A mix of familiar and new actions make up the Sustainable Farming Incentive offer launched last September, which seeks to protect and improve the farmed environment through various sustainable farming practices.

One of the relatively familiar ones is NUM3 – legume fallow. It’s one of three nutrient management actions and is not dissimilar to AB15, the two-year legume fallow in Countryside Stewardship.

But there are some important differences between the two.

See also: SFI 2023: What’s on offer for arable farmers

Under the Sustainable Farming Incentive (SFI), the nutrient management actions are focused on optimising and managing the efficient use of nutrients, reducing costs and waste, and helping to improve farm productivity and resilience.

Environmentally, they should help improve water and air quality, increase biodiversity and reduce emissions through the reduced use of inorganic fertilisers.

The aim of NUM3, which, like AB15, is worth £593/ha, is to establish a legume fallow producing areas of flowering plants from late spring and during the summer months.

This, according to Defra, will help manage nutrient efficiency and improve soil health, provide food for farmland wildlife and support an integrated pest management approach by reducing grassweeds and encouraging natural crop pest predators, if located close to cropped areas.

A key difference between NUM3 and AB15 is that the SFI option can be moved every year, whereas AB15 has to remain in place until at least 15 August in the second summer after sowing.

It is the ability to move it around on farm, along with requiring an area to be producing flowers by late May, that has meant it is the most discussed SFI action in Oakbank Game and Conservation’s offices, says the company’s director, Ian Gould.

“The latitude in the rules for SFI, which allows it to be an annual option, has led growers to look at the opportunity to plant it in the spring and leave it in the ground for only six months,” he explains.

That potentially makes it an appealing spring break crop replacement, he acknowledges, if you can meet the action’s aim of having flowering plants from late spring (see “Why it might be difficult to meet NUM3 aims”).

© Tim Scrivener

Drilling

However, the most consistent way to meet the aims would be to plant in August/early September or in spring, when the legume fallow is planned to be left in place for at least two seasons.

“It’s important to sow when conditions are right, not just because of a calendar date,” Ian says.

“Typically, I would suggest a light surface cultivation to create a weed-free, fine, firm seed-bed with some tilth, prior to either drilling shallowly or broadcasting and rolling in.”

For autumn establishment, baling previous crop residue will also help reduce slug pressure, he says.

“Direct drilling can be successful in the right situation; the key is not putting these small seeds in too deep.

“I often find a drill is more effective because the metering systems are better on a drill than any sort of broadcasting equipment. It is very difficult to broadcast small seeds.”

Be careful of the herbicide history of previous crops, he warns. “We’re seeing quite bad effects from products such as diflufenican, clopyralid and sulfonylureas, particularly in direct-drill systems.”

Species

Autumn-planted and longer-term mixes for NUM3 are likely to be similar to what growers use for AB15, with and without added grasses.

Those include species such as red and alsike clovers, bird’s foot trefoil, winter vetch, sainfoin, lucerne and crimson clover.

Short-term spring-sown legume fallows are more likely to include annual clovers, such as berseem and crimson clover, combined with fast-growing flowering species such as phacelia, buckwheat and mustards, Ian suggests.

“Those will typically have a seed rate of 15-20kg/ha and cost about £80-£100/ha, while the mixes you expect to last a bit longer, that have more clovers, might cost £100-£120/ha.”

Where a longer-term legume fallow is planned, it’s also possible to add grass species such as perennial ryegrass or fescues, where blackgrass is a problem.

That might increase costs to about £150-£180/ha, he notes.

© Adobe Stock

Management

Not being able to graze this option, or cut it and use it for forage does make management trickier.

On the longer-term legume fallows, cutting to prevent grassweeds from heading is allowed, but some growers have struggled to improve grassweed situations when using this as an AB15 option, and this may mean it is not the best choice for fields with grassweed problems.

Otherwise, in-season management should be straightforward, but note that grazing, fertiliser or manure, or pesticides can’t be used, except certain herbicides for treating injurious or non-native invasive weeds, nettles and bracken.

“Perennial thistles can be a problem, as you can’t control them by mowing,” Ian adds. “So I wouldn’t use this option if I knew there was a legacy of thistle problems.”

Autumn-drilled cereals are a decent option to follow a legume fallow, particularly where grasses haven’t been part of the mix.

Whether it needs to be sprayed off before drilling will depend on what drill is available.

Disc drills that can deal with trash could be used to drill directly into the legume fallow, while tine drills will need it sprayed off a little in advance, he concludes.