AHW8Whole crop spring cereals and overwinter stubble

What it actually is

Two things joined together. First, a spring cereal grown and taken off as whole crop silage rather than combined, with the grain and the straw removed from the land together. Second, the stubble left behind, standing through the autumn and the winter.

GOV.UK requires you to establish a spring cereal crop, not maize or sorghum, harvest it as whole crop silage, remove the grain and straw from the land, and then leave the stubble over the autumn and winter months. You may undersow a seed mix and you may use a blend of cereals, provided the aim can still reasonably be expected to be achieved.

Source: GOV.UK, AHW8 action page, checked 04/08/2026.

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 8 hectares is an illustration.

Is it worth it on your ground?

Step one: why this one is not a straight comparison. On the actions that take ground out of production, the payment is set against the crop you gave up and that is the end of it. Here you have not given the crop up. You have changed what it is: a whole crop silage instead of grain and straw sold separately. So the payment is not doing the whole job. It only has to cover the difference between what the silage is worth to you and what the combined crop would have been worth.

Step two: what the ground would otherwise return. Gross margins per hectare for England, non-organic, in the 2023/24 crop year. Variable costs have already been taken off these figures, so there is nothing further to deduct.

Source: Farm Business Survey, Crop Production in England 2023/24, Rural Business Research, England, non-organic, 2023/24 column, checked 02/08/2026. The winter wheat figures come from a sample of 572 farms.

The agreement runs three years, so the comparison has to run three years too, and that ground will not be in wheat for all three of them. Three rotations, worked from the crop figures above:

Source: arithmetic on the crop gross margins in step two, from the Farm Business Survey, Crop Production in England 2023/24, checked 02/08/2026. These three are illustrations. Work your own out from the same crop figures.

Step three: what the silage has to be worth. The payment plus the silage has to match the rotation. So rather than guess at a silage value, here is the figure it has to clear.

Source: the rotation averages in step two less the payment rate at the top of this page. The figures are subtraction. Establishment and harvest costs are not in them.

The Farm Business Survey publishes gross margins for grain crops sold as grain. It does not give us a value for a spring cereal taken as whole crop silage, and we have not found a published figure we would put on a page about money, so we have not invented one. The table above is the honest form of the question instead: whatever your silage is worth in your clamp or in your buyer's, it has to beat £168 to £240 a hectare for this to hold its own against a grain rotation.

Three things to set against those figures. What follows is Tilth's own reading rather than scheme guidance.

The survey reports one winter wheat figure, not first and second wheat separately. A rotation with two wheats in it carries a second wheat at the same gross margin as the first, which is unlikely to be how it turns out on your ground. We have not found a published split to cite, so we have not applied a discount of our own invention. Read the rotation averages as the generous end for the crop, which means the thresholds above are the demanding end.

It is one year, and not a strong one. The same report's 2022/23 column put winter wheat's gross margin at £1,570 a hectare against the £988 above for 2023/24. A three-year decision resting on a single crop year is a shaky thing, and this particular year was the lower of the two. In a strong grain year the threshold the silage has to clear goes up sharply.

The costs on both sides of that line are not the same costs. A grain crop is combined, carted, dried and stored. A whole crop silage is mown, carted, clamped or wrapped, and it is a different set of kit and a different set of contractor invoices. The thresholds above are worked on gross margins, which do not carry either. Whether that moves in your favour depends on what kit you have and what you would have to hire.

Where that leaves it. The question this action asks is not really about wildlife payments at all. It is whether you have a use or a buyer for whole crop silage. On a farm with stock, a clamp and a neighbour who buys forage, £168 to £240 a hectare is not a demanding threshold and the payment does most of the work on its own. On an all-arable farm with no clamp, no market within a sensible haulage distance and no wish to acquire either, the crop still has to go somewhere, and no payment fixes that.

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.

One gap has to go at the top of this section, because it runs through everything below it.

Conservation Evidence assess an action called Leave overwinter stubbles, and they define it as leaving crop stubbles in fields until at least February or March. Every study behind it is a stubble left after the crop was combined for grain. What makes those stubbles worth anything to a bird is spilt grain and the seed of the weeds that grew in the crop and shed into it. AHW8 does not produce that stubble. It asks for the cereal to be cut as whole crop silage, green, with the grain and the straw taken off the land together, before the grain has ripened and before most of what grew in the crop has shed. So the studies below describe a stubble made a different way from the one this action pays for, and neither we nor they can tell you how much of the food is still there afterwards.

That is not a reason to disregard the work. It is a reason to read it as evidence about stubbles in general and to hold the difference in mind throughout.

The graded assessment. 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. Leaving overwinter stubbles comes out at Likely to be beneficial, on 20 studies, with 90 per cent for effectiveness, 50 per cent for certainty, and harms not assessed. Those two scores are not the same thing. Effectiveness scores only the size and direction of the reported effects, and Conservation Evidence 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. A high effectiveness score next to a middling certainty score means the effects that were found were large and the panel was less sure they carry across everywhere.

Source: Conservation Evidence, action 695, Leave overwinter stubbles, Farmland Conservation synopsis, checked 11/08/2026. Cite as Dicks et al. (2020), Farmland Conservation, pages 283 to 321, in What Works in Conservation 2020, Open Book Publishers.

What the studies found, both ways. Thirteen studies from Finland, Switzerland and the UK found evidence of some benefit to plants, insects, spiders, mammals or farmland birds. A 2007 systematic review by Roberts and Pullin, pulling together five papers from experiments run between 1992 and 2002, found significantly higher densities of farmland birds in winter on fields with stubbles than on conventionally managed fields. A controlled trial in southern Finland found around 20 spiders a trap on uncultivated barley stubble against around five in a growing spring barley crop, with no difference in ground beetles or in unsown plants.

Against that, several large studies found little or nothing. Parish and Sotherton, across 20 arable farms in eastern Scotland over two winters, found that of 23 bird species recorded only skylark was significantly more abundant on stubble than on wild bird cover or conventional crops. Stevens and Bradbury, across 256 fields on 84 farms, found only two of twelve farmland bird species positively associated with stubble, set-aside or seed mixtures taken together. Davey and others surveyed 2,046 one kilometre squares of lowland England in 2005 and again in 2008 and found no consistent association, with grey partridge and tree sparrow the only species showing more positive population change, and that effect small. Field and others, across 75 fields in East Anglia and the West Midlands, found no difference in seed-eating birds or skylark between Environmental Stewardship stubbles and non-stewardship stubbles.

On plants, Critchley and others compared ten conservation measures across 75 farms and put overwinter stubbles at an average of 4.2 plant species, against 6.7 for wildlife seed mixtures, 6.3 for uncropped cultivated margins and 5.9 for undersown cereals. Stubbles came out high on total plant cover and low on the number of species.

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". The individual studies run from 2000 to 2010, so all of them predate this scheme and this action.

Source: Conservation Evidence, action 695, key messages and supporting evidence from individual studies, checked 11/08/2026.

What we have not found. Nothing at all on a stubble following a whole crop silage cut, which is the practice this action pays for. Nothing putting a figure on how much seed is left in a field after the crop has gone off green. And nothing measuring AHW8 itself.

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

Which cereal comes up more than once, and it points the same way both times. Moorcroft and others, across 122 stubble fields on 32 farms in central England over two winters, found linnet, skylark, reed bunting and corn bunting on intensively farmed barley stubbles more frequently than on wheat stubbles, and recorded weed cover of 51 per cent on intensive barley against 40 per cent on intensive wheat and 28 per cent on organic wheat. A Defra study across 205 cereal stubble fields in south Devon found that seed-eating species preferred barley fields overall, and that the preference for barley held independently of the broadleaved weed density, which the authors say should be taken into account when prescriptions are written.

Herbicide input runs the same way. The same Devon study found barley stubbles following low-input herbicide were better for cirl bunting than wheat or conventionally managed stubbles, with roughly four times the seed abundance and broadleaved weed cover. Field and others found more seed-eating songbirds on stewardship stubbles, which carry herbicide and cultivation restrictions, than on conventionally managed ones in the West Midlands, at 6.0 birds a hectare against 2.5, though the same comparison in East Anglia was not significant at 3.5 against 0.7.

Grazing appears once and the finding is one-directional: in the Devon study, fields where stubbles were grazed over winter had significantly lower densities of seed-eating birds in general.

Undersowing cuts both ways, and it is worth reading both. Moorcroft and others found the highest March weed seed densities on undersown stubbles, and the smallest loss of seed across the winter, at an 11 per cent decline between October and March on undersown fields against 23 per cent on intensive wheat stubbles and 35 per cent on intensive barley. Ewald and others, across English farms from 2004 to 2008, found that where stubbles were used in conjunction with undersowing spring cereals they were negatively associated with year-on-year change in grey partridge density and with overwinter survival.

On stubble height the two studies do not agree, which Conservation Evidence report as different species benefiting from different heights. Butler and others, across 20 wheat fields on 12 farms, split each field and cut half to about 6 centimetres against an uncut control of about 14 centimetres, and found seed-eating and invertebrate-feeding birds more abundant on the cut half while skylark and partridges were more abundant on the uncut half. A later study by Whittingham and others recorded seed-eating and invertebrate-feeding birds at higher densities on uncut stubble, 404 and 244 against 77 and 7 on cut, along with skylark, partridges, pigeons and meadow pipit. The same study found more skylarks and invertebrate-feeders on lightly tilled sections than on untilled controls.

Two figures on scale, both about the landscape rather than about a field. Gillings and others found national population trends of 16 of 26 bird species positively influenced by the presence of overwinter stubbles, and predicted ten-year population stability for yellowhammer and skylark at stubble coverage of 15 and 20 hectares respectively within a one kilometre square. A 2008 review by Vickery and others put the figure for skylark at about 0.1 square kilometres of stubble per square kilometre, and suggested that having the patches over a kilometre apart would maximise winter use.

Source: Conservation Evidence, action 695, supporting evidence from individual studies, checked 11/08/2026.

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 whole crop question is the one we would want answered before entering ground, and nothing we can find answers it. Every finding above rests on a stubble holding seed, and the two sources of that seed are grain the combine missed and weeds that shed into the crop before harvest. A whole crop silage cut takes the crop before either has happened. What is left standing is a stubble with the architecture the studies describe and, on the face of it, less of the food. Whether the undersown mix this action permits fills that gap is exactly the sort of question these studies were built to answer, and nobody appears to have asked it.

Which makes undersowing the lever on this page rather than a detail. It is one of the few things AHW8 leaves to you, Moorcroft's work found undersown stubbles both starting the winter with more seed and losing it more slowly, and on a stubble that has had the crop taken green it is the obvious candidate for putting the food back. Set against that, Ewald's partridge results ran the other way where stubbles and undersowing were used together, and we would not pretend that is settled.

Two of the prohibitions on this page run the same way as the findings, which is worth saying plainly because it is more use than another positive result. AHW8 forbids grazing the stubble, and the Devon study found grazed stubbles held significantly fewer seed-eating birds. AHW8 restricts the herbicide programme to five actives, and low-input herbicide stubbles came out with about four times the seed abundance of conventionally managed ones. The requirement and the research point in the same direction on both.

On which cereal, the action says spring cereal other than maize or sorghum and leaves the rest open. The research on stubbles keeps landing on barley. That is a finding about a combined barley stubble and not about a whole crop one, so it is a lead rather than an answer, but it is the only steer the evidence offers on a choice you are making anyway.

None of it settles the money. The threshold on this page is what your whole crop silage has to be worth, and no study here has anything to say about that.

What you actually have to do

Establish a spring cereal crop, not maize or sorghum. Harvest the cereal crop as whole crop silage. Remove the grain and straw from the land. After harvest, leave the stubble over the autumn and winter months.

You may undersow a seed mix and you may use a blend or mix of cereals, provided the aim can still reasonably be expected to be achieved.

You must also keep written evidence that land entered into this action is not at risk of soil erosion or surface runoff.

Source: GOV.UK, AHW8 action page, checked 04/08/2026.

What you cannot do on it

Do not apply insecticides to the spring cereal crop after around mid-March, until it is harvested. Do not top or graze the stubble area. Do not apply any fertilisers, manures or lime to the stubble. The only herbicides permitted are those containing amidosulfuron, clodinafop-propargyl, fenoxaprop-P-ethyl, pinoxaden or tri-allate.

Source: GOV.UK, AHW8 action page, checked 04/08/2026.

Where it can go

Arable land used to grow crops, registered as arable land and declared with an arable crop or a leguminous and nitrogen-fixing crop code, along with temporary grassland under TG01 and arable land lying fallow under FA01.

The action is rotational or static, so you can move it for the second and third years or keep it in the same place.

Source: GOV.UK, AHW8 action page, checked 04/08/2026.

AHW8 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.

The market for the silage is the decision, not the payment. Everything on this page follows from whether the whole crop has somewhere to go. Settle that first, and ideally settle it with somebody who will actually take it, before the ground is committed for three years.

Removing the grain and straw is part of the requirement. Whole crop silage takes the lot off together, which is a different job from combining and baling and leaves you a different stubble. It also means there is no straw crop to sell off this ground, which is worth putting in the sum if straw is normally part of what that field earns.

No insecticide after around mid-March on a spring crop is most of the season. A spring cereal drilled in March and cut for whole crop is under that restriction for essentially its whole life. Look at that against what you would ordinarily do on a spring crop rather than against a winter one.

The herbicide list is five actives and nothing else. Check it against the programme you would ordinarily run before committing ground, not in the spring when a problem has already appeared.

No topping and no grazing on the stubble. On a farm with stock, an autumn stubble is a natural place to put them for a few weeks, and this action rules that out on the ground it covers. That is easy to agree to in an application and easy to forget in a dry October.

The not-at-risk assessment is yours to make and yours to write down. The requirement is written evidence that the land entered is not at risk of soil erosion or surface runoff. That is a document that has to exist, made by you, before the action rather than after.

Rotational or static, and the choice has consequences. If it moves, a spring cereal cut for forage has to be found a home in the cropping plan in each of three years. If it stays, the same ground carries a spring crop and then a bare stubble three years running.

If the parcel is an SSSI, or has historic or archaeological features on it, read the eligible land section of the action page against your own parcels. There are extra steps in that part of the page that do not apply to ordinary arable ground.

Keeping the evidence

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

Two separate records. First, the erosion and runoff assessment, which GOV.UK explicitly says you must keep in writing. Second, evidence of what you have actually done.

This action is better served by ordinary paperwork than most of the others on this site, because it generates real documents: a seed invoice, a drilling record, a mowing or contractor invoice for the whole crop, and a movement of forage into a clamp or off the farm. Between them those show a spring cereal established and taken as whole crop silage, which is the half of the action that is hardest to prove after the event. The stubble half is the usual problem of proving a negative, and the answer there is the same as on the other stubble actions: an operations record for the parcel that runs across the autumn and winter and shows what went on it, with dated photographs, since a stubble in September and the same stubble in February look nothing alike.

Tilth keeps the drilling, the harvest and the forage movement against the parcel, and the stubble period against the same parcel afterwards, so the two halves of the action sit on one record.

The part only your own ground can answer

The threshold on this page is £168 to £240 a hectare of value from the whole crop silage, and there is no national figure that tells you whether you clear it. It depends on what your silage is worth where you are, what it costs you to make, and whether that field is one that has been returning below your rotation average anyway, in which case the threshold drops. Tilth keeps the yield history field by field, alongside the operations that produced it, which is where that comparison has to start. Request an invite.