https://defrafarming.blog.gov.uk/grow-legumes-in-grassland-to-replace-nutrient-inputs/
Grow legumes in grassland to replace nutrient inputs
The guidance on this page is for SFI pilot participants only. Please visit GOV.UK for the official Sustainable Farming Incentive scheme guidance.
Find out how land managers can reduce their carbon footprint, improve water and air quality and protect wildlife by using less nitrogen.
If you’re completing this action as part of the Sustainable Farming Incentive pilot, how you do it is up to you.
The advice on this page can help you get better environmental and business benefits, but you do not have to follow it to get paid.
Benefits of legumes in grassland
You can sow legumes like clover to help reduce the need for manufactured nutrients containing nitrogen.
Legumes take nitrogen from the air in a process known as ‘fixing’. This helps reduce the amount of nitrogen lost to the atmosphere through leaching and runoff.
Using legumes can:
- maintain grassland productivity
- produce high quality forage
- improve soil health
- provide food for pollinating insects like bees
- contribute to cleaner drinking and bathing waters by reducing the amount of nitrogen that enters watercourses
Using less nitrogen can:
- help protect wildlife and sensitive wetland habitats
- promote a greater range of plants and wildlife
- reduce your farm’s carbon footprint
You can reduce the amount of ammonia lost to the atmosphere to improve:
- the condition of sensitive habitats and species
- air quality, to benefit human health
Where to use legumes in grassland
You can sow legumes on:
- permanent grassland
- temporary grassland, including leys in arable rotation
It’s suitable if you’re moving from a high input to a low input system.
You can use legumes on fields where loss of nitrogen has been identified as a risk to water quality. Check the Environment Agency map to find out if there are Nitrate Vulnerable Zones and Drinking Water Safeguard Zones in your area.
If your land is in a Catchment Sensitive Farming (CSF) area you can get advice from your local CSF officer.
Use a nutrient management plan to make sure you only add nutrients at levels that meet crop requirements.
If you have arable land you can also create herbal leys.
How to add legumes to grassland
Before you start
You’ll need to identify and fix causes of poor grass production. These include:
- soil compaction
- underground drainage not working properly
- low levels of nutrients like phosphates and potassium
- inappropriate pH levels, which you can fix using a nutrient management plan
Prepare the grassland
Before sowing the seed mix, mow or graze the grass to reduce competition from existing plants. You can apply a low rate of a broad-spectrum herbicide to help suppress the existing sward.
March or April is a good time to prepare the grassland. There is usually moisture in the soil and a long season ahead to help with establishment.
Alternatively you can apply the seeds after a silage cut, as the grassland should be more open. You may get better results after a second silage cut as the regrowth is less vigorous.
To increase seed establishment:
- create at least 20% to 25% bare soil
- control perennial weeds before you sow the seed
On permanent pasture, avoid wholesale destruction of the sward before sowing.
What to sow
In cut grass use:
- red clover
- alsike clover
- sainfoin
- lucerne
In grazed grassland, it’s best to use:
- white clover
- bird’s-foot trefoil
You can use sainfoin, lucerne, red and alsike clover in grazed grassland. You’ll need to follow a rotational grazing system that allows for sufficient rest periods. You can manage the grazing to let plants flower before you return stock to the field to graze.
Sainfoin is more likely to grow well on calcareous soils.
On historic features, do not grow plants whose roots could damage the features. These include deep rooted legumes like sainfoin and lucerne.
The proportion of legumes in the seed mix will depend on:
- size of legume seed
- percentage and species of grass seeds
- seed rate
- current soil nitrogen levels
- establishment method
You can consult your seed supplier for advice on seed mix, to make sure you have the right proportion of legume seeds.
You must use organic seed if you farm organically or are converting to organic farming. You’ll need approval from your organic certification body to use non-organic seed.
How to sow
You can use any suitable equipment you have for over sowing, like a:
- fertiliser spreader
- grass seed broadcaster
- seed drill
If the soil is dry enough, roll immediately after you broadcast (scatter) seed to:
- improve seed-to-soil contact
- keep in moisture
- reduce the risk of slug damage
You can graze the area with lighter animals like sheep to help trample the seed mix in. You must keep livestock out of the field while the seedlings establish. This will prevent new grasses or legumes being grazed out.
Historic features
If there are historic features present, do not use a disc or power harrow as these will cause damage to the features. Do not roll the ground.
To avoid disturbing the feature you can:
- use minimal cultivation methods like direct drilling and seed slotting
- broadcast seed by hand or use a light machine
Maintain productivity
Replacing manufactured nitrogen with legumes will reduce some productivity. Productivity will increase over time as the legumes become established.
To promote legume and grass growth, soil phosphate (P) and potassium (K) levels should be maintained at an index of 2. You can use manufactured P and K or organic manure.
Aim for a lower P index of 1 if you plan to create species-rich grassland. Do not sow white clover or lucerne as they will outcompete wildflowers.
Do not add legumes to the sward if you’re already managing species-rich grassland.
You may need to apply lime to achieve the right soil pH for legume growth. Ideal pH is:
- 6 to 6.5 for most legumes
- 7.0 for sainfoin and lucerne
How to manage legumes in grassland
Weed control
You may need to manage weeds. Only apply herbicides using precision application systems like spot sprayers.
Livestock bloat
Too many legumes in the sward can cause bloat in ruminants like cattle and sheep. Legumes that cause bloat include:
- red and white clover
- alsike clover
- lucerne
You should:
- make sure grazed grassland consists of less than 50% legumes
- check livestock for signs of bloat and remove affected animals from the field
Avoid turning out livestock on:
- new pastures if animals are hungry
- pastures after a frost, rainfall or dew
To reduce the risk of bloat you can:
- provide hay before and during livestock turn out
- include bird’s-foot trefoil or sainfoin in the seed mix
Other ways to reduce nitrogen
You can:
