hori with few faint strong brown mottles, over 18-19 cm sandy loam or silt loam Cwgl horizon with ab~n zon with a moderately developed fine nut structure combe silt loam and Halcombe hill soils occur on of a firm greyish brown clay loam Bgl horizon with dant light olive grey and strong brown mottles _with over 8-10 cm of a friable light greyish brown clay t~e rolling and moderately steep sides of valleys few yellowish brown and strong brown mottles and dissecting the terraces west of Feilding in the Man similar structure and cracks to the above honzon. loam Ag horizon with a weakly developed nut soft black noaules over 10-20 cm of a compact light This overlies 12-20 cm of a light grey pumiceous structure, few strong brown mottles and many small awatu County and are formed from loess on sand olive grey clay loam Bg2 horizon with abundant stone and gravels. They also occur on the rolling sand (Aokautere Ash) which in turn overhes a fi~m black nodules, over 10-20 cm of a firm light olive strong brown and yellowish red mottles and many surfaces and on the moderately steep and moder light olive grey to olive silt loam Cwg2 honzon with grey clay loam Bg horizon with many strong brown distinct hard black nodules, over 11-15 cm of a many strong brown mottles and a moderately mottles and a similar structure to the above hori ately steep to steep slopes of the dissected inter compact light grey clay loam Bg3 horizon with mediate and lower coastal terraces in the Rangitikei developed very coarse prismatic structure. zon, over 44-48 cm of a very tirm pale olive clay many large strong .brown mottles concentrated along County. They are imperfectly to poorly drained and With increasing distance from the source, the Btg horizon with few to many strong brown mottles distinct vertical cracks. This horizon becomes san and weakly and moderately developed coarse pris are formed from quartzo-feldspathic loess over dier at depth and overlies gravels at about 90- Ohakea loess thins and is fmcr textured, and forms sedimentary rocks and terrace cover beds. Hal the parent material of the Milson soils on the inter matic structure breaking to a strongly developed 120 cm. coarse blocky structure. This overlies 10-12 cm of c1mbe hill soils are mapped in the southern part mediate terrace surfaces (referred to as the Milson 0 the Wanganui County and occur mainly on The physiographic position of the yellow-grey Terrace by Cowie (1978)). The terraces arc char white pumiccous sand (Aokautere Ash) which in turn overlies a 35-40 cm hard, very compact, light Inod~rately steep and moderately steep to steep land earths is outlined in diagrammatic cross section in acterised by widely spaced shallow valleys giving a associated with high terraces. They are formed from Fig. 1. 19 18 Intergrades between central yellow-grey earths drained and well drained, and occur in the hill and and yellow-brown earths arc extensive in the Man stecpland country. Kumeroa hill soils are formed awatu-Wanganui regions and form primarily as a from moderately consolidated silty sandstone while result of a slightly higher rainfall (I 020- 1300 mm). Wilford soils are formed from moderately consoli varying parent materials, and possibly under a dif dated sandy siltstone to mudstone and have heav ferent vegetation. The topsoils are similar to those ier textures, deeper profiles with increasing amounts of yellow-grey earths but the subsoils are more yel of rock fragments in the profiles. lowish brown, less mottled. and have a coarse nut or blocky structure. Tuapaka series soils arc mapped as hill soils formed on the valley sides under black beech from Shannon silt loam soils occur on the rolling a wide range of parent materials including sand slopes of the dissected terrace land on the sloping stone, loess, gravels, and mudstone, or mixtures of fans bordering the Tararua Ranges in Kairanga these. They arc mapped only in a small area band County, and are formed from loess. They were also ing Forest Hi ll Road on the south-eastern side of originally mapped as the Kokotau set by Gibbs the Manawatu River in Kairanga County. Profiles (1957) in Horowhenua County between Tokomaru show I 0 cm of a greyish brown fine sandy loam Ah w and Shannon. Soil profiles have 20 cm of dark horizon over 20 cm of a pale yellow compact sandy ~ brown silt loam topsoil over I 0 cm of a light olive clay loam Bgl horizon with many distinct yellow 0::: g 0::: . brown silt loam Bgl horizon with a few faint strong ish brown mottles, over 28 cm of a light yellowish w ·.;: ., ~ brown and olive mottles, over a light olive brown brown sandy clay loam Bg2 horizon with many yel V>" - ~ ::> or pale olive firm clay loam Bg2 horizon with many lowish brown and pale grey mottles and which rests .:: i: 8 < e yellowish brown mottles; over 15- 20 cm of a pale on a greyish yellow sandstone with yellowish brown :t: ...0 0 ....0 olive clay loam Bgt horizon with abundant yellow mottles and few grey vertical veins . ""- 0 ish brown mottles and weakly developed clay ~ coatings. The Makotuku series includes Makotuku fine sandy loam and Makotutu hill soils. The former is Soils of the Raumai series are well drained and a moderately well drained soil formed from fine are mapped in Kairanga County on the terrace sandstone and loess, and occurs on rolling areas of scarps and valley sides south-east of the Manawatu. the south-eastern part of Pohangina County. Mak They are formed from sandstone and loess. Rau ---- otuku hill soils are mapped on the eastern side of (01)W1J.s nJ•WO>tOl mai sandy loam formed from loose sandstone and the Pohangina River and in the Mt Richards area, lU'fUWa'tj 8:J'!JJa .l UOSl!\.-J E loess, and Raumai hill soils formed from loose and are formed from fine sandstones and siltstones ------~ J.U z z 20 21 INFLUENCE OF CLIMATE ON THE DISTRIBUTION OF YELLOW-GREY EARTHS AND OTHER SOIL GROUPS IN HA WKE'S Table I Mean monthly Penman evaporation for Napier (mm) Station Annual Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jui Aug E. Griffiths, Soil Bureau, D.S.LR., Havelock North (ReceiYed February 1982) Napier 962 63 99 127 145 149 116 93 56 33 20 23 38 ·~ '-----y--" ~ '---:r----' Spring Summer Autumn Wmter INTRODUCTION the mean monthly rainfall from the mean monthly 289 410 182 81 evaporation~ and surpluses were calculated for the Soils now known as yellow-grey earths were first remaining months where rainfall exceeds evapo Annual rainfall (mean monthly in mm) recognised in the early surveys in Hawke's Bay ration. These data were plotted, but showed much (Pohlen & Harris 1937). It was noted that hard-pan overlapping and only slight differences between stations, even at the extreme ends of the range. Station Annual Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jui Aug formation occurred in subsoils formed on muddy rainfall sandstones under a mean annual rainfall of less than However, if leaching is the key process, then it is about 1000 mm. Where the mean annual rainfall likely that the total volume of water passing through the soil is more important than its distribution in I Te Wairerc 1922 153 127 120 141 145 145 146 193 181 176 194 194 was between 1000 and 1125 mm the pan was still 2 Ngamoko 1851 137 159 133 175 123 11)8 146 149 177 190 174 173 present but there was a distinct change in the pro time. To test this, the deficits in the 'dry' months 3 Esk Forest 1635 117 112 104 124 117 102 135 135 173 165 168 183 file, and the pan was not present when the rainfall and the surpluses in the 'wet' months were cumu 4 Tangoio 1432 94 102 86 112 102 lJ7 124 114 152 155 142 152 was above 1125 mm. This general relationship was lated to give seasonal deficits and surpluses (see Fig. 5 Maungaharuru 1394 108 103 84 108 112 113 102 124 134 125 142 142 l ). The annual water balance (Fig. 2) and the 6 Tutira 1381 96 95 80 95 98 104 117 121 154 133 152 137 confirmed in later surveys and became a part of the 7 Putorino 1260 88 86 78 80 90 104 96 129 138 Ill 137 115 N.Z. Soil Classification. The Zona! Soil Classifi monthly water status for each station were also cal 8 Wairoa 1253 89 80 69 77 75 98 105 134 132 134 143 119 cation, introduced in 1948 (Taylor l 948) to classify culated by cumulating the deficits for the 'dry' sea 9 Rissington 1113 76 79 67 78 83 84 106 9J 117 107 l 12 Ill soils from siliceous rocks. grouped soils according son, and from this subtracting the surplus in each 10 Gwavas 1096 81 81 72 86 89 85 88 90 106 103 112 102 to the rainfall. The soil group with an upper rainfall consecutive month until the deficit is eliminated. I I Dannevirke 1090 84 IOI 91 98 78 72 78 86 100 105 103 94 and then cumulating the remaining surpluses (if 12 Whanawhana 1086 79 85 7 l 89 94 87 100 84 100 95 110 99 limit of approximately 1000 mm were called yellow 13 Eskdale 1070 70 77 64 79 83 83 IOI 93 Ill 104 108 100 grey earths, the group with a lower rainfall limit of any) to give the annual surplus. 14 Aramoana 1068 74 74 63 75 67 76 83 89 121 117 118 110 approximately 1250 mm were called yellow-brown Table 2 gives the soil groups represented at the 15 Waimarama %8 69 66 57 63 67 73 78 87 106 104 108 94 earths, and the soils between were classified as 16 Waipukurau 838 58 59 54 79 63 61 62 70 77 85 90 81 rainfall stations. the annual surpluses and deficits. 17 Te Mata Peak 824 58 54 49 56 59 59 63 70 87 89 94 86 intergrades (Taylor 1948. N.Z. Soil Bureau 1954). and the differences and ratios between them. 18 Hastings 812 54 56 51 55 65 64 63 70 86 82 90 77 The relationship between rainfall and morphol ogy of some humid and sub-humid zonal soils was studied by Pohlen (1973). He concluded that (a) in DISCUSSION detail the distribution or the soils is modified by the distribution of the rainfall as well as by the total From Fig. 1 it can be seen that the duration and mean annual rainfall; (b) the distribution of the soils size of deficit can be related to the soil groups. The is not influenced by rain days with less than 2.5 mm podzolised soils have a small total deficit of less Table 2 Soil group and mean annual surplus and deficit of rain, and is related to seasonal moisture and than 100 mm during only 2-4 months (between leaching rather than to seasonal dryness. November and February). The yellow-brown earths Station Soil group Annual Annual .\nnual Surplus The improving availability of climate data for have a total deficit of 100-250 mm during 4-5 surplus deficit water Oc11ciT Hawke's Bay makes the task of defining the rela months (between October and February). Inter balancet tionship between soils and climate easier. This may grades between yellow-grey earths and yellow-brown also provide an insight into the genesis of yellow earths have total deficits of 200-325 mm during 5- l Tc Waircrc *YBP (podzolisedl 964 16 +948 60.3 grey earths and test the hypothesis that soil mor 6 months (between October and March). Yellow 2 Ngamoko YBL (podzoliscd) 916 54 +862 17.0 phology and distribution is related more to soil grey earths have total deficits of over 325 mm 3 Esk Forest YBP (podzoliscd) 763 90 +673 8.5 4 Tangoio YBE 610 140 +470 4.4 moisture and leaching than to seasonal dryness. during 7 months (between September and March). 5 Maungaharuru YBP (YBE) 555 120 +435 4.6 There is some overlapping in the amounts of the 6 Tutira YBL (YBE) 584 164 +420 3.6 deficits and their duration. so that even though there 7 Putorino YBP (YBEl 478 198 +280 2.4 is a general tendency for the total deficits to get 8 Wairoa YBE 530 237 +293 2.2 METHOD larger in the yellow-grey earths. there is no clear 9 Rissington YCiE-YBE 395 245 +150 1.6 10 Gwavas YGE-YBE 361 227 +134 1.6 separation from the other groups. I l Dannevirke YGE-YBE 341 213 +128 1.6 Long-term means were used for all available 338 230 +108 1.5 Both the seasonal surpluses and the seasonal def 12 Whanawhana YGE-YBE stations in Hawke's Hay (N.Z. Meteorological 13 Eskdale YGE-YBE 361 250 +Ill l.4 Service 1979), and 30-ycar normals were used for icits form a sequence. with the most leached soils 14 Aramoana YGE-YBE 396 291 +105 1.4 Esk Forest and Tangoio (N.Z. Meteorological (the podzols) having the highest surpluses in winter 15 Waimarama YGE-YBE 335 325 +10 l.03 Service 1973). Long-term Penman potential evap and the lowest deficits in summer. while the least 16 Waipukurau YCiE 233 356 123 0.65 leached soils (yellow-grey earths) have the lowest 17 Tc Mata Peak YCiE 266 394 128 0.68 oration data for Napier (Table 1) were used for all 18 Hastings Recent (YCiE) 235 384 149 0.61 calculations. Evaporation is much more uniform surpluses in winter and the highest deficits in sum over large areas than is rainfall, and it is assumed mer. The seasonal surpluses show a greater degree of separation of the groups than the seasonal def *YBP=Yellow-brown pumice soil YBL=ycllow-brown loam YBE=yellow-brown earth YGE=ycllow-grcy earth that the evaporation rate at Napier represents that YGE-YBE=intergradc between yellow-grey earth and yellow-brown earth of Hawke's Bay. icits. especially between the yellow-grey earths and the intergrades between yellow-grey earths and tSurplus minus deficit Moisture deficits were calculated for the months yellow-brown earths. where evaporation exceeds rainfall by subtracting /;: /3 4 + 600-I I I / 5 ------8 7 +5001 11////~ 14 9 +400~ I I I ////./ ~ 13_10 11 / / / / / / / ./ ./ .,,,,....,,,------15 sE cg -i-300 e- :::J (j) +200 +100 N N 0 - Soil group Station No. -100-I '-....."'"'~ ~~ ~" podzolised 1-3 soils E s I ~~~ YBE 4-8 -u -200 ~ YGE-YBE 9-15 0 YGE 16-18 -300 ~14 -400 I· I I I I I ~17I I I I I I I I SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT Fi~ure l Curnulatin~ dcllcits and surpluses (mean monthly in mm) +600 +500-1 Soil group Station No. 4 podzolised 1-3 soils Ill ~5 ~ +4001 YBE 4-8 YGE-YBE 9-15 %+3001 YGE 16-18 8 .... I I I // ~7 :::J (j) +200 I I II I/ / 9 11 t..l / // // / .,,,...,------___ I."'!.~,...... ,., +100 I 0 15 -100 E s -200 -<:i ~ 0 -300 -4oo:i;;;:----;:J;;--~~-;;-~~;;-~-;;r.;-~---;~~~;=r:~==~~=--;:::-:;-~~~~~,-~~--.~~~~~-sEP OCT NOV DEC JAN FEB ~MAR APR MAY JUN JUL AUG SEP OCT Figure 2 Annual water balance (mean monthly in mm) 24 25 In Fig. 2 the annual wa_te~ balanc_e is shown .on show that soil moisture levels and leaching have a a monthly basis. When this 1s used m conjunction more important bearing than seasonal dryness on with Table 2 it can be seen that alth~mgh at most soil distribution. of the sites there is an overall surplus, m the yello":"' KEY grey earths there appears to ~e an overall deficit. However, potential evaporation (Penman) figures used in the calculations assume that water evapo CONCLUSIONS li[~:i'.111 Yellow-grey earth~ rates constantly at potential rates until all soil The data in Table 2 and Fig. 2 show that there moisture is completely gone. whereas it is known ii Yellow-grey earth intergrades to yellow-brown earths that actual evaporation decreases as soil moisture is a reasonably good correlation between soil groups decreases; actual evaporation is therefore much less and the mean annual moisture deficit or surplus. than potential. The yellow-grey carths do have a Where there is an annual deficit the yellow-grey • Yellow-grey earth-related steepland soils surplus in the 'wet' season as can be seen in Fig. earth soils are found. As the mean annual surplus l. increases, the following sequence of soils occurs: < 200 mm intergrades between yellow-grey The annual water balance gives the best sepa earths and yellow-brown earths ration, as is shown on the right-hand side of Fig. 2 200-600 mm light yellow-brown earths and in Table 2. These annual surpluses represent > 600 mm podzolization the excess water in the system and, therefore, the amount of water available for leaching. The groups These data suggest that the surplus water in the are clearly separated by this means which may well system may have a major influence on the type of soil developed. NORTH ISLAND NEW ZEALAND DISTRIBUTION AND DESCRIPTION OF YELLOW-GREY EARTHS IN THE WAIRARAPA K.W. Vincent, Soil Bureau, D.S.I.R., Lower Hutt (Received January 1983) t INTRODUCTION the mountain ranges. Hence there is a strong oro graphic effect and the rainfall distribution shows Regions of the Wairarapa where yellow-grey some steep gradients. earths occur have been scantily covered by soil sur . Scale 1: 1000000 vey publications. Apart from the 'General Survey On the peaks of the Tararua Range the annual of the Soils of North Island, New Zealand' (N.Z. rainfall is probably as high as 6000 mm. To the east t Soil Bureau 1954) and 'Soils of New Zealand' (N.Z. of the ranges the annual rainfall falls somewhat Soil Bureau l 968b), the only publications are the suddenly to a lowest value of 706 mm near Mar 'Soil Map of Whareama Catchment' (Gibbs 1965) tinborough, but increases again to about 1200 mm which covers an area of steepland soils, and the towards the east coast. Figure 1 Map showing distribution of yellow-grey earths and related soils in the Wairarapa Region (from 'Soil Map of the North 'Interim Report on Soils of Wairarapa Valley' Island. New Zealand'. N.Z. Soil Bureau I 968b) (Heine 1975). DISTRIBUTION OF YELLOW-GREY EARTHS IN THE WAIRARAPA CLIMATE OF THE WAIRARAPA (summarised from Thompson 1982) The yellow-grey earths, together with the inter grades between yellow-grey earths and yellow-brown ing land, to the east. These land forms are consid DESCRIPTION OF YELLOW-GREY EARTHS The Wairarapa is notable both for its windiness, earths, and associated steepland soils, occur on the ered to represent remnants of erosion cycles of IN THE W AIRARAPA especially in summer when dry north-west winds eastern side of the main valley and on the eastern Probable late Pleistocene age. The soils are become Fohn-like and induce drought, and also for hill country (Fig. 1) . This distribution corresponds developed dominantly in loess and are between 1 m Heine (1975) notes that yellow-grey earths are its rainfall, most of which tends to occur when the to the area of low annual rainfall (750-1200 mm). and 2 m deep. On the Eastern Hills, however, the characterised by the presence of compact claypans surface winds are southerly. soils tend to be 'more like yellow-grey earths if they Heine ( 1975) refers to two main areas of distri in the subsoils, and continues 'In the Wairarapa, The prevailing winds of the Wairarapa are south bution of yellow-grey earths: (I) The Central Plain have sandy parent materials and occur on rolling yellow-grey earths can be subdivided into soils with slopes'. The distribution of yellow-grey earths westerlies and north-westerlies which occur as a and (2) the Eastern Hills. Yellow-grey earths of the a less distinct claypan in areas receiving 1140- throughout the Eastern Hills therefore tends to be result of deflection of the westerly airstream around Central Plain occur on river terraces and undulat- 890 mm rain and soils with a distinct dense clay Patchy. pan in the 890-760 mm rainfall zone'. 26 27 SUMMARIES OF FOUR REPRESENTATIVE SOIL loess over siltstone. PROFILES 18 cm dark greyish brown silt loam, Wharekaka silt loam. Yellow-grey earth 55 cm pale yellowish brown heavy silt loam with developed in loess. Widespread on the eastern side orange mottling (slightly compact), of the main valley, on dissected river terraces and over yellow siltstone. on undulating, rolling and hill land. Taihape steep/and soils. Steepland soils related to Description generalised from Pollok ( 197 5). intergrades between yellow-grey earths and yellow 20 cm greyish brown and pale brown silt loam; brown earths. Formed in siltstone on steep slopes. fine crumb and medium nut structure, 25 cm very pale brown silty clay loam with 15 cm dark greyish brown silt loam, lntergrades between Yellow-grey brownish yellow and light grey mottles; 30 cm pale yellow silty clay loam with orange earths and Yellow- brown earths coarse prismatic and blocky structure, mottling, and related steepland soils on 20 cm strong brown silty clay loam; coarse plates over yellow siltstone. rolling and hilly land and blocky structure, Hururua steep/and soils. Steepland soils related El 80+ cm light brownish grey to light olive grey silt to intergrades between yellow-grey earths and .hilly and steep land loam with yellowish red mottles: strongly yellow-brown earths. Formed in greywacke and m developed very coarse polygonal structure argillite on steep slopes. (fragipan). 12 cm greyish brown heavy silt loam, The following three descriptions are generalised from Heine (1975). on dull greyish yellow stony clay loam, grad Pirinoa silt loam. Intergrade between yellow-grey ing into pale yellow weathered argillite earth and yellow-brown earth. Occurs on undulat below 50 cm. ing, rolling and hilly land, and is formed in shallow t Upper Hutt N •Lower Hutt DISTRIBUTION OF YELLOW-GREY EARTHS IN THE WELLINGTON REGION Eastbourne J.G. Bruce (Ed.), Soil Bureau, D.S.l.R., Gore (Added to volume February 1983) Intergrades between yellow-grey earths and hilly and steep land - Paremata and Terewhiti soils. yellow-brown earths and their related stcep l ~nd so!ls extend in a narrow coastal strip 2- 3 km wide (Fig. Within the Wellington urban area, Milne and I) from near Paraparaumu southwards to Cape Northey (1974) described the soils in more detail Terewhiti and Sinclair Head and continue north and separated the intergrades between yellow-grey earths and yellow-brown earths into separate soil wards along the south-west side of Port Nicholson Turakirae Head to Thorndon, being widespread over much of Wel mapping uni,ts: lington City. On the eastern side of Port Nicholson Porirua fine sandy loam and hill soils - 0 5 10 km they occur in a similar strip south of Eastbourne developed on sandy loess and colluvium; to Pencarrow Head and along the south coast to Turakirae Head. Further occurrences are on Mana Paremata silt loam and hill soils - developed on Island, a small island on the west coast lying about thin silty loess and colluvium overlying older heavy 8 km offshore from Porirua Harbour, and on Somes textured loess and colluvium; and Figure l Generalised distribution of intergrades between ye ll ow-grey carths a nd yell ow-brown eart hs and related steepland soils in Island in Port Nicholson. In this coastal region, Terewhiti hill soils and steepland soils - !he Well ington Region (after G ibbs 1960) annual rainfall is between about 900 mm and developed on grcywacke. 1000 mm but in places rises to more than 1250 mm. Detailed profile descriptions, as well as chemical The soils of the Wellington District have been and physical analyses, for the reference soils Pori briefly described by Gibbs ( 1960) in which the rua fine sandy loam and Paremata silt loam are intergrades between yellow-grey earths and yellow included in 'Soils of New Zealand' (N.Z. Soil Bureau brown earths are included in soil associations on 1968b). rolling land - Porirua and Pukerua soils. and on 28 29 DISTRIBUTION AND DESCRIPTION OF YELLOW-GREY EARTHS IN NELSON-MARLBOROUGH Q) u Ul l1l Ul .C H QJ OI H I.B. Campbell, Soil Bureau, D.S.I.R., Nelson 0 ·M QJ H .C .µ (Received December 1981) INTRODUCTION consistence, weak or moderate mottling, and sub soils with distinctly heavier textures than the hori The distribution and description of yellow-grey zon above. The soils from loess have a fragipan earths and the associated intergrades in the Nelson which is variable in its development, although it is Marlborough region is known mainly from the work normally massive and hard when dry. The soils of Gibbs and Beggs (1953) from the survey of the from the other materials generally lack a distinctive soils and agriculture of Awatere, Kaikoura. and part fragic horizon. · Marlborough Counties, and from Chittenden et al. ~ At the higher end of the rainfall range (850- Q) (1966) from the description of soils of Waimea 1200 mm), the following soils have been separated: ·-" > County. Additional information on these soils is l1l Loess Sedimentary rocks Greywacke/ Q) also available from particular studies such as those greywacke (/) by Laffan & Cutler (1977a, I 977b), and others. conglomerate i:: s Jordan Kuhutara Waka tu 0 ;::l Q) i:: ·M u Medina Kekerengu Harekeke 0 Ul :> H l1l DISTRIBUTION 'tl Ul ;::l Q) H Mapua 'tl Q) ....-! .µ H Q) ....-! i:: Q) Yellow-grey earths in Nelson-Marlborough are (/) s l1l ·M .µ found chiefly in a large area between the Wairau .-i N These soils differ from the lower rainfall yellow ~ ~ River and Ward, in patches on the coast from Cape grey carths in having somewhat browner or yellow N .µ .µ ~ s Campbell to Kaikoura, in a small strip along the ish brown subsoil colours ~ more distinctive subsoil 'tl ;::l Q) north side of the Wairau River, and in a small mottling, and coarse blocky to prismatic subsoil 0 ·M u 0 > H l1l coastal area between Motueka and Nelson. They structure with firm to very firm (rather than very ~ ;::l Q) H .c 'tl ....-! .µ H occur within the annual rainfall range of about 590 Ul ....-! ....-! i:: Q) firm or hard) consistence. Like the drier yellow-grey .µ to 1200 mm. That their occurrence is closely related earths however, they also have much heavier tex al1l 0 l1l ·M to rainfall is clearly illustrated by their distribution tures in the subsoils than in the upper horizons .µ pattern. For example, in rain-shadow areas, yellow while the soils that arc formed from loess also have d s grey earths occur as thin narrow strips on the lower a distinctive fragipan. Those on parent materials ··M ;::l a) l1l • ·M u surfaces of valleys such as the Clarence and Awa other than loess generally do not have a fragic .µ H :> H l1l ·M Q) ;::l Q) H tere Rivers, while in places such as the north side .µ horizon. H .µ ....-! H '"c: of the Wairau River, where rainfall increases ;::l i:: r-1 i:: Q) 0 H l1l ·M .;.J ::E: ~ abruptly, the transition from yellow-grey earths to · ~ yellow-brown earths occurs over a very narro\\'. '- 0 distance. RECENT YELLOW-GREY EARTJJ STUDIES ~ s io:x: ·Ill d Q) c IN MARLBOROUGH ;::l r1l 0. ~ i:: ;::l H 0 The fragipan has long been regarded as an s ;::l ....-! ~ H Q) ~ 0 0 ,..-1 0 < l1l ,..-1 .µ " However, as illustrated by the comparison of the tau The drier yellow-grey earths (rainfall between soils listed.above. it is characteristic of yellow-grey ·0ii u Ul 0 550-850 mm) can readily be separated from the earths formed from loess. rather than yell,ow-grey Q) 0 ;::l .:i: Ill d § Q) ....-! ..c: wetter yellow-grey earths (intergrades between earths in general. l1l .µ ·M u ·M ....0. H i:: :> l1l '+. 0 yellow-grey earths and yellow-brown earths) on the ·M Q) ;::l H 0 E Recent detailed soil mapping and pedological l1l u ....-! ~ H H '- basis of their morphology. At the lower end of the Q) 0 investigation in the Awatere Valley suggests that ::: Q) ....-! 0 ~ l1l ....-! .µ °' rainfall range are the following soils: the formation of clay-rich horizons might be more 0 0 Loess Stony Sedimentary Greywacke/ diagnostic of soil development under a subhygrous ,..-1 rocks greywacke alluvium moisture regime than development of a fra&ipan. s i:: conglomerate ;::l Q) 0 .µ ·M u In the Awatere Valley, (rainfall 560-800 mm) soil i.:: :> l1l - 'tl development is illustrated by a sequence of soils Q) ;::l H Q) Seddon Renwick Ward Weld u ,..-1 ~ H Ul Q) Woodbank that occurs on the ri vcr terraces (Fig. I). Awatere, Q) ,..-1 0 l1l Sea view Dash wood Flaxbournc ~ l1l ,..-1 .µ Ill Wither Medway Hald on Wairau, Omaka. Muritai and Dashwood series are soils formed from alluvium of various ages ( < 10 e, I I Sedge mere Leader_ 0 0 - c. 12 OOO years). Progressive soil dt!velopment Uo 0 0 Wharanui N c.o occurs in these soils as illustrated by the soil hori <1' "" They are characterised by pale (olive dominanO zon descriptions given in Fig. I. In these young and colours, coarse structures, very firm to hard subsoil dominantly ' coarse . t~xtured soils, the accµmulation 30 JI of clay as films on peds and stones is a feature which distinct and progressive increase within the profiles Table 1 Results of particle size analyses for soils on a terrace sequence in Awatere Valley (continued) can be seen developing progressively (along with from the youngest to the oldest soils with Seaview, horizon segregation, development of structure, etc.) Sedgemere and Jordan soils showing marked bulged Soil type to the point where, in the Dashwood soil, the pro- texture profile forms (Cutler 1981). The fine clay Lab. No. Horizon Depth Sand % Silt% Clay% Fine Fine/ portion of clay is such that gravel is cemented and values (Fig. 5) show the clay bulge even more (cm) 2-0.05 0.05- < 0.002 clay% Total clearly, with the sharp decline in the lower part of 0.002 < 0.0002 clay forms a discrete horizon. Seddon, Seaview, Sed- (mm) gemere and Jordan series represent further stages the profile occurring at the top of the fragipan. in soil development (c. 12 OOO - c. 20 OOO years+) Dashwood moderately deep silt loam SB9378A A 0-18 26 41 33 14 0.42 but an important difference is that these soils, which B AB 18-28 27 41 32 have well developed profiles, are formed from loess 12 0.38 SUMMARY c B, 28-51 38 38 24 8 0.33 rather than gravels. Seddon series is the youngest D B, 51-78 75 14 11 4 0.36 of the loessial soils. Although the subsoil is corn- E B11 78-100 84 7 9 3 0.33 Soil development is accompanied by distinct F pact and tending to massive, it lacks a distinctive Bic 100-125 90 4 6 3 0.50 profile texture changes with decreases in sand and Seddon silt loam fragipan. Clay movement and accummulation SB9287A A 0-20 18 62 20 11.6 0.49 increases in clay and silt. B B11 20-36 19 through the lower horizon is, however, quite evi- 63 18 9.3 0.48 c B,_, 36-50 22 61 17 8.2 0.48 dent in the field. Seaview, Sedgemere and Jordan Where a fragipan is absent or weakly developed, D B, 50-60 30 53 17 8.1 0.51 series occur on successively higher surfaces. It is clay passes into and may accumulate in deeper E 60-76 39 47 14 6.2 0.45 possible that in these soils the loess includes some horizons in the profile, but where one is present F B11 76-90 53 37 10 4.5 0.43 later thin accumulations. The lower horizons, how- clay accumulates in horizons above it, forming dis- G Bic 90-110 69 20 11 3.1 0.52 H c I 110-140+ 64 28 8 3.5 0.71 ever, clearly show incremental development of the tinctive clay-rich horizons. On the oldest surfaces Seddon tine sandy loam SB9385A fragipan, mottled and clay rich horizons. A11 0-25 26 48 26 10 0.38 there may be up to 45% clay in some B horizons. B A,, 25-37 25 45 30 14 0.47 Even in younger coarse textured soils formed from c AB 37-48 Results of particle size analyses are given in Table 25 46 29 14 0.48 alluvium (i.e. Dashwood) the trend is apparent. D B11 ·48-71 23 50 27 12 0.44 1 and the particle size differences for sand, silt, and Heavy B horizon textures of other soils with dif- E B,, 71-92 20 54 26 9 0.35 clay, and fine clay are illustrated in Figs. 2-5. Figure F B,,f 92-120 24 49 ferent parent materials (i.e. Flaxbourne and Ward 27 12 0.44 2 shows that there is a steady decrease in the G B, 120-134 22 53 25 11 0.44 soils from Tertiary sedimentary rocks, Gibbs & Seddon silt loam (2) amount of sand in the soils from the youngest SB9384A A I 0-21 20 53 27 II 0.41 Beggs 1953) indicate the same distinctive pedo- (Awatere-Wairau) through to the oldest soils (Sed- B B11 21-37 19 54 27 12 0.44 logical trend and show that marked clay accumu- c B,, 37-54 17 gemere-Jordan). In the older soils lowest amounts 55 28 13 0.46 lation is not confined to soils from alluvium or D B,,, 54-77 16 56 28 II 0.39 of sand are in the Bw, Bg and Bgt horizons and the loess. In the Nelson-Marlborough region, therefore, E B,,, 77-110 sand % increases in the lower horizons of these pro- F B, 110-135+ 24 50 26 12 0.46 the formation of a clay rich or argillic horizon may Scavicw sill loam files. The silt fraction increases through the sequence SB9533A A, 0-23 15 56 29 12 0.41 provide a useful expression of pedogenesis under a B AH 23-27 13 57 and in the older soils tends to be in similar amounts subhygrous moisture regime. 30 15 0.51 down the profile. The total clay (Fig. 4) shows a c BW, 27-47 16 56 28 13 0.46 [) BW,, 47-62 II 54 35 20 0.57 E BW,, 62-96 10 53 37 22 0.59 F BW,, 96-122 10 57 33 18 0.55 G BX, 122-144 14 58 28 12 0.43 H BX, 144-165 24 54 22 11 0.50 Results of particle size analyses for soils on a terrace sequence in Awatere Valley I BW, 175-190 48 40 12 7 0.58 Table 1 Scdgcmcre silt loam SB9J83A A 0-21 13 57 30 14 0.47 B B11 21-31 14 57 29 13 0.45 Soil type Lab. No. Horizon Depth Sand % Silt% Clay% Fine Fine/ c B,, 31-47 13 54 33 17 0.52 (cm) 2-0.05 0.05- <0.002 clay% Total D B,,, 47-76 11 51 38 23 0.51 0.002 < 0.0002 clay E B.,,, 76-106 10 53 37 21 0.57 (mm) F B,,, 106-109 16 53 31 19 0.61 G B,.. 109-110 23 55 22 7 0.32 H B, 110-120+ 27 55 18 4 0.22 A watere loamy sand SB9373A (A) 0-8 47 39 14 Jordan silt loam SB9386A A, 0-15 10 62 28 14 0.50 B C, 10-25 50 48 2 B B, 15-53 10 63 27 10 0.37 C21 35-45 88 9 3 c c B,, 33-47 6 54 40 23 0.58 D C22 55-65 87 8 5 D B,, 47-68 6 48 46 29 0.63 Wairau loamy sand SB9372A A 0-15 51 44 5 E B." 68-92 7 49 44 27 0.61 B 15-30 52 39 9 F B,,,, 92-110 7 51 42 24 0.57 c B, 35-50 66 28 6 G B, 110-112 11 42 47 32 0.68 D C, 70-85 90 8 2 Omaka fine sandy loam SB9374A A 0-15 34 42 24 12 0.50 B B, 20-30 33 45 22 11 0.50 c B" 35-50 34 49 17 5 0.29 D B32 55-80 47 35 18 3 0.17 E c, 85-108 81 12 7 2 0.29 Muritai fine sandy loam SB9375A A 0-15 33 42 25 12 0.48 B B11 20-30 37 39 24 11 0.46 c B,2 35-45 48 30 22 9 0.41 D B3, 50-60 69 20 11 4 0.36 E· B32 70-90 80 12 8 3 0.38 F C, 90-120 85 6 9 1 0.11 Dashwood fine clay SB9288A A 0-18 23 54 23 10.7 0.46 B B11 18-36 25 51 24 12.4 0.51 c B,2 36-58 29 46 25 8.2 0.50 D B21 58-82 81 10 9 3.8 0.60 E B22 82-100+ 81 7 12 5.6 0.72 0 /o Sand 32 '/.,Silt 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 25 30 35 33 s d 20 20 DISTRIBUTION OF YELLOW-GREY EARTHS AND ASSOCIATED SOILS IN CANTERBURY AND UPPER WAITAKI BASIN 40 40 T.H. Webb Soil Bureau, D.S.I.R., Lincoln and E.J.B. Cutler, Soil Science Department, Lincoln College (Received March 1982) 60 60 INTRODUCTION 60 However, the term yellow-grey earth should strictly w 60 be confined to soils in which fragipans, or subsoils Yellow-grey earths and associated yellow-brown of high density and coarse structure, occur (Taylor shallow and stony soils occur over extensive areas & Pohlen 1979). The associated soils from collu 100 100 (almost 1 million ha) of the sub-humid downlands vium on hilly and steep land cover a range of soils and plains of eastern Canterbury. They extend from yellow-grey earths (sensu strictu) developed g d inland from the coast to the foothills where they 120 from silty parent materials tci shallow and skeletal 120 grade into yellow-brown earths. Extensive areas also soils which lack 'fragic' properties and mottle char s s occur in the drier parts of the Upper Waitaki Basin. acteristics. Some of these soils, particularly those For convenience this report includes the soils of 140 on older landforms, increase in clay content with 140 Otago which occur in the Upper Waitaki Basin, west depth, reflecting clay illuviation and/or composite of Duntroon. parent materials. Some have B or C horizons of high density but these cannot be considered to be 160 160 The group is divided into four sub-groups based on soil moisture regime and associated pro fragipans. Few of the associated steepland soils are file characteristics viz.: dry subhygrous subgam yellow-grey earths; most arc either intergrades between yellow-grey earths and skeletal soils or are 180 160 mate yellow-grey earths which are free from v mottling or only weakly mottled; subhygrous gam skeletal soils (with variable amounts ofilluvial clay). The soils from shallow and stony alluvium are Depth (cm) Depth (cm) mate yellow-grey earths with weakly to moderately developed mottling; dry hygrous gammate yellow mainly formed from late Pleistocene outwash grey earths with weakly to moderately developed deposits and do not conform to the yellow-grey mottling; dry hygrous gammate to net gammate earth concept. They do not have fragipans, do not 0 show evidence of perched gley features, and gener /o Clay "/., Fine Clay yellow-grey earths with moderately to strongly 5 10 15 20 25 30 ally have chemical features similar to yellow-brown 0 developed reticulate mottling. Each of these ,.-~-5'--~~10L--~J15~~2~0~~2~5~~3~0~--l35 subgroups may be further subdivided on the basis earths. They are classified as yellow-brown shallow of parent material into soils formed from deep fine and stony soils associated with yellow-grey earths. 20 textured deposits (in situ loess, fine textured allu Approximate areas and some trends in soil prop 20 vium or Tertiary material), soils from colluvium, erties and processes of these subgroups are given and soils from shallow or stony deposits (Table I). in Table I. 40 40 60 60 g Table 1 Areas (ha) (from Long 1966) and soil property trends of yellow-grey carths in Canterbury. (The area of dry subhygrous soils includes that part of the upper Waitaki Basin which extends into Otago) 60 Parent material Soil moisture class Total area Dry subhygrous Subhygrous Dry hygrous 100 100 m Deep fine deposits 85 OOO 95 OOO 205 OOO 385 OOO d Colluvium 140 OOO 60000 190 OOO 390 OOO 120 120 Shallow and stony 46 OOO 280 OOO 326 OOO KEY Total 271 OOO 435 OOO 395 OOO I IOI OOO Rainfall (mm) < 550 550-700 650-900 140 w Wairau 140 Natural drainage* well imperfect poor a Awatere o Omaka Gammation* subgammate gammate net gammate m Muritai 160 160 Natural nutrient status d Dashwood Organic matter accumulation s Seddon v Seav1ew Clay illuviation 180 g Sedgemere 180 I Jordan *Applies to soils from deep fine parent material and lo a lesser extent to colluvial deposits Depth (cm) Depth (cm) Figure 2-5 Particle size difkrcnccs for sand. silt. clay and line clay (rcspccli\'l'iy) for soils on a terrace sequence in Awatere Valley 34 35 DRY SUBHYGROUS YELLOW-GREY SUBHYGROUS YELLOW-GREY EARTHS EARTHS are of limited extent and mainly occur on rolling fragipan occurs deeper in the profile and commonly These soils occur under rainfalls of 550-700 mm downs and terraces at the base of the foothills. South has a net gammate mottle pattern. Subsoil textures These soils occur where rainfall is less than per annum and occupy 435 OOO ha, of which about of Orari River they occur in a large block of rolling are commonly clay loams. Soils formed on coarser 550 mm per annum, and are largely confined to the 2/J arc associated yellow-brown shallow and stony to hilly land with associated fans at the base of the textured sediments or soils from colluvium have south and east of the upper Waitaki Basin, the Wai soils. steep land and, in places, extend to the coast. South better natural drainage and are less gleyed, and are taki Valley and the lower part of the Hakataramea of the Rangitata River, steepland units occur in only weakly gammate. Steepland soils are very Soils derived from greywacke loess and their Valley. The Grampian set. previously recognised as inland valleys where a rainshadow effect occurs extensive in the dry hygrous zone, particularly in associated soils from colluvium on hilly slopes are a brown-grey earth (N.Z. Soil Bureau l 968a), is now between mountain ranges. the north, and occupy over I 00 OOO ha. Profiles are mainly confined to downlands. (A small area considered to consist mainly of yellow-grey earths generally shallow gravelly silt loams with weakly ( 16 OOO ha) occurs on fans and terraces where deeper This subgroup is characterised by more inten and the Dalgety and Mackenzie sets, previously weathered angular fragments of greywacke through alluvium or loess have accumulated). In the south, sive gleying than in the subhygrous zone and the recognised as yellow-brown earths, are now consid out the profile, and are only weakly mottled. large areas are mapped to the west of Morven, in ered to be yellow-brown shallow and stony soils the upper Hakataramea Valley and to the west of associated with yellow-grey earths. Timaru. In the north, most units occur on low-lying Soils formed from in situ loess cover about downland within a triangle between Amberley, 85 OOO ha, occur on terraces and fans, and have Harwarden and Cheviot. A considerable area also morphology which mainly varies with the texture occurs on the lower slopes of Banks Peninsula. of the loess mantle. Where loess has a high pro Principal profile characteristics of this subgroup are portion of fine sand, profiles lack a fragipan but silt loam topsails with nut or crumb structure over have distinct clay bands, usually below 60 cm, and lying a pale yellowish brown worm-mixed horizon DISTRIBUTION AND DESCRIPTION OF YELLOW-GREY EARTHS IN NORTH have very friable weak crumb structure above the often with small iron nodules and weak mottling. OTAGO clay accumulation. Where texture is more silty a This horizon rests on compact silt loam with coarse dense fragipan is formed below 30-60 cm. Water prismatic structure and with prominent grey veins F.G. Beecroft, Soil Bureau, D.S.I.R., Dunedin commonly perches over the pan for short periods. (weakly to moderately gammate fragipan up to I m Distinct clay skins occur within, or just above, the thick). Profiles vary from the modal profile accord (Received November 19112) fragipan and flecks of CaCO, commonly occur ing to texture, topography and drainage. For within or below the fragipan. instance, the Waipara set has paler subsoil colours and shows an increase in clay down the profile while INTRODUCTION YELLOW-GREY EARTHS WITH A DRY Associated yellow-brown shallow and stony soils the Takahe set, in coarser loess, has weaker SUBHYGROUS MOISTURE REGIME cover about 46 OOO ha terraces and fans mainly in development of subsoil structure. Where the loess The North Otago region is bounded on the north the upper Waitaki Basin. Morphology mainly var cover is thin and underlying sediments form part by the Waitaki River and on the south by Macraes Otiake soils (5625 ha) and Struan soils (160 ha) ies with age of soil development, with older soils of the soil, gammate features may be absent or only Flat, the Kakanui Mountains and the Hawkdun and occur along the southern bank of the Waitaki River having greater subsoil clay accumulation. The weakly developed. Soils from colluvium are formed St Bathans Ranges. The western boundary is formed and up contributary streams between Kurow and Mackenzie set has very sandy, and often very stony, from a mixture of erosion deposits derived from by the Lindis Pass and the Benmore Ranges, and Duntroon. They also occur to a limited extent texture and has very weak structure and negligible loess and underlying rock. Profiles have varying the eastern by the Otago coast. around Lake Waitaki and Awahokomo Creek. clay accumulation. Soils on older surfaces (Dalgety amounts of stones and gravels and morphology can Yellow-grey earths in the region (Fig. I) formed The soils are formed on terraces and fans from and Struan sets) have silt loam textures and well be quite variable. Generally profiles have more developed clay pans within the gravels. under tussock grassland or forests, on loess and/or a thin cover of loess over greywacke gravels and, weakly developed structure, less mottling and weakly consolidated fine textured sedimentary in rare cases, sandstone. They contain a moderately Soils developed from slope deposits cover about weaker fragipan development than the modal pro rocks. The sediments are predominantly loess allu to strongly developed subgammate fragipan at 30 140 OOO ha and occur on hilly and steep slopes on file from in situ loess. vium, and slope deposits; but also include marine to 50 cm. The depth and development of the fra the east and south of the upper Waitaki Basin, in Yell ow-brown shallow and stony soils occupy sandstones, siltstones and mudstones. Rainfall gipan is dependent on the depth of loess. the Waitaki Valley and on the east of the Haka ranges from 500 mm to l OOO mm per year. At the 280 OOO ha, most of which occur on the extensive Kurow soils (275 ha) and Kurow hill soils taramea Valley. The Omarama steepland set has plains of central Canterbury between Ashley River drier end of the rainfall range yellow-grey earths also been mapped under higher rainfall in the merge with brown-grey earths whilst at the wetter (5585 ha) occur south of the Waitaki River between in the north and Orari River in the south. Large Lake Waitaki township and Basalt Hill at altitudes vicinity of Lakes Ohau, Pukaki and Tckapo and in areas also occur in the Culverden Basin in the north end yellow-grey earths are usually separated from the Rangitata Valley. The inclusion of these soils yellow-brown earths by intergrades between yellow of 300 to 600 m. These soils are formed on easy and in the Morven-Glenavy area in the south. The rolling to rolling downlands from thick loess on in the Omarama set is presumably based upon their morphological and chemical properties of these soils grey earths and yellow-brown earths. In this dis very low water holding capacity and high surface cussion, the drier intergrades have been included greywacke gravels and sandstone. They have little resemble yellow-brown earths. They are friable with or no mottling above a moderately developed runoff which induce summer draughtiness. How nut and crumb structure throughout and overlie in the yellow-grey earths as a hygrous group. ever, higher rainfall will make these soils more subgammate fragipan. Subsoils are compact, espe sandy gravels. Base saturation decreases with depth, North Otago contains over 230 OOO ha (c. 6.5%) cially at the contact with underlying gravels. leached, and more frequent summer rainfall allows the soils have relatively high Ca/Mg ratios, low greater plant growth than in drier regions. of the Otago region's yellow-grey earths. The dis exchangeable Na and a slight maximum of oxalate tribution pattern is complex and reflects the inter Meyer soils ( 160 ha) occupy a small area of easy Landforms mapped in this subgroup are com soluble Fe and Al in subsoil horizons. action of a wide soil moisture range on different rolling downland south of Mount Horrible. They monly exposed to the drying influence of north-west parent materials and varied landforms. Yellow-grey are developed on thin loess over greywacke. Meyer winds. The soils are formed from stony slope earths are subdivided on the basis of four moisture hill soils (13 350 ha) occur mainly between Ote deposits with a thin cover of loess in places. Pro matata and Corbies Rock and south of the Waitaki DRY HYGROUS YELLOW-GREY EARTHS classes: dry subhygrous, subhygrous, dry hygrous files range from near skeletal soils on sites where and hygrous (Taylor & Pohlen 1979). The distri River between Lake Waitaki Settlement and Kurow, the soil mantle is unstable or eroded to weakly and bution and properties of each soil is at the soil set with smaller areas between Manuku Creek, little moderately developed yellow-grey earths on gently These soils occur under rainfalls of 650-900 mm Omarama Stream and the Ewe and Wether Ranges. per annum and occupy 395 OOO ha. North of Ash level (as described in N.Z. Soil Bureau I 968a). sloping ridge crests or toeslopes. Most areas have Yell ow-grey earths in the North Otago region are They form a complex mosiac of soils on strongly suffered widespread wind and sheet erosion, par ley River, large areas occur on all landforms from rolling to hilly land where loess deposition has been fans and terraces to steep land, and extend from described in more detail in 'Soils of the Downs and ticularly during periods of high rabbit infestation. Plains of Canterbury and North Otago, N.Z. (Kear of variable thickness. Both soils have similar pro the coast to the foothills where they reach altitudes file morphology with thin subgammate fragipans at of750 m. Between the Ashley and Orari Rivers they et al. 1967) and 'Soils of the Waitaki Plains' and 'Oamaru-Ngapara Downlands N.Z.' (Wilson et al. 30 to 50 cm that vary in depth and thickness depending on the thickness of the loess deposits. in prep.). 36 37 Omarama steepland soils (44 850 ha) occur from soils are formed from weakly weathered sandy tex the Waitaki River to the hydro-electric power lakes; tured loess over sandstone. Both soils are weakly and along the sides of the Wether, Hawkdun and to moderately leached and weakly clay illuvial. St Marys Ranges, north-west of Kurow. Subsurface horizons are compact and an incipient fragipan has developed. The soils have developed from a thin veneer of loess and greywacke colluvium over greywacke. In Taiko soils ( 1400 ha) and Taiko hill soils most localities the soil is degrading and shows few (2600 ha) occur at elevations between 120 and yellow-grey earth features. However, incipient fra 250 m from Airedale to Kia Ora and the Otekaieke gipans or compact subsurface horizons occur on River in the Georgetown - Ngapara area. They have some hilly and steep slopes where colluvium or formed on easy rolling, rolling and hilly slopes. The deeper loess has accumulated. soils are developed in shallow fine sandy loess over strongly weathered greywacke gravel, or from loess gravel colluvium. Both soils lack fragipan develop ment but are moderately to strongly compact in the YELLOW-GREY EARTHS WITH A C horizons. SUBHYGROUS MOISTURE REGIME Pukeuri soils (7350 ha) occur along the coast from 15 km north of Oamaru and spread inland YELLOW-GREY EARTHS WITH A DRY near Georgetown. HYGROUS MOISTURE REGIME They are formed in deep loess and interbedded Wakanui soils (850 ha) occur on flat to undulat marl and sandstone on flat to gently undulating ter ing terraces and fans near Waiareka Stream and the races and sloping fans. Pukeuri soils are weakly clay adjacent areas between the townships of Ngapara illuvial and are weakly to moderately mottled above and Totara. Most of these soils are located in infilled a subgammate fragipan which occurs at depths of channels and poorly drained depressions around the 30-60 cm. toes of fans. They are developed from shallow silty Timaru soils (6000 ha) and Timaru hill soils textured loess overlying loess alluvium, are weakly (./') leached and have an incipient fragipan. z (3900 ha) occur below 150 m between Pukeuri E <( >- Junction, Kakanui Point and Otekaieke. They are _;,(. ....J Waitohi soils (300 ha) occur in several small (./) u...... J formed in deep moderately argillised silt textured t: I areas from north of the Shag River to Katiki and z 0 loess (Wilson et al. in prep.) on easy rolling, rolling Trotters Gorge. They are formed from deep silty ::::> z 0 and hilly land. Timaru soils are weakly clay illuvial <( textured loess on flat to gently sloping terraces and g z 0 and weakly mottled above a gammate fragipan. (./') <( >- fans. I lJ.J z Erosion on steeper slopes has produced truncated Cl. lJ.J Where erosion has been extensive, greywacke grav and have strong mottles above a fragipan which 39N'v'CI NOlSll>lt!l>I !l'...... lo lJ.J 0 lJ.J ..... els outcrop near the surface. develops from 35-65 cm from the surface. Subsoil i75 ..... ~u (./') colour patterns are gammate to net gammate . > 11 7 50 I Ngapara soils ( ha) occur between Pukeuri Cl. 0- a:: "' Junction, Kakanui Point and Otckaickc. Below Claremont soils (23 OOO ha) and Opuha soils 0<.v 150 m these soils have developed on easy rolling (7100 ha) occur on downlands between Livingstone and rolling land, but above 150 m they arc restricted and the Waianakarua River mouth and up to 6 km t 0 ~ O!J to rolling interfluves. Ngapara hill soils (3300 ha) inland from the coast between Kakaho Creek and 6"" generally occur above 150 m between Airedale, Kia Moeraki Point. Smaller areas are located along the Ora and the Otekaieke River. They have developed Shag River from Shingly Creek to Shag Point and .:::,~ ~ ~ z0 on moderately sloping terraces, edges and hill at Palmerston. These soils are developed from thick, ~ c:: slopes. Both Ngapara soils and Ngapara hill soils silt loam textured loess over greywacke gravels on ~~ Cl) (./') are developed on deep fine sandy loess over soft easy rolling to rolling downlands. Both soils are UJ ::> ..c:"' Cl) t: sandstones and siltstones. The soils are weakly similar and exhibit gammate colour patterns and Cl) 0 (./') Tengawai steepland soils (20 200 ha) develop Karitane hill soils ( 1450 ha) occur at elevations above 200 m elevation between the east break of between 300 and 450 m north of the Shag River 2. Yellow-grey earths restricted to Western Cen or sandy loams, but small areas of shallow, stony, the Awakino River and the Maerewhenua River. from Shingle Creek to Waihemo. They have tral Otago or poorly drained phases may also occur. They also occur above 300 m near Kurow. Otaike, developed from calcareous sandstone with a thin and Otekaieke Rivers, south of Shag River. The discontinuous cover of loess. 3. Yellow-grey earths restricted to Southern and Subsoil colour patterns are subgammate and have soils are formed on stony slope deposits of collu Eastern Central Otago. weakly developed fragipans which commence vial loess, schist and greywacke, although in some Mass movement is common and hill slopes often between 30 and 50 cm depth. Shallow or eroded exhibit slumping or earthflow erosion. Conse Eighty percent of the region's yellow-grey earths places loess has accumulated on the surface. Most occur in a dry subhydrous moisture regime. Of the phases have fragipans at or near the soil surface. soils have stony silt loam or stony heavy silt loam quently soil development has been inhibited and Subsurface ho~izons are often firm and compact, the soils are shallow. Typical yellow-grey earth fea remainder, 2% are subhydrous and 18% dry textures and firm or very firm subsurface horizons. hydrous. Soils have developed on three major phy and may contain a cemented layer of gravels at the tures are therefore only weakly expressed or absent. interface of fine and coarse material. Soils lack a fragipan or mottling but subsurface siographic units: horizons are firm to very firm. Cluden soils ( 11 600 ha) occur at the northern YELLOW-GREY EARTHS WITH A l. Terraces and fans end of the Strath Taieri Valley and along the Abbotsford hill soils ( 1100 ha) have developed western side of the Manuherikia Valley, where they HYGROUS MOISTURE REGIME 2. Rolling and hilly country from shallow silty textured loess over mudstone. are formed on high smooth fan remnants with They occur on Moeraki Point, near Puketapu east Kakahu soils (6700 ha) occur on rolling down 3. Steepland gently sloping surfaces. The fans are formed from of Palmerston and at Watkins Creek. The uncon lands at elevations between 450 and 620 m from soliftuction material, rewashed tertiary sediments solidated parent material is characteristically The geographic distributions of soil moisture Danseys Pass township to Little Table Hill. The and gravels overlain by thin (usually less than slumped and consequently Abbotsford hill soils lack regimes and physiographic units are illustrated in soils are developed from silt loam textured loess 20 cm) silty to fine sandy loess, creating a mosiac much of the profile morphology typical of deep Fig. l and 2. over greywacke and greywacke gravels. Most soils of soils from loess and/or alluvium. loessial yellow-grey earths. These soils have few develop a zone of strong mottling over the fragi Detailed descriptions of yellow-grey earths in weak mottles in the subsoil and firm to very firm Topsoils are very dark greyish brown with pan. In shallow profiles the fragipan is absent but Central Otago are available in a number of Soil subsurface horizons. medium and fine nut structures. Subsoils are olive compact subsurface horizons are common. Kakahu Bureau Bulletins and Reports (McCraw 1964, grey and contain weak to moderately developed hill soils (22 200 ha) occur at elevations between Warepa soils (1500 ha) occur between Stony Leamy & Saunders 1967. Leamy & Wilde 1972. fragipans commencing between 30 and 50 cm. 450 and 600 m north of Morrison from Trotters Creek and Pleasant River rising from the coast to Hewitt 1978, Beecroft in prep). In this general Mottling and subgammate colour patterns are com Gorge settlement to the south branch of the Waian 150 m around Mt Royal. They are developed on account however, the soil names used are those of mon, especially in finer textured soils. Reddish akarua River, and from the south branch of the deep loess on undulating to rolling land. The soils the soil sets in the 'General Survey of the Soils of brown clay accumulations develop in the under Maerewhenua River to Fern Hill. They have shal are moderately gleyed and have strongly mottled South Island, New Zealand' (N.Z. Soil Bureau lying gravels. lower profiles than Kakahu soils and often contain subsoil horizons over a gammate to net gammate l 968a). abundant fragments of greywacke in the subsoil. fragipan. Erosion can expose the fragipans which are often near the surface. Soils on undulating and easy rolling land YELLOW-GREY EARTHS OCCURRING Naseby soils ( 16 OOO ha) were formerly thought THROUGHOUT CENTRAL OT AGO to occur in a dry hygrous soil moisture regime (N.Z. Soil Bureau l 968a). However, subsequent surveys Nine soil sets occur extensively throughout Cen and average rainfall data recorded by the Otago tral Otago and account for 65% of the region's Catchment Board place these soils in the dry sub yellow-grey earths. They occur in the dry-subhy hygrous soil moisture regime. drous moisture regime and are developed predom inantly on loess over weathered in situ schist or on Naseby soils occur at the extreme northern ends a mixture ofloess and schist colluvium or alluvium/ of the Maniototo and Manuherikia Valleys, between DISTRIBUTION AND DESCRIPTION OF YELLOW-GREY EARTHS IN the Maniototo and Ida Valleys and on the western side of the Cardrona Valley. Parent materials are CENTRAL OT AGO Soils on flat, gently sloping and undulating thin sandy loam textured loess over weathered terraces and fans greywacke gravels and sands of Pliocene and Plies F.G. Beecroft, Soil Bureau, D.S.I.R., Dunedin Middlemarch soils (13 900 ha), Struan soils tocene age (Maori Bottom Gravels). Topsoils are (19 250 ha) and Oturehua soils (I 0 550 ha) are dark greyish brown sandy loams with nut struc (Received November 1982) developed on fluvial deposits and have closely tures, subsoil horizons are compact yellowish brown related properties and distribution patterns. They sandy to sandy clay loams over dark brown, very are closely associated at the northern ends of the firm clay bound gravels and sands. INTRODUCTION This pattern breaks down in the Roxburgh Manuherikia, Maniototo and Ida Valleys. adjacent (southern extreme) and Strath Taieri (eastern to streams flowing from the St Bathans, Hawkdun Yellow-grey earths in Central Otago occupy over extreme) valleys because the modifying influence of and Kakanui Ranges respectively. Middlemarch and Soils on easy rolling, rolling and hilly land 477 OOO ha. Distribution is related to the distinc topography on climate does not continue. The Blue Struan soils occur in association in Strath Taieri. tive climate and topography of the region. The Mountains, Lammerlaw Ranges and Taieri Uplands Middlemarch soils also occur in the Styx Valley Blackstone soils ( 14 500 ha) occur extensively Southern Alps intercept prevailing cyclonic wester have insufficient altitude to shield these valleys near Serpentine Creek and the Taieri River. in the between the Poolburn and Manorburn Dams, adja lies and effectively shelter much of the region from completely from moisture saturated southerly and Maungaweka Valley, on Hawea Flat. near the Lin cent to the Clutha River between Butchers Gully rain-bearing clouds. Within the region the basin and easterly winds which increase rainfall and lower dis River and in the Frankton-Arrow Basin. Struan and Roxburgh, and on the northern flanks of the range topography influences local weather, produc temperatures. Consequently yellow-grey earths soils occur adjacent to the Clutha River Basin Pisa Range. They are developed mainly in 20- ing a climatic catena from semi-arid brown-grey occur on the valley floors and sides of valleys at between Teviot and Ettrick. 30 cm of fine sandy loam textured loess over schist, earths along most valley floors to humid yellow low altitude. The distribution pattern of yellow-grey but loess thickness is usually deeper on south facing brown earths and alpine soils on the crests of earths can be divided into three separate groups: Middlemarch soils are developed on schist loess slopes. Blackstone soils are characterised by very mountain ranges. Between these two extremes, the and alluvium over a mixture of schist and grey dark greyish brown topsoils with strongly developed yellow-grey earths form a band from low to mid I. Yellow-grey earths occurring throughout Cen wacke gravels. whilst Struan and Oturehua soils are nut structures and olive brown subsoils with altitudes encircling most valley systems. tral Otago developed from loess and greywacke alluvium over moderately compact moderately developed nut and greywacke gravels. The soils are mostly developed block structure. Profiles often contain well defined, in moderately deep to deep. free draining silt loams worm mixed AB horizons. 40 41 0makau 9 M norburn eservolf Greenland Reservolf Lake Ons/ow ~ t Lake Mahmerang1 Raes Junction• N 10km ~ Outram• SOIL MOISTURE CLASSES PHYSIOGRAPHIC UNITS / 0 10km 0 DRY SUBHYGROUS TERRACES AND FANS / I I ROUGH 0 SUBHYGROUS ROLLING AND HILLY COUNTRY STEEPLAND ~ DRY HYGROUS SOIL MOISTURE CLASS PHYSIOGRAPHIC UNITS T TERRACES AND FANS 0 DRY SUBHYGROUS A ROLLING AND HILLY COUNTRY Figure l Distribution or yellow-grey earths in Eastern Central Otago s STEEPLAND Figure 2 Distribution of yellow-grey carths in Western Central Otago 42 43 Blackstone hill soils (42 300 ha) are predomi terns. These soils all occur in the dry subhygrous nantly mapped in association with Arrow steepland moisture regime (Fig. 2). formed on deep silt loam textured loess over grey soils. They are one of the most extensive yellow YELLOW-GREY EARTHS RESTRICTED TO wacke gravels. grey earths in Central Otago and occur along the SOUTHERN AND EASTERN CENTRAL Soils on flat, undulating and easy rolling terraces OT AGO sides of all the major valleys. On stable sites pro and fans Profile development includes very dark greyish files are similar to Blackstone soils but have coarser brown topsails over bright yellow heavy silt loam sandy loam textured loess. As slope increases, col Shotover soils (5900 ha) occur below 600 m in Yellow-grey earths restricted to southern and subsoils with nut and blocky structures over luvium dominates the parent material and the soils the Frankton-Arrowtown basin and adjacent to the eastern parts of Central Otago (Fig. I) cover over moderately to strongly developed very firm pris have stony sandy loam textures. Soil depth and tex Kawarau and Shotover Rivers. They have 151 500 ha. This sub-region is characterised by matic structures. Soil colour patterns are gammate ture vary depending on position in the landscape. developed from deep sandy to silt loam textured cooler temperatures and higher effective moistures with some very weak mottling. Fragipan develop loess overlying alluvial gravels and sands from and is sub-divided into dry subhygrous, subhy ment occurs from 30-60 cm. Tiroiti soils (15 450 ha) occur in the Nevis Val schist. Soil characteristics are greyish brown top grous and dry hygrous soil moisture classes. ley; at the northern end of the Manuherikia, Ida, soils with moderately developed granular and Maniototo and Strath Taieri Valleys; and on Taieri crumb structures over olive to pale olive subsoils Soils on steep land Ridge near Horse Burn and Manor Bum. Soils are DRY SUBHYGROUS YELLOW-GREY EARTHS with weakly developed coarse prisms and subgam Spylaw steepland soils (5280 ha) occur west of formed from a thin mantle of fine sandy loam tex mate colour patterns. Subsurface horizons are Soils on easy rolling, rolling and hilly land tured loess on tertiary sediments. In the Upper the Clutha River and at low altitudes between weakly to moderately compact over schist gravels. Manuherikia Valley, Tiroiti soils are found adja Tima soils (4600 ha) occur in the Roxburgh dis Dumbarton and Raes Junction. They are developed cent to the edges of dissected fans where erosion trict, mainly on narrow ridges separated by deep on schist colluvium over weathered schist. Soil profile development includes dark greyish brown has exposed the underlying sediments. Soil profile Soils on easy rolling, rolling and hilly land gullies. They also form an association with Tima silt loam topsails with weak fine crumb structure development is uniform regardless of slope. Stone hill soils between Ettrick and Dumbarton. Tima hill over pale yellowish silt loam subsurface horizons lines are common at the loess sediment contact. Wanaka soils (9750 ha) occur at the northern end soils (7650 ha) are extensive between Roxburgh East with very firm to hard, very coarse prismatic struc Natural drainage is impeded by the underlying of the Upper Clutha Valley between Wanaka and and Minzion Burn. These soils are developed in tures with fragipan development commencing sediments and in many places the soils are easily Hawea and around Lake Wanaka. They are formed deep silt loam or fine sandy loam textured loess waterlogged. Topsoils develop fine nut structures on rolling to strongly rolling moraine deposits of over schist. Soil profile development is character between 60 and 80 cm. Soil colour patterns are gammate with few distinct brown mottles above and subsoils have coarse prismatic structure with unstratified glacial till consisting of schist, grey ised by dark greyish brown topsoils with moderate distinctive mottling and subgammate colour pat wacke and quartz gravels with basalt fragments, in nut structures over pale olive brown to dark brown the fragipan. terns over fragipans commencing between 30 to a matrix of sand and silt. Scattered boulders pro subsoils containing thick firm fragipans which 50 cm. The associated Tiroti hill soils cover trude through thin fine sandy loam textured loess become very hard upon drying. The fragipan is DRY HYGROUS YELLOW-GREY EARTHS 5300 ha. which covers the moraine. penetrated throughout by grass roots, although con Soils on easy rolling, and hilly land Profile development is weak and the soils have centrations of roots still occur down the cracks sur rounding weak subgammate prisms. Subsurface Soils on steep hmd pale colours. Subsoil horizons are weakly to Pukerangi soils (42 650 ha) cover extensive areas moderately compacted with a few clay coatings. layers contain pale oval or lensoidal segregations south and east of Strath Taieri and the Styx Valleys Arrow steepland soils (I 71 OOO ha) are the most Shallow soils contain a sharp boundary between of fine sand which usually contain thin dark brown and between North Rough Ridge and the Manio extensive yellow-grey earths in Otago. Formed at loess and moraine, suggesting post-glacial loess to dark yellowish brown dentritic, vertical and sub toto Plains south of Gimmerbum. Pukerangi Hill low to mid-altitudes on steep sided valleys, gorges deposition. horizontal cutans. soils (22 OOO ha) occur in southern Strath Taieri, and passes, these soils often bridge major valley the Styx Valley and west of Ettrick. Both soils are Shotover hill soils (900 ha) occur near the mouth Matarae soils (33 500 ha) occur adjacent to the systems (Fig. 2). Parent materials are local loess and Clutha River between Alexandra and Roxburgh and developed from silt loam to fine sandy loam tex loess-schist colluvium. Soil development is of the Shotover River and at low altitudes between tured loess, usually less than I m thick, over schist. Frankton and Arrowtown. Soil profiles are very as an association on rolling and hilly land east of extremely variable with very shallow soils on eroded Strath Taieri. These soils have developed on shal They are moderately enleached, subgammate soils backslopes and deep soils on accumulation sites at similar to Shotover soils, although they tend to be with weakly developed fragipans. Gleyed features somewhat shallower. low silt loam and fine sandy loam textured loess the base of many slopes. Deep soils are more com over schist. On many sites colluvial loess-schist and mottling occur in all Pukerangi soils but are mon on south facing slopes where increased loess Meyer hill soils ( 1500 ha) occur on the north mixtures occur, especially at the base of long hill more pronounced in poorly drained phases. Puker accumulation has occurred. Most soils, however, eastern side of the Dunstan Mountains near Dun~ slopes. Soil profile development varies depending angi soils often occur in association with Matarae are less than 45 cm deep. The shallower soils have stan Pass, on moderately steep hills and ridges with on the depth of loess and degree of colluvial mix soils on the Taieri Uplands. dark greyish brown sandy loam topsoils and yel rock outcrops. They are developed on thin fine ing. Topsails are dark greyish brown to dark grey lowish brown gravelly sandy loam subsoils. Deeper sandy to silt loam textured loess over greywacke with weak nut and granular structures. At many Soils on steep land soils have strongly compacted subsoil horizons, gravels. Profile development includes dark greyish sites subsoils are thin, but where loess is deeper often mottled with subgammate, humus stained brown topsails with weak nut and crumb structures than 25 cm coarse prismatic structures with Tengawai steeplands soils (7800 ha) occur to the prismatic structures. The deep compacted horizons over yellowish brown firm, stony subsoils with subgammate colour patterns develop. Mottling and north of the Maniototo and Ida Valleys, around the form a barrier to percolating water, which contri moderate nut structures over greywacke gravels. gleying is common in poorly drained sites. The base of the Hawkdun Range from Danseys Pass to butes to shallow slumping and erosion on many associated Matarae hill soils cover 4550 ha. Long Gully. They are formed on ancient stony slope slopes. deposits, loess, schist greywacke and conglomerate. Soils on steep. land SUBHYGROUS YELLOW-GREY EARTHS Profiles vary with changing parent materials, but Omarama steepland soils ( 1OOO ha) occur to the on stable sites where loess has accumulated, top Soils on easy rolling and rolling land north of the Manuherikia Valley around Falls Dam. soils are very dark brown stony silt loams with YELLOW-GREY EARTHS RESTRICTED TO They develop on steep mountain sides containing Hakataramea soils (4450 ha) occur at the north granular structure, and subsurface layers are com WESTERN CENTRAL OT AGO many rock outcrops. Parent materials are loess and ern end of the Maniototo Plains, between the Kye pact pale yellowish brown stony silt loams with nut greywacke colluvium, with a thin covering of recent bum River and the Kakanui Mountains. They are and blocky structures. The soil forming factors dominating this small loess. They are extensive in North Otago and a brief group are locally derived soil parent materials, and profile description is given in the previous article. the effects of the Southern Alps on weather pat- 44 45 DESCRIPTION OF IN SOUTH >-a:: OT AGO I-z :::> F.G. Beecroft, Soil Bureau, D.SJ.R., Dunedin (J) 0 !:::: () z (J) (Received November 1982) z >- :::> <( _J _J u.. _J <( altitude. Parent materials are weakly argillised loess I INTRODUCTION g 0 or loess and schist alluvium. Soil textures are pre I z 0 dominantly silt loams. Both soils are moderately CL <( z Yellow-grey earths in South Otago occupy <( (J) <( to strongly leached, strongly mottled, and have 0::: approximately 186 OOO ha (Long 1966). The distri w gleyed B horizons over a fragipan commencing <.9 () (.!) bution pattern is relatively simple and represents between 35 and 70 cm depth. Soil colour patterns 0 <( z the rainfall pattern and soil parent materials of (J) a:: _J are gammate to net gammate. >- a:: _J Coastal Otago. Yellow-grey earths extend in an arc I w 0 from the North Otago region along the coast to the CL I- a:: Clutha River and Romahapa, and inland to the Blue SOILS ON EASY ROLLING, ROLLING AND Mountains and Raes Junction. HILLY COUNTRY .... a: The region's yellow-grey earths have only dry Te Houka soils (23 OOO ha) occur west of Lake hygrous and hygrous soil moisture regimes, reflect Tuakitoto, and south of the Clutha and Pomahaka Rivers from Stirling to the Blue Mountains. Alti ing higher coastal rainfalls (635 mm to 1000 mm), (J) lower temperatures, and lack of significant 'rain tude range is from sea level to 185 m. The parent LU materials of the soils are schist loess and colluvium (J) shadow' effects from hills or mountains. However, (J) (J) over schist. The soil pattern forms a complex mos <( :::> near Clydevale soil characteristics exhibit a tran _J sition towards the subhygrous moisture regime. aic dependent on loess depth and slope. Textures 0 0 are predominantly silt loam. The soils are moder a:: (J) w (.!) This discussion classifies the drier hygrous inter ately leached, strongly mottled and have weakly to 0::: :::> :::> >- 0 grades as hygrous yellow-grey earths. Detailed moderately gleyed B horizons over strongly f- I (J) a:: descriptions of yellow-grey earths in South Otago developed fragipans commencing between 50 and >- (.!) are available in a number of Soil Bureau bulletins 70 cm depth. Soils contain weakly developed net 0 a:: >- and reports (Wright et al. 1952, Cutler et al. 1957, ~ 0 I gammate and strongly developed gammate colour _J Ragg & Miller 1973, Leslie 1976, Campbell l 977b, patterns. 6 Ragg & Miller 1978, Tomlinson & Leslie 1978, (J) ~ Kennedy in press). In this general account how Clydevale soils (22 OOO ha) and Clydevale hill ever, the soil names used are those of the soil sets soils (2000 ha) occur north of the Pomahaka and in the 'General Survey of the Soils of South Island, Clutha Rivers from Stirling to the Blue Mountains 0B ~ New Zealand' (N.Z. Soil Bureau 1968a). with small areas near Raes Junction, Beaumont and Lawrence. The soils are developed on deep sandy loam textured loess and colluvium. Clydevale soils are similar to Te Houka soils but have coarser tex DRY HYGROUS YELLOW-GREY EARTHS tures and weaker profile development. Profiles are E moderately to strongly leached, weakly to moder .::£ This moisture regime occurs in drier areas near ately mottled and gleyed over a very weak to weakly the northern boundary where hills or low moun developed fragipan at 50-70 cm depth. Colour pat tains have produced a weak 'rain shadow' effect terns are subgammate to gammate. 0 Oil (Fig. 1). Soils are developed on two landform These soils occur in the driest areas of the lower ell systems. ] 0 Clutha basin and well drained sites contain prop -5 :l erties diagnostic of yellow-grey earths in subhy 0 1. Flat, undulating, and easy rolling terraces and grous moisture regimes. CfJ fans .:: Kononi soils (2100 ha) occur around Kononi ..<:::"' t:: 2. Easy rolling, rolling, and hilly country ell township and Four Mile Creek at altitudes between YELLOW-GREY EARTHS OF SOUTHLAND AND WEST OTAGO 1 WAIMEA PLAINS YELLOW-GREY EARTHS J .G. Bruce, Soil Bureau, D.S.l.R., Gore EASTERN & NORTH-EASTERN 2 RELATED STEEPLANO SOILS (Received February 1982) • 3 CENTRAL & WESTERN . ASSOCIATED YELLOW-BROWN NORTHERN • SHALLOW AND STONY SOILS INTRODUCTION soils (84%, 240 600 ha) occur on terraces and_roll 4 ing downlands at elevations between 30 m and Yellow-grey earths and associated intergrades approximately 300 m. A further 13% (37 500 ha) • cover some 287 OOO ha (Long 1966) of the season occur on hilly land, largely at the margin of the Figure I Generalised distrihution of yellow-grey earths and associated soils in Southland and West Otago ally dry inland regions of Southland and the adja downlands, and in places reach elevations of up to cent parts of West Otago (Fig. I). Most of these 500 m. Associated soils on steepland (3%; 8900 ha) 48 49 have a limited distribution in drier northern par!s Hokonui soils occur on fans and terraces on the lower flanks of the Hokonui Hills. They are include Kaweku, Knapdalc, and Whitcrig soils the soil morphology and loess stratigraphy between of the region on the flanks of the Eyre and Ga:v1e mentioned in Waimea Plains area. these two areas is shown in Fig. 2. mountains. With increasing rainfall (and elevation) developed on tuffaceous grcywacke sandstone and the yellow-grey earths grade into ycllow-brow_n colluvium with varying amounts of loess. They are Other associated yellow-brown shallow and stony In the western part of the area, Ohai soils, earths. Throughout the region annual ramfall 1s characterised by dark brown well developed nut soils are included in the Oreti set and occur on the developed on weathered sediments including sand between 750 mm and 1100 mm and is fairly eve~ly structured topsoils on yellowish brown subsoils higher terrace (Wendonside Plain) south of Wai stones, mudstones, and gravels with a thin loess spread over the year, with lowest values occurrmg overlying a firm purple tinged subsolum which kaia. They have been severely deflated and show cover, occupy rolling and hilly land. They have thin in July, August and September. contracts with transecting grey gammations. The strong compaction of the gravels at shallow depth. greyish brown firm topsoils on yellow or yellowish fragipan is less well developed than in other soils These soils differ from Oreti soils of the northern brown subsoil with mottles overlying a compact and In the general survey of the soils of the South in the region. area and should be separated in future surveys. blocky yellowish C horizon with prominent mot Island (N.Z. Soil Bureau I 968a) the yellow-grey tles. As with many yellow-grey earths developed on The associated yellow-brown shallow and stony earths of the region were included in 20 soil sets parent materials other than loess they do not have and placed in three broad groups; dry hygrous Oreti/Hororata soils - provisionally renamed Riv ersdale in this area - are developed on stony grey a fragipan. In places the morphology of these soils yellow-grey earths and related steepland soils CENTRAL-WESTERN REGION (53 800 ha) indicate that they may also be polygenetic soils. (37 OOO ha); hygrous intcrgrades between yellow wacke alluvium with a silty matrix on younger grey earths and yellow-brown earths (225 OOO ha); surfaces and differ in being less weathered than This region includes the central Southland plains and the associated hygrous yellow-brown shallow other ~hallow and stony soils elsewhere in in the Winton-Otautau districts and rolling land in and stony soils (25 OOO ha). During more recent Southland. the west at Ohai. Annual rainfall is more variable NORTHERN REGION (87 700 ha) surveys (Bruce in prep; O'Byrne in prep_.)~ nun:ber than in other districts ranging from 750 mm at of the original sets have been subd1v1ded mt_o Winton to I 068 mm at Otautau adjacent to the This region extends northwards along the Oreti separate series. However for the purposes of this EASTERN AND NORTH-EASTERN REGION Longwood Range. and Aparima river valleys from Taringaturu Hills account soil set names will largely be used. (112 400 ha) to Mossburn and Lumsden, and beyond in the Yellow-grey earths in the region can be divided upper Mataura Valley to Garston south of Lake On the basis of the distribution pattern, four into two groups; soils on terraces ( 44 I 00 ha), and Wakatipu. It comprises a succession of narrow ter regions are recognised and the soils are described This region extends from near Gore n<:~rt~-w~st soils on rolling and hilly land (9700 ha). to Waikaia and eastwards to the Tapanm d1stnct races, plains, and fans with rolling land marginal according to these regions. to hills, as well as the Five Rivers Plain north of of West Otago. It comprises broad rolling down Soils on terraces are developed on tuffaceous lands with marginal hilly land in the north and ter greywacke loess of varying thickness over gravelly Lumsden. Rainfall is variable but is mostly less than 900mm. W AIMEA PLAINS (33 100 ha) races in the west adjacent to the Waimea Plains. alluvium. The latter may come within the zone of soil formation in places. Typical soils include The downlands and lower hill slopes are man Yell ow-grey earths and related soils in this region The Waimea Plains extend north-west from near Pukemutu, Aparima, and Oreti soils as well as the include Dipton, Nokomai and Mossburn soils, tled by thick loess deposits, though in man~ places Gore to Lumsden and are bounded on the south newly separated Isla Bank soils (O'Byrne, in prep.). erosion and deflation have brought underlymg rock Tengawai steepland soils, and shallow and stony by the Hokonui Hills and on. the north by t~e In general they have greyish brown to dark greyish Oreti soils. Mataura River and the foothills of the Garvie and gravels within the zone of soil fo~mation. Th.e brown silty topsoils with firm mottled silt loam typical yellow-grey earths of the area mclud~ W_ai Mountains. They comprise a broad plain subsoils, overlying a very firm and compact silty Dipton soils occur on low and intermediate ter terra~e koikoi Crookston, Waimumu and Tapanm s01ls, with marginal rolling land and fans agamst the clay loam or clay loam fragipan with prominent races and fans and are widespread in the southern though they were originally included with inter enclosing hills. With an annual rainfall mostly gammate colour patterns. Most of these soils have part of the region and parts of the Waimea Plains. ~ess grades between yellow-grey earths and yellow-brown than 850 mm the Waimea Plains are the dnest strongly impeded drainage. They are developed on gravelly alluvium with earths. These soils are characterised by deep grey overlying loess up to 50 cm thick. In general they region in Southland. ish brown friable silty topsoils on light yellowish Recent studies indicate that in many cases the have brown friable silty topsoils over light grey silty Yellow-grey earths include the Kawcku soil~ brown or olive brown subsoils that in many places fragipan is a relict feature that has undergone at subsoils with prominent mottles, overlying com (16 700 ha), Balfour soils (5450 ha) and Hokonm are strongly mottled. They have well deve~oped f:a least two periods of weathering (the current cycle pact and rounded gravelly alluvium which in places soils (5950 ha). The associated yellow-brown shal gipans that are traversed vertically by bnght thick and one prior) whereas the solum comprises a later is cemented by iron and manganese. O'Byrne (in low and stony Oreti/Hororata soils cover 5 OOO ha. gammate colour patterns. loess deposit weathering under the present climate, prep.) has subdivided the Dipton soil set to include i.e., many of these soils arc polygenetic soils. The shallow and stony soils with incipient iron banding Kaweku soils are developed on thin loess over Soils that do show features of both yellow-grey present fragipan may be regarded as a paleofragi at depth (Lowther soils) and poorly drained soils weathered gravels and cover the major part of the earths and yellow-brown earths have been sepa pan rejuvenated by current processes. This tenet is on loess over gravels with strongly cemented grav plains. The underlying gravels (at 25 cm to c. 50 cr:i rated from the Waikoikoi set though their mor supported by the increase in clay in the fragipan in elly iron pan below 50 cm (Caroline soils). depth) are very firm and weathered and show ev~ phology suggests that they are closer to yello~ comparison with the solum. the apparent stronger dence of deflation in the form of lag gravel at their brown earths. They include Arthurton and Mait leaching of the fragipan than in other yellow-grey Nokomai soils cover a small area near Garston. upper contact. They have no ~ragipa!1, but the com land soils (Bruce I 973b, Bruce in press), which are earths on loess in the Southland region (e.g. Wai They are developed on deep loess on older easy pact subsolum is a marked impediment to wat~r characterised by a well developed yellowish brown koikoi), and the disintegration of the upper part of rolling terraces and fans and are characterised by movement. They are considered to be polygenet1c solum with little mottling (yellow-brown earth fea the fragipan into discrete blocks, indicating pro deep friable dark greyish brown silty topsoils on soils with a younger solum of loess on a deflated tures) on a light yellowish brown weakly developed gressive destruction. pale olive firm silty subsoils with faint mottling. paleosol on gravels. In recent surveys in the ?eneral fragic horizon that has faint vertical gammate colour Underlying is a moderately developed fragipan with area Kaweku set has been subdivided to mclude patterns at depth. These soils have chemical prop The general morphology of the soils indicates weakly developed gammations. Knapdale soils - moderately deep loess (c. I m) on erties that are also intermediate between yellow pedosphere stripping of the sol um down to the top gravels; Whiterig soils - thin loess on less weath grey earths and yellow-brown earths. of the original fragipan, and later deposition of a Mossburn soils and associated hill soils are the ered lower terrace gravels; and as yet unnamed_deep younger loess of near comparable thickness to that most extensive soils, covering over half of the area Soils occurring on eroded and deflated parts of loess soils ( > l m) on higher parts of the plam. of the deflated solum. Total loess thickness in the of yellow-grey earths in the region. They are the downlands have been classified as yellow-brown central Southland region is much less than in other developed on greywacke loess in which underlying Balfour soils are developed on deep loess on shallow and stony soils associated with yellow-grey parts of Southland/West Otago, and in places two greywacke and gravels may come into the zone of rolling land near the north-western margin of the earths. They include Chatton and Benio soils (Bruce lower paleosols may be encountered below the fra soil formation. In general they have brown friable plain in the lee of the Garvie foothills. They have in prep.) which are developed on compacted quartz gipan at depths of less than 2 m. In West Otago silty topsoils and pale yellowish brown silty sub greyish brown friable silty topsoils on firm yellow rich gravels with a varying, though generally shal loess, soils do not show these features - the first soils with blocky structure and prominent mottles ish brown mottled subsoils overlying a well low to very shallow, loess cover. major break in the loess sequence coming at about overlying a compact fragipan with strong man developed compact fragipan with prominent Soils on terraces in the western parts of the area 2 m. Soils in this latter area are considered to be ganese staining and paler gammate colour patterns. gammations. developed on a single loess layer. A comparison of As in the Central-Western area the fragipan may so 51 be a rejuvenated paleofragipan. Associated hill soils included in this set in the Southland region. have only a thin loess cover but show the charac >- teristic morphology of the soils on rolling land. Such soils have been separated as Beaumont soils in the CONCLUSION recent survey of Wallace County (O'Byrne in prep.). One of the conclusions drawn from this account Steepland soils related to yellow-grey earths are of the yellow-grey earths of Southland and West confined to the flanks of the Eyre and Garvie Otago is that soils in the eastern region are 'single " .... s mountains in the Garston district. With increasing :·.·,,,.,.","' q cycle' soils, whereas in other regions many of the z '\•.,• ,· altitude they grade into steepland soils related to 0:: ., ·.:•,» ' soils are of polygenetic origin. UJ ' . . high country yellow-brown earths. Parent material I- ; :.;·":·" In the polygenetic soils the solum is developed Cl) ...... ' ' consists of greywacke and greywacke colluvium with <( ~~-.:·.:·~ . .. on what appears to be younger loess deposits while , .. ., '\ ' a thin loess cover. The soils are dominantly shal UJ ,:·.1·"" ' I, I low and have poorly differentiated horizons. Soils the subsolum, whether it be loess, weathered grey z ·~ .. ~3 . ... - ' I ~ t, .... . ;_\. in this region are included in Tengawai set which wacke, or weathered gravels, was initially weath I- Q ... ..·;. .. 0:: • J ... • t . has almost 90% of its 188 OOO ha area in the dry ered during a prior cycle. In some soils the subsolum CJ ,.'"a - ' 0 UJ ... ,.... ' -' . .i;. hygrous regions in Otago and Canterbury. is a paleofragipan which has been rejuvenated under z 0:: \"..·:.. . .,. . present weathering conditions. Where the sub <>($ ... ,''. •,-f . - , ...... The yellow-brown shallow and stony Oreti soils solum is not a paleofragipan, the compactness of I' ,D ',\ z ~ Jb associated with the above yellow-grey earths are 0:: ·" l'... l .. . . . -. this subsolum horizon(s) nevertheless makes it an UJ :>' .. ' (" typically developed on the Five Rivers Plain and I- '\·:1! . - impermeable boundary and comparable to the fra (f') . ' ' -- . r adjacent terraces of the Oreti River. Profiles are ?"'· .... ·? . • . gipan of single sequum yellow-grey earths. It is <( . . -. i'... poorly differentiated and somewhat loose and in UJ :.,,., ~:":/.,, . probably because of this compact horizon that some .. • -- ' ·\.,. general have a sandier matrix than other soils of these soils were classified as yellow-grey earths . I I z x 0 () j::: () <( ~1 z 0 Na: 0 ID ~ J: <( 3: <( m ....! I -:;-..... ~a. z .s: 0:: UJ I l o:: 0 z <>($ w w w w w w 0:: z a:: z a:: z u:l a::w..a-' w w (!) :::::i w C!) :J We>::I> o.._zIzw ~zw ~z w~ Cl) Cl.. 0 ~i~(!j l~~CJ 09:1- o~e ~ Cl a:: Cl) oii'.t;Ii~ CL Cl) ....! 52 53 In the subhumid climates of New Zealand there are of fine sandy texture is extensive on the Canterbury large areas of soils formed on parent materials with Plains to the south of the large braided rivers, par these characteristics and on which yellow-grey ticularly the Rakaia and the Waimakariri. earths with fragic horizons have formed. The Southern North Island Region covers areas Where the parent materials differ, the soils do near the margin of the major Late Pleistocene not conform to this concept. For example, soils tephra deposits. Most of these loesses contain sig PARENT ""•"'"~ri.,,_,.._,, OF YELLOW-GREY EARTHS AND RELATED formed on the stony alluvial deposits, with or with nificant quantities of volcanic glass, as in the Mar AND ASSOCIATED SOILS out thin loess cover, do not have fragic horizons ton soil (Claridge & Weatherhead 1978), and in because of the coarseness of the texture of the many places bands of tephra (Cowie 1964a). Other matrix; the soils formed on parent materials con wise these loesses are similar to those of the East E.J.B. Soil Science Department, Lincoln College taining free calcium carbonate do not have fragic ern region. No significant areas of Holocene loess (Received February 1982) horizons; soils formed on rocks rich in ferrom are recorded in this region. agnesian minerals such as volcanic tuff weather rapidly and contain smectite clays which, because Palemmls the loess deposits INTRODUCTION is described by various authors (Raeside l 964b; of the high shrink-swell properties, yield fine struc N.Z. Soil Bureau 1968b, and others) as being tured horizons; sandstones do not form fragic hori Most of the loess of late Pleistocene age consists Before discussing the nature of the parent dominantly quartz, feldspar, mica assemblages zons because of the low clay and high medium and of several deposits, on some of which paleosols have materials of the yellow-grey earths it is necessary with a relatively low weatherability. In the North coarser sand content; and clayey preweathered Ter developed. Many paleosols are clearly expressed and to define what a yellow-grey earth is, and the range Island, volcanic glass also occurs in the parent tiary and older Pleistocene alluvial deposits have some occur within the present day soils. Those of profiles which it encompasses. Taylor and Poh material (Vucetich 1968). too high a clay content to form fragic horizons. below the soil may have a significant influence on len (1962) defined 'Palliform soils' (equivalent to (c) Clay mineralogy: the clay minerals include the soil through modification of the hydrology of the yellow-grey earths) as soil that 'have well mica, chlorite, and intergrades to vermiculite, the system. Even within a particular loess layer there developed A, horizons, grey to very dark brownish with minor amounts of other clays. The amount is no certainty that the initial materials were uni grey in colour, with weak structure. They have a of extractable iron and aluminium indicates low THE PARENT MATERIALS OF YELLOW form and it may well be that there were short fragipan or genetically similar massive horizon, in content of free oxides or amorphous constitu GREY EARTHS WITH FRAGIC HORIZONS periods of soil formation during minor flucuations most places at depths below 25-60 cm and com of loess deposition. Consequently it is unwise to ents, even in the soils in which there is a sig AIRFALL LOESS DEPOSITS monly yellowish in colour, with a gammate or reti nificant component of volcanic glass, as shown assume uniformity of parent material when con culate pattern of grey veins.' in the Matapiro soil (N.Z. Soil Bureau 1968b). The literature on air-fall loess deposits is exten sidering the genesis of the yellow-grey earths. Thus the existence of textural changes within soil profiles This definition excludes many soils which have sive (Smalley & Davin 1980) and the general fea (d) Calcium carbonate: free calcium carbonate is tures of the loess deposits on which the yellow-grey may, in many cases, be determined by the past his been loosely called yellow-grey earths, as well as rarely found in fragipans or fragic material and tory of the deposit rather than be due to soil for soils 'related' to yellow-grey earths as on much of earths occur are derived mainly from Raeside when present, as on lower slopes of the Port Hills, (1964b), Bruce (1973c), Bruce et al. (1973), Cowie mation in the present cycle. the South Island hill and steep lands within the it is inferred that it has accumulated after the subhumid climatic zone, and 'associated' yellow and Milne (1973), Ives (1973) and McCraw {1975). Late Pleistocene loess deposits have well formation of the fragipan. Fragipans are not The loess is discussed under four regions. brown shallow and stony soils of the Canterbury found in silty calcareous parent materials. developed soils at the surface because loess input Plains. Yellow-grey earths also include soils formed In the Southland Region, south and west of the has been negligible for the last 10 OOO years. Below on pre-weathered mudstones, siltstones, and (e) Fragipans and fragic materials normally con Hokonui Hills where extensive late Pleistocene loess the present-day soil the loess has features indicat weathered Pleistocene deposits but many of the soils tain less than 1% organic matter. sheets are soil forming, the loess is silty in texture ing that weak pedogenic processes were operating formed on these are not strictly yellow-grey earths (t) Soluble salt soluble salt may be present in some and consists of feldspar which may exceed 60%, throughout the period when the loess was being because they lack fragic characteristics. drier soils but the concentrations are low. some quartz and horneblende and accessory mag deposited rapidly. These C horizons have some netite, reflecting the mineralogy of the tuffaceous pedological organisation, such as worm channels, (g) Exchangeable cations: %BS ranges very widely volcanic greywackes of Southland. Minor areas of clay domains in pores, and some local accumula from less than 50% to near l 00%; exchangeable Holocene loess occur near the Mataura and other tion of iron oxide. The Holocene loess (such as at THE SIGNIFICANCE OF PARENT mangesium sometimes exceeds calcium and in rivers draining the mountains to the north of the Barrhill) shows weak pedologic development MATERIAL IN THE FORMATION OF some soils exchangeable sodium is greater than Southland Region. This loess probably contains less throughout the deposit and in the present-day soil, YELLOW-GREY EARTHS 15% of the exchangeable cations. It must be feldspar and hornblende and more mica and chlor consistent with a relatively uniform rate of depo noted, however, the exchangeable cation status, ite than the older Pleistocene loess. sition for the whole deposit with no change in rate If we accept the view that a yellow-grey earth as well as the soluble salt content, in the present of deposition or soil development. soil has as one of its essential characteristics the day soils may well be substantially different from In the Otago Region, from the Southland Region presence of a fragipan or similar massive fragic that of the initial parent material in which the to the Kakanui Mountains, the loess ranges from horizon, we can list the specific set of characteris fragic characteristics developed. coarse silty to fine sandy texture in Central Otago Pedogenk changes after deposition tics which the parent materials of such soils must to silty texture near the coast and in South Otago. It can be seen from the data above that the char Any definition of the nature of the initial loess have; characteristics which accord well with those The mineralogy is dominated by quartz and feld deposits must take into account those pedogenic discussed by Grossman and Carlisle ( 1969). In the acteristics of the parent materials of yellow-grey spar (up to 70%) and accessory mica and chlorite. earths (in the strict sense) cover a very narrow range. changes which have taken place since deposition. New Zealand case these are: Holocene loess of similar composition occurs along Soil formation will have increased the clay content, The features which stand out are the texture grad the Clutha Valley and in minor occurrences ing which is conducive to formation of fragic especially in the more weatherable loesses and in (a) Texture: dominantly silt loam with a % clay elsewhere. the older North Island Late Pleistocene loesses. range from 12-15 at the coarse end to approxi material of high packing density; relatively inert sand and silt mineralogy; low enough clay content, The Eastern Region is from North Otago through Other changes consist of increased content of poorly mately 35 at the fine end. Coarse fragments of Canterbury to Marlborough. Late Pleistocene loess ordered oxide clay minerals, accession of soluble rock may also be present as in some loess col particularly of expanding clays, for the shrink-swell to be low thus reducing the likelihood of structure deposits are very extensive throughout this region salts, and exchangeable cations including signifi luvium. Medium and coarse sand content is usu although the thickness and areal extent is less to cant amounts of sodium near the coast. Physical ally very low and normally less than 5%. development; the low content of poorly ordered colloids; and the general absence of calcium car the north of the Waipara River in North Canter changes are striking, particularly the development (b) Mineralogy: the sand mineralogy of the soils bonate in the initial parent materials. All these fea bury. The loess is composed of almost equal pro of the giant prismatic structure systems so common in which fragipans of New Zealand are formed tures are conducive to rapid slaking of the material. portions of quartz and feldspar which make up in the loess deposits. Such changes may well be of about 90% of the non-clay fraction. Holocene loess major significance in reducing the stability of loess 54 55 regoliths on hillsides, because the processes of soil for the difference is that the soils of this class are formation change a relatively homogeneous loess formed on coarse textured late Pleistocene outwash essentially like loess; and basalt colluvium with loess or extensive on the sheet into a structured, weathered, and chemically gravels which have a sandy matrix. In those areas some loess. Laffan and Cutler (1977) describe three altered system. Locally, accessions of calcium car where loess is absent and the parent material of the greywacke and mountains of the drier parts of soil landscape systems on the Wither Hills; the the South Island. The texture of these materials is bonate have also occurred. It is therefore almost soils is sandy gravel to the surface, hardpans may Wither hill soils derived mainly from stratified air too coarse for fragic horizons to develop. Such certain that no loess deposits exist in the state in be found in the subsoils at depths ranging from 60 fall loess and loess colluvium with minor admix deposits are the principal parent materials of most which they were deposited. to 90 cm as in the Steward soil of North Otago. tures of greywacke gravels; the Vernon hill soils steepland soils as for example the Tengawai and Such pans are not cemented although they contain formed from mixed loess and gravel colluvium with Omarama sets. These soils are not yellow-grey slightly more clay than the horizons above and LOESS COLLUVIUM DEPOSITS a thin veneer ofloess; and the Waihopai steepland earths, although some of the chemical and miner below and contain more extractable iron oxide. soils formed on thin colluvium derived principally alogical properties are similar to those of the yellow Over large areas of the yellow-grey earth zone, They cannot in any way be likened to fragic hori from Pliocene weathered gravels. grey earths. the regolith on hill and steeplands consists of mix~d zons, and if anything they have more affinity to the deposits derived in part from airfall loess and m chelluvic horizons of podzols (Segalen et al. 1979). In both studies it was found that the soils formed part from the rock waste of the regolith on which Where the gravelly alluvium is covered with even on the loess colluvium and the mixed colluvium THIN REGOUTH MATERIALS a few cm of loess the hardpan is not found. The were yellow-grey earths with fragic horizons (where the loess fell. Although such deposits are wide In some parts of the South Island the soils of the spread they have not been studied very much. Wilde parent materials of the shallow and stony yellow the regolith thickness is greater than about l m), hilly and steep lands are formed on thin regolith brown soils should therefore be divided into three but the soils formed on the colluvium derived (1972) in a study of the soils of the Roxburgh dis materials, commonly less than about 60 cm thick trict in Central Otago described slope deposits of classes. mainly (the percentage of loess in the colluvium is not given) from the underlying rocks were not. over relatively unaltered rock. The Haldon set of coarse to fine schist rock waste which contain much North Canterbury is typical of this class. Within fine material which he suggested was derived from SANDY GRAVELLY ALLUVIAL DEPOSITS Ives (1970), in a detailed soil survey of the Mow that set there are soils ranging from Rankers through a former loess deposit. Laffan and Cutler (l 977a) bray Catchment, described the parent materials of lithosol-Ranker intergrades to shallow yellow-brown describe in some detail a section through loess and These deposits are typified by the Late Pleisto yellow-grey earths and related hill and steepland earths (Mr P.J. Tonkin, pers. comm.). loess colluvium on the Wither Hills in Marlbor cene outwash gravels without any loess cover and soils. He recognised six different kinds of parent ough. Trangmar ( 1976) describes yellow-grey earths without fine textured material in the surface. The material: loess (including composite loess depos formed on loess colluvium on the Port Hills. When Steward soil is characteristic of this kind of parent its), loess over mixed loess colluvium, mixed loess THE PARENT MATERIALS OF SOILS the texture of the matrix becomes sandy, or when material. Soils of this kind have Uniform Texture colluvium, greywacke colluvium, greywacke weath WITHOUT FRAGIC HORIZONS AT the deposit becomes very gravelly or stony, fragic Profiles of sandy skeletal texture (Cutler 1981). ered in place, and loess over alluvium. PRESENT CLASSIFIED AS YELLOW-GREY horizons are not formed. When one considers the extent of hilly and steep EARTHS GRAVELLY ALLUVIAL DEPOSITS WITH FINE land in the drier eastern part of the country and FINE TEXTURED ALLUVIAL DEPOSITS TEXTURED SURFACE LAYERS recognises the great importance of the nature of the Significant areas of soils lacking fragipans which INCLUDING REWORKED LOESS Gravelly alluvial deposits commonly have a thin regolith to the properties of the soils as well as the are included in the yellow-grey earths occur in These deposits occur extensively on Holocene cover ofloess or fine textured alluvium partly mixed hydrology and stability of the soil-landscape sys inland Otago, North Canterbury, Marlborough and surfaces in the South Island. The deposits on which into the gravels to depths of less than 60 cm. This tems, the lack of quantitative data is quite remark the eastern North Island. These soils are formed the Templeton and the Wakanui soils of Canter kind of parent material characterises the Lismore able. Mr P.J. Tonkin (pers. comm.), in a recent on Tertiary sandstones, siltstones and weathered bury are formed are predominantly silty textured soil as defined in Mid-Canterbury (N.Z. Soil Bureau study of the soils of the Doctors Range in North Pleistocene gravels. They commonly have a higher and are considered to be alluvium because of the 1968b). Such soils are characterised by Gradational Canterbury, assembled data on the relationship of clay content in the B and C horizons, mainly vertical and lateral variability of texture. The older Negative Texture Profiles. the thickness and textures of the thin regolith in because they consist of composite parent materials parts of these surfaces have soils with distinct fragic relation to the kinds of soil. of greatly different age. These clay-rich horizons fit best the concept of paleo-argillic horizons of the horizons only where the texture of the subsoil is SANDY GRAVELLY ALLUVIUM WITH A THIN The kinds of parent materials of the hill and silty and where the thickness of the fine alluvium Soil Classification of England and Wales (A very LOESS CAP steepland soils related to yellow-grey earths may be l 980). The main kinds of parent material in this is greater than about 90 cm. summarised as follows: Some gravelly alluvial deposits have a thin cap category are as follows: of loess with an abrupt textural change at the con OTHER FINE GRAINED PARENT MATERIALS tact of the two materials. Soils formed on thes.e LOESS COLLUVIUM TERTIARY MUDSTONES Gibbs ( 1964) states that yellow-grey earths with kinds of parent materials have Duplex Negative The relatively pure loess colluvium deposits are fragic horizons are formed in fine grained sedi Texture Profiles. The Luggate soils of the Upper These parent materials are formed from prew generally, but not always, stratified. Such parent ments such as siltstones, argillites and fine sand Clutha area belong to this class. eathered materials high in clay, commonly with a materials occur in each of the loess regions. Typical stones containing micaceous clays. Some soils high shrink-swell potential. The soils formed on soils formed on deposits of this nature are the belonging to the Kauru set of North Otago belong them have strongly developed nut, blocky or Wither Hill series, the Kiwi series of the Port Hills, medium to fine prismatic structure. Upper parts of to this class, but the fragic horizons do not occur and the modal soils of the Spy law set of the Clutha on the coarser deposits. PARENT MATERIALS OF THE HILL AND profiles commonly contain incorporated loess. STEEPLAND SOILS RELATED TO Valley. Texture profiles are usually Gradational Positive, YELLOW-GREY EARTHS some Duplex Positive and a few Uniform. Most of MIXED LOESS AND ROCK COLLUVIUM these soils have pale colour in the B and C hori PARENT MATERIALS OF THE SHALLOW Information on the parent materials of the soils zons, and usually are mottled to varying degrees. AND STONY YELLOW-BROWN SOILS of the hilly and steep land associated with yellow Mixed loess and rock waste colluvial deposits Fragic horizons are absent, and some soils, espe ASSOCIATED WITH YELLOW-GREY grey earths is rather meagre, yet large areas of soils, commonly contain enough loess or fine textured cially those in drier environments, show some evi EARTHS particularly in the South Island, fall into this cate material for fragic horizons to develop, provided dence of clay illuviation. These soils are very similar gory. Soil survey bulletins and reports give very the thickness of such material is more than about to the Pelosols of Europe and should be classified The Lismore soil of Canterbury can be consid brief descriptions such as 'mixed loess colluvium l m. The Vernon soil series of Laffan and Cutler accordingly. Many of the soils of the Abbotsford ered a typical member of this class. Its profile form from schist', etc. Trangmar (l 976) described the (1977) is typical of this class. set belong to this class. and chemical and mineralogical characteristics are parent materials of yellow-grey earths on the Port different from those of the Canterbury yellow-grey Hills and recognised three classes of parent COLLUVIUM WITH LOW CONTENT OF FINE TERTIARY SANDSTONES earths. Even its hydrological features differ mark materials; loess colluvium with few basalt frag TEXTURED MATERIAL edly from that of the yellow-grey earths. The reason ments; locss-basalt colluvium, which behaves These parent materials are generally very sili Mixed colluvium deposits which contain little ceous but commonly have some incorporated loess 56 57 in the upper horizons. They generally have Uni occur in the Hakataramea Valley, and in North form or Gradational Negative texture profiles but Canterbury. The parent materials, like those of the have higher levels of total cations and percent - Very prominent strong brown and pale grey mot some have Bulged Texture profiles. They are com two preceeding classes, are usually composite and age base saturation. They are regarded as weakly tling to the B horizon monly weakly structured and sometimes massive consist of in situ weathered gravels with mixed sur leached members of the subgroup developed under more xerous conditions than Hatuma silt - A pale grey fragipan-like horizon with many in the subsoil, but fragic horizons are rare. They face horizons with incorporated loess or mixed slope strong brown veins are typified by some members of the Kauru set of deposits. Profiles are commonly Gradational Posi loam. north Otago and the Onepunga set of North Can tive, but Duplex Positive profiles occur particularly 2. In mid-Hawke's Bay, between yellow-grey - Pale grey veins in the yellowish brown parent terbury. Their properties are more similar to those on the high terraces of the Maniototo and Haka earths of the Matapiro district are developed on material of the yellow-brown earths but vary greatly. taramea Valleys. These soils do not have fragic lands situated on the eastern fringe of deposits - A moderate level of extractable iron horizons because of the high clay content of B and from volcanic eruptions in the Taupo region. The C horizons, and also because of the high stone con WEATHERED PLEISTOCENE GRAVELS soils contain pieces of pumice and up to 30 cm In addition to the mixed andesitic rhyolitic vol tent. They do not fit readily in any soil classifica of the upper soil may be derived from accu canic ash component, the areas are more humid Parent materials of this kind occur mainly in the tion. They are more like the Paleo-argillic Brown mulations of volcanic ash deposits over sandy than for the Matapiro soils and the more hydrous inland areas of Otago, particularly in the northern Earths of southern England than any other soil or silty loess or alluvium. The outstanding conditions are considered to be the major factor for Maniototo, Ida and Manuherikia Valleys. They also group. difference in morphology is the occurrence of an the morphological differences. The inclusion of the extremely hard deep subsoil horizon equivalent Marton soil in the central yellow-grey earths has to a densipan in being difficult to disperse in been questioned, with the alternative of gley soils water and becoming rock hard on drying. It is being considered. At present it is a strongly gleyed possibly a product of silica cementations derived central yellow-grey earth. from the weathering of pumice, but as yet ana The soils form interesting subgroups for their YELLOW-GREY EARTHS lyses have been unable to confirm or deny this distinct differences from the more homogenous hypothesis. yellow-brown earths formed in similar materials. A 3. The Manawatu district also contains soils superficial resemblance to podzols led to a prelim H.S. Gibbs, of Earth Sciences, University of Waikato mapped in the central yellow-grey earths, formed inary classification with that group during the early (Received December 1981) on the southern fringe of volcanic eruptions. survey, but to the credit of the early pedologists the These soils, represented by Marton silt loam, are false correlation was realised and the soils given the characterised by: separate name. Correlation with overseas groups is This subgroup of the yellow-grey earths com prismatic structure. Prism joints are col~ured still unsatisfactory in that they would split the pale grey with colloidal material (? clay skms). prises a range of soils occurring extensively on ter - Numerous concretions in the lower A horizon subgroup between two or three classes. race rolling and moderately steep uplands of Over weakly weathered fine sandy loess, alluvium subhumid mesothermal regions of Hawke's Bay, or colluvium of Late Quaternary Age. The upper Wairarapa, Manawatu and Marlborough: In the boundary is irregular and begins about 1 m from comprehensive study of New Zealand soils (N.Z. the surface. Soil Bureau l 968b) the subgroup was represented by Matapiro silt loam and the description and ana Chemically the total cations and percen~age base saturation increase from moderate to high levels lyses of that profile serve as ~ ba~is o.f refe~ence f?r SOUTHERN YELLOW-GREY these notes.* Equivalent soils d1ffenng shghtly m with depth the organic matter and nitrogen decrease moderate to low levels with depth, parent material compos~tio.n an~ in tex~ure are fro~ mapped in Wharekaka soils m W airarapa, m T.ok? the available phosphorus and iron and phos D.S.I.R., Gore maru soils in Manawatu, and in Sedgemere soils m phate retention are low throughout the profile. (Received March 1982) Marlborough. Common morphological character Physically the clay contents of illite, hydro~s mica istics of these soils are as follows: and vermiculite attain maximum levels m the. B horizon and decrease below it. Macroporos1ty Yellow-grey earths and intergrades occupy almost earths are given in a number of surveys, reports, Greyish brown to dark grey friable loamy A hori decreases and bulk density increases to a maxi 2.43 million ha of New Zealand (Long 1966; Rob and papers concerning the soils of southern New zons with moderately developed fine granular to mum in the fragipan. erts and Jarman 1979). Of this area, l.93 million ha Zealand. Most of these publications are listed in crumb structure. Below 15-20 cm the horizon the bibliography at the end of this volume. If a par These characteristics illustrate the genetic class of (approximately 80%) are included in the southern becomes paler in colour, bleaching to pale grey ticular soil can be regarded as being typical of this moderately leached, central yellow-grey earths yellow-grey earth subgroup. in road sections, and containing fine dark brown broad subgroup it is Timaru silt loam, because of from weakly weathered feldspathic sedimentary concretions. Southern yellow-grey earths are widespread on its modal environmental position. Details of its drift materials. the seasonally dry subhumid terraces and down An indistinct and irregular boundary to a brownish morphological, physical, and chemical properties Associated soils differ in texture because of either lands (1.04 million ha) and associated hilly (0.47 are included in Soils of New Zealand, part 3. (N.Z. yellow to yellow firm clay loam B horizon w~th million ha) and steep (0.42 million ha) land of east a weakly developed coarse blocky structure with coarser or finer parent materials, and in the latter Soil Bureau I 968b). case fragipan development is very weak or absent. ern Canterbury and Otago, parts of central Otago, discontinuous clay skins. Strong brown and pale Environmental differences, in addition to vari Others show less horizon development due to f - Yellowish brown to pale yellowish brown firm compact horizon - no fragipan in the strict sense. loamy subsoils with a blocky structure and vary Vertical fissures in compact horizon with asso ing degree of mottling. ciated faint colour patterns at depth (gammaform). Soils in this moisture regime, and with this form, B.C. Barratt, Soil Bureau, D.S.I.R., Auckland - Compact to very compact pale yellowish brown are intergrades to yellow-brown earths. to olive yellow horizon (fragipan) with a gross (Received January 1982) prismatic structure and variously traversed by In many respects the characteristic features of gammate colour patterns (Taylor & Pohlen 1979) the southern yellow-grey earths, and yellow-grey comprising pale grey central portions, associated earths in general, seem to revolve about the fragi INTRODUCTION MICROMORPHOLOGY with fissures, and having a strongly rust mottled pan, its genesis, its occurrence, its properties, and selvedge. its relation to the soil moisture regime. *Fragipans These notes are based on micromorphological For convenience the soils are examined in four are regarded as soil horizons (Soil Survey Staff studies of four soils from southern regions of the groups: - In deeper soils, underlying material is similar but 197 5), though Raeside ( l 964b) considered them to North Island (Barratt 197 l) and eight soils from the less compact, and vertical colour patterns or be relict features that are being destroyed from the South Island (Barratt 1971, 1981) using the ter dry yellow-grey earths (dry subhygrous to comparable fissues continue. top down. Grossman and Carlisle ( 1969), in their minologies of Barratt (1969, 1971) for general fea subhygrous) tures, and of Brewer (1964) for specific bodies such - Profiles have a similar texture throughout with a treatise on fragipan soils in eastern United States, as cutans. In addition, some New Zealand soils from moist yellow-grey earths (dry hygrous to hygrous) slight increase in clay with depth (apart from arrived at a number of unresolved problems and loess have been described by Kubiena (1964), using polygenetic soils which have a marked increase concluded that the genesis of fragipans was obscure. yellow-grey earth to yellow-brown earth intergrades More recent studies, however, particularly those of his own terminology (Kubiena 1970), derived from (hygrous) in percentage clay with increasing depth). the names of European soil groups. Harlan et al. ( 1977) and Steinhardt and Franzmeier yellow-brown earths (hygrous to hydrous) At the dry end of the subgroup range, subsoils ( 1979), indicate that the binding of particles in fra tend to be paler and somewhat browner in colour, gipans is largely due to silica. Barratt (1981) has The broad relationship between soil moisture and the soils superficially resemble the adjacent also shown that individual grains in fragipans, when classes, macromorphology and micromorphology brown-grey earths. However, at the moister end of seen in ultra-thin section, exhibit a very thin col SITE CHARACTERISTICS are shown in Figures la and 1b. the range subsoils become brighter in colour, and loid coating which may be acting as a cement. the lower compact horizon loses much of the induration of a fragipan as the soils grade to yellow It is probable that the morphological features that The classification and site characteristics of the DRY YELLOW-GREY EARTHS relate to the 'fragipan' have a number of manifes soils are summarised in Table l. brown earths. These are represented by the southern Cluden tations. Such manifestations could include (and all Yellow-brown earths will form the subject of a and Timaru profiles (N.Z. Soil Bureau 1968b). They Major sequential changes in morphology could be, at least partially, correct): throughout the range relate to increasing rainfall and separate volume, but examples with similar char have dark to very dark greyish brown A horizons acters, such as vertical fissures or colour patterns, with weak structure, over olive to yellowish brown, in particular increasing soil moisture, with its effect I. A soil horizon forming under the present on mottling above the compact horizon (fragipan), are included here for comparison. firm, compact B horizons with massive to colum weathering regime, as m Barrhill soils nar sti:ucture and some mottling, over massive, hard and the changes in shape and contrast of gammate (Canterbury). The yellow-grey earths occur under moisture colour patterns within and below the fragipan regimes that range with altitude and latitude from C honzons. (Bruce 1972). 2. A compacted 'geological material' which is semi-arid to humid; and temperature regimes that In thin section, A horizons show a mixture of undergoing soil formation, as in Tima soils range from cool temperate in the South Island to massive to blocky and pelleted or spongy micro < 600 mm - soils show little or no mottling (Otago). above compact (fragipan) horizon. Faint vertical warm temperate in the North Island (mesothermal structure, and measurable porosity (above about gammate colour patterns with little contrast pene 3. A feature of a soil of the present cycle that is 1 of Cox 1968). 0.05 mm) is quite high, from 45% near the surface, trating the upper part of the compact horizon out of step with its current environment and is Most of the soils are from loess. Those in the decreasing with depth to 20-30%. The soil matrix (subgammate). being modified, as in Waikoikoi soils (West South Island are from greywacke, granite and schist is dominated by mineral skeleton (sand and silt) Otago). with abundant quartz and weatherable minerals that 500 mm-c. 700 mm - weak to moderate mot rock sources, whereas those in the North Island have sedimentary origins. include feldspar and muscovite. The scarce plasma tli?g above fragipan. Gammate colour patterns, 4. A relict feature of a 'stripped' prior soil with a (colloid) is an intimate clay-humus complex bndged at top and extending deeper into the fra new sol um, that is being destroyed and modified At the time of European occupation the natural (mullicol). gipan and underlying horizon (gammate). by current soil forming processes but retains vegetation was probably tussock grassland over the some of its prior features, as in Pukemutu soils drier yellow-grey earths of the South Island and B horizons have more or less massive micro c.625 mm-850 mm - moderate to strong mot (Southland) and Ashley soils (Canterbury). structure with low porosity, about 7-15%, mainly tling above fragipan. Gammate colour patterns beech-podocarp forest over most of the moister yellow-grey earths. Broadleaved species were mainly as non-connecting pores. The proportions of skele (primary gammations) extend deeper into sub 5. A relict feature of an 'unmodified' prior soil ton and plasma in the matrix resemble those in A solum and show more contrast. Gammate colour incorporated into current soil formation, as in confined to forests on the soils in the North Island. Most of the soils now carry pasture, but its quality horizons but the plasma is mainly clay (argillicol) patterns extending laterally (secondary gamma Warepa soils (South Otago). with a little staining by organic colloid (mullicol varies with climate and land use. tions) between primary gammations (net gammate). These possible manifestations of 'fragipans' sug argillicol intergrade) in the Timaru profile. A few 800 mm-c.900 mm - strong mottling above fra gest that some southern yellow-grey earths may be In Figure la (after Bruce 1972) yellow-grey earths diffuse mottles are present in the Timaru profile ~p~n. Primary gammate colour patterns increasing of polygenetic origin. in the South Island are arranged in a climatic matrix, together with yellow clay separations, both m size and contrast and having broad 'necks' at the sequence, with drier members that are morphol as islands in the matrix and as cutans (argillans) upper surface of the fragipan (supragammate). Dis ogically more like brown-grey earths, and wetter lining pores. C horizons resemble B horizons, but connected secondary gammations deeper in the fra members that are more like yellow-brown earths. are somewhat lower in porosity, about 7-10%. *Recently Smalley and Davin ( 1982) have prepared a com Between these two extremes, under conditions of gipan, and many short (tertiary) gammations prehensive bibliographic study and review of fragipan horizons extending into the upper surface of the fragipan. in soils. which lists selected works chronologically, discusses the fluctuating soil moisture, the yellow-grey earths with MOIST YELLOW-GREY EARTHS concepts. and summarises the theories and questions on the striking mottled patterns occur. These include the 850 mm-c. l OOO mm - faint or no mottling above nature and formation of fragipans. (Ed). Warepa and Waikoikoi soils, formerly classified as These are represented in the South Island by the intergrades between yellow-grey earths and yellow Otokia, Warepa and Waikoikoi southern yellow brown earths (N.Z. Soil Bureau l 968a). The soils grey earths (Bruce 1973b), and in the North Island of the North Island tend to fit into the wetter end by the Matapiro and Wharekaka central yellow-grey of the sequence illustrated from the South Island. earths (N.Z. Soil Bureau 1962, l 968b). Table 1 Soil classification and site factors Soil and classification Annual rainfall Parent material Topography Vegetation Climatic class (Altitude, slope Past Present and aspect) Matapiro silt loam 840mm Moderately weathered Pleistocene 150m Broadleaved forest Pasture moderately leached Subhumid mesothem1al I silts over siltstone O" or femland central yellow-grey earth Wharckaka silt loam 1020 mm Windblown loess from greywacke 76 m Broadleaf - podocarp Pasture moderately leached, moderately gleyed Subhumid to humid B 9°NW forest central yellow-grey earth mesothermal l Porirua fine sandy loam J020mm Moderately weathered windbome 40m Coa:>tal broadleaved Pasture with moderately leached central yellow-grey Subhumid - humid B drift on sand, over greywacke 12° N forest Danthonia earth - yellow-brown earth intergrade mesotherrnal l Paremata silt loam 1020-1150 mm Moderately weathered drift from 76m Coastal broadleaved Semi-extensive pasture moderately leached, moderately saluviated Subhumid - humid B greywacke on weathered greywacke 9° N forest and manuka and suburban yellow-brown earth mesothermal l Cluden fine sandy loam 600mm Loess and solif!uction schist debris 370 m Hard tussock Pasture with Dantho- weakly leached southern yellow-grey earth Semi-arid mesotherrnal 1 over schist gravels grassland nia and broom Timaru silt loam 600mm Moderately weathered loess from 60m Silver tussock Pasture with couch moderately leached, moderately gleyed Subhumid mesothermal l greywacke grassland southern yellow-grey earth °'0 Otokia silt loam 700mm Moderately weathered loess from 27m Tussock grassland Pasture with ryegrass moderately leached, moderately gleyed Subhumid mesothermal l schist with manuka and white clover southern yellow-grey earth Warepa silt loam 800mm Loess from schist 60m Broadleaved forest Improved pasture moderately leached, moderately gleyed Subhumid - humid A southern yellow-grey earth mesothermal I Waikoikoi silt loam 750 mm Loess from schist 183 m Podocarp - beech Unimproved pasture moderately leached, B-gleyed Subhumid - humid B oo forest, then tussock with cocksfoot and yellow-grey earth mesothermal I brown top Arthurton silt loam 950mm Loess from schist 183 m Podocarp and silver Unimproved pasture moderately-strongly leached yellow-grey Subhumid - humid A 1° E beech, then tussock earth - yellow-brown earth intergrade mcsothermai l Waikaka silt loam 1000 mm Loess from schist 213° Podocarp and silver Unimproved pasture strongly leached southern yellow-brown earth Humid A mesothermal l 4° w beech, then tussock with bracken Waikiwi silt loam 1150mm Loess from basic greywacke and 64° Podocarp - Pasture with cocks- strongly leached southern yellow-brown earth Subhumid - humid A schist dicotyledon forest, foot, browntop mesothermal I then tussock .,., .., ri I'>! :s:: ..... c ...... 0 ):> ------. -~~~.--~----=--- -~-..:;.o~==---=--==---, --'------62 63 This is virtually absent from both the ~rier a~d Structure ranges from massive to weak blocky and (mullicol-argillicol intergrade), which probably In the field these soils ar~ ch~racterised by dark wetter groups, which have silasepic plasm1c fabncs some mottles or nodules are present. reflects the increased influence of organic and greyish brown friable topsolls with granular t~ nut in these horizons. weathering regimes at this depth in the wetter soils. structure, iron mottles, and black concretions. In thin section A horizons have spongy to upper B horizons are firm, and heavy-textured, coarsely pelleted microstructure. In the Paremata with blocky structure and prominent mottles, and INTERGRADES BETWEEN YELLOW-GREY soil it weakens with depth to partly massive. Por tend to 'funnel' between the c~lumnar structures of EARTHS AND YELLOW-BROWN EARTHS isity ranges with depth from I 0-25% to about 5% PEDOGENESIS lower B horizons. Lower B honzons.are firm to very These are represented in the South Island by the mainly as pores and shrinkage cracks. Weatherable firm light olive brown to yellowish brown clay Arthurton soil (Bruce l 973b) and in the North mi_nerals in the southern profiles include feldspar, The soil micromorphology indicates processes loams with black concretions, and coarse colum~ar Island by the Porirua soil (N.Z. Soil Bureau l 968b). ep1dote, hornblende and tourmaline, with muscov that can be explained in terms of the organic wast breaking to blocky structure, separated by ve~1cal ite in the Waikiwi profile. The Paremata central ing and drift regimes (Taylor & Pohlen 1979>' which fissures. They are penetrated at the tops and sides In the field these profiles differ from the previous soil contains feldspars and muscovite. All have are controlled by the soil forming factors of which of columns by a network of fissures. These are bor group in their slightly redder hue, less firm con mullicol plasma. A few black nodules are present, in these soils, climate is the most notabie. ' dered by narrow, grey outer ped margms, eac~ sistence and weaker development of columnar and in the Paremata soil, a few argillans also. flanked by a narrow strong brown zone; Cx. hon~ structure and its associated mottling patterns. Fra ORGANIC REGIME gipans are absent although C horizons are firm, and zons are somewhat paler. massive. hard frag1p~ns B horizons have massive to pelleted microstruc few roots penetrate to this depth. ~limate is a factor controUing the organic regime, that slake in water. They are penetrated by vertical ture, and low porosity ranging between 1-2% in the fissures continuous with those from above. In thin section A horizons have mainly spongy actmg through organic matter production and its lower B horizon of the Waikaka profile and 5-7% subsequent breakdown and incorporation. In the In thin section, upper A horizons typically ha~e microstructure which becomes massive with depth in upper and lower B horizons of the Waikiwi pro sequence from dry yellow-grey earths to yellow spongy to pelleted microstructu.re, and about 25 Yo in the Arthurt~n profile. Their poros~ty is h~gh, up file, mainly as discrete pores and fissures. Weath brown earths these trends are shown by soil micro porosity (ranging from 7-10% m the Whare~aka, to 40% near the surface in the Ponrua soil, and erable minerals such as tourmaline and muscovite structure and composition of the matrix. to 50% in the Otokia soil). The weath~rable mmeral ranging from 20 to 25% in the ~rthurton soil. The are slightly more abundant than in A horizons and skeleton of the southern members mcludes feld weatherable mineral skeleton mcludes feldspars, the plasma is mullicol-argillicol intergrade e~cept In the dry yellow-grey earths, pelleted micro spars, micas, epidote, chlorite and hornbl~nde and muscovite and in the Arthurton soil, epidote also. in the Paremata soil, with mottled argillicol. Black structures are confined to topsoils, but in the moist that in the central yellow-grey earths mamly coi:i- The matri~ plasma is mullicol, with ~lack n_odules nodules are present, and cutans, argillic in the Wai yellow-grey earths they extend down fissures and feldspars, muscovite and augite. The matnx in both soils, and mottles in the Ponrua soil. kaka soil, probably ferric in the Waikiwi, and both in the moister intergrades and yellow-brown ~arths argillic and organic in the Paremata soil. coarser spongy microstructures become predomi plasma is mullicol. B horizons have massive microstructure and lo"." nant. This indicates the progressive influence of Lower A horizons have massive or near-mass~ve porosity, ranging from 3 to 5% ~n the Arthurt?n soil C horizons have massive to pelleted microstruc macrofauna such as arthropods and finally casting microstructure, and their porosity is !owe'., rangir,tg and 7 to 10% in the Porirua sod, mostly as discrete ture, with associated porosity increase with depth earthworms as soil moisture increases and the less from 5-25%. The matrix plasma is a mulhcol-arg1l pores and shrinkage cra~ks .. In the w~atherable to 5-10% in the southern profiles, although in the xerophytic tussock grassland gives way to beech licol intergrade and a few nodules in the central mineral skeleton, muscovite mcreases with d~pth. Paremata profile it remains unchanged at 2-3%, as podocarp and broadleaved forest. yellow-grey earths appear to be lithorelicts. In the Organic plasma penetrates into upper B honzo~s fissures. Weatherable skeleton minerals such as Warepa profile this horizon appears bleached. as mullicol-argillicol intergrade, but lower B hor_i feldspars and muscovite show a further increase Organic decomposition products as clay-organic zons have mottled argillicol with negligible ?rgamc with depth and the matrix plasma in the southern ~omplexes ~lso penetrate progressively more deeply Upper B horizons have ~assiv~ o~ blocky to enrichment. A few black nodules are prese~t m th~se profiles is mullicol-argillicol intergrade. Some nod mto ~he m1~era_I soil with increasing precipitation. platy microstructure and their porosity is very low, horizons and day separations include arg1llans lm- ules and argillans occur in the southern profiles. Mul11~ol, high m organic colloid is present in all 1-5% in the southern, and 10% m the c~ntral rellow ing pores. Dark cutans in the Paremata profile are probably topso~ls, but wherea~ in the dry yellow-grey earths grey earths. Porosity within peds is higher m grey organans and ferrans. topsods are underlam by B horizons with matrix C horizons tend to show more irregula'. micr~ mottled areas close to fissures and tends t? sho"." pla~ma hig~ in clay (argillicol) this is replaced, in structure than B horizons, and in the Ponrua s01l parallel alignment _with them: The plasma is typi mo1s~er so1!s,_ by mullicol-argillicol intergrade. cally argillicol and is mottled m more than one half porosity increases to 15~/o, mos~ly as discret~ pores. MICROSCOPIC CHARACTERS OF THE FRAGIPANS ~ulhcol-argllhcol intergrade penetrates progres of the soils. In the southern members clay sepa Diffuse mottling associated with the vei::1cal fi.s sively deeper through the soil sequence until in the rations, including argillans, are present an? also sures persists into this horizon, together with arg1l- Fragipans are recognised in the Matapiro and yellow-brown earths it extends throughout the C black nodules, probably of mangamferous lans in pores. Wharekaka central yellow-grey earths, and in all of horizons. composition. the southern yellow-grey earths apart from the Clu den and Arthurton profiles. They are absent from The deepening organic regime is tied to the Lower B horizons resemble upper. B horizo~s, YELLOW-BROWN EARTHS the yellow-brown earths. weathering regime, and is followed, if not pioneered, but the proportion of weatherable r:nmeral grams by plant roots. including muscovite has increased shghtly, and the In the sequence from the South I~la_n~ these are In thin section, all the Bx and Cx (fragipan) hori represented by the Waikaka and Waik1w1 southe~ matrix is less mottled except near fissures, where zons exhibit massive microstructure, low porosity, WASTING REGIME strong brown mottling, nodules, and also black, yellow-brown earth profiles, (Bruce l 973b, N.Z. Soll mostly as non-connecting pores, dense packing of probably manganiferous, cutans (ma_ngans) all. tend Bureau l 968b) and in the North Island by the Par skeleton grains high in silt-sized particles, and The wa.sting regime includes the weathering, to concentrate. In places mangans disrupt arg1llans emata profile, a moderately saluviated central plasma is sparse with weak or no preferred orien concentration, and removal of elements in the soil yellow-brown earth (N.Z. Soil Bureau 1968b). that line pores. tation (silasepic to masepic plasmic fabrics). Clay system. separations do occur, however, as argillans lining and Cx horizons have massive In the field these profiles have dark greyish c micr~str_ucture pores, and as islands in the matrix, probably cut . W~athering appears to increase with precipita and very low porosity. between l-l 0 Vo m the brown, friable topsails with nut to gr_anular struc tion m the southern sequence, as shown by finer southern profiles, 5-7% in the central ones. Poros ture including earthworm casts. B honzons are yel off ~y movements induced by seasonal wetting and drymg. Detailed examination of extra-thin sections te~tures ~nd incr~ased clay. This is supported by ity tends to be higher close to fissures. The J?lasma lowish brown to brownish yellow, friable to firm thm. sections, which show an increase in the pro is unmottled argillicol, and the proportion of silt loam to clay loam or clay, with coarse _blocky also reveals extremely thin, pale yellow coatings around sand and silt grains that probably act as a portion of fine to coarse silt in the moister soils weatherable minerals has further to prismatic breaking to finer structure, vert1~al fis in~reas~d. Bl~ck cement when dry. compared with the drier yellow-grey earths. The nodules are present, and clay separations, mcludmg sures black nodules or concretions, and coatmgs of increasing depth to which mullicol-argillicol inter argillans that line pores. vario~s colours and composition on structure faces. Comparison of B and C horizons, in wetter soils grade penetrates through the soil moisture sequence C horizons range from brow~ish yello~ to yellow In the southern representatives of this g~oup. of 'Yithout fragipans, with Bx and Cx horizons shows is probably also closely associated with increased ish brown, and from friable silt loam m the south ~Ittle difference except the tendency for the plasma weathering of skeleton minerals, such as feldspars soils, B and C horizons show ~triated ~xtmctl_on ern profiles to firm clay in the Paremata profile. and micas, to form clay. patterns in their matrix (masep1c plasm1c fabnc). in the wetter soils to be darker and less birefringent 64 65 AN HYPOTHESIS ON FORMATION In the fragipan, weathering of skeleton minerals fragipan is not a product of the current pedological YELLOW-GREY EARTHS is rather weak, with little clay formation. Clay coat environment but is related to the period of loess ings on grains are extremely thin, and the fragipan deposition (Raeside l 964b), and that it has field R.L. Parfitt and J.D.G. Milne, Soil D.SJ.R., Lower Hutt characters of a pedological nature (Soil Survey Staff possibly results mainly from physical processes. Its (Received FcbrmuJ 1983) porosity is very low, with few interconnecting pores, 1975). but no interlocking or recrystallisation of skeleton grains is observed. The present work shows no mineralogical evi dence for a lithological break at the top of the fra Recent studies at Soil Bureau on the Marton and the bulk density of the surface soil would be low Argillans that line voids in fragipans may be gipan or its weathered contact horizon, although a Tokomaru silt loams (NZMS 1 N 144/040648, through biological activity. relict, a result of a previously warmer, moister pause in the deposition of the loess, with consoli N149/123300), which are gleyed yellow-grey earths, has led to a new hypothesis on the formation of Potential soil water deficits of 160 mm (or postglacial climate (Raeside 1956), and Kubiena dation, cannot be disproved. Matrix fabrics also dif 270 mm in l 0 year droughts) lead to plant roots (1964) associates this 'braunlehm' content with a fer little between fragipans and adjacent horizons the high bulk density B and C horizons of these yellow-grey earths (Table 1). exerting suctions of several bars in B horizons. submediterranean to subtropical environment. The and are either silasepic or masepic. Argillans tend These suctions can be transmitted through the water upper limit of the argillans could represent the to be best developed in the fragipans and may be In our studies we have noted that the maximum in pores in such silt grade materials and cause original top of the fragipan. As shown in Fig lb, in relict. In places they are penetrated by younger dry bulk densities of the yellow-grey earths range shrinkage which is equivalent to putting the soil the southern sequence this upper limit follows a mangans that appear to be associated with the mot from 1.64 to 1.69 g cm 3 while the maximum bulk under a compressive stress of this magnitude (Rus line roughly at the top of 'gammation' or columnar tling process. However they could still be forming densities of associated intergrades between yellow sell 1973). This leads to an increase in bulk density structure, but diverges progressively upwards, away in pores that interconnect and they could have been brown earths and yellow-brown loams, e.g. Dan of the soil. The soils in drier areas will experience from this zone, towards the moister yellow-brown isolated quite recently by movement in pores that nevirke silt loam (Table I), do not exceed greater suctions and attain higher bulk densities. are non-connecting. 1 earths, - a trend that tends to be duplicated in the 1.50 g cm • We have also noted that yellow-grey Because the lower horizons arc below the main zone central yellow-grey earths. However the presence of Seasonal wetting and drying are probably essen earths occur where potential soil water deficits of biological activity the soils will not only develop argillans could be at least partly due to current exceed 150 mm in summer whereas the intergradc but also retain a high bulk density and indeed dens pedogenesis. The presence of layered argillans in tial for the development of these soils, and result in considerable inorganic mixing, as shown by par soils occur where deficits are less than 150 mm ities will increase as these silty soils go through suc connecting pores could represent successive incur (Table 2). cessive wetting and drying cycles. sions of clay from above, and where they infill dis allel microstructure and porosity in grey areas along vertical fissures; by argillic material infilling pores crete pores in the matrix, they could have been cut Putting these two pieces of information together Eventually these soils achieve a sufficiently high off by recent soil movement in response to wetting that no longer interconnect, and by strings of spher in our study area, and making the assumption that bulk density so that drainage is impeded in winter. and drying. ical pores that represent partial collapse of tubular the present day trends in soil water deficit from This leads to reducing conditions and decreased soil pores or fissures. yellow-grey earth zones to the intergrade soil zones acidity in winter followed by oxidation and Mottling of pseudoglei type (Kubiena 1964, 1970) occurred during the formation of the soils, leads to increased acidity in spring and summer (Russell is present in the yellow-grey earths that have mot our current hypothesis. 1973). This in tum will lead to more rapid weath tled B horizons over the weathering fragipan. The The maximum rate of accumulation ofloess and ering and clay formation, particularly in yellow-grey presence of similar material in the network of veins earths in areas which have wetter winters. Weath that penetrate into, and the fissures between, col tephra can be estimated from the thickness of soil CONCLUSIONS above the Aokautere Ash. Even at the maximum ering of magnesium chlorites will give vermiculites umnar structures in fragipan horizons, indicates that which have high exchangeable magnesium values. the fragipan is being destroyed from the top, down rate of accumulation it is unlikely that accumula Soil micromorphology supports field evidence 1 tion exceeded 0.2 mm y or about 2 tonnes ha 'Y 1• wards. Destruction of the fragipan has been shown that the yellow-grey earths form a moisture This hypothesis needs further testing but it does by a combination of techniques, including optical As the loess and tephra accumulated, similar appear to explain many of the properties observed sequence, with drier members more like brown-grey 1 1 amounts (2.5-4.0 tonnes ha y ) of litter from in yellow-grey earths. microscopy, X-ray and infrared methods (Barratt earths and wetter members more like yellow-brown 1981), to be accompanied by weathering of sand vegetation would also be added to the soil, and thus earths. and silt-sized muscovite and biotite, and the for mation in grey mottles of interlayered hydrous Both weathering to form clay and deepening of Table 1 Bulk density (BD) of soil horizons mica. More recently Pollok ( 1981) has also found the organic regime appear to increase with mois pedogenic chlorite forming at the junction of the ture. At the same time the consistence of B hori Yell ow-grey earths fragipan with the horizons above. zons ranges from hard to firm in the yellow-grey Yellow-brown earth to yellow-brown loam intergrade earths, and friable in the yellow-brown earths. Tokomaru 53279 Development of the mottled horizon seems con Marton SB9369 Danncvirke SB937 J The fabric and mineralogy of the fragipan Horizon Depth BD Horizon Depth BD sistent with periodic swelling and shrinkage of the 1 Horizon Depth BD (cm) (g ) 1 cm (cm) (g cm ) vertical fissures (Raeside l 964b). This movement resembles that of horizons formed from loess both (cm) (g cm-3) gives rise to vertically orientated strucutre and above and below it, and therefore it does not rep Ap 0-22 1.25 Ap resent a change in lithology. However the possi 0-18 1.23 Ap 0-7 0.82 porosity along the tissues, and is possibly also a Apg 22-32 1.35 AB 23-28 1.43 AB 17-27 0.86 cause of the masepic plasmic fabric (streaks of bility of a pause in deposition of the loess above ABg 32-40 l.38 Btgl 33-48 1.46 Bwl 28-42 0.88 orientated colloid in the ped matrix). Destruction the fragipan cannot be disproved. Btgl 40-60 1.52 2Btg2 53-63 1.25 Bw2 60-80 1.30 Btg2 60-82 1.64 Btg3 of the fragipan in the moister yellow-grey earths is 63-73 1.55 c 83-93 1.10 The fragipan exhibits close packing of sand and Cxgl 82-117 1.69 Cg thought to have continued further (Bruce 1972). The 73-96 1.64 2C2 96-106 0.90 silt grains consistent with compaction, as well as Cxg2 117-141 1.58 overall faintness of mottles, however, suggests that 3Cg 108-128 1.48 low porosity. Very the process of pseudogleisation may be decreasing thin colloidal coatings on grains are possibly also acting as a cement when dry. in favour of aerobic weathering and organic activity. Table 2 Moisture regime of soils Clay skins (argillans) that line pores may be partly relict, but in pores that interconnect they DRIFT REGIME Soil Classi llcation could still be forming. Mean annual Potential Duration of The drift regime embraces the mechanical dis rainfall soil water soil water In the wetter yellow-grey earths and intergrades (mm) deficit 1 deficit 1 turbance of the soil system by inorganic agencies. (mm) (months) It includes the processes of erosion, accumulation to yellow-brown earths, the fragipan is being pro gressively destroyed from above through a network Tokomaru and mixing. yellow-grey earth 1050 Marton 160 5 of veins and down the vertical fissures that are a yellow-grey earth 1050 Dannevirke 150 5 Alternative schools of thought suggest that the consistent feature of these soils. yellow-brown earth to yellow-brown 1200 90 4 loam intergrade 1 Calculated from Penman evapotranspiration data assuming a soil water store of 150 mm 66 67 CHEMISTRY SURVEY CHEMISTRY OF L.C. Blakemore, Soil Bureau, D.S.I.R., Lower Hutt (Received January 1982) INTRODUCTION moderately acid with a tendency to be more acid in the gleyed and more strongly leached members. The chemistry of yellow-grey earths was described for the South and North Islands by R.B. The organic matter content of yellow-grey earth Miller and L.C. Blakemore in the 1958 edition of topsoils is usually low to medium and the material 'Soil Groups of New Zealand'. is usually well broken down (low to medium C/N ratios). In the subsoils, the organic matter contents "' It is interesting to note that Miller prefaced his 2 decrease steadily down to the lower B or C hori .c0 . article on South Island yellow-grey earths with a 5;- e.n zons where values of 0.2% C are common. 0 0 statement to the effect that, compared with other .c c: soil groups, yellow-grey earths had been sampled Since the original articles on chemistry of yellow o...- the most frequently, with a multiplicity of horizons grey earths (Blakemore 1958; Miller l 958a) consid having been analysed m great detail. Perusal erably more detailed analyses of phosphorus status through more modem analytical records suggests have been carried out, and examples are shown in that this statement is no longer true and because Table l. One of the outstanding features is the high of the survey areas which have received most proportion of the inorganic phosphorus which is attention since that time, there is a comparative soluble in 0.5M H,S04 • This reflects the fact that dearth of modem analytical information on this soil these soils are not very highly weathered and that z ~===~0000 <""l - OOO 0 - -oor--.,-, group. relatively small proportions of the inorganic phos u ---- phorus are in the occluded form. Another feature The survey chemical data available to Miller and of the soils of this group is the quite high propor Blakemore was somewhat restricted in the number tions of total phosphorus present in the organic C--V'l-OON-.:::tNf""I 01-\0V")'tj"M- V)7\0M f'-0--7"o::t'o::tM7N OOMOO«:t'MN of properties measured, comprising pH, organic N--00000 N-00000 N-oo 0 NOOOOOOO N-0000 form. Saunders ( 1968) reported that in brown-grey c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i c:i ci c:i c:i c:i c:i c:i matter, 'available' (mainly l % citric acid soluble) earths, the proportion of organic phosphorus is phosphorus and cation exchange. However, there usually low (e.g. 12% of total P for Conroy sandy had been considerable work done in studying pro loam) and that with increasing rainfall and plant cesses. This included mechanical analysis of pan N r-- N Q'\ M M N N 00 0 r-- V) -ey- M r-1 0 V'l V'l M 1n 0 properties: (a) the chemical stability of members of these soils - the Seddon soil being much less 0 0 .,.. r-- - - V') r-1 "i:::t r-- I"") r- \0 "'('j" 00 !""'/ \0 r-1 MM \0 0 0 .- r-- t- 0\ 00 0 r-1 - 00 "7' - I.I") M 8880 ::g N'-0-l""')'tj"OOr-O 000\V"IN0'\00 the plagioclase series and (b) the effects of cyclic developed both morphologically and chemically. 0000....:....:....:....: ....:....:o....:....;";o 0 0 0 ci 0 c:)c:)f"")-.Q~~oci-.0 ....:00....:.....:0 salt. In his thesis, Arbuckle (1953) reported that in yellow-grey earths from Manawatu and Hawke's Bay total Mg increased sharply in the C horizons, NNOMlfl000".00 Mf"lt--O"l-\0 0'-00r- r- °'°' - \ONr-0\\00 and that this indicated that magnesium bearing CONCLUSIONS :!~0-:oOcicio-'._; :::!o-'.~ciMN-.0 r-:or-.:o-:oor-:o~ ::oor-:o\N.-= minerals were weathering. He considered that the ------N- increase in exchangeable Mg and the resulting lower One of the main purposes of this article is to Ca/Mg ratios could thus be due to greater amounts remind the reader of the papers which appeared in of Mg being liberated in lower horizons, and the earlier issue of 'Soil Groups of N.Z.'. These because of low effective leaching in the profile, to described some of the chemical investigations which accumulate in these lower horizons. He also con had taken place on yellow-grey earths until then. sidered that the high exchangeable Na could be In addition, examples of more modern survey i:: explained by the fact that as sodium feldspars are 0 chemistry are presented to show the greater range N ·c the most resistant to weathering, they would still of data that is now becoming available. The data 0 be weathering in the upper horizons and accumu illustrate various chemical features of yellow-grey ::r: lating lower in the profile. This explanation of low earths, viz. low to medium organic matter status, Ca/Mg and high Na seems quite feasible but might high proportion of inorganic phosphorus which is not be the sole cause. Many yellow-grey earths are non-occluded, low to medium phosphate reten found in positions which are exposed to the effects tions, low 'available' sulphur, generally medium to of cyclic salt and this could well be a contributing high base status, low Ca/Mg ratios, high exchange factor. Further details are reported by both Miller able Na except apparently in gleyed or weakly (l 958a) and Blakemore (1958). developed members, and low or very low acid-oxa In the examples shown in Table 3, acid-oxalate late extractable AL Fe and Si. More detailed dis Al and Si are very low and the Fe values are low. cussions on K and Mg in yellow-grey earths are These reflect the fact that soils have escaped effects included elsewhere in this issue. 70 71 MAGNESIUM STATUS OF R. Lee, Soil Bureau, D.S.I.R., Lower Hutt (Received May 1981) INTRODUCTION comprise both primary and secondary minerals. The magnesium status of New Zealand soils has Metson (1974) discusses in detail the mineralogical been the subject of a recent series of papers by Met nature of non-exchangeable Mg and relates this to son and co-workers (Metson 1974; Metson & th~ New ~ealand Genetic Classification using the Brooks 1975; Kidson et al. 1975; Lee & Gibson mmeralog1cal data provided by Fieldes and Swin 1976; Metson & Gibson 1977; Metson et al. 1977). dale (1954), Fieldes (1968) and Fieldes and Weath These papers have examined the magnesium status erhead (l 968). Metson and Brooks (197 5) further of the main soil groups of the N.Z. Genetic Soil co!Ilment on the relationship between Mg levels and Classification in terms of exchangeable Mg (Mg_.), mmeralogy in their discussion on the distribution M N reserve Mg (Mg,) and total Mg (Mg,), and have of exchangeable and reserve Mg in the main soil examined both inter-relationships between these groups of the Genetic Classification. Most evidence parameters and relationships between them and indicates ~hat the release of non-exchangeable Mg other soil properties, particularly mineralogy. This occurs m~mly from the clay fraction (Metson 1974), article is largely a review of what these papers had whe:e mmerals of the micaceous or 2: I layer type to say about the Mg status of yellow-grey earths. are important. Sand size minerals of most impor tance are the ferromangesium minerals (horn b~en~es, pyroxenes, and olivines) micas, particularly b1ot1te, and chlorite. 'RESERVE' MAGNESIUM The role of exchangeable Mg in the nutrition of plants has long been understood. In the absence of MAGNESIUM LEVELS ("I"") --r-lNNOO ---- N MN--N-01-:::t 000000 additions of Mg from external sources (e.g. fertil iser), exchangeable Mg levels can only be replen The information presented here is taken largely ished from non-exchangeable sources. Methods for from Metson and Brooks (1975) and Metson and determining non-exchangeable Mg levels in soils Gibson (1977). 00007-NN ON.-NMO\'tj" '-:::tMMV'l tri --M('f""}M-.::f'C"""'1t""i 000~'-i::tV 00000000 0000000 0000 0 00000000 000000 have been reviewed by Metson (1974); largely they ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci have involved the use of acid-extraction. The SOUTHERN YELLOW-GREY EARTHS measure of non-exchangeable Mg used by Metson and co-workers in their examination of New These soils occur under a rainfall of approxi mately 500-1 OOO mm in the eastern lowland regions 00-o::toor-oN-0 NC-0'-0r-r-r- i.n-r---0\ 0\ 000\00~0\r---O OOM-000- Zealand soils is reserve Mg. Mg,. The Mg, method ~~~~~N~M MMMMMMM ~~~~ MMM~~MNM NNM~MN ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci is described by Metson & Brooks (1975) and of the South Island as far north as North Canter mvolves boiling air-dried soil for 15 min with IM bury. The sand fraction comprises largely feldspars HCI at a soil:acid ratio of I : 40. The 'acid-soluble' an~ qu~rtz, with important Mg-bearing minerals Mg figure s.o determined is corrected to give Mg, bemg micas and hornblendes. The clays are princi \O\O..,.~Or---0\00 r---r---r--1f""'"l('"'.l-"'1" MMt--N \0 O\"<::ttri-01n-.::J"'1'"- NOO\OC-tr) ...... - - ...... 0 0 0 ...... 0 t"I N -- 0 ...... - ...... - ...... - ...... - 0 ...... 0 0 by subtractmg the exchangeable Mg figure for the pally 2: l layer type. Average topsoil (down to 15- ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci ci sample involved. 20 cm) and subsoil values (below 20 cm) for Mgc and Mg, are: Whilst it is generally accepted that exchangeable Mg represents a fraction that is immediately avail M~. Mg, No. of able to plants, there is much less conclusive evi (me./100 g) (me./100 g) samples dence regarding the rate, and extent, to which this available pool can be replenished from non Topsoil 1.73±0.98 23.8±8.3 29 i:: exchangeable sources. Kidson et al. (1975) discuss 0 N the literature on this topic and report the results of Subsoil 1.44± 1.08 25.2± 7.5 ·i:: 37 ~ ~ 0 - ('( <"'"1 "" a pot trial examining the extent to which exchange ::i::: <{ i:Q i:Q a:\' a:\' p{ <{ i:Q o:5' a:\' a:\' a:\' rrt i:ci' able Mg and Mg, were related to dry matter yield Fi~. I shows the distribution of Mg,, Mg, and and Mg uptake of white clover. They concluded Mg, m four representative profiles. Cluden fine that the soils used were unable to supply adequate sandy loam, a weakly leached soil from Central Mg from non-exchangeable sources to sustain nor Ot~go, represents the dry end of the group. Mag m~! growth of white clover: only three of the eight nesmm levels are fairly constant throughout and soils used, those with very high Mg, levels, showed ~g, levels are very high at 60-65 me./100 g. Timaru evidence of any release of non-exchangeable Mg. s1l.t loam, a moderately leached soil, is represent ative of the more strongly developed southern yellow-grey earths. Lismorc silt loam is classified as a stony shallow soil associated with southern MINERALOGY yello.w-grey earths. Waikoikoi silt loam, previously considered as an intergrade to yellow-brown earths, The sources of non-exchangeable Mg m soils has recently been re-classified as a southern yellow- 72 73 0 17 21 KEY: 0 23 19 19 20 23 -Mge 18 20 ;: 11 17 40 ~ [[?}Mgr c 0 40 u 16 ;: 29 e > :: o/'i·:"._.. e E. 60 CD ~"""~ ~ E. c .J:. u .J:. 60 0 E. 8 ...... u Lismore silt loam E. : 26 ~ 80 11 .. :\).\; 7586 0 80 u 100 Cluden fine sandy loam Timaru silt loam 100 28 Wharekaka silt loam Merton silt loam 120 7717 7560 8308 7537 120 Matapiro silt loam 7604 140 KEY: .Mge Waikoikoi silt loam 8337 Figure 2 Magnesium le vels in soil profiles representative of central yellow-grey earths Figure I Magnesium levels in soil profiles representative of southern yellow-grey carths grey earth (J.D. Cowie pers. comm.). These three yellow-grey earths and do not show such a marked profiles all show evidence of a decrease in Mg, and subsoil shift. Mg, levels in upper horizons, more so with the Lis THE POTASSIUM STATUS OF YELLOW-GREY EARTHS more profile. Fig. 2 shows the distribution of Mg_., Mg, and Mg, in three representative profiles; Matapiro silt loam from Hawke's Bay, Wharekaka silt loam from R. Lee, Soil Bureau, D.S.l.R., Private Bag, Lower Hutt CENTRAL YELLOW-GREY EARTHS the southern Wairarapa and Marton silt loam from (Received May 1981) These soils occur in a zone of moderate weath Manawatu. ering in the 500- 900 mm rainfall zones of Marl borough and Nelson and the 800-1100 mm zones INTRODUCTION NON-EXCHANGEABLE K AND SOIL of Wairarapa, Manwatu and Hawke's Bay. Mag MINERALOGY nesium-bearing minerals in the sand fraction are Although soil K research in New Zealand has less abundant than in their southern counterparts MAGNESIUM LEVELS IN RELATION TO probably been going on for longer than research The relationship of soil K to the N.Z. Genetic and comprise chlorite, hornblende and mica. Clay OTHER SOIL GROUPS into soil Mg, the K status of New Zealand soils has Soil Classification and soil mineralogy is broadly contents are generally slightly higher, more so in not been the subject of as extensive an inventory similar to that of soil Mg. Like soil Mg, potassium subsoils, with the principal clay minerals illite and Metson & Brooks (l 97 5) and Metson et al. ( 1977) as that applied to Mg (Lee, this issue). In a recent in soils can largely be sub-divided into that held in clay-vermiculite. Average topsoil and subsoil values discuss this aspect and comment that the main report Metson (l 980) discusses K in soils and spe an exchangeable form, which is readily available to for Mg, and Mg, are: groups of the New Zealand Genetic Soil Classifi cifically the K status of New Zealand soils in rela plants, and that in a non-exchangeable form. As K cation, particularly zonal groups, contain soils from tion to the New Zealand Genetic Soil Classification. does not occur in soils in organic compounds Mg, Mg, No. of a diversity of parent materials with varying degrees This report has been summarised by Lee and Met (except as an exchangeable cation), soil mineralogy (me./100 g) (me./100 g) samples of weathering and leaching. A typical or character son ( 1981 ). Less extensive discussions on the K sta is important in determining the magnitude and istic value for any particular Mg parameter cannot tus of New Zealand soils in relation to the genetic behaviour of the non-exchangeable pool and its be predicted from the soil classification from a soil Topsoil 2.80±1.34 11.5±7.6 12 classification have been given by Metson (1960, relationship to the exchangeable pool. Of most group level. Neither is it possible to predict clas l 968a, b) and Metson and Lee (1977). importance are the 2: I layer (micaceous) minerals Subsoil 3.84±1.81 14.1±10.6 19 sification from a knowledge of Mg status. (These of clay size and the largely reversible K-release and points are illustrated by the standard errors reported The information presented here on the yellow K-fixation mechanisms associated with them. Mg, levels are generally higher than in the south in the previous sections). In general terms however, grey earths is abstracted from base data collected Within the zonal groups of the Genetic Classifica ern yellow-grey earths, particularly in subsoils. The one can comment that the yellow-grey earths rep by Alan Metson during his time at Soil Bureau, and tion, as soil development and weathering increases marked increase in subsoil Mg_. levels compared resent one of several less strongly weathered and from Metson (l 980). Whereas it was possible in the so the proportion of clay size 2: l layer minerals with topsoils is a conspicuous feature of the central leached zonal soil groups with a medium to high discussions on the Mg status of the yellow-grey decreases, and this is reflected in a decrease in K yellow-grey earths, attributed to higher subsoil clay Mg status. Mg deficiencies are unlikely to occur in earths (Lee, this issue) to present characteristic pro status (Metson 1980). Important K bearing min contents and intermittent gleying of subsoils. Mg, these soils at present or in the near future (Metson file distributions for exchangeable, non-exchange erals in the sand fractions of New Zealand soils are levels are generally lower than in the southern & Brooks 1975). able and total levels, similar complete profile chiefly the micas biotite and muscovite, the feld characterisations for K in the yellow-grey earths are spars orthoclase and microcline, and volcanic not available. The most complete sets of analyses glasses. Plagioclase feldspars may also over long are to be found in Soils of New Zealand (N.Z. Soil periods be significant sources of K. Detailed Bureau l 968b) for Cluden fine sandy loam, Timaru accounts of mineral weathering in relation to the silt loam, Lismore silt loam, Steward stony sandy Genetic Classification are gi ven by Fieldes and loam, Matapiro silt loam and Marton silt loam; Swindale (l 954) and Fieldes (1968), while Fieldes however, whereas most horizons in these profiles and Weatherhead (1968) have described the sand were analysed for exchangeable and total K, K, mineralogy. (non-exchangeable K) determinations were only carried out on topsoils. Metson et al. ( 1956) and Metson (l 968b) 74 75 POTASSIUM LEVELS developed the K method as a measure of the non and Nelson and the 800-1100 mm zones of Wai Plots of K 0 against %C and K, (total K) against exchangeable K status of New Zealand soils. SOUTHERN YELLOW-GREY EARTHS K, are shown in Fig. I and are taken from Metson rarapa, Manawatu and Hawke's Bay. They have a Following a prior extraction with boiling l M HNOi, (1980). slightly higher clay content than their southern K is the mean of further successive _extract_ions wi_th As mean annual rainfalls increase to over counterparts: the clay fraction still dominated by boiling IM HNO, at a narrower so1l:solu11on ratio. 500 mm the brown-grey earths grade into southern In discussing the K status of these soils, Metson 2: I type minerals, but with a greater proportion of It was proposed not as a measure of an absolute yellow-grey earths, which occur under a rainfall of (1980) states that their mineralogy, co_nsidered in vermiculite. Average topsoil and subsoil values for amount of non-exchangeable K, but as a measure approximately 500-1000 mm in the eastern low relation to K, and K. suggests an efficient mecha Kand K are: of the long-term rate of release from non-exchange rolling downlands of the South Island as far north nism for fixation and release of K by partially able forms. It measures the more unavailable forms, as N. Canterbury. The sand fraction comprises expanded 2: 1 layer clays, which should m~intain ~ K. K No. of dependent chiefly on soil mineralogy; those forms largely feldspars and quartz. The clay fraction is supplies adequately under pastoral farmmg. This (me./100 g) (me./100 g) samples which are less subject to external influence and dominated by illite and hydrous micas, with smaller statement is qualified however, by the comment which could thus be expected to give some indi amounts of expanded micas. Average topsoil (down that under intensive cropping the natural rate of Topsoil 0.65±0.64 0.26±0.10 36 cation of the inherent K status of a soil. The use to 20 cm) and subsoil values (below 20 cm) for release of K from soil minerals may be insufficient. Subsoil 0.27±0.25 0.29±0.09 14 of K as an index of plant-available, non-exchange exchangeable K (KJ and K, are: These statements agree with the information given able K is therefore limited: the method was designed by During (1972) concerning the use of K fertilise~s Plots of K against % C and K, against K are principally as a possible aid to understanding and K. K No. of on southern yellow-grey earths, although appreci shown in Fig. l. interpreting the Genetic Classification. However, (me./ 100 g) (me./100 g) samples able K fertiliser could be required by southern Metson (l 968a, b) did suggest a response level of yellow-grey earths intergrading to yellow-brown As these soils are more strongly weathered than 0.30 to 0.35 me./100 g for Kc for a pastoral situa Topsoil 0.73±0.48 0.51 ±0.16 47 earths. the southern yellow-grey earths they generally have tion, where there is considerable recycling of K. lower K, and K values. Apart from a few high K Subsoil 0.17±0.11 0.49 ± 0.1 7 32 values (which markedly influence the average values CENTRAL YELLOW-GREY EARTHS given above), K. levels generally are relatively low These soils are moderately weathered and occur also, showing little variation with depth or C con in the 500-900 mm rainfall zones of Marlborough tent. Metson ( 1980) considers that an equilibrium • 'Topsoils' (0-20cm, approx) • 'Subsoils' (20+cm. approx.) 3 60 n = number of data points -en Cl> g 40 0 2 0 .._, .s@ 0 Southern (S) ::..:"' /::;. Central (C) Y = 0•1 7x + 0-09 Y=45•9X+15•8 Northern (N) r=0-67 ... r=0·79o··· • (n= 63) (n = 27) 60 0 5 10 15 20 0-0 0-2 0-4 C/YGE 3 60 o- -- BGE C/YGE - , 0- --- -S/YGE 2 40 C/YBE - , : ' , 0------U,HC/YBE S/YBE --- : ... ''/::;. S/Podz - - o O L:S. y = 0•21 x - 0•18 Y= 57•1x+14•6 00 00 r= 0•61° r= 0•762° 20 (n= 33) (n= 29) • •- -N/Podz 0 10 15 20 0-0 0-6 -- -N/YBE C(%) Figure I Plots of K, against % C and K, against K, for southern and central yellow-grey earths (S/YGE and C /YGE); *** denotes O•O regression line significant at 0.1 % (me/1 Figure 2 Mean K, and K, values for zonal groups of the grnetic classification: BGE=brown-grcy earths, YGE=yellow-grey earths, YBE=yellow-brown earths. Podz=podzols 76 77 POTASSIUM LEVELS IN RELATION TO fixation-release mechanism in micaceous clays .with MICROMORPHOLOGY VARIABLE CHARGE expanding interspaces maintains K,. at a relatively OTHER ZONAL SOIL GROUPS low level. In soils with low K a~d K, ~evels Micromorphological examination of the profile In order to test this hypothesis, the measure for responses to K fertiliser would appear hkely. F1eldes Fig. 2 (taken from Metson 1980) shows for K1 and K, the position of the southern and central (Pollok 1981, with acknowledgment to masterate variable charge used by Blakemore and Parfitt (1962) notes that some central yellow-grey earths student R.C. DeRose) also indicates a profound ( 1979), was adopted and applied to each horizon. may not respond to low rates of application beca1:1se yellow-grey earths in relation to the other zonal soil groups. This figure is based on average values how difference in soil properties between pseudogley This method endeavours to measure the difference of K fixation by expanded 2: l layer clays. Dunng horizon and fragipan. The latter shows closelv between the cation exchange capacity at pH 8.2 and ( 1972) discusses reponses to K fertiliser on central ever, whilst considerable overlapping of data for the different groups does occur. packed skeletal grains with matrix surround a~ the cation exchange capacity at field pH, which yellow-grey earths. expected, together with a few fine channels rimmed difference is ascribable to pH induced, i.e. variable, with ferriargillans. Neoferrans, iron oxide mottling charge. The respective cation exchange capacities delicately dispersed among the grains, and small are not, however, measured directly. The CEC at Fe/Mn concretions are also in evidence. By con high pH is estimated by adding the sum of trast the pseudogley horizon displays a much more exchangeable bases to the extractable acidity at pH dramatic micromorphology. The skeletal grains 8.2. The CEC at field pH is estimated by adding with matrix surround are no longer so tightly the value for KCl-extractable aluminium (Alm) to SILT packed. Large and sinuous channels and strongly the sum of exchangeable bases. In summary (in OF developed argillans are clearly visible, with decay me./100 g): LOAM ing roots sometimes occupying the voids. Strong iron oxide mottling surrounds highly irregular iron variable charge=CEC"11 x2-CEC1ic1<1 rH =(extractable acidity" +TEB) stone concretions, often containing iron-enriched 11 82 -(Ali-:.< + TEB) J.A. Department of Soil Science, Massey University, Palmerston North clay domains. The micromorphological evidence 1 =extractable aciditypH -Ali-:.ci (Received December 1981) all points to the pseudogley horizon as a seat of 82 active soil transformation. The only laboratory determinations necessary are INTRODUCTION ern methods of clay mineralogical analysis, were a extractable acidity at pH 8.2 and aluminium dis portent for the future. placed by l M KCl, all results being expressed in Tokomaru silt loam is classified as a Fragiaqualf PHYSICAL MEASUREMENTS terms of me./ I 00 g. The values obtained in this way in Soil Taxonomy and as a Pseudogley in the Euro for Tokomaru silt loam are given in Table 1, as pean tradition. Formed from non-calcareous loess, This view is supported by physical measure follows: the soil possesses two striking profile features - a AUTHOR'S CONTRIBUTION ments for bulk density, porosity, soil water reten Table 1 pseudogley horizon overlying a fragipan. Detailed tivity and saturated hydraulic conductivity Pollok (1975) examined the soil at a different sit_e published by Scotter et al. ( 1979a) for the same soil, profile descriptions are given in Pollok (1975), and Horizon Extractable Al" I Variable Cowie (1978). In the discussion that follows, the on the Massey property. He designated the B hon but again at a different site on the Massey property. Acidity (field pH) charge Aokautere Ash (20 OOO years BP), which forms a zon as a Btg (pseudogley) horizon in accordance It is as though the values recorded for these param (EA) (EA-AIKCI) valuable marker band at depth in the profile, has with the FAO-Unesco system of horizon designa eters deliberately set out to confirm the field mor (pH 8.2) tion and recognised the upper part of the C horizon phology of the soil. been omitted so as not to obscure the main thrust me./100 g of the argument concerning the development of as a Cxg horizon (fragipan). His chemical analyses variable charge in this soil. confirmed those of Fife so far as total exchangeable bases, exchangeable magnesium and exchangeable Ahl 18.6 I. I 17.5 FERROLYSIS Ah2 15.8 1.0 14.8 calcium were concerned. Furthermore, he noted that ABg 10.4 0.3 10.1 the values for LipH (pH in water minus pH in lM Btg 13.5 3.3 10.2 WORK KCl) were extremely large in the C ~orizon ( 1. 7 for The author's investigations of Tokomaru silt Cxg 6.5 0.8 5.7 the fragipan and 2 to 2.3 for the honzons ?eneath), loam were made as part of a larger study compar Cwgl 5.1 0.2 4.9 0.3 3.2 From the beginning, Tokomaru silt loam was but reduced to 1.4 in the pseudogley honzon and ing the properties of certain New Zealand and Ger Cwg2 3.5 recognised as a very wet soil, with a heavy textured further to 0. 9, 0.8 in the horizons closer to the man soils formed from loess. With the 1981 B horizon (Hudson & Fife 1940). Fife ( 1945) con International Conference on Soils with Variable surface. The results indicate a marked break between the firmed the presence of a clay bulge and at the same Charge in the offing, he studied with more than a At the same time he presented results of detailed lower horizons and the upper horizons at the junc time reported important changes in soil chemistry little interest Brinkman's, 1979, account of Ferro down the profile. Total exchangeable bases were at clay mineralogical studies which indicated pro lysis, a soil forming process in hydromorphic con tion of the fragipan (Cxg) and the pseudogley hori their lowest in the B horizon and increased again found changes at the junction of the pseudogle_Y ditions. Many of the soils described in that zon (Btg). All three parameters are affected, with a horizon with the fragipan. The fragipan and ho~1- particularly high value for Ali-:. showing up in the in the C. Whereas exchangeable calcium exceeded publication, for example the profile from Hard 11 zons beneath were dominated by mica/illite (10 A) pseudogley horizon. exchangeable magnesium in the A and AB hori 0 thauser Wald, closely resembled the German soils zons, it crossed over in the upper B until in the and clay-vermiculite (14 A) in the clay assembla~e. in the author's own study. Clearly the process of lower B exchangeable magnesium exceeded Only a little pedogenic chlori\e was present and vir ferrolysis had the capacity to produce aluminium exchangeable calcium and continued to do so down tually no interstratified (12 A) clay. The moment polymers that could occupy interlayer positions in into the C horizon. Amounts of exchangeable mag the pseudogley horizon was reached, however, there the clay assemblage of pseudogley horizons. Brink nesium in the C horizon increased from 5.4 to 6.8 was a noticeable decrease in mica/illite and clay man noted the same increase in pedogenic chlorite me./100 g with depth. In addition, Fife noted a vermiculite and a corresponding increase in pedo in the pseudogley horizons of his soils as the author ORGANIC COLLOID marked increase in free sesquioxides (Fe201+Al20.i) genic chlorite (14 A collapsible to 1~ A with _K-Cl had already found in Tokomaru silt loam. If alu in the horizons lying above the C - so much so saturation and heating to 550°C) and mterstrat1fied minium polymers could be produced by the pro The organic colloid also contributes to variable that he commented that this was further evidence clay (l 2A), this change continuing .into the horizons cess of ferrolysis, then the prospect opened up for charge. To obtain a qualitative estimate of its influ for establishing the lower limit for the B. A change above. The change in layer lattice clays was as the development of at least an element of variable ence, it is helpful to compare the figures for organic in the silica/sesquioxide molecular ratio also striking as was the change in free sesq~ioxides and charge in the horizons above the fragipan in the carbon with those for variable charge, as in Table occurred at this junction. These latter observations, the silica/scsquioxidc molecular ratios recorded Tokomaru soil. 2: made as they were before the availability of mod- earlier by Fife (1945). 78 79 The evidence for variable charge is one more Table 2 strand that may be added to the total body of infor 5. Organic carbon mation pointing to the zone above the fragipan as Horizon Variable charge (me./100 g) (%) the active seat of present-day soil formation in Tokomaru silt loam. 3.3 Ahl 17.5 2.1 Ah2 14.8 ABg 10.1 2.0 Btg 10.2 0.8 0.1 SECONDARY IRON OXIDES IN YELLOW-GREY EARTHS Cxg 5.7 CAUTIONARY NOTE Cwgl 4.9 0.1 Cwg2 3.2 0.1 The method used for determining extractable C.W. Childs, Soil Bureau, D.S.l.R., Lower Hutt acidity at pH 8.2 was that currently in vogue in (Received December 1981) Clearly the organic colloid must be contributing New Zealand (Blakemore er al. 1977). This involves to the relatively large values for variable charge in shaking the soil overnight with a. barium salt buff the Ah 1 and Ah2 horizons. A considerable amount ered at pH 8.2 by triethanolamme (T~A), rather INTRODUCTION (as far as was dug) on 12 August 1980. Note, how of organic carbon is still present in the ABg horizon than leaching with the same. The shak1.ng method ever, that positive tests were not obtained in the but it falls off noticeably in the Btg horizon, becom may give higher values than the leachmg one, of Yellow-grey earths are characterised by compact face of the Pit itself. Non-typical results can be ing negligible in the Cxg and horizons beneath. the order of 0. 7 to 3.1 me. (Blakemore et al. 19"}7). subsoils which have low porosities. Impeded drain obtained on soil faces which are not very freshly Any increase in extract~ble a~idity is reflected 1~ a age often leads to perched water tables and inter exposed (e.g. road-cuts, ditches) because the local corresponding increase m cation exchange capacity water and oxidising/reducing regimes will be REASONABLE CONCLUSION mittent reducing conditions, particularly in lower at pH 8.2 and ultimately in variable charge, as these A and in B horizons. These conditions give rise to affected. parameters have been calculated in this paper. It therefore seems reasonable to suggest that the mobile iron (in its+ 2 oxidation state) which can change in variable charge at the junction between The author had in fact used the full Mehlich move in response to diffusion gradients and soil the fragipan and pseudogley horizon is in part due leaching procedure for the direct de~ermination of solution flow until conditions become sufficiently MINERALOGY OF SECONDARY IRON to the change in clay mineralogy (Pollok 1975) and cation exchange capacity at pH 8.2 m the analyses oxidising for the oxides and oxyhydroxides of OXIDES tamm extractable free sesquioxides (Fife 1945) that carried out at the University of Bonn some years Fe(III) to become stable, and precipitation occurs. takes place there. This may be linked to a mecha ago (Pollok 1975). When these were consulted they This general mechanism of iron segregation leads Established soil mineralogical procedures involve nism of ferrolysis (Brinkman 1979) responsible for were found to be lower than the indirect ".alues to the formation of mottles and concretions in removal of secondary iron oxides by one of the attack on the original clay assemblage and the pro reported in this paper by an order of magnitude, yellow-grey earths, and has been discussed in more dithionite methods before size fractionation and duction of exchangeable aluminium polymers and similar to that reported by Blakemore et al. (1977) detail elsewhere (Childs 1972). This mechanism is determination of minerals. Individual iron oxides pedogenic chlorite. for extractable acidity. It is therefore possible that also the reason for the name yellow-grey earth being are thus not determined, but are often quoted col the 'true' values for variable charge in Tokomaru coined - yellow for regions or horizons where sec lectively as 'free iron oxides', i.e. the amount of The very large /1 values obtained for the fra- ondary iron oxides are present; grey for horizons silt loam may be lower by as much as 2 to 3 iron, expressed as Fe 0 , removed in the dithionite gipan and horizons below reflect a high degree of 2 3 me./ 100 g than those repor:ted in this paper. But where they are, at least in part, absent. permanent charge associated with the strong ver treatment. The levels of 'free iron oxides' in the the 'true' value is now turnmg upon methodology miculite component in the clay assemblage there. Iron-rich concretions are often enriched in man yellow-grey earths listed in 1968 (N.Z. Soil Bureau, and it is clear that if further progress is to be made The decrease in /1 pH in the horizons above the ganese, which can redistribute in soils by a mecha l 968b) are all within the range 0.5-3.6% of soil fragipan may be correlated with the development more detailed sampling and more refined analyses nism similar to that for iron. As little as l % (0.35-2.5% as Fe) whereas total Fe levels lie in the range 2.5-5.5% (3.5-8.0% as Fe ). In general, of a moderate amount of variable charge in that will need to be carried out. manganese is suficient to make the concretions close 20 3 somewhat less than half of the total iron in yellow part of the profile. to black in colour. On the other hand, mottles, by implication from their colour, arc not usually grey earths is determined as 'free iron oxides', enriched in manganese. The explanation for this though this fraction, because of the small particle difference probably lies in the following factors: (i) size and high reactivity of iron oxides (Schwertman manganese is less readily oxidised in a thermody & Taylor 1977), is an important influence in deter namic sense than is iron and is hence able to remain mining aspects of soil chemistry. mobile longer under fluctuating conditions (Kraus Recently, Moessbauer spectra have been kopf 1957); (ii) evidence that the oxidation of Fe(II) obtained for a few samples from yellow-grey earths. and Mn(II) occurs at different rates and by different These have shown the presence of goethite (et mechanisms (Stumm & Morgan 1970, pp.525-544); FeOOH) in mottles and iron-manganese concre and (iii) the nature of the oxidising/reducing fluc tions. Examples of the spectra are shown in Figure tuations. It may be reasonable to regard iron-man l for samples from a core through Marton silt loam ganese concretions as some sort of end-point in the near Fielding (NZMSl Nl44-040648). Fig. l(a) and segregation process, and mottles as iron which has l(b) are typical of the spectra obtained for concre become trapped (possibly only temporarily) en tions and mottles in the upper tephric loess layer. route. A similar view appears reasonable for the With the sample at 295K (22°C) (Fig. l(a)) only a intermittently wet and dry soils of the Manawatu ferric doublet (I) is obtained, but at 78K (-l 95°C) sand country (Cowie 1968). (Fig. l(b)) a magnetically-split 6-line component (II) The field test for fen-ous iron (Childs 1981) has and a ferric doublet (I) are obtained. The magnetic the potential to show when iron in yellow-grey field at the Fe nucleus may be calculated for II from earths is mobile. To date it has not been used sys the absorption peak positions. This field is 472 kG tematically on a yellow-grey earth. However, one and allows II to be identified as goethite. (Other 'spot' result is worth mentioning. The Tokomaru relevant parameters are 8 (isomer shift relative to 1 silt loam adjacent to 'Pollok's Pit' on the Massey Fe)=0.45 mm s 1, and £=-0.12 mm s- ). Further, University Campus gave strong positive tests for because the magnetic splitting is absent at 295K the Fe 2 ~ ions in the topsoil and down to about 0.5 m goethite is superparamagnetic, i.e. it does not dis- 80 81 figure I Moessbauer spectra for samples from cores (Soil Bu reau nos. S2591, S2592) through Marton si lt loam (gleyed ye ll ow-grey arth) approximately I 0 km north of Feilding (NZMS 1 N 144-040648). T he velocity scale is ca librated wi th respect to iron metal. ~amples were air-dried and li gh tl y ground before analysis. (a) Hand-picked concreti ons (5YR 2/3 and 4/6) and mottles (7.5YR 4/6) composite from B2cy horizon (33-48 cm: Soil Bureau laboratory no. SB9369C) at 295K (room temperature). (b) Same sample as in (a) run at 78K (liquid nitrogen boiling point). \ (c) Hand-picked strong brown (7.5YR 5/8) mottles from IB horizon ( 124-149 cm: SB9369H) at 78K. (d) Hand-picked black concreti ons from llA (?)horizon (149-164cm: SB93691) at 78K. The spectral components. labelled I and II. are discussed in the text. I • • • I• .... -:.::/:'!:· ;....;, ...... (\•1\~· • • •• o ...... I \ :- 't!···· ...... _ v..,• . ....:... ····: .. '!'.t': ·:._ r .. "..\"_ ~ .· ...... :.:..--::...... ···-: .• ~.... : ·: ' b .. ,...... •••..., ...! ·: ... . -., Figure 2 High resolution electron micrographs of samples from depth 149-1 64 cm (sec Fig. 1). Identi ficat ion was confirmed by ... electron diffraction. (a) Goethite from mottles. Star-shaped twinning is well developed. Hall oysite (scroll s) is also present. (b) Microcrystalline goethitc from mottles. (c) Ferrih ydrite from concretions . .. . .: ·. ···.· .1·' • •••; . ·.. ~ ..· ·: ·~v:· .. , .. ··. ... ·: ... . . ,,,...... -:... . ·.·_.:'.~ .. ·... ·.· .·. · · ··."' •.,. -~·.:1, : . • ',I,··· :·:.\:' .. '.: :: ':~: 11 I'· 11 I I """···. ' . c .. . ·... : ... ..· ·. . " .... , ... 0 ...... +- .. '· 0.. c ... c... . ··. • '1 I A 0 .. ·.... Vl ...... c -...... <{ ·:,,·: :'' I•'\ ... I I 1 1 I :·.' ...... ;._-::.:~. ·.. · ...... ··:·· . ·.:..:. ··.•··. d .. ,..,,_ ...... --:·· .,. .·. ~ ' ,,. .· • .. ·' I ·- . . .. :: ·. I ~ I ][I -8 -4 0 4 8 100 nm Velocity/ mm s-1 ~ I 83 play magnetic splitting until well below the Neel tion with goethite (Schwertmann & Taylor 1977). temperature (393K for goethite) which is the tem B perature below which magnetic splitting occurs for a I?ure, ~ell-?rystallised sample. Thus the goethite e~1dent m this Ma.rton silt loam is of small particle PROPERTIES OF SECONDARY IRON size and/or contains Al substituted for Fe in the OXIDES structure, and this is typical of soil goethites. The extent of Al substitution may be estimated from The property of colour and its relation to the the measured magnetic field and an empirical rela yellow/grey segregations in yellow-grey earths has tionship derived by Golden et al. ( 1979) to be 16 already been mentioned. mole percent, i.e. this goethite structure is 84% Iron-manganese concretions from yellow-grey FeOOH and 16% AlOOH. A similar conclusion earths have been studied and discussed in several may be drawn for component II in Figs. l(c) and papers_ (Childs 1975; Rankin & Childs 1976; Childs l(d). & Leshe 1977) and summarised in the recent NZSSS Component I in Figs. l(b), l(c), and l(d) is par 'Gley Soils' issue (Childs 1978). Some of these amagnetic ferric iron in octahedral co-ordination. references include results on concretions from soils Thus it could represent ferrihydrite or lepidocrocite other than yellow-grey earths. Of particular note is (y-FeOOH) with a probable small contribution from the way that iron-manganese concretions can Fe occurring as a minor component of other min strongly sorb many elements and thereby, at least era~s. X-ray ditfractograms show small peaks in the to an extent, control the availability and chemistry region of 6.3 A which is characteristic of lepido of these elements (Jenne 1968). Anionic species such crocite. However, these peaks remained after heat as phosphate, molybdate, vanadate, and sulphate ing the samples to 500°C for 6 hours and so cannot associate particularly with iron oxides, whereas be due to lepidocrocite, and are probably due to cationic species such as cobalt (see also Taylor & feldspars. Thus I is considered to represent ferrih McKenzie 1966), zinc and nickel associate with ydrite plus octahedral ferric iron occurring as a manganese oxides. In general these relationships minor component of other minerals. may be attributed to the different surface charges of iron and manganese oxides at the natural pH The areas under the peaks indicate an increase values of the soils. Manganese oxides appear to be in the ratio of goethite:ferrihydrite in the order l(b), generally absent from iron-rich mottles, and thus ,, l(c), l(d), which is consistent with increasing age mottles might be expected to be enriched in anionic, of deposit and measured ratios of oxalate-extract but not cationic, species. able Fe:citrate-dithionite-extractablc Fe for whole soil horizon samples. Note that Figs. l(c) and l(d), The presence and distribution of iron oxides is !OOnm being for samples from the second and third loess often implicated in discussions of soil structure (e.g. I layers, are not strictly relevant to present-day Schwertmann & Taylor 1977). Comparisons yellow-grey earths. However, these layers do con between soils with 'good' structure, such as the tain iron segregations similar to those in the over Dannevirke and Ramiha, on the one hand, and soils lying Marton silt loam. The spectrum (Fig. I (d)) for with 'poor' structure, such as the Marton and black concretions is indistinguishable from another Tokomaru on the other, tend to confirm such (not shown) for strong brown (7.5YR 5/ 8) mottles implications. In the Dannevirke and Ramiha soil c from the same depth, indicating, again, a similar the iron oxides are dispersed among other soil iron oxide mineralogy for concretions and mottles components; in the Marton and Tokomaru they are at a given depth. segregated to a large extent. Iron oxides, however, are but one of many interrelated factors implicated The assignment of goethite and ferrihydrite as in structure, and the possibility that poor structure outlined above was consistent with infrared spectra has led to intermittent reducing/oxidising condi !OOnm on the same samples (J.D. Russell, pers. comm.) tions and thence to segregation of iron oxides should and also with high resolution electron microscopy also be borne in mind. I and electron diffraction (J.M. Tait, pers. comm.). Electron microscopy of concretion and mottle samples from the 149-164 cm horizon (see Fig. 1) ACKNOWLEDGMENTS yielded particularly good micrographs of soil goeth ite and ferriydrite. Three of these are shown in Fig. The Marton core was taken as part of a project 2. by several Soil Bureau staff co-ordinated by Des Much more work needs to be done before gener Cowie. Derek Milne described the core. The alisations about iron oxide mineralogy of yellow experimental work on the segregations was carried grey earths could be considered reliable. One out at the Macaulay Institute for Soil Research in interesting question which remains open is the Aberdeen where I received expert and willing extent to which lepidocrocite occurs in yellow-grey assistance from Bernard Goodman (Moessbauer); earths. It is considered to occur in hydromorphic Jim Russell (infrared) and Mervyn Tait (electron soils in other parts of the world, often in associa- microscopy). 84 85 YELLOW-GREY OTAGO Yellow-brown earths: Both the A 1 and A, 1 hori more common in the Eastern Otago soils, being zons of the Teviot silt loam (Nos. PC928/ I and abundant in both horizons of the Pukerangi soil. G.J. D.S.I.R., Lower Hutt PC928/2) contain mica-vermiculite (very abun Claridge (1978) also noted high concentration in dant) and kaolin (present). Only these horizons were Eastern Otago soils. As discussed by Churchman (Received December 1981) examined. In the Waipori silt loam, the A horizon (1978) and Hewitt and Churchman (1982) for these (PC931/l) contains abundant mica-vermiculite with and other soils in Otago, kaolin, while being wide CLAY MINERALOGY smectite and kaolin present, the B horizon spread, appears in particularly high concentrations INTRODUCTION (PC93 l/2) is dominated by mica-vermiculite (very in soils in certain geographical areas. It is consid The clay mineral compositions of the various abundant) while chlorite and kaolin are both pres ered to be a relict of mineral transformations which Some features which distinguish the mineral occurred under a warmer climate (Churchman soils are summarised as follows: ent, and the C horizon (PC93 l/3) contains abun compositions of yellow-grey earths may be sug dant mica-vermiculite while mica, chlorite and 1978) and its occurrence therefore reflects locality gested by an examination of the day, and in some kaolin are all present. but not present-day weathering. Hewitt and cases also, the sand, and silt, mineralogy of these CENTRAL OT AGO SOILS Churchman ( 1982) show that, while these occur soils, in the context of their relationships to neigh rences of kaolin often contain high proportions of bouring soils. In this way the mineral compositions Yellow-grey earths: Mica is very abundant ( > c.70% of the clay fraction) in all horizons of both kaolinite, considerable halloysite can also be pres of a number of yellow-grey earths are compared SAND MINERALOGY ent, probably depending on the position of the with those of other nearby soils which are classified soils; interlayered hydrous micas (including chlor ite-vermiculite) are the only other mineral present sample in the landscape and/or in the soil profile in other groups. The sand mineralogy of the Central Otago soils in relation to a significant source of halloysite. in significant proportions (c.10-30%) in these soils. (Table 2, Churchman 1978) shows that the two Brown-grey earth: This soil also has very abun yellow-grey earths contain all major minerals from With kaolin excepted, a common feature of the SOILS AND DATA SOURCES dant mica, together with a significant presence of the parent schist rock (muscovite, chlorite, albite, mineralogy of five yellow-grey earths which have the combination of chlorite-vermiculite and inter quartz and epidote) to at least a 5% level of occur been examined is that minimal mineral transfor Two yellow-grey earths in Central Otago (Clu rence. The brown-grey earth has < 5% of chlorite mation has occurred during the course of their for layered hydrous mica. mation from the parent rocks. One of the most den silt loam and Tima silt loam) are compared in its BC horizon, otherwise its sand mineralogy is Yellow-brown earths: Mica-vermiculite is very weatherable of the primary minerals in the with three other soils (a brown-grey earth - Conroy similar. In the yellow-brown earths, chlorite was abundant in the clay fractions of all horizons of sequences under study, mica, is the dominant clay shallow silt loam and two yellow-brown earths - only found intermittently in the horizons exam both soils. Other clay minerals present in signifi Tawhiti silt loam and Carrick fine sandy loam) that ined, but all of the other major primary minerals mineral in each of the yellow-grey earths examined, cant amounts in any horizons of the soils include while the single most weatherable mineral in the form, with them, a part of a climosequence of soils are present in significant amounts. interlayered hydrous micas, both chlorite and mica parent rocks, chlorite, is often present in the clay in tussock grassland and on chlorite subzone 4 (in the lowest horizon of the soil <;inly) and fractions and was even more common in those sand schist. The sand, silt and clay mineralogies of these Tawhit~ kaolin (in two horizons of the Camck soil). and silt fractions that were examined. The clay soils are compared. Two yellow-grey earths in North SILT MINERALOGY fractions of the yellow-grey earths in Central Otago Otago (Killermont hill soil and Berwen hill soil) a:e (Detailed analyses of the clay mineralogy of these compared with two yellow-brown earths (Quail which were studied by Claridge (1978) were dom soils are given in Table 5. Churchman 1978 and The appearances of minerals in the silt fractions bum hill soil and Kirkliston gritty silt loam), all inated by illite (i.e. mica) or an 'interlayered hydrous Table 2, Churchman l 980a). of an upper and a lower horizon of each of the Cen four soils being members of an alto-climosequence mica'. By Claridge's (1978) definition, 'interlayered in tussock grassland on very weakly argillised semi tral Otago soils are noted in Table 4 of Churchman hydrous mica' could include mica-vermiculite. schist at Tara Hills. A further yellow-grey earth NORTH OT AGO SOILS (1978). Both of the yellow-grey earths, together with Nevertheless. Claridge's ( 1978) results, together with the brown-grey earth, show x-ray diffraction peaks those of the present study, suggest that the clay (Pukerangi silt loam) from Eastern Otago i~ col'.1- Yellow-grey earths: Mica is very abundant_in the for all of the major primary minerals with the occa minerals in yellow-grey earths show no or only a pared with two yellow-brown earths (Tev1ot silt upper horizons and abundant (c.40-600 Yo) m t~e sional exception of epidote, but no secondary min small amount of transformation from primary loam and Waipori silt loam) which were sampled lower (C) horizons; mica-vermiculite is present m erals except for interlayered hydrous micas. The silt in the same catchment area (Deep Stream catch minerals. The brown-grey earth which was studied significant amounts in both A ~nd C horizons ?f fractions of the yellow-brown earths generally con ment) in tussock grassland on chlorite subzone 4 here (Conroy soil) is indistinguishable from the the two soils, while the C honzons also contam tain fewer of the major primary mineral types than schist. The clay mineral compositions only of the yellow-grey earths under investigation on the basis interlayered hydrous mica, and, in one case, pedo those of either the yellow-grey earths or brown-grey of degree of change from the primary minerals, but North and Eastern Otago soils are described. genic chlorite, in significant proportions. earth. Of these primary minerals, chlorite is shown the yellow-brown earths analysed here, with one Environmental features of the Central Otago soils Yellow-brown earths: One soil in this group in only the Tawhiti soil lower horizon, evidence for exception (Quailburn soil), exhibit significantly are given by Molloy and Blakemore (1974) and (Quailburn hill soil) has a clay mineralogy which epidote is missing in patterns for the lower hori greater degrees of mineral transformation. By con Churchman (1978, 1980a), those of the North Otago is very similar to that of the two yellow-grey eart~s. zons of both soils, and mica is not detected in the trast, the yellow-grey earths of Eastern Otago which soils by Churchman (1980a), by derivation from The other (Kirkliston gritty silt loam) has mica upper horizon of the Carrick soil. The secondary were studied by Claridge ( 1978) showed a very data of Mr K.R. Dreaver (pers. comm.), and those merely present (c. l 0-30%) in the A hori~on, thoug_h minerals appearing in the silt fractions include mica similar clay mineralogy to the yellow-brown earths of the Eastern Otago soils partly by Mark and abundant in the C horizon. The A honzon of this vermiculite in both horizons examined from both in the same study, indicating that the clay miner Holdsworth (1979) and partly by Mcintosh and soil has abundant mica-vermiculite while the C yellow-brown earths, interlayered hydrous micas in alogical differences between yellow-grey earths and Backholm (1981 ). The sand, silt and clay mineral horizon has both chlorite and pedogenic chlorite the two analysed horizons of the Tawhiti soil, and yellow-brown earths can be very minor. ogy of the Central Otago soils are from Churchman present in significant amounts. the related chlorite-vermiculite in the two Carrick (1978) while the clay mineralogy of both these and soil horizons which were examined. In the sand and silt fractions, as in the clay frac the North Otago soils are given in Churchman (Detailed analyses of the clay mineralogy of these tions, the limited number of analyses suggest that ( l 980a). The clay mineralogy of the Eastern Otago soils are given in Table 2, Churchman l 980a). yellow-grey earths contrast with yellow-brown soils have been determined for a study of lysimeter earths in showing a lower degree of weathering transformation of minerals from the parent rocks. leachates and soil solutions being carried out by EASTERN OT AGO SOILS DISCUSSION G.J. Churchman and H.J. Percival (unpublished While the yellow-grey earths which have been data). Clay mineral occurrences are compared on Yellow-grey earth: Both the A and B horizons of Kaolin, regarded as a group designation, is ubiq examined have significant amounts ofall of the pri the basis of semi-quantitatively determined rela the Pukerangi silt loam (Nos. PC929/1 and PC929(2 uitous in the clay fractions of these soils, whether mary minerals in their two coarse fractions taken tive abundances (as in Churchman 1980a), using respectively) contain mica (abundant) and kaolm yellow-grey earths or otherwise. It is rare in the together, primary minerals, particularly chlorite, the analytical methods of Churchman (I 980b). (abundant). North Otago soils (G.J. Churchman, unpublished were often not detected in these fractions of the data), usually rare though sometimes present in sig yellow-brown earths. nificant amounts in the Central Otago soils, but 86 87 grey earths appears to be dominated by ~i~a. Sm~ll remove amorphous matter and wet sieved at 63 µm. Quartz is occasionally bipyramidal especially amounts of mineral transformation are md1cated m The > 63 µm fraction was dry sieved while the where associated with Aokautere Ash, but, in some of the samples by the appearance of interlay All yellow-grey earths th~t were . examin.ed < 63 µm fraction was treated by the settling and general, forms either as relatively rounded grains showed little or no transformation of pnmary mm ered hydrous mica (and chlorite-vermiculite) and, centrifuge technique of Jackson (1956). The with dusty inclusions or as angular clear fresh frag erals. The degree of transformation was almost less commonly, mica-vermiculite. Kaolin appears > 125 µm and the 125-63 µm fractions were passed ments with a conchoidal fracture. There is a broad to be ubiquitous in Otago soils. It is likely to be a always less than that in yellow-br?wn earths fo~med through a magnetic separator and split into mag group offeldspars which have a low refractive index nearby on similar parent matenals. Over this set relict of mineral transformations under a different netic and non-magnetic fractions. After impregna and contain dusty inclusions or sericite. These are of Otago soils the clay mineralogy of the yellow- climate. tion in epoxy resin under vacuum, thin sections that interpreted as being albite derived from sediment contained a magnetic and non-magnetic example of ary rocks and are referred to as sedimentary pla each sample were prepared. gioclase. There is a second group of fresh feldspars with high refractive index, commonly containing inclusions of brown glass, opaques, pyroxenes and hornblende, which is interpreted as volcanic pla RESULTS gioclase. This plagioclase is complexly zoned and is typical of acid or intermediate volcanic rocks. Samples were taken from the same locality Optical data indicate a core of An 00-An65• The SILT AS AN INDICATOR described by Pollok ( 197 5). Grain size analysis (Fig. colourless glass (rhyolitic) forms grains of pumice, 1) demonstrates that, except for Aokautere Ash at H•, ... , PROVENANCE keel- or Y- shaped shards or tabular flakes and can 2.21-2.34 m depth, the loess has a relatively uni commonly contain crystallites. The opaques are form grain size distribution below 0.6 m. Above usually euhedral and often have glassy selvages. R.C. Wallace and V .E. Neall, of Soil Science, Massey University, Palmerston North 0.6 m the clay and coarse silt fractions show a sys Biotite can be highly altered to chlorite. tematic and antipathetic variation. (Received September 1982) The mineralogy of the sand fraction is highly variable due to the diverse provenance. Inventories (l 973) conducted X-ray diffraction analyses of some of the minerals present in the magnetic and non DISCUSSION of the topsails from Mt Egmont to Palmerston magnetic splits are presented in Table 1. Tokomaru silt loam (Cowie l 964b, 1978; Pollok North and included two samples from Tokomaru The grain size distribution emphasises the uni 1981) is a yellow-grey earth (or Fragiaqualf) that is silt loam in their study. Quartz and feldspar were formity of the loess below 0.6 m and the hetero widespread on the high terrace to the east of the the dominant minerals with minor hornblende and geneity above. There is a significant increase in clay Manawatu River. The parent material is domi mica. No volcanic glass was identified. There is also content between 0.5-0.6 m and Pollok (1975, 1981) nated by non-calcareous greywacke-derived loess. an unpublished qualitative mineralogical analysis attributed this to pedogenic formation of clays in Table l Mineralogical constituents of the the pseudogley horizon. However there has also been a significant tephra of Tokomaru silt loam by N.Z. Soil Bureau on a > 125 µm fraction of the Tokomaru silt loam input, on~ such addition, the Aokautere Ash (Cowie sample taken from between 0.68 and 0.72 m d~pth. The influence of Aokautere Ash on the grain size l 964a· Howorth et al. 1980), forming a valuable It shows quartz and acid feldspar to be dommant distribution is significant. Unlike the physical Magnetic split mark~r horizon in the loess. The loess was derived with minor glass, augite, hornblende, hypersthene boundaries of the ash, which are sharp, the miner from a former aggradational floodplain of the Man and magnetite. Major Minor Accessorv Augite Microcrystalline Garnet alogical evidence shows that rhyolitic material is a awatu River (Ohakea Terrace) during the last sta significant component in the profile for up to 0.6 m dia! of the Otiran. Aokautere Ash (Cowie l 964a; Vucetich & Hypersthene volcanics Zircon Howorth 1976) is an important marker horizon in Hornblende Brown glass Sphcne above the upper boundary of the ash. This rhyolitic Although dry in summer, Tokomaru silt loam is the loessial soils of the Manawatu district (Rhea Biotite aggregates (obsidian) Diatom material is thought to be ash blown off the Ohakea Epidote aggregates Opaques aggregates surface. very wet and has a perched water table in .winte:. 1968; Cowie 1978). Vucetich and Pullar (1969) cor Epidote group minerals (Biotite/chlorite) This feature was recognised by the early mvestl related Aokautere Ash with the Oruanui Forma Non-magnetic split The mineralogical data are more varied than the gators (Hudson & Fife 1940). Fife ( 1945) undertook tion, and more recently Vucetich and Howorth Major Minor grain size data and the distribution of the signifi the first detailed study of the soil. He showed that (1976) have proposed a new name (Kawakawa Quartz Muscovite cant phases down the profile is plotted in Figs. 2 there was a significant increase in clay content in Tephra Formation) that includes Aokautere Ash. Sedimentary plagioclase Microcline and 3. These data show that there is an antipathetic the B horizon and that whereas exchangeable Ca Radiocarbon dating (see Vucetich & Howorth 1976) Sericitic aggregates Apatite relationship between grains with a sedimentary exceeded Mg down to the AB horizon this rela has established that Kawakawa Tephra was erupted Quartz aggregates Zircon Volcanic plagioclase Sponge spicules origin and the colourless glass, the volcanic plagio tionship was reversed in the B horizon. Fife also c. 20 OOO yrs B.P. Mineralogical data on the tephra clase or the magnetic fraction (where hornblende showed that there had been a movement of iron (Howorth et al. 1980) show the ferromagnesian suite and pyroxenes dominate this fraction). Based on down the profile and that iron was concentrated in to be dominated by hypersthene with minor augite this distribution, two non-sedimentary prove the lower B horizon, which contains iron concre and hornblende. nances can be identified (Table 2). First, the con tions. In a chemical study of the concretions, Brooks This paper reports on the principal constituents comitant abundance peaks of colourless glass, (1965) showed that there were no significant differ The hornblende (a brown-green variety), clino obsidian and hypersthene are a distinctive marker ences between the concretions and host soil. The of the sand fraction of Tokomaru silt loam. pyroxene (pale green augite) and orthopyroxene for a rhyolitic assemblage. This is c~msistent with amorphous inorganic materials were described by (pink hypersthene) contain inclusions of brown glass the mineralogy of Aokautere Ash in this profile. Kirkman (l 973a, b). In a detailed study P~llok and commonly have glass selveges. Towards the Second, there is an assemblage typified by horn (1975, 1981) recognised that the lower B honzon SAMPLE PREPARATION base of the profile the pyroxenes are highly etched blende and/or augite, volcanic plagioclase and a was a pseudogley horizon resting on a fragipan. He so that their terminal faces are composed of jagged high magnetic fraction, which is thought to be an showed that there were significant changes in the For the present investigation, continuous sam pinnacles. However above 0.5-0.6 m this etching andesitic assemblage. It is therefore possible to clay type, micromorphology and variable charge at ples were taken at 10 cm intervals, to a depth of is absent or at least much less marked. There is a locate pulses of tephra in the loess and identify these this boundary. Physical measurements by Scatter 2.5 m, in 'Pollok's Pit' (NZMSl Nl49/l 15319) near significant amount of microcrystalline volcanic as being of rhyolitic (0-0.2 m; 0.3-0.4 m; 0.65- et al. (l 979a) also demonstrate a marked change at Massey University. After airdrying, the samples fragments. These consist of very fine grained pla 0. 75 m?; 1.l-l.2 m and 2.21-2.34 m depth) or the base of the pseudogley. were treated with 1M NaOAc-HOAc (pH 5) and gioclase, pyroxenes, hornblende and opaques, or andesitic (O.l-0.4m; l.l-l.3m; l.5-l.6m and Very little mineralogical data from Tokomaru H,0, to remove carbonates and organic matter. combinations of these minerals in a clear or brown l.85-2. l m depth) origin. Below 0.5 m, where loess silt loam has been published. Symes and Wells They were then treated with sodium dithionite to glass matrix. dominates, the tephras are relatively discrete but 88 89 Sample Number POLLOK cm cm 25 A h1 Table 2 Summary of the mineral occurrences and depths (m) that detine two volcanic 10 s assemblages in the Tokomaru silt loam 24 Ah2 < 2yrn 63 - 20 ym 250 -125J1m 20 23 Assemblage I (rhyolitic) 30 ABg Mineral Constitue/l/s 22 38 Colourless glass 0-0.2 0.3-0.4 0.65-0.75 1.05-1.2 2.21-2.34 Brown glass 0-0.2 I.I -1.2 2.14-2.4 21 Hypersthene peaks* 0.1-0.2 0.3-0.4 I.I -1.2 2.25-2.42 so 20 Assemblage H (andesitic) Btg Mineral Constituents Btg2 Volcanic plagioclase 0.1-0.2 0.3-0.4 1.1-1.3 1.5 -1.6 1.85-2. l % magnetic/total sample 0.1--0.4 1.1-1.25 1.55-1. 7 1.9 -2.14 75 Hornblende dominates* 1.2-1.4 1.5 -1.6 1.8 -2.0 76 Augite dominates* 0.1--0.5 1.2-1.3 1.85-2.14 *The phases named reached a maximum or dominate the igneous fcrromagncsian assemblage (hornblende, augite 16 and hypersthenc) 15 Cxg 4 Cxg above this level rhyolitic glass+volcanic plagio- a marked peak in clay content which indicates a 13 clase+magnetic fraction (mainly volcanic) consti- marked stratigraphic break at 0.5 m. It indicates a 12 tute 50-70% of the material studied and there has significant hiatus in loess accumulation probably been considerable mixing of contemporaneous marking the end of the Otiran Glacial Stage. 11 145 tephras. The marked change in the mineralogical properties at 0.5 m approximately corresponds with The relative abundance of tephric material in 10 the change from etched to unetched pyroxenes. The Tokomaru silt loam, especially the upper 0.5 m, variation in physical properties detailed by Scatter suggests that there are probably no North Island 9 et al. (l 979a) and the switch in exchangeable bases soils, except recent soils. that do not contain some accretions of volcanic material. s ratio (Fife 1945; Pollok 1975) is immediately above Cwg1 7 Cw91 6 s 4 221 3 34 2 10 20 30 40 50 60 5 1 0 % Whole Sample Figure 1 Variation in grain size distribution of the clay, coarse -very coarse sill and fine sand in the Tokomaru silt loam. Horizon boundaries of Pollok (1975) and the present study arc according to the FAO/Unesco horizon designation 90 91 OPX CPX HBLDE ·... ·. <...... O·S ····· ·... 0·5 \ I I I I 1·0 1·0 \ I E / I / E :::c \ I- \ CL I 1..1..1 Cl I ...... \ 1·5 ..... ···· \ 1·5 \ \ " '-- ·- ····· ...... - ...... >··~ .--····· --- 2·0 ------~ __:..···~·--· ::-:- --- ...... _ - --········ ········.:..:..: .. .-:-:-:: ...... -·· ...... ········· -- 20 40 60 60 10 20 10 20 30 10 20 30 % of >12Sym non - magnetic: fr act ion % of > 12sym magnetic traction · I · I , (B) and grains of sedimentarv origin (C) as a function of depth in · · · f h 1·t'1 · la ·s ( L\) volcanic p ag10c asc . Figure 2 D1stnbut10n o r yo ic g s. · ..• th ion magnetic split of the > 125 ,1m fraction Figure 3 Distribution of hypersthcne (OPX). augite (CPX) and hornblende (HBLDE) as a function of depth in the Tokomaru silt 1 the Tokomaru silt loam. The samp1 cs arc 1om c ' - ' · loam. The samples arc from the magnetic split of the > 125 ,1111 fraction 92 93 likely to be further accentuated by confinement of vides room fo! shrinkage cracks through the veins, roots, where they reach the C horizon, to the grey and thes~ fac1htate rc-_wetting in the autumn. During vem_s. Dunng summer water must migrate several the wet s~ason, swelling of the grey material closes centimetres laterally from the centres of the blocks these dra~nage. channels and Watt ( 1977) observed !O the roots. The indications are that this migration a Cx honzc:m imposing control on the movement is a rather slow process. _Gradwell ( 1979 - Table 2) of wat~r, with_ a perched water table existing in the has shown the hydrauhc conductivities of some overly1'.1g honzon. for up to 140 days in a wet win DENSITY SUBSOIL HORIZONS AND ITS EFFECTS ON PORE-SIZE yellow-grey earth C horizons at a tension of 100 cm ter. This o_b_struct_10n to drainage can prevent true DISTRIBUTION, PERMEABILITY AND STORAGE of water (about field capacity) to range from 3X 10 s field eapac1t1es bemg attained in yellow-grey earths. to_ l.5X 10-• cm/h. These are low values compared Gradwell (l 974 -: Table 9) recorded tensions of only with m~st. Table 1 Mean volumes of pores of various sizes in two soil groups. Pore volumes are INTRODUCTION contended th_at structural deterioration on yellow grey_ earth~ ?1d not proceed in direct proportion to expressed in percent of soil volume Yellow-grey earths have a reputation for being fall I? ~ert1h_ty. Thus, on the Timaru silt loam pro S!ruc_turally unstable and erosion prone under cul du~tiv1ty might fall by 50% and remain at this level 100-200 200-400 400-1000 0-50 50-100 t1vat10n (Raeside l 954a Packard 1958 B. II wh1l~ structure was progressively destroyed. He Range of tensions in which 1972). ' , irre pores drain (cm of water) considered that of the cropped yellow-grey earths 60-30 30-15 15-7.5 7.5-3 Equivalent cylindrical diameters > 60 of South Canterbury, I 0% had adequate structure Tops?il physical ~rop~rties which influence plant of pores (µm) showed moderate structural deterioration and growth mcl_ude: avaliabJ!Ity of soil water and soil 60~o 2.5 30 Yo showed strong structural deterioration. 6.6 1.2 1.2 I.5 oxygen, soil temperature and penetration resist B horizons yellow-brown carths I.2 1.4 2.9 ance. As ~e.llow-grey earths tend to have high dry A variety of cultivation techniques have been yellow-grey carths 6.2 I. I 1.9 bulk dens1_t1~s and low porosities even under pas test~d o!l these soils, ranging from conventional full 5.7 I.I 1.0 I.2 C horizons yellow-brown carths ture cond1t10ns (N.Z. Soil Bureau I 968b), this cult1vat10!1 t~ zero-tillage. The relative merits of 0.6 0.9 1.0 2.0 yellow-grey earths 4.6 means. that proble1:1s of watcrlogging, anaerobiosis these cult1vat1on sy~tems arc discussed by Jackson and high penetrat10n r~sist~nce are likely to be ( 1972). The '.oll~wmg case studies illustrate the accentuated under cult1vat1on. Raeside ( l 954a) effects of cult1vat1on practices commonly used. 94 95 CONVENTIONAL CULTIVATION ON A crop yields. This deterioration in soil properties may W AITOHI SILT LOAM have been averted if sound farm management prac 90 tices had been followed. This seminal paper by Packard & Raeside ( 1952) was the first published study in New Zealand of the 80 Water stable aggregates > 2mm effects of cultivation on soil physical conditions and Water stable aggregates< 2mJ11>1mm productivity on a yellow-grey earth. A cropping CONVENTIONAL CULTIVATION ON A Water stable aggregates <1mm>0·5mm rotation of two years cropping followed by four W AKANUI SILT LOAM , Total w.s. aggregates >0-5mm 70 years green feed and pasture and then one year tur p= years under pasture nips and one year rape was described as appropri An unpublished report by E.Z. Arlidge (Com c=yeara of cultivation ate for first class Canterbury soils. For second class parison of Aggregate Stabilities of Two New b.g, = bareground soils the same rotation was used with only one year Zealand Cropped Soils) contains information on the 60 cropping. For the soil described by the authors, a physical behaviour of the Wakanui silt loam under one year wheat, one year fallow rotation had been various periods of cultivation and rates of struc tural recovery under a variety of pasture species. c: used, and poor crop yields had resulted. 0 50 -~ The study area was in the Geraldine District of Two trials on Crop Research Division's, D.S.l.R .. Ol ~ farm at Lincoln were investigated. A Grasslands Ol South Canterbury. Two fields, one recently Ol ploughed, were compared with an uncultivated Division, D.S.I.R .. long-term soil fertility trial (L7) "' 40 headland in predominately cocksfoot pasture. Field was started in 1956 to examine rates of build-up of inspection revealed that the cultivated fields often soil fertility by various pasture species after exhaustive cropping. For three years the trial area appeared waterlogged and presented single grained 30 topsoil structures. The soil was difficult to culti was cropped and intensively cultivated in order to vate, forming large clods if wet and readily pow degrade the soil's nutrient status and physical con dering to dust if dry. dition. After one year of pasture, additional por tions of each pasture plot were cultivated and 20 Chemical analyses revealed significant decreases cropped in kale and potatoes. A median strip in organic carbon and nitrogen. The organic carbon between plots was kept fallow by the use of values fell from 4.2% in the uncultivated headland herbicides. 10 to 2.3-2. 7% in the cultivated fields. It should be noted that in the L 7 trial the dura Four techniques of structural analysis were used: tion of pasture decreased from five to one years as the period under crops increased from one to five 1. End over end shaking followed by wet sieving. years; therefore total period in pasture and crops 4p+Oc 6p+Oc 5p+1c 3p+3c 1p+5c b.g. 2. Moisture characteristic of sieved aggregates. was six years. Unfortunately, the design of the trial did not provide plots with increasing years of crop Figure l Water-stable aggregates. Wakanui silt loam 3. Total porosity. ping following, say a five-year pasture. 4. Large pores, drained at 40 cm tension. The other trial sampled also on Crop Research destruction during cultivation. Division's farm. represented the long-term crop Results from the wet sieving analysis cannot be ping case. From 1933-1951 it was continuously On the long term cropping trial only 10-15% of MINIMUM TILLAGE ON A TIMARU SILT directly compared with the standard Yoder ( J 936) cropped for cereals. potatoes. peas, brassicas and the soil was retained as water stable aggregates LOAM technique. However, results showed 50% water linen flax. From 1951 to 1965 (the time of sam >0.5 mm. stable aggregates > 0.42 cm for the uncultivated pling), it had been in a crop rotation with 2 years On a farm in the Lyalldale area, South Canter headland soil. Internal comparisons which are more in every 5 under pasture, (ryegrass and clover seed Extrapolating from short term records and bury. long term minimum tillage cultivation had reliable showed that if the uncultivated headland production with sheep grazing). assuming a linear decline in aggregate stability with been practiced. The cultivated area had been soil ranked 100 points then the cultivated field soils cropping seasons. 15% water stable aggregates will cropped in barley for I 0 years with a winter green would average 66 points. a marked decline in Aggregate stability analyses were carried out, be expected to occur after 29 years. The actual crop used for stock feed. Cultivation involved a aggregate stability. An apparent anomaly is that the including wet sieving of 2-4 mm air dry aggregates, period of the long-term cropping trial was 33 years. single pass with a 12 m wide grubber behind the uncultivated soil structural stability is unusually using the technique of Yoder (1936). The percent- harvesting header to bury plant stubble. Another high compared with other Canterbury yellow-grey . age of water stable aggregates were recorded. Results From Figure I. structural stability increased after run with the grubber was made just before drilling earths while the cultivated soil is similar to other from the L 7 trial are shown in Figure 1. Percentage four years restorative pasture to over 80% total which was carried out by a triangular array. Until water stable aggregates > 0.5 mm and only a 6% cultivated yellow-grey earth soils which do not water stable aggregates > 2 mm showed a sharp the season previous to sampling, stubble had been increase in the following two years. This was under deteriorate as severely as the soil in this study. decrease after the first season's cropping and then burnt. a gradual decrease with increasing years of crop a perennial ryegrass-clover pasture. Soil under this Technique (2) showed the same trend as ( l) with ping. Accompanying this decrease was a partial pasture mixture had 25% more water stable aggre An adjacent undisturbed site under permanent lower structural stability for the cultivated soils. compensating increase in %water stable aggregates gates > 2 mm than soils with fall fescue and cocks cocksfoot and ryegrass pasture was selected as a foot. Soils under a dominantly clover pasture control. Samples at both sites were analysed for Total porosity and large pores (techniques 3 & 1-2 mm and 0.5-1.0 mm. The net effect over four showed intermediate stabilities. These differences aggregate size distribution, aggregate stability, dry 4) showed declines from uncultivated to cultivated years of cropping was a 6% decrease in aggregates persisted when the soil was returned to cropping bulk density, pore size distribution and moisture soil. However. one field which had been recently > 0. 5 mm, compared with a 16% decrease in aggre for some years. release characteristics. Results are shown in Table ploughed showed similar values to the uncultivated gates > 2 mm. 1. Topsails on bot.h cultivated and uncultivated sites headland. This temporary improvement in aera The area left fallow during the four years of Aggregate stability therefore has been shown to averaged 20 cm depth. However, cultivated sites tion properties would subsequently be obliterated monitoring had the lowest amount of water stable decline with cropping on this yellow-grey earth. with by the action of weather and soil cultivations. showed two subhorizons within the A horizon, and aggregates. This may indicate that the deterioration very low aggregate stability values occurring after therefore upper and lower A horizons were sam 20-30 years cropping. Aggregate stability levels can The authors concluded that deterioration in soil of amount of water stable aggregates in this soil pled at each site. physical conditions and related decline in soil under cropping is due more to the absence of aggre be restored following at least three years cropping Aggregate stability analysis for pasture sites organic; matter contents correlated with decline in gate restorative plant growth than to aggregate with up to four years in pasture. with the most effective pasture species being ryegrass. showed no difference between the upper and lower 96 97 Table 1 Soil physical properties, Timaru silt loam Treatment Aggregate stability Mz B.D. L.P. Total P AWC M( 0 26 460 26 46 Weeks after initial sampling A horizon for 3-2 mm aggregates. For 9-3 mm ceptable deterioration as would probably have hap aggregates, the lower A horizon was more stable, pened under a conventional cultivation system. Figure 2 possibly the result of fewer roots in the lower A 1977) The effects of tillage treatment and time on soil aggregation after dry-sieving. Tokomaru silt loam. (From Hughes & Baker horizon exploiting planes of weakness in the larger aggregates. A RANGE OF CULTIVATION For cultivated sites there was again an increase TREATMENTS ON A TOKOMARU SILT in stability but this applied to both 9- LOAM 3 mm and 3-2 mm aggregates. For both sizes of stability was highest in the lower A Robinson and Jacques ( 1958) investigated the of cultivated soil. This may be due to the effects of pasture species restoring soil structure on organic matter contribution of straw residues Tokomaru silt loam, the ubiquitous yellow-grey buried in this horizon. Over all horizons and soils earth from the Manawatu. 9-3 mm aggregates were more stable, while for both sizes, aggregate stability was overall higher After three years of conventional cropping of kale in pasture soils. and maize, the experimental area was showing ini tial signs of structural deterioration. A variety of plant species were planted: perennial ryegrass, 100 chewings fescue, cocksfoot, white clover and red 80 clover. Analysis of water stable aggregates showed a significant increase in aggregate stability after four 60 months, with the perennial ryegrass plot having the 40 >3·3mm >3·3mm highest aggregate stability, followed by chewings 20 fescue and then the other species. After eight months the only significant difference was between % Ploughed etc. showed an increase with depth in 100 lowest in cultivated upper topsoil chewings fescue and clovers. After 20 months, when virtually identical at both sites below the experiment ended, aggregate stability had BO increased by 40% and chewings fescue samples were porosity declined with depth and was 60 """"'"t'''" in cultivated soil. Large pores again still significantly more stable than white clover samples. 40 "'"'~u'''"'"' with depth, the lowest value being in cul- >3·3mm lower which could be limiting to Hughes and Baker (l 977) compared zero tillage, 20 >3·3mm Available water capacity was conventional ploughing and rotary cultivation on a 0 in the minimum tillage area and Tokomaru silt loam. The experimental area, which 26 460 26 46 \.HC•l-Ull\,U with depth. came out of 40 year old pasture, was cultivated Weeks after initial sampling Overall long term minimum tillage had pro through 1973-74. Control and direct drilled sites duced a soil with weaker aggregate stability and showed the same response to dry sieving, with all aggregates greater than 9.5 mm. Cultivation caused Figure 3 in aggregate sizes. The action of tillage had & a breakdown in aggregate size, with rotary culti 1977) The effects of soil treatment and time on soil aggregation after wet-sieving. Tokomaru silt loam. (From Hughes Baker vUILlLCU large pores and increased bulk density in the lower topsoil. However, the action of cultivat vation causing the greatest breakdown (Fig. 2). ing the soil had increased total porosity and avail Aggregate stability declined under ploughing and able-water capacity and redistributed organic matter rotary cultivation (Fig. 3) while the control and zero within the topsoil. As a medium for plant growth tilled sites showed no decline. the tillage soil had not suffered unac- Ross (1981) reports on a number of cropping 98 99 trials carried out on Tokomaru silt loam soils. The Zero tillage treatment areas had later maize background to the first trial is given by Hughes emergence and slower early growth compared to Table 3 Soil physical properties (0-20 cm) of a Tokomaru silt loam under six different tillage systems (1981). Results are shown in Table 2. Reduced til cultivated areas. This was attributed to soil and in wheel tracks lage systems have resulted in higher dry bulk dens mechanical resistance restnctmg early root ities, lower porosities (especially macroporosity) and development and associated nutrient uptake. Property Rotary Rotary Plough- Once- Once- Minimum Minimum Direct Direct lsd(l(J.' ls Table 2 Soil physical properties (0-10 cm) of a Tokomaru silt loam under three different tillage systems Sampling Traditional Minimum Zero Pasture lsdu_11i Cult. Cult. Cult. Bulk density (t/m') Plant '79 1.16 1.28 l.39 0.06 0.09 Harvest '80 1.10 1.20 1.27 0.11 0.15 minimum cultivation tends to loosen and open up Long term conventional cultivation appears to lead Plant '80 1.09 I. I I 1.41 0.1 l 0.15 the soil from its pasture state which is too compact to significant reductions in soil productivity due to Harvest '81 1.24 1.33 1.44 1.31 0.07 0.10 to be optimal. Zero tillage treatments tend to com deterioration in soil structure. Long term mini Porosity (Macro-) (%) pact the soil, in some cases detrimentally as in the mum tillage appears to be successful although zero Plant '79 57 ( 16) 51 (7) 45 (I) 4 (7) 5 (10) case of the zero tillage maize trial (Ross 1981 ). tillage may have difficulties due to the inherent Harvest '80 54 ( 17) 49 (9) 48 (6) 3 (6) 5 (8) However, conventional cultivation if applied 'compactness' of these soils. The inherently weak Plant '80 57 ( 19) 56 (17) 46 (I) 4 (7) 6 (9) structures and climatic environment of the yellow Harvest '81 54 ( 18) 50 (13) 45 (5) 50 (7) 5 (8) 6 (11) incorrectly may also cause compaction and anaerobiosis. grey earths means that they require only minor Plant water storage 0-10 cm (mm) deterioration in properties to become unsuitable for Plant '79 21 24 24 Aggregate stability decreased in all cases with cropping. However, recovery of structural proper Harvest '80 18 20 22 increased cultivation. Mean aggregate size showed ties under pasture appears to be reasonably rapid. Plant '80 17 20 24 a variety of trends, increasing under minimum til Harvest '81 18 19 19 19 NS lage, and then decreasing again under more intense How much variability in soil physical properties Aggregate mean weight diameter (mm) cultivation (Ross 1981). These differences may be and response to cropping occurs within the yellow Plant '79 7.4 12.0 12.7 3.9 5.4 reconciled by envisaging absence of pasture causing grey earth soil group? Using an aggregate stability Harvest '80 9.3 12.8 16.2 3.7 5.2 assessment method (McQueen 1981), a number of Plant '80 13.l 15.7 17.5 2.6 3.5 clodiness which in turn may be counteracted by Harvest '81 10.6 12.4 15.9 7.1 3.5 4.9 cultivation. yellow-grey earths have been compared (Fig. 4). Aggregate water stability (% retained all sieves) Increased aggregate stability is indicated by higher In general, careful cultivation improved the values of the dispersion and slaking indices. Soils Plant '79 68 71 66 physical properties of this yellow-grey earth. Harvest '80 50 so 38 with high aggregate stabilities plot in the upper right Plant '80 49 52 53 of the figure. while soils with low stability plot in Harvest '81 53 64 58 83 NS the lower left. These soils show a considerable var Carbon(%) iability in structural stability even within the same Plant '79 2.1 2.3 2.2 CONCLUSIONS soil series, e.g., Lismore soils. Packard (1981 ), Table Harvest '80 2.2 2.3 2.3 4, also indicates a range of structural stabilities for Plant '80 2.2 2.4 2.2 What generalisations can be made about the undisturbed soils (i.e. soils under permanent pas Harvest '81 2.2 2.3 2.3 2.'J NS behaviour of yellow-grey earths under cultivation? ture, headlands) and moreover, a variety of Statistical comparisons by least significant differences - lsd (P=0.05; 0.01 ); From Ross (1981) NS=not significant 100 IOI responses to cropping for the same soil. This var Table 4 Aggregation of some yellow-grey earths iability in response is also indicated in the studies outlined in this review, for example, the Tokomaru Locality Brief description Degree of studies of Ross (1981) compared to Hughes and aggre Baker (1977). gation% Soil structural variability may be related to organic carbon content. Plotting resistance to slak Geraldine Headland 55 Heavily cropped paddock 34 ing against organic carbon (Fig. 5), a linear rela Mairaki Permanent pasture 47 tionship with a correlation coefficient of 0.88 is (near Rangiora) Heavily cropped paddock 39 obtained. Organic matter appears to play a crucial Amberley Headland 35 part in maintaining aggregate stability of yellow Heavily cropped paddock 26 grey earth soils. For assessing the suitability of an Methven Field in good structure 51 5 area for cropping, sampling of site specific topsoil Heavily cropped paddock 46 Liemore (H) X properties such as organic carbon, aggregate sta Martin borough Permanent pasture 35 bility, etc. may be the most practical form of mak ing an accurate assessment of cropping suitability. 4 From Packard (1958) (.) ~ 3 Lismore (R) X x X Claremont 0 Tokomaru 2 r•=·1'1 r=·88 y= ·'11 + ·04(x) BO 20 40 eo 100 Slaking Index 60 Figure 5 Organic carbon % versus slaking index (derived from Fig. 4) '"'Q) X Lismore (H) "t:I c: c: .ii?0 40 X Timaru X Claremont Q) 0.. Cl) Ci X Wakanui X Marton Tokomaru X Lismore (R) x 20 Mapua x 20 60 100 120 Slaking Index Figure 4 Yellow-grey carths dispersion slaking plot Mapua: intergrade between yellow-grey earth and yellow-brown earth. orchard site with considerable erosion in the past Lismore (H): Lismore very stony silt loam. locality south of Hinds River Lismore (R): Lismorc shallow silt loam. locality south of Rakaia River 102 103 7. BIOCHEMISTRY mycorrhizae increased clover growth at higher soil Irrigation of cores of I 0 soils, including Toko P levels in the presence of ryegrass than in its maru silt loam and Takapau stony loam, with water absence (Hall 1978a). VA mycorrhizae have also or sewage effluent gave greater microbiological been found to affect the nutrient uptake and growth differences among the soils than between the two of Zea mays varieties in yellow-grey earths (Hall treatments (Cairns et al. 1978). Specific diversity of I 978b). protozoa was high in the two yellow-grey earths, Eroded soils, including Omarama and Tengawai but this is considered to reflect plant productivity rather than a direct soil effect (Stout 1978). Simi BIOLOGY OF YELLOW-GREY EARTHS steepland soils, were found to have low VA mycor rhizal infections (Hall & Armstrong I 979) and larly, soil differences were more important than inoculation often produced large increases in shoot treatment differences in affecting the numbers and G.W. Yeates, Soil Bureau, D.S.I.R., Lower Hutt growth if high rates of P were not applied. The kinds of actinomycetes isolated (Orchard 1978). potential for using VA mycorrhizal infected plants (Received February 1982) in revegetating eroded land or mine spoil is clear. NEMATODES INTRODUCTION YEASTS activity or periods of stress with consequential frag Pasture nematode genera in 13 yellow-grey earths The sampling reported by Lee et al. (1968) from mentation of the mycelium. Populations of the yeast Lipomyces in Wakanui and 6 intergrades were reported by Yeates (1975), seven yellow-grey earths and related soils is the last Nitrogen-fixing Clostridia (anaerobic bacterium) and Matapiro soils were the highest found in a sur and in terms of plant pathogenic genera Heterod comprehensive survey of the biota of these soils. were isolated from 10 yellow-grey earths examined vey of some 40 New Zealand soils by di Menna cra, Praty!cnchus and Paratylenchus were predom (l 966b). All yellow-grey earths examined contained More recent studies have included the enzymology by di Menna (l 966a) but numbers were low. inant, although llelicotylcnch11s has since been of these soils, the effect on them of effluent dis Thornton ( 1965) and Jackson ( 1965) similarly Lipomyces while this was not the case for all yellow found in significant numbers in Tokomaru silt loam posal, and populations of invertebrates such as reported low fungal populations in these soils. Nei brown loams, brown granular loams or recent soils. (Yeates I 978b). Data suggest both H eterodera and The widely fluctuating moisture regime of yellow nematodes, earthworms and insect pests. These ther di Menna (l 966a) nor Line & Loutit (1969) Pratylenchus may be associated with some depres grey earths appears to advantage Lipomyces in rela studies have provided some biological information recovered the free-living nitrogen-fixing bacterium sion of herbage production, at least in Kokotau silt tion to other yeasts. on yellow-grey earths, but in a fragmented. indirect Azotobacter from yellow-grey earths, low available loam. While plant species and cropping history have way. C, N and P as well as soil pH 6.5 or above appar always been regarded as important in influencing nematode distribution and abundance, current work These soils typically have a summer moisture ently being necessary for its establishment. EFFLUENT DISPOSAL on Kokotau silt loam indicates marked differences deficit and rooting is often impaired by a pan. Rhizobium tr(folii, the symbiotic root nodule Effluent studies have included yellow-grey earths, from site to site which may affect results of agro However, the wide geographic and climatic range bacterium, was reported to be present in yellow and in a basic study with the bacteria Escherchia nomic trials (Yeates & Crouchley unpublished). of yellow-grey earths, the strong seasonality of their grey earths in sufficient numbers (16 500/g soil) not coli and Streptococcus bovis Guy and Visser ( 1979) moisture regime and the absence of a comparative to require inoculation (Leamy et al. 1974, Ludecke found that high clay content and low pH appeared A variety of studies have been carried out on biological survey of this soil group mean an inte & Leamy 1972) but a more general survey by Gaur to be responsible for high absorption and short sur Kokotau silt loam (Yeates 1982) and it has been grated account is neither practical nor possible. and Lowther ( 1980) has shown great variability in vival times for S. bovis and a reduced survival time found that the predominant nematode in an old pasture (Pungentus maorium Clark, 1963) appears General descriptions of the earthworm fauna, and R. tr(folii populations and led them to recommend for E. coli; soil group and clay mineralogy were of of forest, grassland and mountain invertebrates are inoculation as insurance against failure to nodulate secondary importance. The survival of S. bovis in to reproduce when plant nitrogen is highest. Table given by Lee (1959) and Knox (1969). when oversowing with white clover. Tokomaru silt loam has been discussed by Guy and l gives comparative nematode data for three soils. Small ( 1977). There are both year to year variations in nematode abundance at one site and responses to irrigation; MYCOLOGY Study of drainage water from an effluent dis the response to effluent irrigation may have been posal site on Tokomaru silt loam showed that in MICROBIOLOGY Thornton (1965) studied fungi associated with reduced by the enhanced earthworm population live roots of ryegrass and white clover in Timaru spring the drainage water included both soil water (Yeates 1981 b). The numerically dominant genera and waste water (Macgregor et al. 1979); under these BACTERIA silt loam and found a relatively low number of root also vary in each soil, reflecting changes in the pro conditions potential adsorption to clay minerals segments infected with fungi, some specific absences duction and decomposition regimes. Insuffient is Stout (1973) found total bacterial populations of (e.g. Fusarium oxysporum) being apparently due to would be academic. known of the ecological and nutritional relations of yellow-grey earths to be larger than those of yellow lower soil temperatures; increase in soil pH (5.0 to brown earths, although within the yellow-grey earths 6.7) by fertilisation may also have been important. the drier sites gave greater counts than wetter sites. The estimated total hyphal length of fungi in In the wetter yellow-grey earths earthworm activity Timaru soil (54.4 m/g moist soil) was shorter than in topsoils is higher, and the nature and distribu Table 1 Mean annual total nematode populations under grazed pasture on three yellow-grey earths; in other soils (Jackson 1965). and individual hyphae each estimate is based on mean of 12 monthly samples. Dominant nematode genera < 10% of the tion of organic substrates for the bacteria is con were shorter and narrower. sequently different. Clearly more detailed sampling total fauna are in brackets having regard to seasonal changes and additional Endomycorrhizae formed by indigenous fungi may benefit phosphorus nutrition of white clover specific metabolic tests are needed to clarify the Total nematodes m ·' Dominant nematode genera Rainfall Herbage picture. in Warepa silt loam at applications of up to 20 kg in 0-lOcm soil mmy' t DM ha I r' P/ha; beyond this there is no significant advantage in the hyphae exploring a larger volume of soil than ACTINOMYCETES Tokomaru silt loam 1 214 OOO Ccpha/ohus, l'11ngrnt11s, Tylenchus, 1015 12 the roots. Inoculation of the soil with vesicular Aporcclaimus Populations of the actinomycete Norcardia arbuscular (VA) mycorrhizae, and subsequent 1 477 OOO Trlc11ch11s. J!cterocephaloh11s, (Anap/ect11S) Effluent irrigated 15-18 asteroides in Kokotau silt loam were followed for infection of white clover, increased P adsorption Kokotau silt loam 1 030 OOO P1111gentw·, ,-Jporcelaimus, 7)1/enchus 848 8.1 24 months by Orchard ( 1981 ), and were found to and white clover growth at low levels of available I 111 OOO P1111gc11/11s, (.-lporcclai11111s), (Panagrolai11111s) 1039 8.4 increase with increasing soil moisture and decreas soil P (Hall et al. 1977). VA infected white clover I 864 OOO 1'1111gcntus, _,111orcclai11111s, (f'anagn1/ai11111s) 833 6.7 ing soil temperature. It is uncertain whether the competes more strongly with ryegrass for soil P than Otiake silt loam 730 OOO (rlrnch11s, J'arat.rlrnchus, (Ccphalr>l>us) 550 3 resulting winter peaks reflect greater metabolic non-mycorrhizal clover and consequently VA I 970 OOO Parat,1·/cnchus, Rhabditidac, Praty/cnchus irrigated 14 104 105 runoff, as well as infiltration, in Tokomaru silt loam the various genera to draw firm conclusions as to included browntop and sweet vernal; the snow tus their role in the pasture ecosystem, despite abun (Sharpley & Syers 1976, 1977; Sharpley et al. 1979; ENZYME ACTIVITIES sock Chionochloa rigida also occurred at the Tima Syers et al. 1979). An increase in availability of P dant data having been collected by uniform site. Topsoil (0-8 cm deep) was sampled adjacent to plants in earthworm casts has also been reported Soil enzymes originate from micro-organisms, methodology. to plants of F. novae-zealandiae at the Cluden site (Mansell et al. 1981 ). and to a variable extent from plant materials and and C. rigida at the Tima site. Organic C and total soil animals. In the extracellular state, they can be N contents, and pH, of the samples varied slightly stabilised by soil colloids (Burns 1978). Although at some of the sampling times, but typical values EARTHWORMS all biochemical transformations in soil are affected ARTHROPODS are recorded in Table 1. by enzymes, the levels of soil enzyme activities may not necessarily be indicative of actual metabolic Information since Lee ( 1959) on earthworms in Starling predation on grass grub (Costelytra ::eal yellow-grey earths has been published by Springett activity under field conditions. Generally, relation andica) was studied in Lismore stony silt loam and ships between enzyme levels and soil fertility are (1981) and Yeates (1976b) for Tokomaru silt loam resulted in mortality of 40-60% on medium and Table 1 Some chemical properties of topsoil complex (Skujins 1978). and Kokotau silt loam. In pasture sprayed with samples of Cluden and Tima soils from tus high (400-1000/m 2) third instar grass-grub popu dairy-shed effluent 525 (January) - 1810 (Novem sock grassland Both Cluden and Tima soils possessed moderate 2 lations (East & Pottinger 1975) which prevented ber) earthworms/m (1590-7110 kg live weight/ha) moderate populations from increasing. However, levels of all of the enzymes investigated. These were found by handsorting over 13 months, the due to the high population levels, such predation Soil Moisture pH included those involved in the hydrolytic decom results being 2-4 times those in adjacent dryland Organic Total C/N is atypical and does not represent a feasible control (%) C(O/o) N (%) position of carbohydrates (sucrose, starch, cellu pasture. Except for December to March over 90% measure. In Ruapuna silt loam autumn cultivation lose, and hemicellulose), organic nitrogen of earthworms found were in 0-10 cm soil. Also in compounds (proteins and urea), and organic phos led to a 92.5% reduction in grass grub populations Cluden silt loam 15 6.0 2.6 0.21 Tokomaru silt loam Springett compared extraction 13 phorus and sulphur compounds (Ross et al. l 975b; 2 (78% from mechanical injury), while 74% of earth Tima silt loam 23 5.8 3.8 0.28 14 methods, in September 1977 finding most (772/m ) worms died as a result of the surface cultivation Ross & Speir 1979). Possible seasonal variations in by handsorting but in August 1978 8% fewer by these activities have not been determined. How 2 (McLennan & Pottinger 1976). This physical Results (except pH) are given on an oven-dry (I 05T) weight handsorting than by formalin immersion (l 299/m ). approach, which has damaging effects on the pas ever, considerable fluctuations in hemicellulase In July 1978 her highest estimates in Kokotau silt basis. and are means of 4 years' samples (Ross & Speir 1979). activity were found in autumn samples taken in 2 ture sward, may be compared with stock treading loam (308-l 360/m ) were also obtained by for used in yellow-brown loams (Yeates & McColl three consecutive years (Ross & Speir 1979). These malin immersion. Consistent application of an effi 1982). fluctuations were greater at Tima than at the other cient extraction technique to a range of sites is climosequence sites, and may have been associated necessary before ecological relationships of earth A productivity study on dryland Lismore soil with variable amounts of'light fraction' in the sam worms in these soils can be determined. Current (Vartha 1977) showed no herbage yield response to MICROBIAL BIOMASS AND ACTIVITIES ples taken at different times. work (Springett 1979, 1980) on the effects of lime insecticide (Diazinon) treatment despite reduction on earthworm populations and activity at a series of the grass grub population from 157 to l 8/m2• Microbial biomass (the mass of living micro of sites in Hawke's Bay and Wairarapa began in organisms) is important in soil because of the key In a grazed pasture trial on Tokomaru silt loam, 1979. role that organisms play in the release of plant RA TES OF BREAKDOWN OF ORGANIC Lancashire et al. ( 1977) found their plant cultivar nutrients from organic matter. Microbial biomass MATTER A series of papers have reported on the effects results confounded by an interaction between was here estimated by three biochemical pro of casting by Allolobophora caliginosa on P and N resistance to stem weevil and soil moisture stress. cedures, all of which gave moderately high values Further evidence for appreciable metabolic for living micro-organisms (Ross et al. 1980). The activity at the Cluden and Tima sites was provided percentage of soil organic C present as biomass C by studies of rates of breakdown of tussock litter was similar in both soils but varied appreciably with and of some of its organic components. After 2 time of sampling, in contrast to Carrick soil (a years' exposure on the surface of the soil, C. rigida yellow-brown earth under tussock grassland) where litter had lost more than 30% of its weight at the no time-of-sampling effects occurred: values aver Tima site; (its decomposition at the Cluden site was aged 2.8 (range 2.2-3.9), 2.2 (range 1.5-2.8) and 2.6 not determined). This loss was at least as great as (range 2.4-2.8) for Cluden, Tima, and Carrick soils that occurring at the other climosequence sites (with respectively (Ross et al. 1981 ). the exception of the warm, moist Harihari site; SOME BIOCHEMICAL PROPERTIES OF TWO SOUTHERN YELLOW-GREY Molloy et al. I 978a). As at the dry Conroy (brown By themselves, the biomass values give no indi grey earth) site and the Harihari site, the absolute EARTHS UNDER TUSSOCK GRASSLAND cation of the metabolic state of the micro-organ amount of nitrogen in the litter increased during isms present, and whether they are highly active or decomposition. Most enzyme activities also mainly 'resting'. Measurements of respiration, D.J. Ross, Soil Bureau, D.S.I.R., Lower Hutt increased during litter decomposition, and were however, clearly showed that the micro-organisms generally at least as high at Tima as at the other (Received August 1981) were capable of appreciable activity under moist climosequence sites (again with the exception of conditions, and could readily oxidise components Harihari; Ross & Speir 1978; Speir & Ross 1978). of the soil organic matter (Ross et al. 197 5a. 1980). INTRODUCTION logical characteristics of the topsoil of these two As in other soils of the climosequence, the actual Cellulose decomposed at moderate rates on the soils are given here. rate ofrespiratory activity was very dependent upon surface ofCluden and Tima soils, and rapidly when Some biological and biochemical properties are temperature, and slowed down markedly below buried in the topsoil (Molloy et al. l 978b; Ross et influenced by all of the major soil-forming factors, Mean annual precipitation at the Cluden and I0°C. al. 1978a). Hemicellulose also decomposed readily but particularly by climate and vegetation. An Tima sites is about 600 and 700 mm respectively, in these soils when buried in kaolinite pellets, One apparent anomaly in the respiratory behav assessment of the effects of climate has been made and mean annual temperature at both sites about whereas lignin decomposed slowly (Molloy et al. 8.5°C (Molloy & Blakemore 1974). Three sampling iour of Cluden and Tima soils has yet to be at Soil Bureau by studying a climosequence of soils l 978b). These results were comparable to those of explained. On incubation of most soils, respiratory formed from similar parent materials (chorite areas were used at the Cluden site and one at the other soils of the climosequence. schist) and occurring under tussock grassland vege Tima site (Molloy & Blakemore 1974; Ross et al. activity generally reaches a steady state after a few tation (Molloy & Blakemore 1974). This collabo l 978b). They all contained moderate numbers of days and eventually declines. In Cluden and Tima One aspect where Cluden and Tima soils dif rative study included two yellow-grey earths the short tussocks Festuca novae-zealandiae and soils, however, an appreciable increase in rate fered from the others was in the recovery of buried (Cluden silt loam and Tima silt loam). Some bio- Poa spp., as well as introduced grass species, which occurred after a few days' incubation at 20° or 24°C kaolinite pellets containing the water-insoluble pro (Ross & Cairns l 978b). tein zein (Ross & Cairns I 978a). Nearly all of the 106 107 zein-containing pellets were recovered after I or 2 climosequence (Ross & Bridger l 978b). It would, years burial at most of the sites, but at the Cluden however, have been somewhat restricted by a defi CORROSION and Tima sites the recovery was generally low; ciency of nutrient elements (Ross & Bridger I 978a). (control pellets with kaolinite alone were mainly Air-drying of both soils markedly stimulated the recovered). Reasons for these losses have not been mineralisation of soil organic N, with most of the experimentally established. but they might include the activity of small animals preferentially ingest mineral-N produced being present as nitrate-N ing and removing the zein-containing pellets. In the (Ross & Bridger I 978a; Ross et al. 1978b, 1979). pellets that were recovered, most of the zein, as at Rewetting of partially air-dried soil in the field could the other sites, had been metabolised after 1 year. therefore be important for the release ofN for plant SOIL CORROSION IN YELLOW-GREY EARTHS growth in these seasonally dry soils. Freezing and Although Cluden and Tima soils generally thawing did not enhance N mineralisation in the resembled each other in their biochemical prop samples tested (Ross et al. 1979). Moderate release H.R. Penhale, Soil Bureau, D.S.I.R., Lower Hutt erties, they did differ in the appearance of their 'light of mineral-N did, however, occur on incubation of (Received June 1981) fraction'. This is material which is separated from one set of field-moist winter samples (although not the soil by flotation in a heavy liquid, and which in another; Ross & Cairns 1981 ). It is therefore pos is composed of non-humified, or partly humified, sible that freezing and thawing could stimulate the MILD STEEL OTHER METALS plant and animal remains (Greenland & Ford 1964). production of mineral-N under some field condi Because of complex interactions it is very diffi Copper and lead are much more resistant than In Cluden soil, the light fraction was comprised of tions before the onset of plant growth in spring. cult to predict corrosion rates from soil properties. mild steel to soils. The use of lead and aluminium clearly recognisable, large plant and microbial The factor(s) responsible for the generally low or Corrosion is influenced greatly by water content, underground is confined to cable sheaths, and pro debris, with moderate to high contents of structural negligible net production of mineral-N in these two resistivity and total acidity. These vary consider tective coatings are always used. carbohydrates and proteins; in Tima soil, it was ably in yellow-grey earths. Corrosion in the two comprised of fine plant and microbial debris, with yellow-grey earths have still to be definitely estab CONCRETE AND ASBESTOS-CEMENT lished (Ross & Cairns 1981 ). They might, however, Timaru sites is very similar in spite of variations a low content of structural carbohydrates (Molloy in resistivity. Obviously there are other factors, in The drier soils with pH near neutral attack & Speir 1977). As with other soils of the climose include the prevalence of the low-fertility intro duced grasses that occurred at both sites. Although particular structure, which affect the A.ow of oxygen cement products extremely slowly (Penhale 1956, quence, the light fraction from both soils was to the surface of buried metals. enzymieally much more active than the remainder all samples were taken adjacent to tussock plants, Romanoff 1957). Soils with groundwaters that are of the soil, probably because of comparatively high they would still have been influenced to some extent The rate of attack decreases with time in oxi high in aggressive carbon dioxide are especially activity of microbial decomposers (Ross 1975; Speir by roots of the inter-tussock sward. The influence dising soils because of the partial protection pro corrosive but yellow-grey earths do not come into 1977). that vegetation and nutrient supply can play in the vided by the adhering layer of rust. In the yellow this category. Structure is important as this affects mineralisation of soil organic N in these yellow grey earths this rate typically drops to about 'h the rate of flow of ground water. grey earths is clearly shown by samples taken under between 2 and 20 years except in Waimumu silt CORROSION RA TES introduced pastures of grazed ryegrass and white loam (which is B-gleyed and hence poorly aerated). NITROGEN MINERALISATION clover. There, net mineralisation readily occurred, Here the rate has changed little with time. Typical corrosion rates are listed in Table l. with mainly nitrate-N produced (Ross & Bridger The availability of nitrogen for plant growth in 1978a; Ross et al. l 978b, 1979). non-fertilised ecosystems is mainly dependent upon the mineralisation of soil organic N to ammonium N; which may be subsequently converted by nitri CONCLUSIONS Table 1 Corrosion rates for mild steel, concrete and asbestos-cement in yellow-grey earths after 20 fying organisms to nitrate-N. In contrast to most years of the soils of the climosequence, net mineralisa Values for most of the biochemical properties of tion of soil organic N in field-moist samples of Clu Cluden and Tima soils under tussock grassland were den and Tima soils was usually very low. This was consistent with the location of the soils in the cli Soil Classification Locality Natural Res is- Total Mild steel Concrete shown by glasshouse pot experiments (Ross et al. mosequence. Generally, they were indicative of water tivity acidity rate or attack and content (ohm-m) (me.%) (pm/y) asbestos- l 978b, 1979) and laboratory incubation experi appreciable biochemical activity under favourable (%dry wt) av. pit cement ments (Ross & McNeilly l 975b; Ross & Bridger conditions of moisture and temperature. rate of l 978a). Negligible net mineralisation of soil organic attack* Cluden and Tima soils did, however, differ from N was also found by Tan ( 196 7) in another field most of the other soils of the climosequence in their moist yellow-grey earth from tussock grassland. Timaru southern Tirnaru 10 9 6 25 100 low inability to produce mineral-N consistently from silt loam yellow-grey earth. Net mineralisation of organic N in Cluden and soil organic N on incubation. Further work is (coastal. moderately weathered. Tima soils should not have been limited by num needed to establish the reason(s) for this, and to IOOm moderately leached bers of ammonifying organisms, which were com determine the actual patterns of mineral-N release from beach) parable to those found in other soils of the in the field. Timaru southern Timaru 11 34 16 23 98 low silt loam yellow-grey earth. (7 km moderately weathered. inland) moderately leached Matapiro central Ha\'clock 38 29 II 18 67 med tine sandy yellow-grey earth. North loam moderately weathered. moderately leached Waimumu southern Gore 22 87 16 13 54 med silt loam yellow-grey earth (B-gleycd) Shotowr southern Shotovcr 200 9 3.5 27 very tine sandy yellow-grey earth. low loam moderately leached *These rates are estimates only - no samples buried in these soils 108 109 9. AGRICULTURE AND LAND USE sionally developed from its traditional phase of Dairying is the predominant land use in the lower pasture renewal. Where cropping is intensive it can Manawatu - Rongotea area. Good production is be sustained in the ratio of two years cereals, one seldom possible until an intensive tile or mole years peas, followed by 4-5 years restoration under drainage system is installed. Stocking rates of 2.5 pasture. cows/ha with replacements is probably the upper MANAWATU limit. Calving dates are generally back on more FARMING YELLOW-GREY EARTHS IN Yields are typically 4.5 t/ha of barley, 4 t/ha of suitable soils, but the pattern of pasture production wheat. Lucerne has been grown from time to time allows for reasonably long lactations. While B. Withell, Ministry of Agriculture and Fisheries, Palmerston North on these soils but only where drainage has been 450 kg/ha or better is achieved by top farmers, good. Life is usually shortened to 6-7 years as there 275 kg/ha would probably be a district average for (Received December 1981) is a risk to the drainage from root penetration. the yellow-grey earths. Yellow-grey earths form the most ext.ensiv.e Manawatu would probably require 3 t/ha of lime group of soils in th~ Manawatu ~rea, especially 1f to bring the pH to a working level of about 5.8. a proportion of the mtergrades with yellow-brown 600 kg of superphosphate woul?. suffi~e as a loams are included. development application of fertiliser. smce the phosphate retention values on these ~<;>ils a_re typ The spread of these soils would lie from hill ically around 35. Maintenance fert1hser . 1s be~t country adjacent to the lower Ruahine Ranges determined by land use intensity but typically is AGRICULTURE AND LAND USE ASPECTS OF YELLOW-GREY EARTHS IN through upper and lower downlands to terrace 250-300 kg of superphosphate, occasionally 15% country adjacent to the Tararuas and across to near potassic. SOUTHLAND flats of Rongotea and Ohakea. Growth performance is dependent on th~ pat All are based on a parent material of loess, pri tern of rainfall and the altitude of the particular P.J. Hook, Ministry of Agriculture and Fisheries, Gore marily derived from the main river beds (Mana site. Yellow-grey earths are easily capable of 12 000- (Received December 1982) watu and Rangitikei). 15 OOO kg of dry matter/year given d:~inage, apr:ro The presence of a marker bed of ash, known priatc pasture species, suitable fert1hser and hme locally as Aokautere Ash, approximately 2 m down, treatments, and of course the best grass The yellow-grey earths make up over 40% of the While these soils are cropped chiefly for cereals, is a good indication of the slow and steady a?cu management. farm land in Southland County and about 6% of they are not the preferred soils for cropping, as even the total land area in Wallace County. A large pro mulation over the period of some 20 OOO years smce Farming systems follow a full spectrum a~d ~t is with intensive drainage they take considerable time that fall was known to occur. not uncommon to find all major types (dairymg, portion of these soils are on steep land where usage to dry out in the spring. causing delays in the sow cropping, sheep) all farming adjacent on the sam.e is limited to grazing. The soils are discussed under ing of cereals. When these soils do dry out a crust Prior to European settlement, the soils were the following headings: may form on the surface which at times can impede phase of yellow-grey earth. The. com~on denomi covered in a mixed association of broadleaf forest. early seedling emergence. Most of this was cleared and stumped in the late nator for effective land use is agam adequate A. Soils with an Agricultural End Use Where drainage has been carried out these soils 1800's to early l 900's and subsequently developed drainage. B. Soils used Predominantly as Pastoral are capable of yielding an average of 5 t wheat/ha for farming. In the nature of development foll.ow Sheep farming on the yellow-grey earths has b~en with individual paddocks yielding above 7 t/ha. ing difficult clearance, subdivision was largely mto traditional in the Manawatu area and farmmg small (typically 40 ha) units and this has had a large intensity is seldom above 16 or 17 stock u~its/ha, Partly through economic necessity and partly impact on subsequent farming patterns. Most .of typically breeding ewes plus replacements with dry A. AGRICULTURAL END USE through problems experienced with winter pugging those units were ultimately amalgamated with cattle bought in to control summer roughage. There on the yellow-grey earths, they are not now used others, but seldom more than four, so that average is limited wintering of heavy cattle because of pug Soils in this group include the true yellow-grey intensively for cattle raising. The predominant cat farm size on these yellow-grey earths is about ging damage risk. earths and the intergrades between yellow-grey tle enterprise now comprises the fattening of bought 160 ha. earths and yellow-brown earths. They occur largely In recent years more intensive sheep farming in calves and the sale of these animals before their on terraces, fans and on easy rolling country, and second winter on the property. Physical characteristics of the soils on easy t? systems have been established and top far~ers are include soils such as Kaweku, Balfour, Dipton, moderate slopes are that there would be approxi now running up to 25 stock umts/ha usmg con Oreti, Waikoikoi, Waimumu and Crookston. Aver mately 120 mm of topsoil developed ove~ 150- trolled grazing systems. The all grass system .o.f the age property size on these soils is 200 ha. The pre 200 mm of subsoil. At the base of the subsoil layer latter has meant a swing away from the trad1t10nal dominate land use is for grazing livestock with B. PASTORAL USAGE there is usually a moderately developed pan ~hich l O yearly pasture renewal cycle via. the summer or cropping a secondary land use. Kaweku, Balfour, has obvious effects on water movement. Dramage winter brassica feed crop, and possibly of the catch Waikoikoi and Waimumu soils in particular Soils in this group include Hokonui, Nokomai is the principal limitation and is of paramount crop of feed barley before regrassing. respond extremely well to drainage and this has and Ohai soils, Waikoikoi, Crookston, Mossburn importance if more intensive land use is contem been a traditional development practice on these hill soils and Tengawai steepland soils. Farming on plated. However, the soils mole drain quite effec A full range of cash crops can be, and are, ~rown on these soils, although they are not fully smta~le soils. The type of systems installed are generally these soils is more extensive than on the agricul tively and the moles have a typical life of 10-15 field tiles with moles pulled at 2 m centres. This tural soils and is confined to sheep and cattle graz years if installed correctly. for some crops. All white straw crops are spnng sown and the sowing date is highly dependent on intensity of drainage is required where stocking rates ing. Drainage requirements and the amount of The soils only have a moderately well developed the degree of drainage. Feed and malting barley is are high. Although the average stocking rate of these drainage carried out are less than on those soils structure in their .natural state and this can be the predominant crop (approximately ~OOO ha(year) soils is approximately 12 stock units/ha, there are already mentioned. Typical property size is between destroyed relatively quickly under intense cultiva but there is a swing to wheat following the mtro individual properties carrying up to 20 stock unit 400 and 800 ha.· Considerable proportions of the tion or abuse under wet conditions by heavy stock, duction of better spring varieties such as Karamu. s/ha with 17 to 18 stock units/ha being readily larger properties are still in native tussock grass etc. Less important crops arc seed and process peas, obtainable using known management techniques. land, though many areas have been improved by grass seed, and occasionally maize and potatoes. Provided drainage has been carried out in these topdressing and oversowing. Under native tussock There are no specific nutrient requirements other soils, they are excellent for livestock production. If grassland and with minimal fencing, stock carrying than the usual phosphate. calcium and some potas Cropping is seldom fully intensive but has occa- drainage is not carried out however they are severely capacity on this class of country is less than 0.5 sium. An undeveloped yellow-grey earth in the limited by an extended winter no-growth period. stock units/ha. With closer subdivision and the 110 111 introduction of clover however, this country is Future increases in livestock output in South capable of carrying up to 8 stock units/ha on a 12 land and West Otago will be obtained largely from THE NEED FOR DRAINAGE 4. GRADES OR FALL month basis. Where the country has been ploughed intensification of usage of the yellow-grey earths. and sown to pasture, an average carrying capacity Known management techniques can increase the These soils form part of a large group of soils Any drainage system is only as efficient and ben is 10 to 11 stock units/ha with a potential of up to ryegrass content of pasture on these soils. With that arc classified as impervious. Water movement eficial as the grades at which it is installed. Mole 15 stock units/ha. Although the initial requirement improved utilisation of this additional ryegrass through the subsoil, whether lateral or vertical is drainage is no exception. In fact the grades for a for development of these soils is phosphate and production on this class of country, an increase of virtually nil. The draw to tiles alone is negligible mole drainage system are more critical than those molybdenum, lime is also important to develop the between 25 and 30% in the output of meat and wool and of little benefit. Because the subsoil is imper for tile drains. Ideally mole drains should be sward fully. products can be expected. vious, water is trapped in the topsoil and gives rise installed with a steepening or constant fall towards to what is known as a perched or surface water table. their outlets. On no account should moles be pulled The aim then is to get rid of the surface water table with a flattening fall towards their outlet. If moles and this can only be effectly accomplished by mole are pulled with a flattening fall, or grade change, draining. without the installation of a tile at the flattening off point, breakdown of the system will be quite rapid. It is the failure to recognise the importance of installing tiles at grade changes which is the most MOLE DRAINAGE common cause of early mole drain breakdown. FORESTRY AND NORTH ISLAND YELLOW-GREY EARTHS 1. SPACING On the intergrades between yellow-grey earths and yellow-brown carths, mole drains can be safely G.M. Will, Forest Research Institute, Rotorna The passage of a mole plough through the soil pulled at falls of up to l in 15, but it is recom profile forms cracks in the subsoil which allows the mended that falls of up to 1 in 20 be used. Falls (Received December 1981) water held in the topsoil to drain down into the of between 1 in 20 and l in 15 should only be mole channel. The mole channel then carries the applied in very special situations. Moles pulled at water away to the tile drain outlets. To achieve Shelterbelts and farm woodlots have been many New Zealand soils, with pans and other falls in excess of I in 15 are liable to scour. Scour drainage of an area, even shattering of the subsoil planted on yellow-grey earths in the Hawke's Bay, impediments to root growth, can be improved by ing of mole channels can form under runners and must be carried out. Because the mole plough only Wairarapa, and Manawatu districts. However these soil ripping. However, in practice it is rarely pos soil slumping. shatters the subsoil for about I m on either side of soils have not been used for the establishment of sible to maintain a ripping depth of more than larger scale plantation forests. Near Wanganui, Lis the blade slit, the moles should be pulled at 2 m 60 cm; this would not penetrate the compact root spacings. 5. DISTANCE OF PULL more Forest is largely on hill soils related to inter restricting zone of yellow-grey earths. grades between yellow-brown earths and yellow-grey The distance that mole drains can be pulled earths. Tree growth is good but hill soils related to Large scale forestry may have no place on the 2. DEPTH before discharging into an outlet is related to the intergrades are hardly a suitable basis for a realistic restricted areas of yellow-grey earths in the North ground surface, the amount of fall available, and Depth of pulling the moles is important for two assessment of a soil group. Island but small plantings of special use trees should rainfall intensity. The lesser the fall, the shorter the not be dismissed. Trees such as high quality veneer reasons: Firstly, the band of finest clay particles in distance. Basically yellow-grey earths have ample nutrient timber trees or those producing nuts would in many the soil profile occurs at around 35 to 50 cm. Pro status for the relatively low demands of New cases warrant and respond to special soil physical viding the mole channel is pulled through this band, In Southland where rainfall intensity of 6 mm of Zealand's major production forest species - Pinus amelioration and/or irrigation. Such tree species are a smooth, shiny surface is made. It is this smooth rain over 24 hours applies, the following table gives radiata. Limiting factors would appear to be root usually more nutrient demanding - suiting the surface which helps mole drains last longer. the maximum distance of pull. ing depth and available moisture. Tree growth on nutrient status of yellow-grey earths. Secondly, moles pulled too shallow are liable to from flat to 1 in 100 80m damage by heavy machinery, while moles pulled too deep require expensive, powerful machinery for l in 100 to I in 60 80 to 180 m pulling, and are also slow draining. in 60 to I in 30 180 to 380 m Practice has shown that the optimum depth to I in 30 to I in 20 pull mole drains is about 45 cm. 380 to 500 m Most of the intergrades between yellow-grey 3. TIME earths and yellow-brown earths are in the 6 mm ON THE INTERGRADES .BETWEEN YELLOW-GREY EARTHS rainfall intensity band for Southland. Time of year is another important factor. Mole AND YELLOW-BROWN EARTHS OF SOUTHLAND drains should be pulled when the topsoil is dry and when the subsoil, at moling depth, is moist. The Ray S. Davidson, Farm Advisory Officer (Agricultural Engineering) Ministry of Agriculture and correct moisture content is when a wad of subsoil CONCLUSION Fisheries, Invercargill is pressed between the hands and no free moisture runs out. (Received May 1982) Providing mole drains are pulled to the stand Normally ideal conditions for moling will be ards and recommendations given above, there is no experienced in the late spring-early summer period, reason why moles should not last for up to 30 years INTRODUCTION benefits can be expected, is mainly installed on the i.e. from September to November. This is also the on the intergrades between yellow-grey earths and flatland to terrace areas, but any area which can be time when two to three weeks of fine weather after yellow-brown earths. Dramatic increases in yields The intergrades between yellow-grey earths and cultivated will lend itself to intensive drainage. pulling the moles allows the smooth surface formed from cash crops can be expected, and in some cases yellow-brown earths make up approximately eight by the mole plug and torpedo to bake hard. It is increases in the stock carrying capacity of up to percent of the total soils in the Southland region. From a drainage point of view, the intergrades this hard surface which adds to the life of moles. 50% can be achieved. Of this eight percent, the flatland and terraces (47%) between yellow-grey earths and yellow-brown earths and the rolling land ( 4 7%) are the areas where are relatively uniform in that mole drains, with tile drainage works are carried out to a greater or lesser drains as outlets, comprise the basic drainage degree. Intensive drainage, from which the greatest installation pattern. 112 113 BRUCE, J.G. 1973b Pedology of some soils on loess in South land and Otago CHITTENDEN .. E.T.; HODGSON, L.; DOBSON, K.J. 1966 New Zealand. ' Soils and agnculture of Waimea County, New Zealand. N.Z. Journal of Science 16: 333-348. N.Z. Soil Bureau Bulletin 30. 66p. Compiled by Jewel E. Davin, BRUCE, J.G. l973c CHURCHMAN, G.J. 1978 N.Z. Soil Bureau, DSIR, Lower Hutt A time-stratigraphic sequence of loess deposits on near Studie.s on a climosequence of soils in tussock grasslands. ~~stal surfaces 1~ the Balclutha district. 21. Mineralogy. .z Journal of (Jeology and (ieophysics /6: 549-556. N.Z. Journal of Science 21: 467-480. This bibliography includes all references used in the papers of this volume on BRUCE. J.G. 1977 CHURCHMAN, G.J. l 980a yellow-grey earths, whether or not they are about yellow-grey earths. Those refer Properties and genesis of a sequence of soils from locss Clay mineralogy of some South Island high country pod zohsed soils. ences which do not contain information on yellow-grey earths are marked with In the South Island, New Zealand. (Summary) N.Z. Soil News 25: 162-163. (unpublished) . Pp.149-154 in 'Soil Groups of New Zealand. Part 5. Pod an asterisk (*). In addition to references used in the papers, other known refer zo~s and Gley Podzols'. (Ed. R. Lee). N.Z. Society of Soil ences to yellow-grey eart~s (up to 1983) have been included. BRUCE, J.G. (in prep) Science, Lower Hutt. 452p. Soils of the Gore-Waikaka District, South Island. New Zealand. *CHURCHMAN, G.J. 1980b N.Z. Soil Survey Report. Clay minerals formed from micas and chlorites in some New Zealand soils. *ARBEITSGEMINSCHAFf BODENKUNDE (SOIL SCI BIRCHAM, J.S.; CROUCHLEY, G.: WRIGHT, D.F. 1977 BR~CE, J.G.; CHILDS. C.W.; FURKERT, R.J. 1981 Clay Minerals I 5: 59-76. ENCE WORKING PARTY) 1971 Effects of superphosphate, lime. and stocking rate on pas Gmde Book for Tour 2, South Island, Soils with Variable Kartieranleitung (Mapping Manual). Hanover. I 69p. ture and animal production on the Wairarapa Plains. II. Charge Conference, New Zealand, 1981.' CLARIDGE, G.G.C. 1978 Animal production. N.Z. Society of Soil Science, Lower Hutt. 135p. Clay mineralogy. N.Z. Journal o( l~>cperimental .·lgriculture 5: 349-355. Pp.47-48 in ·~oil survey of Part Taieri Uplands, Otago, ARBUCKLE, R.H. 1953 BRUCE, J.G.; IVES, D.W.; LEAMY, M.L. 1973 New Zealand. (by J.M. Ragg and R.B. Miller). N.Z. Soil A chemical and clay mineralogical study of a yellow-grey BIRRELL, K.S. 1972 Maps and sections showing the distribution and stratig Bureau Bulletin 39. 56p. earth profile from the Wairarapa. The physical properties of loess soils and the influence of raphy of South Island loess deposits New Zealand M.Sc. Thesis, University of New Zealand. l I 7p. cultivation. 1:1 000000. ' . CLARIDGE, G.G.C.; WEATHERHEAD, A.V. 1978 Pp.29-33 in 'Loess Soils and Problems of Land Use on N.Z. Soil Survey Report 7. Mmeralogy of silt fractions of New Zealand soils. *AVERY, B.W. 1980 the Downlands of the South Island. New Zealand'. (Ed. N.Z. Journal of Science 21: 413-423. Soil classification for England and Wales. J.P.C. Watt). Otago Catchment Board P11/Jlication 4. 138p. *BURNS, R.G. 1978 Soil Survey, Technical Monograph 14. 67p. Enzyme activity in soil: some theoretical and practical COLLIE, D.M. 1968 BLAKEMORE, L.C. 1958 cons1derat10ns. Factors influencing agricultural production on Banks BAILEY, J.M.; GIBSON, A.R.: GILTRAP. D.J.; LEE, R. Chemistry of the yellow-grey earths of the North Island, Pp.295-340 in 'Soil Enzymes'. (Ed. R.G. Burns). Aca Penmsula. 1976 New Zealand. demic Press, London. 380p. M.A. Thesis, University of Canterbury 123p. Effect oflime on luceme composition and soil properties N.Z. Soil News 1958: 218-225. (unpublished) (unpublished) · in Dannevirke, Kiwitea, and Marton silt loams, with par CAIRNS, A; DUTCH, M.E.; GUY, E.M.; STOUT, J.D. 1978 ticular reference to phosphate and sulphate. BLAKEMORE, L.C; PARFITT, R.L. 1979 Effect of imgat10n w1.th municipal water or sewage effluent CORKER, R.B. 1977 NZ. Journal of Agricultural Research 19: 79-90. Variable charge in some New Zealand soils. on the biology of soil cores. I. Introduction: total micro Saturated hydraulic conductivity measurements on the N.Z. Soil News 27: 85-90. (unpublished) bial populations, and respiratory activity. Tokomaru silt loam. BARRATT, B.C. 1968 N.Z. Journal of Agricultural Research 21: I-9. Dip.Agr.Sci. Thesis, Massey University. (unpublished) Micromorphological observations on the effects of land *BLAKEMORE, L.C; SEARLE, P.L.; DALY, B.K. 1977 use differences on some New Zealand soils. Soil Bureau laboratory methods. A. Methods for chem CAMPBELL, LB. l 977a COSSENS, G.G.; RICKARD, D.S. 1969 NZ. Journal of Agricultural Research I I: 101-130. ical analysis of soils. (Revised). Soils of part Wanganui County North Island, New Irrigation in.vestigati.ons in Otago, New Zealand. v. Phys N.Z. Soil Bureau Scientific Report JOA. Zealand. ' ical properties of soils of the Maniototo Plains. BARRATT, B.C. 1969 N.Z. Soil Bureau Bulletin 40. 99p. N.Z. Journal of Agricultural Research 12: 193-213. A revised classification and nomenclature of microscopic BOWLER, D.G.; TURNER, M.A. 1978 soil materials with particular reference to organic Water harvesting on a yellow-grey earth. CAMPBELL, LB. l 977b COSSENS, G.G.; RICKARD, D.S. 1970 components. Proceedings of the N.Z. Grassland Association (1977) 39: Soils of Waikouaiti County, Otago, New Zealand. Irrigation investigations in Otago, New Zealand. VI. Geoderma 2: 257-271. 156-160. NZ. S01! Bureau Bulletin 37. 60p. Physical properties of soils of the Kurow district. N.Z. Journal of Agricultural Research 13: 209-217. BARRATT, B.C. 1971 *BREWER, R. 1964 CAMPBELL, LB. 1979 Micromorphology of some zonal soils of New Zealand. 'Fabric and Mineral Analysis of Soils'. Soils of the Rangitikei County, North Island, New COWIE, J.D. l 964a N.Z. Journal of Science 14: 651-697. Wiley, New York. 470p. Zealand. Aokautere Ash in the Manawatu District, New Zealand. NZ. Soil Survey Report 38. N.Z. Journal Q( Geology and Geophysics 7: 67-77. BARRATT, B.C. 1981 *BRINKMAN, R. 1979 Micromorphology of a yellow-grey earth to yellow-brown 'Ferrolysis, a Soil-Forming Process in Hydromorphic CHILDS, C.W. 1972 COWIE, J.D. 1964b earth soil sequence on loess in Canterbury, Otago and Conditions.' lron-manga.nese concretions in New Zealand soils. Lo_ess in the Manawatu District, New Zealand. Southland, New Zealand. Centre for Agricultural Publishing and Documentation, N.Z. Soil News 20: 137-146. (unpublished) N.Z. Journal of Geology and Geophysics 7: 389-396. NZ. Soil Bureau Scientific Report 45. 44p. Wageningen. 106p. CHILDS, C.W. 1975 COWIE, J.D. 1964c BEECROFf, F.G. (in prep) BROOKS, R.R. 1965 Composition of iron-manganese concretions from some Th,e paHic soils of the Manawatu district. Soils of the Bannockbum Valley. The distribution of elements of the iron family in gleyed New Zealand soils. N.Z. Sot! News 1964: 3-7. (unpublished) and concretionary material in a New Zealand yellow-grey Geoderma 13: 141-152. earth. COWIE, J.D. l964d BIRCHAM, J.S.; CROUCHLEY, G. 1976 N.Z. Journal of Science 8: 88-92. CHILDS, C.W. 1978 The role of loess in soil formation. Effects of superphosphate, lime, and stocking rate on pas Iron-manganese concretions and mottles. NZ. Soil News 1964: 102-103. (unpublished) ture and animal production on the Wairarapa plains. I. BRUCE, J.G. 1972 Pp: 7~- 72 in 'Soil Gr.oups of New Zealand. Part 3. Gley Pasture production and botanical composition. Loess soils in the South Island. S01ls. (Ed. W.C. R11kse). N.Z. Society of Soil Science COWIE, J.D. 1968 NZ. Journal of Experimenwl Agriculture 4: 57-63. Pp. l-28 in 'Loess Soils and Problems of Land Use on the Lower Hutt. 127p. ' Pedology of soils from wind-blown sand in the Manawatu Downlands of the South Island, N.Z.' (Ed. J.P.C. Watt). d1stnct. BIRCHAM, J.S.; CROUCHLEY, G.; AITKEN, M.W. 1981 Otago Catchment Board Pu/Jlication 4. l 38p. CHILDS, C.W. 1981 NZ. Journal o.r Science I I: 459-487. Effects of superphosphate, 1i me, and stocking rate on pas Field tests for ferrous iron and ferric-organic complexes ture and animal production on the Wairarapa Plains. 3. BRUCE, J.G. 1973a (on exchange sites or in water-soluble forms) in soils. COWIE, J.D. 1978 Tooth wear and liver trace clement content. Loessial deposits in southern South Island, with a defin Australian Journal of Soil Research /9: 175-180. Soils and Agriculture of Kairanga County, North Island, N.Z. Journal o( Experimental Agricullur<' 9: 69-72. ition of Stewarts Claim Formation. New Zealand. N. Z. Journal o( COWIE, J.D.; MILNE, J.D.G 1973 EAST, R.; POTTINGER. R.P. 1975 Maps and sections showing the distribution and stratig Starling (Sturnus l'ulgaris L) predation on grass grub *FLEMING, C.A. 1953 GRIFFITHS, E. 1978 raphy of North Island loess and associated cover depos (Costelytra :::calandica (White), Melolonthinae) popula The geology of Wanganui subdivision. Soils ofWaikari District, North Canterbury, New Zealand. its, New Zealand. I: I OOO OOO. tions in Canterbury. NZ. Geological Survey Bulletin 52. 362p. N.Z. Soil Survey Report 29. NZ. Soil Survey Report 6. NZ. Journal of Agricultural Research 18: 417-452. FOX, J.P.; GIBBS, H.S.; MILNE, R.A. 1964 GRIFFITHS, E. 1980 COWIE, J.D.; RIJKSE, W.C. 1977 ELLIOTT, A.G.; LYNCH, P.B. 1942 Soils and agriculture of Kowai County, Canterbury, N.Z. Descriptions and analyses of soils of Waikari District, Soils of the Manawatu County, North Island, New Top-dressing of grassland with phosphates. Part II. The NZ. Soil Bureau Report 4/1964. 53p. North Canterbury, New Zealand. Zealand. effect of various phosphatic fertilizers with and without NZ. Soil Survey Report 56. NZ. Soil Survey Report 30. lime on pasture production and composition. GAUR, Y.D.: LOWTHER, W.L 1980 NZ. Journal <1( Science and Technology A24: 78-90. Distribution, symbiotic effectiveness, and fluorescent GRIGG, J.L 1977 COWIE, J.D.; SMITH, B.A.J. 1958 antibody reaction of naturalised populations of Rhi:::o Prediction of plant response to fertiliser by means of soil Soils and agriculture ofOroua Downs, Taikorea and Glen EVANS, G.L 1977 hium tr(/Olii in Otago soils. tests. V. Soil tests for phosphorus availability in brown Oroua Districts, Manawatu County. Erosion tests on loess silt, Banks Peninsula, N.Z. N.Z. Journal of Agricultural Research 23: 529-532. grey and dry-subhygrous yellow-grey earths. N.Z. Soil Bureau Bulletin 16. 56p. Proceedings of the Ninth lnrernational Conference on Soil NZ. Journal o.f Agricultural Research 20: 315-326. Mechanics m;d Foundation Engineering i 63-69. GIBBS, H.S. 1945 COX, J.E. 1968 Tunnel-gully erosion on the Wither Hills, Marlborough. GRIGG, J.L.; CROUCHLEY, G. 1980 Evaluation of climate and its correlation with soil groups. *FAO-UNESCO 1974 N.Z. Journal o.f Science and Technology A27: 135-146. Relative efficiency ofphosphatic fertilisers in pasture top Pp.33-44 in 'Soils of New Zealand. Part I'. /V.Z. Soil 'Soil Map of the World 1:5 OOO OOO. Volume I. Legend.' dressing. II. On a Kokotau silt loam. Bureau Bulletin 26(1). 142p. Unesco, Paris. 59p. GIBBS, H.S. 1957 N.Z. Journal o.f Agricultural Research 23: 49-65. Provisional soil map of Horowhenua County. COX, J.E. 1978 *FAO-UNESCO 1978 Unpublished Soil Bureau map. *GROSSMAN, R.B.; CARLISLE, F.J. 1969 Soils and agriculture of Part Paparua County, Canter 'Soil map of the World I :5 OOO OOO. Volume X. Fragipan soils of the eastern United States. bury, New Zealand. Australasia.' GIBBS, H.S. 1958 Advances in Agronomy 21: 237-276. NZ. Soil Bureau Bulletin 34. I 28p. Unesco, Paris. 22lp., 2 maps. Notes on yellow-grey earths in the North Island. NZ. Soil News 1958: 215-218. (unpublished) GUY, E.M.; SMALL, J.A. 1977 COX, J.E.; MEAD, C.B. 1963 FAULKNER, A.F. 1968 Survival of streptococci and coliforms of bovine faecal Soil evidence relating to post-glacial climate on the Can Some thoughts on soil potassium with special reference GIBBS, H.S. 1960 origin in drainage water and soil stored at different terbury Plains. to two North Canterbury soils. Soils of the Wellington District. temperatures. NZ. Ecological Society Proceedings 10: 28-38. Dip.Agr.Sci. dissertation, Lincoln College. 89p. Proceedings o.f the NZ. Society o.f Soil Science 4: 4-6. N.Z. Journal of Agricultural Research 20: 13-18. (unpublished) CUTLER, E.J.B. 1967 GIBBS, H.S. 1964 HALL, l.R. l 978a Soils of the Otago Region. FIELDES, M. 1954 Some reflections on soil formation and loess. Effects of endomycorrhizas on the competitive ability of Pp.35-51 in 'National Resources Survey, Part V. Otago The relation of structure in the yellow-grey earths and N.Z. Soil News 1964: 222-225. (unpublished) white clover. Region.' (Comp. Town and Country Planning Branch, yellow-brown earths to the behaviour of the mineral N.Z. Journal o.f Agricultural Research 21: 509-515. Ministry of Works). Government Printer, Wellington. colloids. GIBBS, H.S. 1965 572p. NZ Soil News 1954: 16-19. (unpublished) Soil map of Whareama Catchment. Wairarapa. New HALL, LR. I 978b Zealand. Effect of vesicular-arbuscular mycorrhizas on two vari CUTLER, E.J.B. 1981 FIELDES, M. 1958 NZ. Soil Bureau Map 4/1965. eties of maize and one of sweetcorn. The texture profile forms of New Zealand soils. Clay mineralogy of yellow-grey earths. NZ. Journal o.f Agricul/ural Research 21: 517-519. Australian Journal of Soil Research 19: 97-102. NZ. Soil News 1958: 225-227. (unpublished) GIBBS, H.S.; BEGGS, J.P. 1953 Soils and agriculture of Awatcre, Kaikoura. and part of HALL, 1.R.; ARMSTRONG, P. 1979 CUTLER, E.J.B.; RICHARDS. J.; COLLIE, T.W. 1957 FIELDES, M. 1962 Marlborough Counties. Effect of vcsicular-arbuscular mycorrhizas on growth of Soils of the Lower Clutha Plains. The nature of the active fraction of soils. NZ. Soil Bureau Bulletin 9. 55p. white clover, lotus, and ryegrass on some eroded soils. NZ. Soil Bureau Bulletin 15. 40p. Transactions of the Joint Meeting a,( Commissions IV and N.Z Journal o.f Agricultural Research 22: 479-484. V, International Society HUGHES, K.A. 1981 KIRKMAN, J.H. 1973a Some results from a long-term 'tillage' experiment in the Amorphous inorganic materials in three soils formed from LEE, K.E. 1959 McCRAW, J.D. 1975 Manawatu. loess. I. Application of selective dissolution techniques. The earthworm fauna of New Zealand. Quaternary airfall deposits of New Zealand. Proceedings of the Monsanto 'Conservation Tillage Tech NZ JournalIda Valley, Central Otago, N.Z. Potassium in New Zealand soils. KENNEDY, N. 1983 NZ. Soil Bureau Report 2/1966. 50p. N.Z. Soil Bureau Scienli/ic Report 38. 61p. Soils of Bruce County, South Island, New Zealand. LEAMY, M.L.; SAUNDERS, W.M.H. 1967 N.Z. Soil Survey Repor/ 87. Soils and land use in the Upper Clutha Valley, Otago. McCRAW, J.D. 1966b METSON, A.J.; ARBUCKLE, R.H.: SAUNDERS, M.L. 1956 N.Z. Soil Bureau Bulletin 28. l !Op. Soils of the Lower Shotover Catchment. The potassium-supplying power of New Zealand soils as KIDSON, E.B.; HOLE, F.A.; METSON, A.J. 1975 Pp.9-24 in 'Shotover River Survey (Lower Catchment)'. determined by a modified normal-nitric-acid method. Magnesium in New Zealand soils. Ill. Availability of non LEAMY, M.L.: WILDE, R.H. 1972 Otago Catchmenl Board Bulletin 2. 64p. Transactions. 6th International Congress of Soil Science exchangeable magnesium to white clover during exhaus Soils of the Roxburgh District, Central Otago, New B: 619-627. tive cropping in a pot trial. Zealand. N.Z. Journal of Agricultural Research 18: 337-349. NZ Soil Bureau Publication 478. 118 119 METSON, A.J.; BROOKS, J.M. 1975 MULLER, F.B.; McSWEENEY. G. 1977 Magnesium in New Zealand soils_. II.. Distribution of Movement of plant nutrients through Tokomaru silt loam. POHLEN, I.J. 1956b RAESIDE. J.D. 1956 exchangeable and 'reserve' magncsmm m the mam soil Pot trial. The effects of seasonal moisture-deficiency on yellow-grey groups. Proceedings C!( !he 16th Technical Co1(/"ere11cc, New earths. Yellow-grey carths of South Island, New Zealand. An example of polygenesis in soil development. N.Z. Journal of Agricultural Research 18: 317-335. Zealand Fertiliser Mam!facturers' Research Associalion N.Z. Society of Soil Science Proceedings 2: 29-30. 1: 87-97. (unpublished) Transaclions of the 6th International Congress ofSoil Sci E: 665-672. METSON, A.J.; GIBSON, E.J. 1977 POHi.EN, l.J. 1962 ence Magnesium in New Zealand soils. V. Distribution of *N.Z. METEOROLOGICAL SERVICE 1973 Soil classification in New Zealand. RAESIDE, J.D. 1958 exchangeable, 'reserve', and total magnesium in some Summaries of climatological observations to 1970. Transactions of the Joint ,'Vfeeting o(Commissions 1 V and The yellow-grey earths of the South Island. representative soil profiles. N.Z. Meteorological Scrrice Miscellaneous Publication 143. V. International Society ofSoil Scie1;c1>, New Zealand: 440- N.Z. Journal of Agricultural Research 20: 163-184. 77p. 452. N.Z. Soil News 1958: 206-208. (unpublished) METSON, A.J.; GIBSON, E.J.; LEE, R. 1977 *N.Z. METEOROLOGICAL SERVICE 1979 POHLEN, l.J. 1971 RAESIDE, J.D. 1964a Loess and soil formation. Magnesium in New Zealand soils. VI. Magnesium frac Rainfall parameters for stations in New Zealand and the Soils and their relation to land use. Hawkc's Bay Region. N.Z. Soil News 1964: 99-101. (unpublished) tions and interrelationships. Pacific Islands. Pp.35-57 in 'National Resources Survey. Part VI. Hawke's N.Z. Soil Bureau Scientific Report 31. I OOp. N.Z. Metmrological Serl'icc Miscellaneous Publication 163. Bay Region.' (Town and Country Planning Division, RAESIDE, J.D. l 964b 89p. Ministry of Works). Government Printer. Wellington. METSON, A.J.; LEE, R. 1977 233p. Loess deposits of the South Island, New Zealand, and Soil chemistry in relation to the New Zealand genetic soil N.Z. SOIL BUREAU 1954 soils formed on them. classification. General survey of the soils of North Island, New Zealand. POHi.EN, I.J. 1973 N.Z. Journal of Geology and Geophysics 7: 811-838. Soil Science 123: 347-352. N.Z. Soil Bureau Bulle/in 5. 286p. Influence of rainfall on the morphology of some humid RAESIDE, J.D. l964c and subhumid zonal soils in New Zealand. MILLER, D.E.K. 1971 N.Z. SOIL BUREAU 1962 N.Z. Journal of Science 16: 101-112. Further comment on loess and yellow-grey earths. Soil properties affecting tunnel-gully erosion. Northern tour. N.Z. Soil News 1964: 226-228. (unpublished) M.Agr.Sci. Thesis, Lincoln College. I 40p. (unpublished) Unpublished tour guide for 1962 International Soil Con POHLEN, l.J.; HARRIS, C.S. 1937 RAESIDE, J.D.; BAUMGART, 1.L. 1947 ference, Palmerston North. New Zealand. Hawke's Bay soil survey: Progress report. MILLER, R.B. ! 958a Erosion on the downlands of Geraldine County, South N.Z. Department of Scientific and Industrial Research Canterbury. Chemistry of the yellow-grey earths of the South Island. N.Z. SOIL BUREAU l 968a Annual Report 1936-37: 60-65. N.Z. Soil News 1958: 208-215. (unpublished) General survey of the soils of South Island, New Zealand. N.Z. Journal of Science and Technology A29: 49-57. N.Z. Soil Bureau Bulletin 27. 404p. POHLEN, I.J.; HARRIS, C.S.; GIBBS. H.S.; RAESIDE. J.D. MILLER, R.B. 1958b 1947 RAESIDE, J.D.; CAMERON, M.: MILLER, R.B. 1959 Climate studies in the yellow-grey earth zone. N.Z. SOIL BUREAU I 968b Soils and agriculture of part Geraldine County, New Soils and some related agricultural aspects of mid Hawke's Zealand. N.Z. Soil News 1958: 236-239. (unpublished) Soils of New Zealand. Bay. N.Z. Soil Bureau Bulle/in 13. 64p. N.Z. Soil Bureau Bulletin 26. 3v. N.Z. Department of Scientific and Industrial Research MILNE, J.D.G. 1973 Bulletin 94. l 76p. Map and sections of river terraces in the Rangitikci basin, O'BYRNE. T.N. (in prep) RAESIDE, J.D.: CUTLER, J.B.; MILLER, R.B. 1966 North Island, New Zealand. Soils of Wallace County, South Island, New Zealand. POLLOK. J.A. 1975 Soils and related irrigation problems of part of Maniototo Plains. Otago. N.Z. Soil Survey Report 4. N.Z. Soil Survey Report. A comparative study of certain New Zealand and Ger 69p. man soils formed from loess. N.Z. Soil Bureau Bulletin 23. MILNE, J.D.G.; NORTHEY. R.D. 1974 O'CONNOR, K.F. 1976 Published Ph.D. Thesis, Institut for Bodenkundc, Rhein RAESIDE, J.D.; RENNIE, W.F. 1974 Working report: Soils of the Wellington urban area. An introduction to the Waitaki. ischen Friedrich-Wilhelms-Universitlit Bonn. 3 I 5p. Appendix 2, pp.23-40 in 'Microzoning for earthquake N.Z. Man and the Biu.1phl'f"c Rc11ort I. 90p. Soils of Christchurch Region, New Zealand: the soil factor in regional planning. effects in Wellington, N.Z.' (by T.L. Grant-Taylor, R.D. POLLOK, J.A. 1976 N.Z. Soil Survey Report 16. Adams, T. Hatherton, J.D.G. Milne, R.D. Northey, W.R. ORBELL, G.E. 1974 Towards a definitve account of the Tokomaru silt loam. Stephenson). N.Z. Department of Scientific and Industrial Soils and land use of mid Manuherikia Valley, Central (Summary). RAGG, J.M.; MILLER, R.B. 1973 Research Bulletin 213. 61 p. Otago, New Zealand. N.Z. Soil News 24: 135-136. (unpublished) N.Z. Soil Bureau Bulletin 36. 63p. Soil map and extended legend of part Taieri Uplands, Otago, New Zealand. MOLLOY, L.F.; BLAKEMORE, L.C. 1974 POLLOK, J.A. 1978 N.Z. Soil Survey Report 9. Studies on a climosequence of soils in tussock grasslands. ORCHARD, V.A. 1978 Classification in the Federal Republic of Germany. !. Introduction, sites and soils. Effect of irrigation with municipal water or sewage effluent Pp.31-32 in 'Soil Groups of New Zealand. Part 3. Gley RAGG, J.M.; MILLER. R.B. 1978 N.Z. Journal of Science 17: 233-255. on the biology of soil cores. III. Actinomycete flora. Soils.' (Ed. W.C. Rijkse). N.Z. Society of Soil Science, N.Z. Journal of Agricultural Research 21: 21-28. Lower Hutt. 127p. Soil survey of part Taieri Uplands. Otago, New Zealand. MOLLOY, L.F.; BRIDGER, B.A.; CAIRNS, A. I 978a N.Z. Soil Bureau Bulletin 39. 56p. Studies on a climosequence of soils in tussock grasslands. 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Corrosion of cement-asbestos and concrete pipes in some virke district, New Zealand. New Zealand soils. RAESIDE, J.D. 1948 N.Z. Journal of Geology and Geophysics I 1: 685-692. *MUCKENHAUSEN, E. 1962 N.Z. Journal of Science and Technology B38: 257-278. Some post-glacial climatic changes in Canterbury and their RICKARD, D.S.; COSSENS. G.G. 1966 Entstehung, Eigenschaften und Systematik der Boden der effect on soil formation. Irrigation investigations in Otago, New Zealand. I. Bundesrepublik Deutschland. [Origin, properties and PENHALE, H.R. 1971 Transactions ofthe Royal Society C!( Nell' Zealand 77: 153- classification of the soils of the Federal Republic of Corrosion of mild steel plates in some New Zealand soils. 171. Description and physical properties of irrigated soils of Germany]. N.Z. Journal 1i(Scicnce 14: 336-353. the Ida Valley. · DLG-Verlag, Frankfurt. 148p., 60 plates. RAESIDE, J .D. l 954a N.Z Journal of Agricultural Research 9: 197-217. 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Respiratory activities and their relationships with tem The soil water balance in a Fragiaqualf and its effect on Studies on a climosequcncc of soils in tussock grasslands. perature, moisture, and soil properties. pasture growth in Central New Zealand. 18. Liller decomposition: urcasc. phosphatase, and sul ROBERTS, O.T.; JARMAN, S.M. 1979 N.7.. Journal ()(Science 18: 377-389. Australian Journal of' Soil Rc.1rnrch 17: 455-465. phatase acti vitics. Areas of soils of North Island. New Zealand. N.Z. Journal TAYLOR, N.H.; POHLEN, I.J. 1979 VUCETICH, C.G.; HOWORTH. R. 1976 Soil survey method. A New Zealand handbook for the Proposed definition of the Kawakawa Tephra, the c.20 OOO YEATES. (i. W. 1975 YEATES, G.W. 1981a field study of soils. 1979 reprint. years B.P. marker horizon in the New Zealand region. Nematode genera from some New Zealand pastures. Populations of nematode genera in soils under pasture. NZ. Soil Bureau Bulletin 25. 242p. NZ. Journal of Geology and Geophysics 19: 43-50. N.Z. Soil Bureau Scientific Rc11ort ] I. 22p. IV. Seasonal dynamics at live North Island sites. N.Z Journal TRANGMAR, B.B. 1977 WILDE, R.H. 1976 Slope stability problems in residential areas on the Port Soils of part Waitotara County, North Island, New Hills, Canterbury. Zealand. N.Z. Soil News 25: 77-79. (unpublished) N.Z. Soil Survey Report 26. TRANGMAR, B.B.; CUTLER, E.J.B. 1983 WILMS, T.R. 1979 Soils and erosion of the Sumner region of the Port Hills, An investigation into aspect related erosion forms in a Canterbury, New Zealand. valley in the Port Hills, Banks Peninsula. NZ. Soil Survey Report 70. M.Ag.Sci. Thesis, Lincoln College. 223p. (unpublished) TURNER, M.A.; SYERS, J.K.; TILLMAN, R.W. 1977 WILSON. A.O.; BEECROFT, F.G.; SMITH, S.M. (in prep.) Movement of phosphorus and nitrogen forms through Soils of the Waitaki Plains and Oamaru-Ngapara Tokomaru silt loam. Field observations. Downlands. 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