CNUM3Legume fallow

What it actually is

A fallow with a seed mix and a species requirement attached to it. GOV.UK's stated aim is that there is an established legume fallow with plants that grow and flower from late spring and during the summer months, and that provide green cover over the winter months. The page sets that in the context of managing nutrient efficiency and improved soil health, providing food for farmland wildlife such as pollen and nectar for pollinators and farmland birds, and supporting an integrated pest management approach.

On the established fallow, grazing with livestock is not permitted, the area must not be used for regular vehicular access, turning or storage, and cutting is permitted only to prevent blackgrass setting seed or to control other annual grass weeds.

Source: GOV.UK, CNUM3 action page, checked 02/08/2026.

Our own way of putting that, which adds no requirement beyond what the GOV.UK action page sets out: this is not a rested field. It sits in the nutrient management group of actions, and the restrictions on it are tighter than the word fallow suggests.

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: what the seed costs, and how many times you buy it. The timing requirements mean the seed goes in twice, not once. You establish the fallow by the autumn within 12 months of the start date, maintain it at the same location for a period of time that can reasonably be expected to achieve the action's aim, which GOV.UK says will usually be until the end of the second summer after sowing, and then re-establish it by the following autumn.

Source: Boston Seeds' own listed price and stated sowing rate for the CSS6 Legume Fallow NUM3 mix, looked up 02/08/2026. The site displays prices with an inclusive and exclusive of VAT toggle and £125.00 was read in the inclusive state. The timing that produces two sowings is from the GOV.UK CNUM3 action page, checked 02/08/2026. Everything else in the table is arithmetic on those two figures.

Step two: what the action is worth after seed. Taking the annualised seed cost off the payment leaves between £448.67 and £469.50 a hectare a year, before cultivation and drilling.

Step three: 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 three, 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 four: the gap.

Source: the payment rate at the top of this page less the seed costs in step one, set against the rotation averages in step three. 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.

The gap above leaves out what the fallow does for the crop that follows it. GOV.UK sets the action in the context of nutrient efficiency and improved soil health rather than putting a figure on either, and we are not going to put a figure on them either, because what they are worth depends on your soil, your rotation, your nitrogen prices and how you would have managed the ground otherwise. We have not found a published figure we would stand behind on a page about money.

Where that leaves it. On ground that performs like the rotation averages, the crop is ahead by something in the region of £295 to £387 a hectare a year, and the fallow has to make that up out of the following crop and out of whatever the block was doing badly in the first place. If the block was going to be fallowed anyway, or if it is the field where you already know the nitrogen goes furthest, the picture changes a good deal. On your best land it does not.

What you actually have to do

Establish a legume fallow using a seed mix containing at least six flowering species, including legumes. GOV.UK names alsike clover, bird's foot trefoil, black medick, common vetch and lucerne among the legume options, alongside non-legume flowering species and grasses such as cocksfoot or timothy. Once it is established, you must maintain it, and GOV.UK puts that as managing it in a way, and for a period of time, that can reasonably be expected to achieve this action's aim.

Establish the legume fallow by the autumn, within 12 months of the action's start date. Maintain it at the same location for a period of time that can reasonably be expected to achieve this action's aim, which GOV.UK says will usually be until the end of the second summer after sowing. Re-establish it by the following autumn and maintain it to the end date.

Source: GOV.UK, CNUM3 action page, checked 02/08/2026.

What you cannot do on it

Once the fallow is established: no grazing with livestock. No using the area for regular vehicular access, turning or storage. No fertilisers and no manures.

Cutting is permitted only to prevent blackgrass setting seed or to control other annual grass weeds. Pesticides are not permitted at all, except herbicides to weed wipe or spot treat to control injurious weeds, invasive non-native species, nettles or bracken.

Source: GOV.UK, CNUM3 action page, checked 02/08/2026.

Our own note on those two exceptions, which adds no requirement beyond what the GOV.UK action page sets out: they are separate permissions and they name different weeds. Blackgrass and other annual grass weeds appear in the cutting permission. They do not appear in the herbicide permission, which names injurious weeds, invasive non-native species, nettles and bracken.

Where it can go

Agricultural land below the moorland line, on arable land, temporary grassland, fallow land or permanent horticultural crops, with compatible land covers and land use codes. It can be rotational or static, so you can move it in years two and three or keep it in the same place.

SSSIs are eligible but you must give notice to Natural England and get SSSI consent before the Rural Payments Agency offers you an SFI26 agreement. Land with historic or archaeological features needs an SFI HEFER before you do the action, and GOV.UK says not to sow deep-rooted legumes such as lucerne on the areas it identifies.

Source: GOV.UK, CNUM3 action page, checked 02/08/2026.

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.

Two sowings, not one. The timing requirements put an establishment at the front and a re-establishment before the third year. Anyone budgeting this off a single seed invoice is out by the price of a second one, and on a mix at this price that is not a rounding error.

Six flowering species is a countable requirement, and the bag is the evidence. It is not "legume-rich" as a general description. The number is on the page, so the composition on the invoice is the document that answers it, and a mix sold under the code still has to be read.

Cutting is not a management tool here. It is permitted to prevent blackgrass setting seed or to control other annual grass weeds, and that is the extent of it. Topping a fallow because it looks untidy is not one of the permitted reasons on the page.

No regular vehicular access, turning or storage. A block that is out of cropping is a convenient place to turn, park a trailer or drop a heap, and the prohibition rules that out. Worth knowing before you pick which block goes into it.

Deep-rooted legumes and historic features do not mix. If your HEFER identifies anything, lucerne is specifically the species GOV.UK tells you to keep off it, and that is a decision made when you choose the mix rather than when you drill.

The merchant prices above were read inclusive of VAT. Merchant sites can display either basis, and a quote you are given may be on the other one. Worth settling before the figures go into a budget.

Compatible on the page is not the same as compatible on your parcels. The GOV.UK action page sets out its compatibility lists separately for actions on the same area and actions on the rest of the parcel, and a legume fallow occupies the ground for the whole period, so on those hectares it will not sit alongside an action that requires a crop to be grown.

Keeping the evidence

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

The action page asks you to keep evidence of what you have done, giving field operations at parcel level with their invoices, and photographs or other documentation, as the examples.

For this action the two seed invoices are the backbone, because they are the only documents that show both what went on and that it went on twice, and because the species breakdown on them is what speaks to the six-species requirement. Photographs are worth taking more than once across the year, since a legume fallow in flower and the same block in November look like two different fields, and a single picture speaks only to the day it was taken. Cutting is worth recording with its reason attached, because the permitted reasons are narrow and a cut with no note against it says nothing about why it happened.

The part only your own ground can answer

The gap above is worked on national averages because that is all a website has. What it cannot know is what this block returns in your rotation, or what the fallow is worth to the crop that follows it on your soil. Both of those live in your own records, and Tilth is where we keep them, parcel by parcel and year by year. Request an invite.