CAHL3Grassy field corners or blocks

What it actually is

A corner or a block of an arable or horticultural field that stops being cropped and becomes grass for three years. GOV.UK's stated aim is an intact grass sward throughout the year, without tracks, compacted areas or poaching, allowed to develop tussocky grass. The page sets that in the context of year-round habitat for wildlife and support for integrated pest management next to the cropped area.

You establish it either by sowing or by allowing natural regeneration, within twelve months of the action's start date, and it stays in the same place for the whole three years.

Source: GOV.UK, CAHL3 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 2 hectares is an illustration.

Two hectares is not much of a block, but it is a realistic total once the awkward corners of a whole farm are added up, which is how this action tends to be used.

Is it worth it on your ground?

Step one: what it costs to put in. This is the only action on this site where the answer can be nothing. GOV.UK allows establishment by natural regeneration as well as by sowing. Where the ground will green over on its own, there is no seed to buy.

Where you would rather sow it, an indicative grass seed cost:

Source: ProGreen, own listed price and stated sowing rate for a 4/6 metre grass and buffer strip mix, looked up 31/07/2026. That is a buffer strip mix rather than a mix sold specifically for this action, so treat the figure as an indication of what grass seed costs rather than a quote. Price your own. Cultivation and drilling are your own cost and are not included.

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: the gap.

Source: the payment rate at the top of this page, less the seed cost in step one where relevant, set against the rotation averages in step two. The remaining figures are subtraction.

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.

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.

A field corner is not the field. This is the heart of it, and it is the same argument as the buffer strip page. The gross margins above are field averages. A corner is the ground you double drill, overlap on, turn on and get stuck in, shaded on two sides by a hedge and wetter than the rest. Nobody publishes a yield for it, we are not going to invent one, and the comparison to make is that corner's own return against the figures above rather than the field's.

Where that leaves it. On ground that performs like the field average, the crop is ahead by roughly £174 to £284 a hectare a year and this action does not pay. The case for it is that a field corner is almost never ground that performs like the field average, and that the corners on most farms are where the yield map goes pale. If your corners crop as well as your middles, do not do this. If they do not, this action turns the worst two hectares on the farm into a known figure that arrives every year regardless of the season.

One thing the gap does not carry. Taking a corner out also takes out the passes you make on it: the overlap, the awkward turn, the point where the drill gets lifted and put down again. That is real, and it is time as much as fuel. We have not put a figure on it because it depends entirely on your kit, your field shape and how you cost your own hours, and a made-up number here would be worth less than the honest gap.

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.

The fit first, because it is close but not exact. Conservation Evidence assess an action called Plant grass buffer strips or margins around arable or pasture fields, and define it as planting field margins with a grass-rich seed mixture, unfertilised and only spot-treated with herbicide. That is the same habitat CAHL3 pays for and it is in a different place: a strip round the edge rather than a corner or a block. Two other differences are worth carrying through the section. The assessed practice is sown, where CAHL3 also allows natural regeneration. And most of the studies below manage the sward by cutting, scarifying or spraying a grass-specific herbicide, where CAHL3 rules all three out after the first year.

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. This practice comes out at Beneficial, their top category, on 69 studies, with 90 per cent for effectiveness, 65 per cent for certainty, and harms not assessed. 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.

Source: Conservation Evidence, action 246, Plant grass buffer strips/margins around arable or pasture fields, Farmland Conservation synopsis, checked 22/08/2026. 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. Nineteen studies from Finland, the Netherlands, Sweden and the UK found sown grass margins raised arthropod abundance, species richness or diversity. Nine UK studies found benefits to birds, in numbers, densities, species richness or foraging time. Seven from the Netherlands and the UK found higher plant cover and species richness. Five from Finland and the UK found benefits to small mammals, including higher activity and numbers.

Against that, six studies from the Netherlands and the UK found no clear effect on insect numbers, bird numbers or invertebrate pest populations, and a replicated site comparison found sown grassy margins were not the best option for conserving rare arable plants.

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, action 246, key messages, checked 22/08/2026.

What we have not found. Nothing measuring CAHL3 itself. Nothing on a corner or a block as against a strip, so nothing on whether the shape matters. And nothing putting a figure on the integrated pest management part of the action's stated aim, meaning what the sward next door is worth in the crop.

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.

Start with the word tussocky, because it is the distinctive thing this action asks for and the evidence is directly on it. Woodcock and others, across experimental plots in Yorkshire, found beetle abundance and species richness strongly influenced by the seed mixture. A grass-only Countryside Stewardship mix held more beetles, and more species of them, than a mix of mainly flowering plants containing no tussock grass species at all. A third mix with wildflowers plus both fine and tussock grasses did as well as the grass-only one. Extending the same work across three farms to 2006, they found higher abundance and species richness of predatory beetles in margins containing tussock grass species than in margins of fine grasses only, and that this held whether or not wildflowers were present.

Then how the sward is established, where the findings pull against each other. Critchley and others, across 116 margins in eight regions, found sown margins carried more grass and wildflower species and more foodplants for birds, butterfly larvae and bumblebees than ordinary cereal headlands, and that margins sown with grasses and wildflowers had fewer weed species than unsown sites. But Field and others, working in Essex across seven summers, found plant species richness declined significantly within sown margins between 1998 and 2003 as the sown grasses came to dominate, and that by 2003 a sown 6 metre margin held 20 plant species against 35 on a naturally regenerated one. Critchley and others separately found sown grassy margins more than two years old ran to 87 to 95 per cent grass cover.

Then management, and this is where the action and the research part company. Henderson and others, in a randomised controlled trial across two farms over four years, found that how a margin was managed affected bird use more than which seed mix went into it, with bird densities higher on plots that had been scarified or treated with a grass-specific herbicide than on plots that were cut. Pywell and others, from the same trial, found more bumblebee species on plots treated with grass-specific herbicide in spring. Blake and others, on 6 metre strips in Berkshire, found butterfly species richness higher where scarification and grass-specific herbicide had both been applied than under either alone. Woodcock and others found soil scarification raised the species richness of predatory beetles.

On leaving it alone, two findings run the other way and they are worth holding together. In Finland, field voles were found most frequently in plots left uncut, and mown plots were used less than unmown ones throughout. But Henderson and others found that in winter there were twice as many birds on cut margins as on uncut ones, and twice as many in the second year as in the first.

On what a grass sward will and will not deliver, the pollinator figures set the ceiling. Pywell and others recorded 35 to 47 bumblebees of four species and 18 to 20 butterflies of six species per 125 square metre plot on flower-enhanced margins, against 10 bumblebees of two species and 12 butterflies of five species on grass-only margins. Ogilvy and others, across ten farms, found bumblebee abundance and species richness highest on a tussock grass and wildflower mix and lowest on the standard grass mix, and flower abundance lowest in the standard grass margins. Running the other way, Ramsay and others found sown grass margins held more planthoppers than grass and wildflower margins, at 30 to 70 a plot against 25 to 45. And Carvell and others found 6 metre plots sown with a tussocky grass mix supported no more bumblebees than a conventionally cropped margin.

One figure on time. Across that four-year trial the number of birds using the margins in summer rose by 29 per cent between 2003 and 2006.

Source: Conservation Evidence, action 246, supporting evidence from individual studies, checked 22/08/2026.

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 most useful thing here is that the odd word on the GOV.UK page turns out to be the load-bearing one. Tussocky reads like an instruction to be untidy. In the research it is the thing that separates a margin holding predatory beetles from one that is not, and it held whether or not there were flowers in the mix. If you sow this rather than let it regenerate, our reading is that the species list is worth more attention than the price, and that a mix without tussock-forming grasses in it is a different product from one with them.

The establishment choice is more finely balanced than the money section makes it look. Natural regeneration is free, and the Essex work found a regenerated margin holding 35 plant species against 20 on a sown one after five years, with the sown margin losing richness as its grasses took over. Set against that, sowing gave more foodplants for birds and bumblebees than an unsown headland did, and got there faster. The cheap option is not obviously the poorer one, which is not what we expected to find.

The uncomfortable finding is about cutting, and it deserves stating plainly rather than being tucked away. This action forbids cutting after the first year, and the published work is not one-directional on that. Voles preferred uncut. Winter birds were twice as numerous on cut margins. And the three management treatments that came out best across several of these trials, scarification and grass-specific herbicide in particular, are not available under this action at all. So the sward CAHL3 pays for is not the sward most of these studies found worked best, and a reader should know that before entering ground for three years.

What the action does have, which none of the margin studies tested, is position. A corner is not a strip. It is wider than a margin, it is bounded on two sides rather than one, and it is the part of the field the sprayer, the drill and the combine all struggle with anyway. Whether that shape holds more or less than a strip of the same area is a question nobody in this evidence has asked.

And the age findings sit the same way here as on the beetle bank page. Summer bird use rose across four years, winter use doubled between the first year and the second, and margins under two years old were still behaving differently from older ones. Three years is where this habitat starts becoming what the studies measured rather than where it finishes.

What you actually have to do

Establish and maintain grassy field corners or blocks on the arable or horticultural land entered into the action, by sowing or by allowing natural regeneration, within twelve months of the action's start date.

During the first twelve months you may cut or graze to control weeds and encourage the grass to establish. After that, the aim is an intact grass sward throughout the year, without tracks, compacted areas or poaching, allowed to develop tussocky grass.

The action is static. You must do it at the same location each year of its duration.

Source: GOV.UK, CAHL3 action page, checked 04/08/2026.

What you cannot do on it

Once established: no grazing that would prevent the action's aim being achieved. No cutting, except to control injurious weeds, invasive non-native species, soft and hard rush, nettles or bracken. No regular vehicular access or storage. No fertilisers, manures or lime. No pesticides, except herbicides used for targeted weed control.

Source: GOV.UK, CAHL3 action page, checked 04/08/2026.

Where it can go, and the cap

Agricultural land below the moorland line that is an eligible land type, registered with a compatible land cover on your digital maps and declared with an appropriate land use code. That covers arable crops, leguminous and nitrogen-fixing crops, temporary grassland under TG01, fallow land under FA01, and horticultural permanent crops under TC01. You can enter the total or part of the available area in a land parcel.

Source: GOV.UK, CAHL3 action page, checked 04/08/2026.

CAHL3 is one of the ten limited area actions under SFI26. The rule is that the total eligible area you enter into them must not be more than 25 per cent of the total agricultural area of your farm. The other nine are CIPM2, CAHL1, CAHL2, CIGL1, CIGL2, WBD3, AHW7, AHW9 and AHW11. How the 25 per cent limit works.

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.

Natural regeneration is allowed, but it is not the same as doing nothing. The requirement you are judged against is an intact grass sward, not an absence of a crop. Natural regeneration is a legitimate way to get there and it is what makes this the cheapest establishment on the site. Whether it gets there on your ground, in twelve months, is a question about that particular corner, and the fallback if it does not is buying seed anyway a year later.

Static means three years in the same corner. No moving it in year two because that corner turned out to be where the muck heap needs to go. Pick a corner you are content to farm around for three seasons, and pick it with the whole rotation in front of you rather than this autumn's cropping plan.

The cutting rule reverses after the first year. In the first twelve months you may cut or graze to get the grass going. After that, cutting is only for the named problems: injurious weeds, invasive non-natives, soft and hard rush, nettles and bracken. So the management that establishes it is the management that would breach it later.

Tussocky is the aim, and it will look like neglect. A corner meeting this action properly looks untidy from the road and untidier from the field gate. That is the habitat working rather than a failure, and it is worth deciding you are comfortable with it before you enter the ground rather than reaching for the topper in year two.

No fertiliser, manure or lime. Lime is on the list here, which it is not on every grass action. On ground you would ordinarily be liming, that is worth noticing before rather than after.

A field corner is where things get put. No regular vehicular access or storage. The corner of a field is the natural place for a trailer, a bowser, a heap or a stack of pallets, and the same corner is the natural place for this action. The two want the same ground, so decide which one it is.

Awkward shapes are the whole point, and the area still has to be right. Payment follows the area you enter. A corner is rarely a shape you can pace out, and estimating generously is not a mistake in your favour. Measure it off the boundary rather than guessing at it.

The 25 per cent cap is shared, not per action. CAHL3 draws on the same allowance as CAHL1, CAHL2 and the rest of the ten. Whatever goes into one is not available to the others, so total them together before the form is filled in rather than deciding them separately.

Keeping the evidence

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

This is another action made largely of not doing things, and there is no invoice for a pass you did not make. Where it establishes by natural regeneration there may be no invoice at all.

What that suggests to us is that the useful records are the establishment date, whatever seed invoice exists if you sowed it, any cut made in the first twelve months and why, and any cut made later against which of the named weeds it was for. Dated photographs are doing real work on this one, because the difference between a corner in its first summer and the same corner in its third is the whole aim of the action, and it is visible in a way that a written note is not.

Tilth measures the corner off the field boundary you have already drawn and keeps the operations and photographs against it.

The part only your own ground can answer

Everything above turns on one question we cannot answer from a national survey: what that particular corner actually returns when you crop it. A corner on the field average leaves the crop comfortably ahead. A corner that has been quietly losing you money for years does not, and this action puts a known figure on it instead. Which corners those are is in your own yield records, field by field. Tilth keeps them there alongside the map. Request an invite.