CAHL44m to 12m grass buffer strip on arable and horticultural land

What it actually is

A grass strip on an arable field edge that stays in grass for the whole agreement. It has to be an intact sward all year round, with no tracks, no compacted areas and no poaching. The strip goes on the edge of the arable or horticultural land, buffering a hedgerow, stone wall, woodland, ditch, river or stream, or an upstanding historic or archaeological feature. Area is measured as the length of the strip in metres times its width in metres, divided by 10,000.

Source: GOV.UK, CAHL4 action page, checked 05/08/2026.

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 0.6 hectares is the action page's own measurement rule applied to an illustration: 1,000m × 6m ÷ 10,000.

Is it worth it on your ground?

Step one: what it costs to put in. Grass seed, once, at the start of a three-year agreement.

Source: ProGreen, own listed price and stated sowing rate for a 4/6 metre grass and buffer strip mix sold for CAHL4, looked up 31/07/2026. Price your own mix. 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, 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. After seed, the payment is worth £477 a hectare a year, before cultivation and drilling.

Source: the payment rate at the top of this page, less the £38 a hectare a year of seed in step one, set against the rotation averages in step two. The figures are subtraction. Cultivation and drilling are not in them.

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 was the lower of the two years. Against the stronger year the gaps above widen.

But the field average is the wrong comparison for a headland, and that is the point of this action. The strip does not replace the average of the field. It replaces the outermost four to twelve metres, which is the shaded, compacted, headland-turned ground that carries the field average rather than setting it. We are not going to tell you what your headland returns, because we do not know it and we have not found a published figure we would be willing to put on a page about money. What we can say is that the number to put in the table above is the headland's own gross margin, not the field's, and that the gaps of £287 to £359 shrink by however much your outer few metres fall short of the rest. If you have yield maps, that difference is already in them.

Do not count the input saving twice. The action prohibits fertiliser and manure, and prohibits pesticides other than weed wiping or spot treatment. It is tempting to add those savings on top of the payment. They are already in the figures, because a gross margin is output with variable costs taken off, so the ground you put into the strip gives up its output and its input bill together. The only case where it moves is if you already treat the headland differently from the rest of the field, and then it is your own number to put in.

Where that leaves it. Where the outer few metres return close to the field average, this action is short by something between £287 and £359 a hectare a year, and it does not pay. Where they fall well short of it, the gap closes by that difference, and the ongoing work is one cut a year on ground you are probably not enjoying farming anyway. The whole answer sits in a number that no national survey holds and your own yield maps do.

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.

None of the work below is about CAHL4 by name. It is about grass margins and buffer strips on arable fields, and this action is one way of paying for that practice.

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. Planting grass buffer strips or margins around arable or pasture fields comes out in their top category, Beneficial, 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 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.

Source: Conservation Evidence, action 246, Plant grass buffer strips/margins around arable or pasture fields, Farmland Conservation synopsis, checked 23/08/2026. Cite as Dicks et al. (2020), Farmland Conservation, pages 283 to 321, in What Works in Conservation 2020, Open Book Publishers.

What their studies found, both ways. Nineteen studies from Finland, the Netherlands, Sweden and the UK found grass buffer strips increased arthropod abundance, species richness or diversity. Nine UK studies found benefits to birds, in numbers, densities, species richness and foraging time. Seven found more plant cover and species richness, and five found benefits to small mammals. Against that, six studies found no clear effect on insect numbers, bird numbers or invertebrate pests, and a replicated site comparison found sown grassy margins were not the best option for conserving rare arable plants, which sits squarely alongside GWCT's advice below about light soils carrying an old arable flora. One detail from the individual studies bears directly on a plain grass strip: an early UK experiment found sown margins held more plant cover than naturally regenerated ones, but grass-only seed mixes tended to carry lower plant diversity than grass and wildflower mixes. 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 and supporting evidence from individual studies, checked 23/08/2026.

One study, and it went both ways. GWCT set sticky traps across 12 winter wheat fields and mapped the field margins around each one. Numbers of Tachyporus rove beetles, which overwinter in margins and move into the crop in spring to eat aphids, rose with the total length of field margin per hectare within 750 metres. Soldier beetles did the opposite: fewer were found inside the wheat where there were more margins within 50 metres, which the researchers read as the margins holding them rather than the crop. The work was funded through the Research Councils UK Rural Economy and Land Use programme.

Source: GWCT, Field margins, wheat fields and aerial insects, checked 05/08/2026. The page does not state a publication date or where the fields were.

And the same organisation is blunt about the limits. GWCT's own buffer strip advice says these strips are not a cure-all. They say a buffer strip is of no use as brood cover for pheasants or grey partridges, because the grass is too dense and too wet for chicks to forage in and gives too little protection from predators. On light cultivated soils carrying an old arable flora they point to conservation headlands or uncropped cultivated margins instead, and they say a wild bird seed crop does more for birdlife. That page is written around Entry Level Stewardship, which closed to new agreements, so it predates this scheme.

Source: GWCT, Buffer strips, checked 05/08/2026.

What we have not found. Nothing measuring CAHL4 itself, which is no surprise given how new it is. Within those 69 studies, no assessment of this action's own recipe, a plain grass sward with a part-width late summer cut. And nothing that separates how much of the result comes down to how the strip was sown and cut, which is the part you control.

What the sources say makes it work better. Farm Wildlife, a partnership of conservation and farming organisations publishing a single source of best-practice management advice for wildlife on farmland, advise August or September as the best time to establish a grass margin, and suggest looking first at whether it will come back on its own, because where the seedbank already holds perennial grasses and weed levels are low, natural regeneration can do the job instead of sowing. On composition they advise fine grasses such as fescues and bents with up to 10 per cent of a tussocky grass like cocksfoot or timothy, which traps sediment and gives nesting cover. In the first summer they advise cutting at around 10cm to hold the weeds back, which may take three cuts. After that they advise cutting once every three years and only in autumn, rotated so that rough areas with seed heads stand through the winter for hibernating insects, cuttings off where you can, and nothing cut on wet soil. They advise keeping herbicide, fertiliser and insecticide drift out of the margin. Where the aim is water, they advise spreading the buffers across all the downslope edges of the fields rather than putting one wide strip in one place, and they note that a 6m strip next to a watercourse removes the LERAP requirement. The species they name as benefiting are grey partridge, tree sparrow, reed bunting, whitethroat, yellowhammer, corn bunting, barn owl and kestrel.

Source: Farm Wildlife, Grass margins as buffer strips, checked 05/08/2026.

Their cutting advice and this action's cutting requirement are not the same thing, and it is worth knowing which is which before you plan the year. Farm Wildlife are talking about the whole margin, on a three-year rotation, in autumn. GOV.UK asks for a cut of part of the strip's width, on the side nearest the crop, in late summer after the bird breeding season. What you are paid against is the GOV.UK page.

What you actually have to do

Establish the strip at least 4m and up to 12m wide, on average across each land parcel. It can be wider than 12m, but only 12m of width is paid. Keep an intact grass sward all year, with no tracks, compacted areas or poaching.

In late summer, after the bird breeding season, cut part of the strip's width along the edge nearest the crop or fallow, along as much of its length as you can. The GOV.UK page gives the reason: it provides varied habitat.

Source: GOV.UK, CAHL4 action page, checked 05/08/2026.

What you cannot do on it

No regular vehicular access, turning or storage. No fertiliser or manure. No pesticides, except herbicides used to weed wipe or spot treat injurious weeds, invasive non-native species, nettles or bracken.

Source: GOV.UK, CAHL4 action page, checked 05/08/2026.

Where it can go, and any cap

Arable land used to grow crops, temporary grassland, arable land lying fallow, and permanent crops, all below the moorland line, on the edge of the parcel and buffering one of the features listed above.

Source: GOV.UK, CAHL4 action page, checked 05/08/2026.

CAHL4 is not one of the limited area actions under SFI26, so the 25 per cent of total agricultural area rule that applies to actions like CAHL2 and AHW9 does not apply to it. In practice the ceiling on this action is how much field edge you have and how wide you are willing to go.

Source: GOV.UK, SFI26 scheme rules and guidance, section 4.5, checked 05/08/2026.

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.

Think about where you turn before you pick the field. The action prohibits regular vehicular access, turning and storage on the strip. A grass headland is also a natural place for a sprayer to turn, so the two want the same ground. If the strip would be where you turn, pick a different edge.

The width is an average across the land parcel. That helps where a boundary wanders. It also means the average is what is measured, so a stretch that narrows is only offset if there is a wider stretch elsewhere in the same parcel. Measure the whole parcel, not the narrowest point.

Width is the lever on the arithmetic, and it cuts both ways. Going from 4m to 12m triples the area and triples the payment, and it also takes three times as much ground out. The wider you go, the more of the strip sits on ground that yields like the rest of the field rather than like the headland, which is exactly the ground the sum above says not to enter.

Poaching and tracking are named, not implied. The wording is an intact sward throughout the year, without tracks, compacted areas or poaching. It is worth knowing that those are set out specifically rather than left to judgement.

The late summer cut is a requirement, not an option. One pass, after the bird breeding season, on the crop side of the strip.

It is three years in grass, so think about what comes after. The strip is not rotational. At the end of the agreement you have a three-year-old sward on a field edge and a decision about whether it goes back into the cropping, stays, or goes into a follow-on agreement. That is easier to think about now than in the autumn it happens.

Keeping the evidence

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

The measurement is the one to get right, because the payment is calculated from length times width. Alongside it, the records that would let you show you have met the action are the seed invoice, the establishment date, and the date of the late summer cut.

The cut is the one that goes missing, because it is a single pass in a busy month on ground nobody else is thinking about. Note it against the field on the day rather than at the end of the year.

Tilth measures the strip off the field boundary you have already drawn and keeps the establishment and cutting dates against it.

The part only your own ground can answer

Everything above turns on one number that we cannot give you: what the outer four to twelve metres of that particular field actually return, against the rest of it. GOV.UK cannot tell you, and neither can we from a national survey. A farmer with their boundaries, their yield history and their NDVI in one place can look at it edge by edge and pick the field. Request an invite.