CSAM2Multi-species winter cover crop

What it actually is

You fill the gap between two cash crops with a crop you do not harvest. The seed mix must contain at least two species drawn from two or more of four plant families: brassicas (mustards, radishes, kale), legumes (vetches, clovers, peas, beans), cereals and grasses (rye, oats, ryegrass), and herbs (phacelia, buckwheat, linseed). You sow it early enough to get it established, keep it as a well-established cover with minimal bare ground through the winter months, which GOV.UK gives as typically early December to late February, and then take it out ahead of the following crop.

GOV.UK's stated aim is a well-maintained multi-species cover crop present between cash crops during the winter months, protecting the soil surface, developing root structure to benefit the soil, supporting soil organisms and reducing nutrient loss, erosion and runoff.

You can graze it, provided it stays well established. You cannot harvest it as a commercial crop, and you must not apply fertilisers or manures to the established crop by mechanical means. The action is rotational or static, so it can move with your rotation each year or stay put.

Source: GOV.UK, CSAM2 action page, checked 23/08/2026.

What it pays, and what that comes to

The rate is in the panel at the top of this page. Multiplied out:

Source: arithmetic on the payment rate shown at the top of this page, which comes from Tilth's copy of the GOV.UK action catalogue and carries its own last-checked date. The 20 hectares is an illustration.

Is it worth it on your ground?

Step one: the seed. It is an annual cost, because the cover is re-sown each year. Listed prices for mixes sold for this action:

Source: Boston Seeds, own listed prices and stated sowing rates, looked up 23/08/2026. Price your own mix, and check the one you buy actually meets the two-species-from-two-families requirement on the GOV.UK action page.

Step two: putting it in and taking it out. At contractor rates, drilling a cereal-type crop directly runs at £77.69 a hectare, or broadcasting at £35.93 plus £35.19 for rolling, and an arable spraying pass at £16.97 a hectare before the cost of the chemical. Stack those up and the full job at contractor prices, seed, establishment and a sprayed-off destruction, comes to somewhere around £155 to £172 a hectare, which is more than the rate at the top of this page.

Source: NAAC contractor price survey 2026 to 2027, published by Farmers Weekly, checked 23/08/2026. Averages of member responses; your own figures are the ones that count.

So the payment does not buy the job on its own, and the case is built from the other pieces. With your own kit the cash cost is diesel, wear and hours rather than contractor rates, and the arithmetic can land the other way; that is your own sum. Grazing is allowed while the cover stays well established, and keep in mind sheep on covers is winter feed with a value your own flock or a grazing agreement can put a number on. Destruction does not have to be a sprayed pass on every farm or every winter. And the soil benefits the action is named for are real but slow, which is what the evidence section below is for.

Step three: the cost that is not on any invoice. A field carrying a winter cover is a field not carrying a winter cereal. If the field was going to a spring crop anyway, the cover fills ground that would have sat in stubble and the action costs you nothing in cropping. If entering the action is what tips a field from winter to spring cropping, the margin difference between those two crops on your farm is the real price of this action, and it belongs in the sum before any seed is ordered.

That last paragraph is Tilth's own reading, and it adds no requirement beyond what the GOV.UK action page sets out. The rotation call is yours.

Does it work, and what makes it work better

This section is what we have found in published sources about the practice this action pays for. It is not scheme guidance, it is not Defra's or the RPA's view, and it adds no requirement beyond what the GOV.UK action page sets out. We have named every source and given the date we checked it. What it means for your ground is your decision.

Cover crops are unusually well assessed, and the geography needs saying first. Conservation Evidence hold five assessments that bear on this action. One, Grow cover crops when the field is empty, sits in their Soil Fertility synopsis and draws on studies from the UK, Denmark, Turkey, the USA, Australia and Japan. The other four all assess Grow cover crops in arable fields and sit in their Mediterranean Farmland synopsis, built on studies from California, Spain, Italy, Israel and France, in dry-summer climates and heavily in irrigated vegetable systems. Same practice, but a long way from an English winter, and that distance matters differently for different findings below.

The graded assessments. Conservation Evidence, based at the Department of Zoology at the University of Cambridge, summarises the published studies behind individual conservation actions and has independent subject experts score each one. Effectiveness scores only the size and direction of the reported effects, and they say themselves it does not consider the quantity or quality of the studies. Certainty is the separate score for how many studies there are, how well built they are and how much ground they cover.

Growing cover crops when the field is empty comes out as Beneficial, their top category, on 12 studies, with 75 per cent for effectiveness, 67 per cent for certainty and 16 per cent for harms.

The four Mediterranean assessments each score the same practice against one outcome, and the split between them is the most useful thing on this page:

Source: Conservation Evidence, actions 1345, 1351, 1357 and 1394, assessment scores, all checked 23/08/2026.

Likely to be ineffective or harmful is the lowest category we have written up anywhere on this site. It is carried by the following cash crop's yield, and it sits directly alongside a Beneficial for the soil, from the same synopsis, on the same practice. The panel's judgement, in effect, is that cover crops are good for the field and cost something at the till, in the systems studied.

Source: Conservation Evidence, action 898, Soil Fertility synopsis, and actions 1345, 1351, 1357 and 1394, Mediterranean Farmland synopsis, all checked 23/08/2026. Cite the first as Key et al. (2020), Enhancing Soil Fertility, pages 613 to 634, in What Works in Conservation 2020, Open Book Publishers, and the other four as Shackelford et al. (2017), Sustainable Agriculture in California and Mediterranean Climates, University of Cambridge.

What the studies found on the soil. In the soil fertility evidence, three randomised, replicated studies from Denmark, Turkey and the UK found cover crops improved soil structure and nutrient retention. The British one is the finding we would put first on this page: on sandy soils at two English sites receiving organic manures, growing a winter rye cover cut nitrate leaching by 79 per cent at one site and 42 per cent at the other, against fallow. Reducing nutrient loss is on the GOV.UK page as part of this action's stated purpose, and this is a measurement of exactly that, in this country. Elsewhere in that evidence, a Danish trial found higher soil porosity and interconnectivity under covers, studies found increased soil carbon and nitrogen with covers, and a review of 120 papers found soil carbon storage rising under cover crops, with longer-term use producing considerably larger increases.

The Mediterranean soil assessment points the same way at scale: a meta-analysis and ten replicated controlled studies found more organic matter under winter covers in some or all comparisons, five studies found more microbial biomass, two found less erosion, and two found more water-stable aggregates.

What the studies found on the following crop. In the crop production assessment, six replicated controlled studies found lower cash crop yields after winter covers in some comparisons, three found higher, eight found results running both ways, and seven found no difference. Two findings soften that. Eight studies found higher following yields where the cover was a legume rather than a non-legume, and one found a legume and grass mixture beat legumes alone. And the systems in question were largely irrigated Mediterranean vegetables, which is a long way from a spring barley after mustard in England.

What the studies found on water and pests. The water assessment is a trade-off in a dry climate's terms: covers used water and left less of it in the soil in several American comparisons, while also cutting water loss through runoff and drainage, cutting nitrate leaching in four studies of five, and in one French study cutting herbicide leaching. The pest assessment found fewer weeds under covers in four studies of eight with the rest mixed or neutral, and its strongest results, fewer aphids where covers grew as living mulches between vegetable rows, come from a practice CSAM2 does not pay for.

Conservation Evidence say themselves that studies are not directly comparable or of equal value, and that study size, design, reported metrics and relevance to your own situation matter more than "simply counting the number of studies that support a particular interpretation".

Source: Conservation Evidence, actions 898, 1345, 1351, 1357 and 1394, key messages and supporting evidence from individual studies, all checked 23/08/2026.

What we have not found. Nothing measuring CSAM2 itself, and nothing testing its particular requirement, two species from two families, against simpler covers, beyond the legume findings above. No British measurement of what a winter cover does to the following crop's yield in a combinable rotation, which is the number the money section above says belongs in your sum. And no UK water findings, so the water trade-off arrives untranslated from climates short of it.

What the sources say makes it work better. All of the following comes from the studies listed on those Conservation Evidence pages, and it is a description of what was found rather than advice from us.

Legumes in the mix are the most consistent lever in the whole evidence base: more nitrogen in the soil afterwards in five studies, better following yields in eight, and greater carbon input in the review's account, attributed to legume growth not being limited by soil nitrogen.

Time in the practice matters: the review found longer-term cover cropping produced considerably larger soil carbon increases, and a Spanish study found higher soil quality and more soil water under long-term covers than short-term.

Source: Conservation Evidence, actions 898, 1345, 1351 and 1357, key messages and supporting evidence from individual studies, checked 23/08/2026.

What follows is Tilth's own reading of how those findings sit against this action, and it adds no requirement beyond what the GOV.UK action page sets out.

The shape of this evidence is the shape of the decision. The soil case is the best-supported thing on this page, two Beneficial assessments from two different evidence bases, with a British nitrate result matching the action's stated purpose word for word. The cost case is the following crop, and it is real enough that the panel gave it the worst category on this site, but it is built on irrigated Mediterranean vegetables, softened by the legume findings, and unmeasured in British combinable cropping. So the one number that would settle this action for your farm does not exist in the literature, and it does exist in your yield records: what your spring crops actually do after a cover, against what they did without one.

The legume finding is worth carrying into the seed order. The action's two-family floor can be met by the cheapest rye and vetch mix on the market, and as it happens that mix already contains the one component the evidence keeps rewarding. If you are choosing between mixes, the studies' answer is not the longest species list, it is whether a legume is in it and how much.

And the water trade-off mostly does not make the journey to an English December, where the worry is rarely a cover crop drinking the field dry. Where it might travel is a dry spring on light land, with a thirsty cover stood green into March ahead of a spring crop. The six-week destruction allowance ahead of an early-sown spring crop is the tool the action itself gives you for that, and the leaching findings suggest the cover has done most of its nutrient-holding work by then anyway.

What you actually have to do

Each year of the three year duration, establish a multi-species cover crop that is not harvested as a commercial crop, sowing early enough to achieve the action's aim. The mix must contain at least two species from two or more of these plant families: brassicas, legumes, cereals or grasses, and herbs. Maintain it as a well-established cover over the winter months, which GOV.UK gives as typically early December to late February, with sufficient leafy vegetation protecting the soil and minimal bare ground.

You can graze it with livestock provided it remains well established. You must not apply fertilisers or manures to the established cover by mechanical means. Do not destroy it before winter's end, unless you are establishing an early-sown spring crop, in which case destroy it no earlier than 6 weeks before establishing that crop, and minimise compaction, poaching and erosion when you do. Existing cover crops can go into the action provided they are not already funded under another scheme.

If the agreement's start date makes the first winter too late, begin within 12 months of the start date. In the final year, keep the cover until winter's end or the action's end date, whichever comes first.

Source: GOV.UK, CSAM2 action page, checked 23/08/2026.

The sowing advice, as advice rather than requirement: sow into warm soils in late summer or early autumn, drilling for reliability over broadcasting, rolling in dry conditions for seed contact, and keep 2 metres from the centre of hedgerows in line with the hedgerow regulations.

Source: GOV.UK, CSAM2 action page, sowing guidance, checked 23/08/2026.

Where it can go, and what rules it out

Agricultural land below the moorland line, on eligible land types: arable land under arable or leguminous crop codes, temporary grassland under TG01, arable land lying fallow under FA01, and horticultural permanent crops under TC01. SSSIs need Natural England's consent first. Land with historic or archaeological features needs its HEFER checked, and deep-rooted species must be avoided on identified features, which is worth knowing before a radish goes in the mix. You can enter the total or part of the available area in a parcel, and the action is rotational or static.

Source: GOV.UK, CSAM2 action page, checked 23/08/2026.

CSAM2 is not one of the ten limited area actions under SFI26, so it does not draw on the 25 per cent allowance shared by CIPM2, CAHL1, CAHL2, CAHL3, CIGL1, CIGL2, WBD3, AHW7, AHW9 and AHW11.

Source: GOV.UK, SFI26 scheme rules and guidance, section 4.5, checked 23/08/2026.

Things worth watching

This section is Tilth's own reading of where this action is easy to get wrong. It is not scheme guidance, it is not sourced from Defra or the RPA, and none of it adds a requirement beyond what the GOV.UK action page sets out.

Decide the rotation before the seed. The whole cost of this action can hide in one question: was that field going to a spring crop anyway? Answer it farm by farm and field by field before anything else, because a cover crop that quietly costs you a winter wheat is the dearest hectare on the scheme.

The six-week sum runs backwards. The destruction allowance is counted back from when you will establish the early spring crop, not forward from when the cover looks done. Pick your intended drilling date, count back six weeks, and that is your earliest spray date. A cold, late spring moves both.

Grazing is a privilege with a condition attached. The cover must remain well established while stock are on it. A wet January and a heavy stocking rate can take a compliant cover to poached bare ground in a fortnight, and bare ground is the one thing the action requires you not to have. Lighter, later, and off at the first sign of it going.

"Sow early enough" is judged by December, not by the calendar. The requirement is a well-established cover in the winter months. The same mix drilled in late August and in mid October is two different crops by Christmas, and only one of them looks like the action's aim. If harvest runs late, the honest question is whether there is still time to establish a cover worth the name.

Check the mix against the families, not the species count. Two species will do it, but they must come from two different families, and two clovers or a vetch and a pea are one family. The seed invoice that names the species is also your evidence, so buying a mix sold for the action, and keeping the invoice, does two jobs at once.

Read the HEFER before choosing radish. The deep-rooted species restriction on historic features is easy to trip with exactly the tillage radish this action is popular for. Flag the affected parcels first and give them a shallow-rooted mix.

Keeping the evidence

Also Tilth's own reading. GOV.UK sets the requirements; what follows is a practical suggestion about record keeping.

GOV.UK's examples are field operation records at land parcel level with the seed mix invoices, and photographs or other documentation showing the action was completed.

The two moments worth capturing are establishment and mid-winter. The drilling record with its date and the seed invoice naming the species covers the first, and a dated photograph in January, showing green cover and how little bare ground there is, covers the second, which is the requirement that matters most and leaves no trace once the cover is sprayed off. If you destroy early for a spring crop, the destruction date and the following crop's drilling date belong in the same record, because together they are your six-week arithmetic.

Tilth records operations against the parcel with dates, holds the invoice against the job, and lets you attach photographs, so establishment, the mid-winter proof and the destruction sum sit together.

The part only your own ground can answer

The literature cannot tell you what a winter cover does to a spring crop on your soil, because nobody has measured it here; that was the honest gap in the evidence section. Your own records can. Yields by field and by year, with the cover crop years marked, answer in three seasons what no synopsis can, and the soil is doing whatever it is doing meanwhile. Tilth holds your field records, your operations and your yields in the same place, which is what makes the comparison possible. Request an invite.