SORT OUT YOUR SOIL

A practical guide to Green Manures

By Anton Rosenfeld & Francis Rayns Edited by Ian Wilkinson & Isabel Milner CONTENTS

WHAT IS A GREEN MANURE? 5 CHOOSING A GREEN 14 MANURE CROP What is a cover crop? Soil Type WHY USE GREEN MANURES? 6

Nitrogen management SINGLE SPECIES OR MIXTURE? 16 Soil improvement Long term mixes Ensuring the nitrogen needs of the next Winter mixes crop are met Summer mixes Weed, pest and disease control Forage for livestock GREEN MANURE PLANTS 17

WILL GREEN MANURES 10 LEGUMES SUIT YOU? Crimson Clover 17 Why grow a green manure crop when a cash Fenugreek 18 crop could be grown instead? Lucerne / Alfafa 19 Will a green manure create extra work? Persian Clover 20 Red Clover 21 Won’t it be too late to sow a green manure after harvest? Sainfoin 22 Sweet Clover 23 Will green manure management clash with work on cash crops? Vetch 24 White Clover 25 Does the cost of seed justify the benefi t? Yellow Trefoil / Black Medick 26 Organic seeds

NON-LEGUMES MANAGING GREEN 12 MANURE CROPS Buckwheat 27 Chicory 28 When to sow Cocksfoot 29 What to grow over winter Grazing Rye 30 How to sow and establish Italian Ryegrass 31 Mustard 32 Legumes and inoculation Perennial Ryegrass 33 Mowing Phacelia 34 Incorporation Westerwolds Ryegrass 35 Undersowing

GROWTH HEIGHTS 36–37 AUTHORS 38 WHAT IS A GREEN MANURE?

Left: Grazing rye and vetch A green manure is a crop grown to improve Green manures can be grown for widely Below: Harvesting wheat the soil. Although they may generate a differing periods to suit particular needs. profi t, in most cases their sole purpose is These can vary from six weeks, for a short to benefi t subsequent crops. Once grown, break in an intensive vegetable rotation, they are usually incorporated into the soil to many years as a grass ley. shortly before sowing the next cash crop. Green manures have many different With rising nitrogen fertiliser prices and benefi ts but no one species will offer all an ever-increasing requirement to farm in of these. Grown as a single species, or in an environmentally sustainable way, green mixtures, the right choice of green manure manures are fast becoming a viable way depends on the aims and circumstances to cut input costs, add fertility and improve of each individual farmer or grower. the soil.

There is a wide variety of green manures What is a cover crop? to choose from including clovers, medicks, A cover crop protects the soil, particularly mustards and grasses. Legumes (such over the winter. It helps insure against soil as clover) are very popular as they fi x erosion, nutrient loss through leaching and nitrogen. However other species offer competition from weeds. Within this guide, benefi ts such as improved soil structure however, the term ‘green manure’ is used and weed suppression. to encompass the benefi ts of cover crops as well as all the other advantages of Green manures are fast green manures. becoming a viable way to cut input costs.

4 5 WHY USE GREEN MANURES? WHY USE GREEN MANURES?

WHY USE GREEN MANURES?

Green manures can be used for a whole Preventing nitrogen leaching for this purpose can usually be drilled Overview of green manure plants range of reasons as their benefi ts are very If soil is left bare for any length of time, in late September or even into October, Legumes and Nitrogen diverse. When choosing which to grow, rainfall will leach (or wash) nitrogen and depending on local weather and conditions. N N release Fix or each farmer needs to analyse his or her other nutrients out, especially on lighter Green Manure Plant Type potential Duration rate hold Nitrogen is one of the most important specifi c aims and circumstances and use ground. In many situations reducing nutrients required for plant growth and Soil Improvement Red Clover Legume Large 1–4 yrs Fast Fix development. Plants from the legume these to help make the right decision. The leaching is more important in maintaining White Clover Legume Moderate 2–5 yrs Fast Fix family can take nitrogen from the key variables include soil type, farming soil fertility than fi xing nitrogen. This is Improving soil structure system, previous cropping, future cropping Yellow Trefoil/Black Medick Legume Small 6–18 mths Fast Fix atmosphere and ‘fi x’ it so it becomes particularly true during the winter, when Green manure can improve soil structure available for other crops. This is done plans and climate. Persian Clover Legume Large 6–10 mths Fast Fix legumes are slow to establish and fi x little in a number of ways. Any crop which is grown through ‘nodules’ on the roots, home Sweet Clover Legume Large 6–18 mths Fast Fix nitrogen. Fast growing species with a then incorporated into the soil will add to nitrogen-fi xing bacteria which can The key benefi ts of green manures are: Crimson Clover Legume Moderate 6–9 mths Fast Fix organic matter. This will aid soil aeration, be seen if the plant is carefully dug up. Vetch Legume Large 6–10 mths Fast Fix Nitrogen management increase water and nutrient retention (on The exploitation of legumes can help In many situations reducing farmers make dramatic reductions in light soils) and improve drainage (on heavy Lucerne/Alfalfa Legume Large 2–4 yrs Fast Fix nitrogen fertiliser costs. Short term soil nitrogen boost leaching is more important soils). Organic matter also releases acids Fenugreek Legume Moderate 3–6 mths Fast Fix Fast growing green manures such in maintaining soil fertility which make some plant nutrients more Sainfoin Legume Large 2–4 yrs Fast Fix Non-legumes can be used to ‘hold’ as Persian clover, crimson clover and than fixing nitrogen. readily available to the next crop. Grazing Rye Cereal Large 6 mths Slow Hold nitrogen. They mop it up from the soil fenugreek can be grown in short breaks Mustard Brassica Large 2–4 mths Slow Hold and store it then, when incorporated, between cash crops to boost soil nitrogen. Some green manures species are Buckwheat Polygonaceae Moderate 4–6 mths Moderate Hold make this nitrogen available to future crops. These annual legumes are often used in deep root system are best for preventing particularly good at improving problems Phacelia Borage Moderate 4–6 mths Slow Hold intensive horticultural systems between leaching. Grazing rye (Secale cereale) – with soil structure. Lucerne, chicory and Perennial Ryegrass Grass Moderate 1–5 yrs Slow Hold vegetable crops. As legumes will only fi x different from perennial ryegrass (Lolium sweet clover have a strong tap root that Italian Ryegrass Grass Moderate 1–2 yrs Slow Hold o perenne) – is one of the best species for can break through compacted soils or nitrogen when the soil is above 8 C they Westerwolds Grass Moderate 6–12 mths Slow Hold this purpose, and mustard is also effective. those with a plough pan. The fi brous root are effective between April and August. Chicory Composite Moderate 1–5 yrs Moderate Hold system of cocksfoot is good at improving Cocksfoot Grass Moderate 2–5 yrs Slow Hold soil crumb structure. Red/White clover, Mixture Large 1–3 yrs Slow Fix & A further advantage of green manures and Ryegrass Hold is that they can help prevent soil erosion. Rye/Vetch Mixture Large 6 mths Slow Fix & The root structure of a green manure can (or Ryegrass/Vetch) Hold bind soil particles, greatly reducing the loss Mustard, Crimson/Red/ Mixture Large 4–6 mths Fast Fix & of top soil through wind blow or run off. Persian/Sweet Clover Hold In addition, a leaf canopy offers very good Organic Matter Please note: Nitrogen release will be slower with more mature plants. This is particularly noticeable protection to the soil during heavy rain as it with short term annuals such as mustard. The decaying remains of plant and slows down the speed of water movement. animal life form soil organic matter Winter cereals, on the other hand, have which contains vital nutrients such as Improving soil microbiology Ensuring the nitrogen a very different nitrogen requirement. nitrogen and phosphate. Each year a Organic matter is a food source for needs of the next crop Massive amounts of nitrogen released crop uses between 2-5% of the soil’s microbiological life which thrives in are met from a green manure in the autumn are organic matter and on many farms in healthy, well aerated soil. When soil is low not benefi cial for a newly emerging cereal the UK, especially stockless ones, on organic matter it is more susceptible Once a green manure is incorporated seedling. This would result in excess winter levels have become seriously depleted. to becoming anaerobic which can lead to it releases nitrogen into the soil. The rate growth but a lack of nitrogen when the Nothing improves soil more than a build up of toxins emitted by soil micro- at which this nitrogen becomes available cereal really needs it in spring and early adding organic matter. Green manures organisms. Under the right conditions, depends on the type of green manure and summer. In this case, a slower releasing are unsurpassed in this, adding both these micro-organisms play a key role in its growth stage at incorporation. Fleshy green manure, such as a mature mixture fertility and organic matter after they Long term soil nitrogen enhancement A further advantage of nutrient availability and disease containment legumes like vetch release nitrogen quite of clover and grass, would be best as are incorporated. This contrasts with within farming systems. This is an area fast making most of it available in the fi rst costly inorganic fertilisers which only Slower growing perennial legumes it would break down slowly, releasing green manures is that that is still little understood and, although few weeks after incorporation. Other plants, contain nutrients, adding nothing to such as red and white clover, sainfoin nitrogen over a longer period. green manures are undoubtedly benefi cial, like grasses and grazing rye, are much soil structure. and lucerne (alfalfa) are used to add they can help prevent there is still much work to be done in slower to release nitrogen. Green manures rich in nitrogen, such nitrogen to the soil over a long period. soil erosion quantifying this. Carefully planning as legumes, decompose quickly whereas These crops are relatively slow to establish Knowing this about green manures means grasses break down more slowly and but are persistent, so reduce the need for they can be manipulated to meet the the integration of so have a longer term impact on the soil. resowing. They are most commonly sown in When soil is cultivated in late autumn it is needs of the next cash crop. For example, green manures into the Manipulating mixtures means nutrient very important to sow a fast-growing crop a mixture with grasses, and are often used caulifl ower is nitrogen-hungry over a short rotation will maximise release can be phased to meet the needs for silage or grazing in extensive livestock (such as grazing rye) in order to minimise Left: Sweet clover tap root and nodules period so would benefi t from a spring of the next cash crop (see page 16). systems while they improve the soil. the risk of nitrate leaching. Suitable species Right: Yellow trefoil roots fi xing N incorporation of over-wintered vetch. their benefits.

6 7 WHY USE GREEN MANURES?

As livestock have differing grazing habits, the choice of species for forage is vital. Weed, pest and disease control Fast growing green manures are very effective at suppressing weeds. Mustards and phacelia produce good ground cover rapidly and so are excellent for this. Other species, such as red clover and Persian clover, that can be mown frequently, will also result in fewer weeds.

Allelopathy When some green manures, including many clovers and grazing rye, are destroyed and Silage incorporated their presence in the soil is Many green manures can be cut for ‘allelopathic’, preventing the germination silage. As with grazing, crops for silage of weed seeds in the soil. Although this is are most commonly grown as mixtures to very useful for weed control, it must be give a balanced and high yielding forage managed carefully as it can also inhibit the (see page 16). Typical mixes include red establishment of the next crop, particularly and white clover and ryegrass. Short those that are direct drilled. If drilling a term, single season mixes of vetch and cash crop next, as long as six weeks must westerwolds ryegrass are also used. be left between incorporation of the green Cutting time is key with clover and grass manure and drilling for the allelopathic mixtures as they provide a more palatable effect to subside. and nutritious silage if cut before fl owering.

Pest and disease suppression If cutting a crop for silage some of the Some mustards (caliente types see page Forage for livestock nutrients in the plant are, of course, 32) have been shown to reduce soil pests exported out of the fi eld to the clamp. and diseases. However, for them to be Many green manures such as white and This must be taken into account when effective, the conditions under which they red clover, lucerne and sainfoin provide calculating the benefi ts of the green are incorporated are critical and these are excellent high protein forage for livestock manure. On the plus side, cutting the not easy to control on a farm. To attempt it, while also benefi ting the soil. crop and removing the fodder will stimulate large amounts of biomass must be grown growth and more nitrogen fi xation by A major advantage of using legumes in then chopped, incorporated, irrigated and the legumes in the mix. However, taking grazing swards is that they will dramatically covered with plastic rapidly to realise silage cuts will always deplete potash and cut the need for nitrogen fertiliser, so saving the benefi ts. phosphorus, so levels of these essential considerable input costs. nutrients should be monitored frequently and boosted when needed. Fast growing green Grazing Legumes are nearly always mixed with manures are very effective grasses to produce a balanced grazing at suppressing weeds. sward and higher yields (see page 16). Bloat and Fertility In recent years perennial ryegrass has There is some risk of bloat with swards been the most popular species, but there Blackgrass that have a very high percentage of clover, are many other grasses that can be so this should be watched. Sainfoin, Blackgrass is a major issue on many included (such as timothy, cocksfoot however, is bloat free. arable farms. Growing a two year ryegrass and fescues). Ewes should also be taken off red clover or ryegrass/red clover green manure will six weeks before and after tupping as signifi cantly reduce this issue. As blackgrass As livestock have differing grazing habits, the plant contains phyto-oestogens that is an annual, leaving the green manure in the choice of species for forage is vital. For can affect sheep fertility. for two years suppresses germination of the example, sheep tend to graze close to the blackgrass so reducing the population. On ground so the small and medium leaved Left: Dairy cows grazing red clover arable farms, using ryegrass in this way can varieties of clover are best, as they tolerate and cocksfoot also produce a cash crop of excellent quality this. The higher yielding large leaved Right centre: Phacelia hay or silage. varieties can be grazed by cattle. Top right: Cutting sainfoin for silage

8 9 WILL GREEN MANURES SUIT YOU?

WILL GREEN MANURES SUIT YOU?

When considering using green manures, Will green manure there are many issues to think about. Some of the most important are explored below. management clash with work on cash crops? Why grow a green Cash crops will nearly always be prioritised manure when a cash over green manures. During periods of peak labour, such as June in horticultural systems, crop could be grown it is important not to neglect green manures. instead? Early mowing is often important for weed control in green manures and can really Sowing a green manure instead of a make the difference between a good and cash crop can seem like a loss of income. bad crop. This management time should be However, when put in the context of rising factored in when planning workloads. nitrogen prices, this is less clear cut. It is hard to quantify exactly how much nitrogen a green manure delivers in comparison Won’t it be too late to Does the cost of seed sow a green manure justify the benefits? The cost of growing a good after harvest? The cost of green manures varies widely green manure should be depending on the species and the sowing outweighed by the profitable Many crops, particularly horticultural rate. Generally speaking, larger seed is ones, continue to produce well into October. sown at a higher rate, making it more yields of subsequent crops. This can create a dilemma: continue to expensive per acre. harvest the crop, or turn it in and sow to bagged fertiliser, especially as green a green manure. Left: Grazing rye manures deliver signifi cant additional In reality, as most most vegetable crops When calculating the cost of a Above: Cash crops nearly benefi ts in soil improvement. However, always take priority produce much more slowly towards the end it is best to think about green manures Bottom: Vetch of the growing season, it can often be worth green manure, the huge saving as a long term investment in future crops, sacrifi cing the last of the cash crop in order rather than a short term quick fi x. The cost to get a green manure well established on N fertiliser is a major factor. of growing a good green manure should before winter as this will boost subsequent be outweighed by the profi table yields of cash crops in the rotation. subsequent crops. Organic seed If the cash crop is left in the soil as long as Will a green manure possible it is likely to be too cold afterwards The need to use organic seed can also Seed Sizes to drill a leguminous green manure. increase costs. On certifi ed farms, organic Small create extra work? However, in this situation, grazing rye is a seed must be used, where available, at All clovers, lucerne and very good option as this will establish into trefoil species Growing a good green manure crop is more 100% in straights or 65% for mixtures October and effectively prevent leaching than just buying and drilling some seed. (although this fi gure may change). Medium over the winter. Mustard, fenugreek Nearly all but the shortest term species will Availability of seed can be checked on www.organicxseeds.com. Organic seed is Large require cutting to control weeds, stimulate As some vegetable crops, such as generally available for the more commonly Grazing rye, vetch, sainfoin growth and reduce the number of fl owering sweetcorn and runner beans, lend used species such as clover and vetch, but Grazing rye, a large seed, is sown at and seeding heads. The amount of cutting themselves to undersowing this is another a high seed rate, making it relatively not for the more unusual green manures needed will depend on the particular very good option. The green manure can expensive to grow. However as it is such as Persian clover. growing season and soil type. Where then be sown at the right time but while the by far the best species for preventing possible, using livestock to graze the crop nitrogen leaching, the benefi ts far cash crop is still productive. In this case, outweigh the costs. will help reduce the need for mowing. it is a good idea to experiment to fi nd the When calculating the cost of a green optimum sowing time for the particular manure, the huge saving on N fertiliser farming system and green manure crop. is a major factor.

10 11 MANAGING GREEN MANURE CROPS

Incorporation of a green manure can be done by rotavating or ploughing.

Legumes and inoculation Sweet clover and crimson clover should Undersowing only be topped at a moderate height (16- It is the symbiotic relationship that legumes 20cm), which can be an issue if weeds Undersowing is a very effi cient way of have with Rhizobium bacteria which results are a problem. ensuring that a green manure is established in nitrogen fi xation (see page 7). The as quickly as possible after harvesting a bacteria take nitrogen from the air and turn Cutting also helps promote lush vegetative cash crop. This is most commonly done with it into compounds which plants can use. growth and delays the crop going to seed. cereals, although it can work well with This process only takes place when the Without topping most crops will become other crops too. soil temperature is above 8oC, so fi xation woody and diffi cult to incorporate. generally occurs from March till September. When undersowing a cereal it is best Ideally it is best to remove cuttings as Most legumes will not establish successfully In many species of green manure – such to use one of the less aggressive green this encourages more nitrogen fi xation after the beginning of September as the soil as red and white clover, vetch, crimson manure species such as white clover or in legumes. When leaving the cuttings, the clover, Persian clover and yellow trefoil – yellow trefoil. The green manure should temperature will be falling quickly. rotting material will release nitrogen which the correct species of bacteria, Rhizobium be sown into a spring cereal when it is suppresses nitrogen fi xation. In reality this trifolii, is already in the soil. around 15cm high (normally around April). is not often practical, but should be done This technique is popular on organic However, there are some species – such wherever possible. farms as sowing can be combined with as lucerne, sweet clover and fenugreek – mechanical weeding. The green manure When cuttings are not removed, a fl ail where the correct bacteria is unlikely to be should establish and grow slowly before mower should be used to distribute the present and these need to be ‘inoculated’ the cereal is harvested. Then, once the cut material evenly. with Rhizobium meliloti. This culture is cash crop is removed, it will grow much bought in sachets and mixed with the seed more quickly. MANAGING GREEN at the time of sowing. It is a relatively simple Incorporation process and only needs doing once per crop. The success of undersowing can vary Incorporation of a green manure can be with site, but in many cases undersown MANURE CROPS done by rotavating or ploughing. Before crops perform better than pure stands as Mowing doing this it is generally best to cut the the cereal acts as a ‘nurse’ crop, protecting When to sow manure which will prevent overwinter crop with a fl ail mower (which will chop the green manure in its early stages. Mowing is an essential part of growing leaching, such as grazing rye. A legume up the cuttings) as this makes the job Spring or autumn are the best times to sow most green manures. It is very important would not be the right choice in this much easier. When sowing the next crop green manures. This is mainly to ensure o in weed control, especially when the crop instance as the soil will be below 8 C for after incorporation the allelopathic effects there is suffi cient moisture for germination. is young. Early mowing can make the Top left: Drilling a green manure crop the majority of the time the green manure of some crop residues should be taken If there is enough rainfall or an irrigation is in the soil, preventing nitrogen fi xation. difference between a well-established Top right: Seed and inoculant into consideration (see page 9). Bottom right: Topping clover system, summer planting can therefore be green manure and one which is persistently an option. Most legumes will not establish If the overwinter green manure is going weedy. Most species – including red clover, successfully after the beginning of September to be followed by a crop to be sown later white clover, lucerne, Persian clover and as the soil temperature will be falling quickly. in the year, such as vegetable transplants yellow trefoil – can tolerate being topped in June, then a fast growing legume (such close to the ground to control weeds If sowing must be done late in the as vetch) would be the best choice as year, grazing rye is the best option. there will be time for considerable nitrogen However, not all species of green manure This establishes rapidly and is very good fi xation to take place from March onwards. can be mown. It is most likely to kill off at preventing nitrogen leaching over the fenugreek and vetch. Luckily both of these winter. It is generally a bad idea to plant crops establish rapidly and compete well other green manures late as the necessary How to sow and establish against weeds, making mowing unnecessary. cultivations can increase the risk of leaching. Green manures can be broadcast or drilled. If the ground is level, then drilling controls What to grow over winter seed depth better. However broadcasting Early mowing can make distributes seed more evenly. The depth of The choice of green manure to grow over sowing is very important and the correct the difference between winter is usually determined by plans for sowing depth is given for each green a well-established green the next crop. If the green manure is going manure later in this guide. to be followed by an early, spring-sown manure and one which cereal then it is best to choose a green is persistently weedy.

12 13 CHOOSING A GREEN MANURE CROP CHOOSING A GREEN MANURE CROP

CHOOSING A GREEN SOIL TYPE • Acid soils – most legumes do not • Free-draining soil – with this type MANURE CROP grow well on acid soils of soil deep-rooting grasses like The first stage in deciding which The soil type will cocksfoot and/or tap-rooted legumes • Alkaline soils – sainfoin and lucerne like sainfoin and red clover should be species or mixture to grow is to influence the choice of thrive on soils with a higher pH and selected. Lucerne prefers a free- were traditionally grown on the chalky determine your aims. These will green manure as some draining soil and will not grow under downs of Southern England. then help you make the right choice. species are better waterlogged conditions. Plentiful • Neutral soils – most green manures rainfall is fi ne, as long as the soil is Sowing a mixture of plants will suited to certain soils. thrive on soils with a neutral pH free draining. combine the benefits each offers.

All green manures will add organic matter All green manures will add organic matter

AIM: AIM: Improve soil structure Fix N Improve soil & fix N Lift N & control weeds

1-12 1Yr 1-12 1Yr 1-12 1Yr 1-12 1Yr months plus months plus months plus months plus

Overwinter Summer Overwinter Summer Overwinter Summer Overwinter Summer

Vetch Mustard Cocksfoot Vetch Sweet clover Red clover Grazing rye/ Red clover Red clover Grazing rye Mustard Perennial Grazing rye Sweet clover Red clover Vetch Sainfoin vetch mix Vetch Sainfoin Italian ryegrass Phacelia ryegrass Cocksfoot Westerwolds Vetch Chicory Red clover Lucerne Sweet clover Sweet clover Westerwolds Westerwolds ryegrass Red clover Sweet clover Yellow trefoil Sweet clover Lucerne ryegrass ryegrass Persian clover Sainfoin Crimson clover White clover Phacelia Buckwheat Lucerne Buckwheat Fenugreek

14 15 SINGLE SPECIES OR MIXTURE?

Below: Ryegrass SINGLE SPECIES and clover mix OR MIXTURE? LEGUMES As no one green manure species can offer acts to delay the release of this nitrogen, manures. Incorporation is carried out from every benefi t, it is very common to drill a as it is higher in carbon and acts like a February until late April. Although grazing mixture. By doing this multiple advantages sponge, holding the nitrogen for longer. rye is the best nitrogen holder, westerwolds Crimson can be exploited simultaneously. This is especially important when the green ryegrass can be used as an alternative to manure is to be followed by an autumn- bring the seed cost down. The strength of mixtures is most obvious sown crops such as winter wheat where with a grazing rye/vetch mix or clover/grass Clover the highest demand for nitrogen can be six ley where two or more different species or seven months after the green manure Summer mixes will grow successfully together performing [Trifolium incarnatum] has been incorporated. Diverse annuals mix quite separate functions, the legumes fi xing nitrogen and the other species improving Cocksfoot There is often an opportunity during warm weather to grow a fast-growing, soil structure. For leys that will be in the ground for annual green manure. These crops add longer than two years, using cocksfoot A mixture also offers more weed organic matter, hold surplus soil nitrogen, instead of ryegrass with the clover will competition and removes the risk of a suppress weeds and act as a break crop increase the benefi ts signifi cantly. The deep single species failure. by interrupting pest and disease cycles. roots of cocksfoot improve soil structure N fixer, short term Suitable mixtures can comprise up to four and add massive amounts of organic Very short term and competitive green or fi ve crops such as mustard, crimson Crimson clover is a short term annual grown to provide manures like mustard or phacelia are in matter. Another bonus with this species clover, phacelia and Persian clover. a rapid boost to soil fertility. It is commonly used for short the ground for only a few weeks and are is its drought resistance. This can mean it breaks in intensive horticultural systems. It also produces usually sown on their own. needs topping more often, but this extra Summer green manure mixtures are a spectacular array of fl owers, which is often cited as a management is paid for by the increased planted from late spring onwards on organic matter gained. reason for growing it. Multiple advantages can be exploited simultaneously. Sowing rate: 15 kg/ha or 1.5 g/m2 Biomass Seed of crimson clover is small and should be broadcast or drilled at This crop produces around 3-4t/ha of biomass, less bare ground or immediately after whole a shallow depth (not more than 10mm). Sowing too deep will reduce than red clover. the germination dramatically. The soil should be rolled after sowing crop silage or any early cereal harvest in Nitrogen fi xing potential June or July. A good summer green manure to increase soil moisture contact with the seed. It is not clear how much N is fi xed but according to estimates will be ready for turning in after only 8 – 10 Ideal sowing time it is between 100-150kg N/ha annually. weeks and will therefore be incorporated before the sowing of a winter cash crop. March – May is the ideal time for sowing in the spring. It will germinate in the summer, but frequently there is insuffi cient Persistence These crops give good leaf canopy cover moisture in the soil to allow this. Mid to late August is the best time Being an annual, this crop is fi nished after fl owering, so it is short to block out light, suppressing weed growth. for an autumn sowing. Establishment is less likely to be reliable if lived. It has often fl owered then died back by July – August. They are easy to establish with many sowing extends too far into September. Topping regime species able to grow on the soil surface without the need for cultivation. The seed Suitable varieties Crimson clover does not take kindly to hard topping, so should is cheap and the crops are usually very There is limited information on varietal performance. Contea is a be topped 10cm above the ground. This may limit the options for reliable. One further advantage of these commonly grown variety which gives satisfactory results. weed control. Long term mixes Winter mixes fl eshy annual plants is that incorporation Frost tolerance Pest and disease problems is simple. The mixture should be worked Grass clover mixes Grazing rye or westerwolds ryegrass into the soil at least three weeks before Crimson clover sown in autumn will survive as small plants through The information on pest and disease tolerance in crimson clover and vetch mix Growing a mix of red and white clover with sowing the next cash crop. This will allow frosts over the winter. In spring the growth rate increases and a full is limited. Its tolerance to sitona weevil and downy mildew are perennial ryegrass is a very good option Growing a nitrogen holder such as grazing for the allelopathic effect to wear off (a canopy will form. similar to red clover. It is not attacked by the same types of stem for improving soil fertility and structure. rye and a fi xer such as vetch together is shorter time with these species than nematode as red clover, so can form an alternative crop in the Weed competitiveness To realise its full potential the mix should a good way of improving soil in the months with other green manures where plants rotation to prevent the build up of this soil pest. be grown for at least one full year before over winter. Grazing rye and vetch are are more woody when incorporated). It Once established, crimson clover rapidly produces a canopy that incorporation. Red and white clover can excellent companions and can be sown is important to ensure all summer green is effective against weed control. This canopy often recedes at the fi x up to 300 kg N/ha which is released from mid September until mid October, manures are destroyed before setting seed onset of fl owering allowing some weed growth, and the plant then rapidly after incorporation. The ryegrass a later sowing window than other green to prevent weed problems in the next crop. dies away once fl owering is fi nished.

16 17 GREEN MANURE PLANTS LEGUMES GREEN MANURE PLANTS LEGUMES

N fixer, longer term Fenugreek Lucerne/ A superb high protein forage crop, lucerne is usually grown on its own and is very good on drought-prone [Trigonella foenum-graecum] N fixer, very short term soils. It establishes relatively slowly, producing signifi cantly Alfalfa more biomass in the second and third years. It is particularly Fenugreek is one of the most rapidly establishing well suited where it will be used as a silage or hay crop green manures, and produces a quick boost to soil [Medicago sativa] as well as a green manure. Lucerne should only be grown fertility in just a few months. It is not commonly on free-draining, alkaline soil (minimum pH 6.2). grown but has potential to fi ll short breaks in intensive horticultural systems.

Sowing rate: 20 kg/ha or 2.0 g/m2 Seed of lucerne is slightly larger than clover seed, and should be sown at 1cm. The soil should be rolled after sowing to increase soil moisture contact with the seed.

Ideal sowing time Lucerne can be sown in spring or summer. For a spring sowing, March – May is ideal. It will germinate in the summer, providing there is suffi cient moisture in the soil. For an autumn sowing, August is the best time. Later sowings in September are less likely to establish well as the soil temperature cools.

Suitable varieties Currently, the most commonly used varieties are Verko, Mercedes and Vela, although other lesser known varieties such as Daisy, Diane, Marshal and Pondus also produce good yields.

Frost tolerance Foliage of lucerne dies off over the winter, but it survives as a tap root which resumes growth in the spring.

Weed competitiveness 2 Sowing rate: 25 kg/ha or 2.5 g/m Biomass Lucerne is slow to establish initially, but once it gets going shows Seed of fenugreek is slightly larger than clover seed, so can be This crop rapidly produces large amounts of biomass. good competition against weeds. It will withstand being topped for sown deeper (1cm is ideal). The soil should be rolled after sowing weed control. to increase soil moisture contact with the seed. Nitrogen fi xing potential There is very limited information on N fi xation with just one fi gure Biomass Ideal sowing time of 30kg N/ha annually. It must be borne in mind that this crop has Lucerne is slow to produce biomass initially but this increases Fenugreek is generally sown in the spring, March – May is ideal. an extremely short life cycle, so the fi gure for annual N fi xation will over the second and third years with 15t DM/ha possible once It will germinate in the summer, but frequently there is insuffi cient be lower than that of a perennial crop. To fi x N, this legume requires fully established. moisture in the soil to allow this. seed inoculation with an effective strain of Rhizobium meliloti at the time of sowing (see page 13). Nitrogen fi xing potential Suitable varieties There are a wide range of estimates for N fi xation in lucerne ranging Topping regime There is limited information on varieties, with growers frequently Persistence from 125 – 500kg N/ha annually. A typical fi gure is 150kg N/ha. Lucerne will generally need topping 2 – 3 times per growing season. just accepting what is available. This crop has a very short persistence, as it will start to fl ower To fi x N this legume requires seed inoculation with an effective The frequency depends very much on season and soil type. and set seed after a few months. It is only suitable as a short term strain of Rhizobium meliloti at the time of sowing (see page 13). Frost tolerance green manure. Pest and disease problems Despite being a Mediterranean crop, fenugreek will show a Persistence Observations suggest that lucerne is slightly more susceptible surprising resilience to hard frosts. Topping regime Lucerne shows good persistence, and is ideally grown for a period to downy mildew and attack from sitona weevil than red clover. It is best not to top fenugreek at all as, in most cases, this will kill it. of 2 – 3 years although it can be grown for longer than this. Its It can also suffer from stem nematode and Verticillium wilt. There Weed competitiveness Its growth is vigorous enough to compete against weeds without the persistence depends on factors affecting survival of the tap roots. should therefore be a four year break between lucerne crops. Some Fenugreek grows extremely rapidly, so will compete well against need for cutting. It will not thrive on waterlogged soils and poaching or wheel varieties such as Vela have been shown to have good resistance to weeds. It does have quite an erect growth habit, so may need damage will also impact on its longevity. both of these disorders. sowing at higher rates on weedier sites to provide adequate Pest and disease problems ground cover. Fenugreek has few pest and disease problems.

18 19 GREEN MANURE PLANTS LEGUMES GREEN MANURE PLANTS LEGUMES

Persian Red Clover 0 cm 1 Clover [Trifolium pratense] [Trifolium resupinatum]

N fixer, short to medium term

Red clover is one of the most tried and tested green manures for short to medium term leys, especially popular N fixer, short term annual with organic farmers. Once established, it is capable of Persian clover is an annual capable of rapid growth, rapid growth and shows reasonably good persistence up ideal for providing a quick boost to soil fertility where to three years. Red clover silage has very good protein there is a window of 5-12 months. Most growers in the levels and is a valuable by-product. UK are not familiar with Persian clover which, like many legumes, originates from the Middle East. It grows on Sowing rate: 15 kg/ha or 1-5 g/m2 Nitrogen fi xing potential most soils and was adopted commercially in Australia Clover seed is small and should be broadcast or drilled at a shallow Estimates of N fi xed show a wide variation from 150 – 450kg N in the 1970s and is grown successfully in other countries depth (not more than 10mm). Sowing too deep will reduce the annually. 150kg N/ha per year is a typical fi gure for a ley that is with similar climates to ours such as New Zealand. germination dramatically. The soil should be rolled after sowing cut and mulched, but this could be considerably increased if the to increase soil moisture contact with the seed. material is removed for silage. In other words, cutting and removal stimulates N fi xation. Ideal sowing time Sowing rate: 10 kg/ha or 1 g/m2 Biomass March – May is the ideal time for sowing in the spring. It will Persistence Clover seed is small and should be broadcast or drilled at a shallow This crop produces large amounts of biomass very quickly. The stem germinate in the summer, but frequently there is insuffi cient The crop should persist for two years, and with varieties such as depth (not more than a few mm). Sowing too deep will reduce the material has less tendency to turn woody than many other green moisture in the soil to allow this. Mid to late August is the best Milvus may extend beyond this, although the population tends germination dramatically. The soil should be rolled after sowing to manures, making it easy to incorporate. Biomass can be increased time for an autumn sowing. Establishment is less likely to be to decline if left longer. The red clover plant is a perennial that increase soil moisture contact with the seed. if grown with aggressive short-lived westerwold or Italian ryegrass. reliable if sowing extends too far into September. survives over winter as a crown. It is survival of the plant crowns that determine the longevity of the crop. The crowns gradually Ideal sowing time Nitrogen fi xing potential Suitable varieties deteriorate over time, becoming diseased, damaged by cutting, March – May is the ideal time for sowing in the spring. It will There is little information on the N fi xing potential of this crop, with Considerable resources have been devoted to developing varieties traffi cking or trampling by livestock. germinate in the summer, but frequently there is insuffi cient only one estimate of 100kg N/ha annually published. of red clover. Milvus is one of the most commonly grown, but moisture in the soil to allow this. Mid to late August is the best time there are others that have been developed more recently. Merviot Topping regime Persistence for an autumn sowing. Persian clover will not establish under cold produces large amounts of biomass and has shown some resistance Red clover should be mown regularly whenever it reaches a height temperatures and is unlikely to be successful if sowing extends too This crop is an annual but shows greater persistence than other to Sclerotinia rots. AberRuby also produces very large amounts of 30cm. The fi rst cut may be before this if there is a severe weed far into September. annuals such as crimson clover. It will start to die off by October of biomass. problem. The frequency of mowing will vary widely between sites. from a spring sowing in April. On a dry sandy soil, it may only need cutting twice in the season. Suitable varieties Frost tolerance Topping regime Conversely, on a fertile soil in a warm wet summer, it may need There are a number of cultivars in production. One of these, Laser, The leaf cover of red clover will die back over the winter, and the cutting as frequently as once every ten days. has been tested in the UK and has performed reliably under a range Persian clover is usually only cut once and may be cut at an early plant over-winters as crowns. This structure should be tolerant of of conditions. Others from Australia, Greece and Italy are also stage if weed control is required. If cut at full fl owering there will all but the most severe frosts. Pest and disease problems being imported. be little regrowth. Red clover is more susceptible than other species to the soil borne Weed competitiveness disease Sclerotinia trifoliorum and the stem nematode, Ditylenchus Frost tolerance Pest and disease problems Although not the most rapid to establish, red clover generally dipsaci. They were responsible for the clover sickness observed in The leaf cover of Persian clover will be knocked back by frost, but The pest and disease problems of Persian clover are not well competes well against weeds. Once established, it produces large many red clover crops in the 1970s and 80s resulting in a concerted will recover to provide a reliable crop. documented in the UK. As stem nematode races are very species amounts of biomass that smother weeds. It also grows back rapidly effort to breed more resistant varieties. For this reason, there should specifi c, it is unlikely to suffer from the same nematode problems after topping, which is important in out-competing weeds. Weed competitiveness be a four year gap between red clover crops. As these disorders are as red clover. Therefore alternating this crop with red clover may reasonably specifi c to red clover other fertility-building crops, such On emergence this plant produces very small leaves, but after the reduce the chances of stem nematode populations building up in the Biomass as white clover, can be used as an alternative. 4 – 5 leaf stage, expansion is rapid, producing a thick canopy that soil. This crop may be slightly more susceptible to damage from the This green manure is one of the most productive, typically producing is extremely competitive against weeds. sitona weevil than other clovers, although this does not signifi cantly an annual dry matter yield of 10 t/ha. Biomass can be increased reduce productivity. signifi cantly by sowing with grass.

20 21 GREEN MANURE PLANTS LEGUMES

N fixer, short to medium term Sweet clover is a tall biennial plant. There are two Sweet forms, one white fl owered and one yellow, with little difference between them. Once established, it is aggressive, producing a large tap root and Clover signifi cant biomass. [Melilotus officianalis]

Sowing rate: 15 kg/ha or 1.5 g/m2 Topping regime Seed of sweet clover is small and should be broadcast or drilled Sweet clover does not take kindly to hard topping, so should be at a shallow depth (not more than a few mm). Sowing too deep will topped 10cm above the ground. This may limit the options for reduce the germination dramatically. The soil should be rolled after weed control. sowing to increase soil moisture contact with the seed. Pest and disease problems Ideal sowing time The information on pest and disease tolerance in sweet clover is limited. March – May is the ideal time for sowing in the spring. It will Observations suggest that it is considerably more susceptible to germinate in the summer, but frequently there is insuffi cient sitona weevil and downy mildew than red or white clover. moisture in the soil to allow this. Mid to late August is the best time for an autumn sowing. Establishment is less likely to be reliable if sowing extends too far into September.

Suitable varieties There are no varieties available. Seed is sold as ‘commercial’ N fixer, medium term which means it is not a particular cultivar. Seed can contain both white and yellow types. Sainfoin Sainfoin is a perennial with an erect growth habit, producing characteristic pink fl owers. It is extremely Frost tolerance [Onobrychis viciifolia] palatable to animals and has a very good nutritional Sweet clover will survive over winter as a tap root and by the end balace. It can be grazed, or fed as hay or silage. of the winter leaves will be absent. It is suitable for the large area of chalk and limestone Weed competitiveness soils in England. Sweet clover has an erect growth habit, resulting in an open canopy that is not suited to competing on soils with high weed Sowing rate: 70 kg/ha or 7.0 g/m2 Biomass burdens. It also does not favour being cut too low to the ground, Sainfoin seed is large and should be drilled to a depth of 2cm. This crop produces up to 15t DM/ha once it is established. which restricts the options for early weed control. The soil should be rolled after sowing to increase soil moisture contact with the seed. Nitrogen fi xing potential Biomass There is very little information on the N fi xing potential If this crop establishes well, it is one of the most prolifi c Ideal sowing time of sainfoin, although it is thought that it fi xes slightly less than for producing biomass rapidly. Sainfoin is traditionally sown as a spring crop, so ideal sowing red clover. time is April – May. Adequate moisture is essential for good Nitrogen fi xing potential establishment, so sowing later in the summer may be less reliable. Persistence Sweet clover can fi x large amounts of N, around 150kg N/ha. This crop has the potential to persist for 3 – 4 years, provided its To fi x N this legume requires seed inoculation with an effective Suitable varieties tap roots are not damaged. It is best to avoid heavy grazing and strain of Rhizobium meliloti at the time of sowing (see page 13). There is limited information on varieties, although the EU ‘Healthy poaching which can reduce the population of viable tap roots. Hay’ project collected 355 samples, many of which are being Persistence evaluated for their potential. Topping regime As this is a biennial, it will die off after fl owering. It can set seed Sainfoin will generally need topping 2 –3 times a season, and come back in subsequent crops and, although the plants are Frost tolerance although this may vary considerably with season and soil type. very conspicuous, they tend to be in relatively small numbers, so Sainfoin is extremely tolerant to frosts. their impact on the next crop is limited. However, volunteers should Pest and disease problems not be allowed to contaminate subsequent cereal crops. Even a Weed competitiveness Sainfoin can be susceptible to crown rot, which can reduce very small amount can cause a coumarin taint, which can lead to Sainfoin can be slow to get going, but produces enough ground the persistence of the crop. rejection of malting barley. cover to compete against weeds once it is well established.

22 23 GREEN MANURE PLANTS LEGUMES GREEN MANURE PLANTS LEGUMES 0 cm 1 N fixer, medium to long term Vetch White Clover White clover is one of the most tried and tested of all the green manure species. It does not establish rapidly but [Vicia sativa] [Trifolium repens] once it gets going it produces respectable amounts of biomass over an extended period. It is commonly used for medium to long term leys, especially where livestock is grazed. The less aggressive varieties are also particularly suitable for undersowing in cereal or vegetable crops.

N fixer, short term Medium leaved varieties: can be grazed by cattle or lightly grazed by sheep, also good for a cutting mix. Varieties include AberHerald, Vetch (also known as winter tares) is very popular, AberConcorde and Crusader. providing a rapid fi x of nitrogen. It is particularly good at competing against weeds. Large leaved varieties: most productive and best suited to cutting or non intensive grazing. Varieties include Alice and Barblanca.

Frost tolerance The leaf cover of white clover will die back over the winter, and Suitable varieties the plant over-winters as an underground stolon structure. This Early English is a commonly grown variety. Other varieties are sown structure should be tolerant of all but the most severe frosts. but it is important to use winter types when sowing in the autumn. Weed competitiveness Frost tolerance White clover is slower to establish than some green manures and Winter vetch has good frost tolerance and will maintain a canopy will benefi t from early topping to control weeds. However biomass over the winter. increases later in the season and in subsequent years, offering good weed control. The larger leaved varieties are more aggressive against Weed competitiveness weeds than the smaller. Vetch is extremely competitive against weeds, forming an aggressive canopy rapidly. When incorporated, the residues also Biomass have an allelopathic effect, inhibiting germination of new seeds This crop produces a slightly less annual biomass than red clover (see page 9). This effect persists for around six weeks, and an at around 7t DM/ha, but persists for a greater number of years. adequate interval should be left if drilling direct sown crops after It may be mixed with grass which increase biomass to 13t+ DM/ha. incorporating vetch. Nitrogen fi xing potential Biomass Estimates for N fi xing potential of white clover vary very widely This crop rapidly produces large amounts of biomass. from 50 to 450kg N/ha annually. A typical fi gure is 150kg N/ha if Sowing rate: 10 kg/ha or 1 g/m2 cut and mulched. Nitrogen fi xing potential Clover seed is small and should be broadcast or drilled at a shallow Estimates of annual N fi xation range from 100 – 250kg N/ha. depth (not more than a few mm). Sowing too deep will reduce the Persistence A typical fi gure is 150kg N/ha. germination dramatically. The soil should be rolled after sowing to White clover is one of the most persistent of the green manure increase soil moisture contact with the seed. crops and will commonly last for 7– 8 years. It proliferates through Persistence an underground stolon structure, so even if one part becomes Being an annual, this crop is fi nished after fl owering, so it is short Ideal sowing time damaged the crop can regenerate. lived. It has often fl owered then died back by July – August. March – May is the ideal time for sowing in the spring. If undersowing a spring cereal, it should be sown in April or May. Topping regime Topping regime It will germinate in the summer, but frequently there is insuffi cient White clover should be mown regularly whenever it attains a height It is best not to top vetch at all, as it does not recover well. Its moisture in the soil to allow this. Mid to late August is the best time of 30cm but can be cut before this if weeds are a problem. The growth is vigorous enough to compete against weeds without the frequency of mowing will vary widely between sites and seasons. Sowing rate: 85 kg/ha or 8.5 g/m2 for an autumn sowing. Establishment is less likely to be reliable need for cutting. if sowing extends too far into September. Seed of vetch is larger than clover seed, so should be sown deeper, Pest and disease problems (1-2 cm is ideal). The soil should be rolled after sowing to increase Pest and disease problems Suitable varieties A lot of breeding effort has gone into varieties of white clover and, soil moisture contact with the seed. Generally vetch has few pest or disease problems. Sitona weevil There is more variety choice for white clover than any other green as such, many have good tolerance to the common pests and can attack it during its early stages, but this generally has little diseases such as Sclerotinia and stem nematodes. Ideal sowing time manure. The growth habits of varieties vary considerably, and are effect on the subsequent success of the crop. Pigeons can sometimes grouped into small, medium and large leaved types. These are used March – May is the ideal time for sowing in the spring. It will set back the development of the crop if there is little else for them for different purposes: germinate in the summer, but frequently there is insuffi cient to eat. There is a suggestion that growing vetch results in fewer moisture in the soil to allow this. September is the best time for slugs in the subsequent crop, although further work needs to be Small leaved varieties: best for hard grazing by sheep. Varieties an autumn sowing. It can be reliably sown later than clovers. done to verify this. include AberAce or S184.

24 25 GREEN MANURE PLANTS LEGUMES

Yellow Trefoil/ N fixer, short to medium term NON-LEGUMES Black Medick Yellow trefoil (or black medick) is a short-lived annual/ biennial with a low growth habit making it a common [Medicago lupulina] choice for undersowing. Weed suppressor and Buckwheat P provider, short term Buckwheat does not fi x nitrogen but is a very rapidly Sowing rate: 10 kg/ha or 1 g/m2 Biomass [Fagopyrum esculentum] growing annual crop. It is good at scavenging for Seed of yellow trefoil is small and should be broadcast or drilled at This crop produces a slightly smaller annual biomass than phosphate in the soil which it then takes up and makes a shallow depth (not more than a few mm). Sowing too deep will red clover. available to subsequent crops after incorporation. reduce the germination dramatically. The soil should be rolled after sowing to increase soil moisture contact with the seed. Nitrogen fi xing potential Although there is very little scientifi c information on the N fi xing Ideal sowing time potential of this crop, practical experience from growers suggests March – May is the ideal time for sowing in the spring. If it is that it is as good as white clover. to be undersown in a spring cereal, it should be sown in May. It will germinate in the summer, but frequently there is insuffi cient Persistence moisture in the soil to allow this. Mid to late August is the best time This is a short-lived plant which will die off after fl owering. However, for an autumn sowing. Establishment is less likely to be reliable if it sets large quantities of viable seed very rapidly, making the crop sowing extends too far into September. behave as if it were perennial. Although seeds may come back as weeds, they are rarely a major problem. Suitable varieties There is limited information on varieties and, particularly on organic Topping regime units, growers frequently just accept what is available. Virgo Pajbjerg Yellow trefoil should be mown regularly whenever it attains a height is the only variety currently used in the UK. of 20cm. The fi rst cut may be before this if there is a severe weed problem. Mowing is important to maintain the viability of a yellow Frost tolerance trefoil crop. The frequency of mowing will vary widely between sites. Yellow trefoil will survive over the winter and fl ower the following year. On a dry sandy soil, it may only need cutting twice in the season. However, on fertile soil in a warm wet summer, it may need cutting Weed competitiveness more often. Yellow trefoil shows reasonable competition against weeds. It is not the most rapidly growing of species but its low growth habit is good Pest and disease problems for covering the ground and smothering weeds. The information on pest and disease tolerance in yellow trefoil is limited. Observations on the variety Virgo Pajbjerg suggest that it is slightly more susceptible to sitona weevil and downy mildew than red or white clover, but neither of these is considered serious. Sowing rate: 70 kg/ha or 7 g/m2 Biomass Buckwheat seed is relatively expensive and as it is a short-lived Buckwheat grows vigorously and will produce relatively large green manure it has limited commercial appeal. amounts of biomass if allowed to grow throughout the summer.

Ideal sowing time Nitrogen fi xing potential Any time after April / May when there is no risk of frost. Buckwheat does not fi x N but will prevent it leaching. It is also thought to make phosphate more available to subsequent crops. Suitable varieties Presently there is little choice of varieties available. Persistence Buckwheat has good growth over the summer from a spring Frost tolerance sowing. It will continue producing leaves and fl owering throughout Buckwheat has very poor frost tolerance and will break down at the summer until it is killed off by the fi rst frosts. the fi rst sign of frost. Topping regime Weed competitiveness Buckwheat does not generally need topping Buckwheat has large leaves which are good for suppressing weeds, although ground covering weeds such as chickweed often survive Pest and disease problems under it. This crop is generally free from problems with pest and disease.

26 27 GREEN MANURE PLANTS NON-LEGUMES GREEN MANURE PLANTS NON-LEGUMES

Deep rooting pan buster, medium Chicory to long term This herb has roots capable of penetrating to great [Cichorium intybus] depth. The main root looks like a long thin carrot and there are many pencil-like projections from it. These roots will break through plough pans and leave the soil aerated, aiding drainage and crop root development.

Sowing rate: 15 kg/ha or 1.5 g/m2 Biomass Chicory is a relatively small seed and should be sown at around There is little data on chicory biomass. Estimates put yield around 1cm deep. The soil should be rolled after sowing to increase soil 11-13t DM/ha. moisture contact with the seed. Nitrogen fi xing potential Ideal sowing time Chicory does not fi x N. It is important to sow into a warm seedbed either between March and early May or in the autumn between August and early Persistence September. Sowing later than this is risky as chicory is relatively Chicory lasts for up to ten years. In order to get the full effect it slow to establish when conditions cool down. should be left in situ for at least two years.

Suitable varieties Topping regime There are a limited number of varieties. The commonly used variety Chicory will need topping regularly at around three week intervals is Puna, which is imported from New Zealand. to control growth. Alternatively it can be grazed by sheep or cattle and makes an excellent forage. It has anthelmintic properties Frost tolerance making it useful to ruminant livestock farmers. Chicory is tolerant to frost. Pest and disease problems Weed competitiveness There are generally few pest and disease problems with chicory. N holder, medium to long term Initially weeds can be a problem during establishment, but this is a long term crop and most annual weeds will disappear once Cocksfoot Cocksfoot does not fi x nitrogen but is a good store a mowing or grazing regime becomes established. of it. It is usually sown with red clover as a ley for [Dactylis glomerta] around four years, providing good grazing. Its root structure is excellent for improving soil and it grows well in drought-prone areas.

Sowing rate: 20 kg/ha or 2 g/m2 Biomass Cocksfoot seed is small and should be sown to a depth of 1cm. Cocksfoot will produce 13t DM/ha per hectare annually. The soil should be rolled after sowing to increase soil moisture contact with the seed. Nitrogen fi xing potential Cocksfoot does not fi x N. It is a good store however and releases Ideal sowing time N over a long period of time when ploughed in. In common with other grasses, cocksfoot should be sown between March – early May or in the autumn between August Persistence and September. Cocksfoot is very persistent and is suitable for between 2-10 years.

Suitable varieties Topping regime There are many varieties available. Commonly used are Prairial, Cocksfoot will need topping or frequent grazing for weed control Sparta, Abertop and Niva. and to prevent it fl owering. If left it can become stemmy and develop into tussocks. Frost tolerance Cocksfoot is extremely tolerant to frost. Pest and disease problems There are generally few pest and disease problems with cocksfoot. Weed competitiveness Cocksfoot is a dominant grass which, when grown with red clover, is very good at suppressing weeds.

28 29 GREEN MANURE PLANTS NON-LEGUMES GREEN MANURE PLANTS NON-LEGUMES

Grazing Rye Italian [Secale cereale] 0 cm 1 Ryegrass N holder, short term [Lolium multiflorum] Grazing rye does not fi x nitrogen but is one of the most effective crops for reducing leaching over the winter.

Sowing rate: 30 kg/ha or 2-3 g/m2 N holder, medium term Optimum sowing depth is 1-2cm. The soil should be rolled after sowing to increase soil moisture contact with the seed. Italian ryegrass is one of the most rapidly growing grasses and is commonly grown in mixes with Ideal sowing time: red clover or vetch. Italian ryegrasses can be sown in March and April but, for optimum spring yields, is best sown in August or by late September.

Suitable varieties There is a wide range of varieties available.

Frost tolerance Italian ryegrass will grow through the winter, but frost tolerance is improved if surplus growth is removed in the autumn.

Weed competitiveness Italian ryegrass grows very rapidly so is competitive against weeds. As it benefi ts from early cutting this can also help combat weeds.

Biomass Italian ryegrass produces large amounts of biomass over a growing season. Yields can be as high as 15t DM/ha.

2 Sowing rate: 180 kg/ha or 18 g/m into consideration when sowing direct drilled crops after grazing rye Nitrogen fi xing potential and an interval of six weeks should be left. Grazing rye seed is large and should drilled to a depth of 2 – 3 cm. Italian ryegrass does not fi x N but is effective at reducing leaching The soil should be rolled after sowing to increase soil moisture Biomass provided there is a well established canopy. contact with the seed. It is sown at a high rate, making it an expensive crop to establish, so particular care should be taken Grazing rye rapidly produces large amounts of biomass. Persistence to ensure that sowing conditions are optimal. Nitrogen fi xing potential Italian ryegrass has a shorter persistence than perennial ryegrass, Ideal sowing time Grazing rye does not fi x N but is one of the best crops for preventing generally only lasting from 1–2 years, depending on conditions. Persistence can be reduced by drought. Grazing rye is usually sown in the autumn in order to establish it leaching over the winter. over-winter cover. It has an advantage over legumes in that it will Persistence Topping regime still grow successfully if sown in September or October. This is Italian ryegrass needs topping or grazing regularly to prevent useful if a cash crop is still being harvested in autumn. Grazing rye is a short lived cover crop, and is normally incorporated in March after an autumn sowing. it seeding and becoming stemmy and diffi cult to incorporate. It Suitable varieties benefi ts from being cut or grazed earlier than perennial ryegrass. Topping regime Frequency depends on soil fertility and growing conditions. There is limited information on varieties Grazing rye may need topping in March or early April, either for Pest and disease problems Frost tolerance weed control or to prevent it fl owering and becoming stemmy. Italian ryegrass is susceptible to a number of pests and diseases, Grazing rye is extremely tolerant to frost. Pest and disease problems including mildew, and ryegrass mosaic virus. It can also build up Weed competitiveness There are generally few pest and disease problems with grazing rye. pest problems such as leather jackets, slugs and wireworms that can pose problems in subsequent crops. Grazing rye establishes very quickly and competes against weeds effectively. The residues, when dug in, have an allelopathic effect against germination of seed (see page 9). This should be taken

30 31 GREEN MANURE PLANTS NON-LEGUMES GREEN MANURE PLANTS NON-LEGUMES

N holder, short term N holder, long term Mustard Mustard does not fi x nitrogen but is a rapidly growing Perennial ryegrass is the most commonly grown grass, Perennial annual nitrogen lifter for growing over the summer. particularly in grazed grass/clover leys. It shows good [Sinapsis alba] It is also very good at suppressing weeds. persistence, lasting for up to six years. Ryegrass [Lolium perenne]

Sowing rate: 20 kg/ha or 2 g/m2 Biomass Sowing rate: 35 kg/ha or 3 g/m2 Seed of mustard is small and should be shallow sown at not Mustard rapidly produces large amounts of biomass Ideal germination depth is 1-2cm. The soil should be rolled after more than a few mm or surface broadcast. sowing to increase soil moisture contact with the seed. Nitrogen fi xing potential Ideal sowing time Mustard does not fi x N but is effective at preventing it leaching. Ideal sowing time Either autumn or any time after March as a short term crop. Ideal times are April or September when there is adequate moisture Persistence for establishment. Suitable varieties Mustard has a very short persistence and can start to fl ower after There are many varieties of mustard available. Caliente type 4 – 6 weeks. Suitable varieties mustards have been bred to reduce various soil borne pests and There is a wide range of perennial ryegrass varieties available, with diseases (see page 9). Their effectiveness depends very much on Topping regime many bred especially for their palatability and digestibility. Varieties growing conditions and the manner in which they are incorporated. It is not usual practice to top mustard, except immediately prior that seed later in the season are best for green manuring as these to incorporation. are less likely to create issues for the next crop. Varieties include Frost tolerance Calibra, Twystar, Aberdart and Tivoli. Mustard’s frost tolerance is relatively poor, with leaves breaking Pest and disease problems down after a few mild frosts. This can be useful as it allows the Mustard will suffer from all the pests and diseases normally Frost tolerance crop to be easily incorporated. associated with growing brassicas. If sown in spring, fl ea beetle Perennial ryegrass will withstand most frosts throughout the winter. can hamper the establishment, although most crops will grow Weed competitiveness through this. As with all brassicas, pigeons can cause devastation Weed competitiveness Mustard is vigorously competitive against weeds from an early at any stage. It is important to bear in mind that mustard is Annual and perennial weeds may be a problem during stage, and most mustard crops have very few weeds. susceptible to clubroot (Plasmodiophora brassicae) so should be establishment, but the crop will gain a competitive advantage grown in the brassica part of the rotation. when mown. Biomass Perennial ryegrass produces around 13t DM/ha of biomass over a growing season.

Nitrogen fi xing potential Ryegrass does not fi x N but is effective at reducing leaching, provided there is a well established canopy.

Persistence Perennial ryegrass will persist for at least 5 – 6 years.

Topping regime Perennial ryegrass needs topping or grazing regularly to prevent it fl owering and becoming stemmy and diffi cult to incorporate. Frequency depends on soil fertility and growing conditions.

Pest and disease problems Perennial ryegrass can suffer from crown rust or mildew. It can also build up pest problems such as leatherjackets, slugs and wireworms that can pose problems in subsequent crops.

32 33 GREEN MANURE PLANTS NON-LEGUMES

Westerwolds Ryegrass [Lolium westerwoldicum]

Sowing rate: 35 kg/ha or 3.5 g/m2 N holder, short term Ryegrass seed should be drilled to a depth of 1cm. The soil should be rolled after sowing to increase soil moisture contact Westerwolds ryegrass does not fi x nitrogen but is with the seed. one of the most effective crops for reducing nitrogen leaching over the winter. Ideal sowing time Westerwolds can be sown in the autumn in order to establish over- winter cover. It has an advantage over legumes in that it will still grow successfully if drilled in September or October. This is useful if a cash crop is still being harvested in autumn. Alternatively it may be sown in the spring as a short term summer green manure.

Suitable varieties There are many varieties available. Hellen, Mendoza and Lifl oria are commonly sown.

Frost tolerance Most varieties of westerwold ryegrass are tolerant to frost. N holder, weed suppressor, short term Weed competitiveness Phacelia Phacelia does not fi x nitrogen but is a very rapidly Westerwolds ryegrass establishes very quickly and competes growing annual nitrogen holder crop for growing over against weeds effectively. [Phacelia tanacetifolia] the summer. It is particularly good at attracting bees, hoverfl ies and wasps into the area. Biomass Westerwolds ryegrass rapidly produces large amounts of biomass. If left in situ for the spring and summer (after an autumn sowing) it can produce 15t DM/ha. Sowing rate: 10 kg/ha or 1 g/m2 Biomass Nitrogen fi xing potential Seed of phacelia is small and should be shallow sown at not more Biomass production is less prolifi c than in other green manures than a few mm or surface broadcast. as much of the canopy comprises a fi ne leaf structure. Westerwolds ryegrass does not fi x N but is one of the best crops for preventing it leaching over the winter. Ideal sowing time Nitrogen fi xing potential Persistence Any time after March. Phacelia does not fi x N but is effective at preventing it leaching. Westerwolds ryegrass is a winter-hardy annual. If it runs to seed Suitable varieties Persistence it will stop growing. Cultivars are imported from Europe and Balo is a common strain. Persistence over the summer is good, and it will continue producing Topping regime leaves and fl owering until it is killed off by the fi rst frosts. Frost tolerance Westerwolds ryegrass will need topping or grazing either for Phacelia has poor tolerance to cold and will break down after Topping regime weed control or to prevent it fl owering and becoming stemmy. a moderate frost. Phacelia generally does not need topping. Pest and disease problems Weed competitiveness Pest and disease problems There are generally few pest and disease problems Phacelia has a fi ne leaf structure but nonetheless grows vigorously This crop is generally free from problems with pest and disease. with westerwolds. showing good weed suppression.

34 35 37 1m 90cm 80cm 70cm 60cm 50cm 40cm 30cm 20cm cult to incorporate.

Italian ryegrass This can easily attain a height of over 1m, but should be topped this to maintain before palatability and prevent it becoming tough and diffi Italian Ryegrass Italian Westerwolds Ryegrass Westerwolds owering. Once owers, the height

Westerwolds This ryegrass will attain a height of at least 80cm. Mustard Mustard Depending on the a mustard cultivar, canopy will attain a height of 50 – 70cm fl before it fl can be at least 1m.

Non-Legumes Cocksfoot

cult to Perrenial Ryegrass Perrenial

Cocksfoot This will attain a height of at least 80cm. Perennial Ryegrass Perennial Ryegrass can easily attain a height of over 80cm, but should be this topped before to maintain palatability it becoming and prevent tough and diffi incorporate.

Phacelia Chicory owers

owering Grazing Rye Grazing

Phacelia to around This grows 40 – 50cm. Chicory After leaf development 60cm, the at around plant quickly bolts to a fl produce head at 100 – 150cm. This is unsightly, although the fl attract many insects. Buckwheat

Grazing Rye This will attain a height of at least 1m. Buckwheat This will reach a height of up to 90cm.

e Trefoil Tr

l Yellow Yellow Ye Y

Cl Clover

White White Wh

White clover a This will reach height of 20 –30cm, depending on leaf size. Allowing the crop too much to produce plant material runs the risk of smothering if cut and the crop mulched. trefoil Yellow a This will reach height of 20 – 30cm if not mown.

Vetch Sweet Clover Sweet cult

Sainfoin

Vetch to a This will grow 50cm, height of around in or higher if grown conjunction with a cereal (eg grazing rye or oats) support. to provide Sweet clover to a This can grow height of over 2m if left uncontrolled, although at this stage it will have become woody and diffi to incorporate.

Red Clover Red

Fenugreek Lucerne/Alfafa Sainfoin to a This will grow 1m. height of around Red clover a height This will reach of at least 60cm if left unchecked. Allowing to produce the crop too much plant material runs the risk of smothering the crop if cut and mulched.

Persian Clover Persian of avoid

be cut Crimson Clover Crimson if not mown, Lucerne will attain The crop a height of at least 1m but should this to before an abundance woody material. Fenugreek This will to a height grow 1m. of around of 70cm if can reach a can reach Legumes 1m 90cm 80cm 70cm 60cm 50cm 40cm 30cm 20cm GROWTH HEIGHTS Crimson clover This height not cut. Persian clover a This will reach height of at least 60 – 70cm if left unchecked. It is normally mown at this point. 36 Acknowledgements We wish to acknowledge Defra and HDC who funded much of the work over the last 15 years that formed the basis of this booklet. We would like also to acknowledge input from Stephen Briggs (Abacus Organic Associates), Peter Knight (Vegetable Consultancy Services) and Roger Hitchings (Organic Research Centre). Thanks should also go to Duchy College, IBERS, Warwick HRI and the many farmers who participated in trials. Thanks to NIAB for supplying some of the photographs in this publication.

AUTHORS EDITORS

Francis Rayns BSc PhD Ian Wilkinson Francis is currently Horticulture Research Manager at Garden Ian is the Managing Director of Cotswold Seeds where he has Organic (formerly known as HDRA). He has been involved in a worked for over 25 years. He has a particular interest in legumes large number of projects (funded by Defra, HDC, WRAP, the EU and and their application in modern farming systems and is associated private companies) concerned with fertility management, particularly with the promotion of red clover in the UK. He trained in Farm and in organic fi eld vegetable systems. This has included studies of the Grassland Management at Berkshire College of Agriculture. effects of a range of green manures, composts, animal manures and other soil amendments. He has worked to develop computer models for rotational planning and has been responsible for long Isabel Milner term experiments to compare the effects of different rotations on Isabel works at Cotswold Seeds, advising farmers and growers soil quality and crop performance. on grass and forage crops and coordinating communications for the company. She graduated with a First from the Royal Agricultural Anton Rosenfeld BA MSc PhD College’s Graduate Diploma in Agriculture in 2010 after a 15 year career in the media, mainly working at the Guardian and Anton is currently Research Offi cer at Garden Organic. He has Observer newspapers. worked in a number of projects concerned with sustainable strategies for vegetable production and also projects focusing on uses of green manures and composts to build soil fertility funded by Defra, HDC and WRAP. He has worked closely with growers both in the UK and overseas and is currently coordinating a project to develop a resource of knowledge and varieties for growing exotic vegetables. He also delivers training on a range of horticultural topics including soil fertility. Cotswold Seeds Garden Organic

Cotswold Seeds was founded in 1974 and deals with over Garden Organic, the UK’s leading organic growing charity, has 8,000 farmers throughout the UK. The company has a specialist been at the forefront of the organic horticulture movement for interest in grass and legumes and offers advice on growing and 50 years and is dedicated to researching and promoting organic managing these crops to those working in the livestock, arable gardening, farming and food. and horticultural sectors. The company is also involved in a wide range of research projects across the EU. www.cotswoldseeds.com www.gardenorganic.org.uk