Incorporate grain legumes in crop rotations to reduce emissions

With rising demand for homegrown protein for human and livestock diets, grain legumes offer market potential and a lower-emission option to farmers.

What are grain legumes?

Grain legumes, also known as pulses, are protein-rich crops. In the UK, peas and beans are the most commonly grown, but as demand for nutritious grains increases, some commercial growers are also planting lupins, lentils and chickpeas.

• Reduce fertiliser needs: Legumes fix nitrogen (N) from the atmosphere, significantly reducing the need for nitrogen fertilisers. This cuts greenhouse gas (GHG) emissions, particularly nitrous oxide (N₂O) and emissions associated with fertiliser manufacturing. Some varieties can fix over 300 kg N/hectare/year
• Provide residual N for following crops: Grain legumes leave behind N in the soil, helping to reduce fertiliser needs for the next crop. Research shows that fertiliser requirements after grain legumes can be reduced by 23–31 kg/ha, and cereal yields are often 0.5–1.6 t/ha higher than after cereal pre-crops. Even with a 60 kg/ha fertiliser reduction, yields can remain viable
• Improve soil health: Their root systems improve soil structure, enhance microbial activity, and help break pest, disease and weed cycles. This increases the resilience and biodiversity

• Additional income stream: Even when hit and miss in themselves, they can provide good entry into the next cash crop in the rotation, improving rotational performance and reducing input costs
• Lower input costs: Grown alone or in bi-crop/intercrop systems, legumes fix atmospheric N reducing competition for soil N with companion crops like cereals or brassicas
• Increase yield potential: Intercropping offers the possibility of producing greater yields from the same farm acreage, making better use of land and resources
• Support human and livestock nutrition: Legumes are high in dietary fibre, protein and complex carbohydrates, making them valuable for human diets and as a sustainable alternative to imported soya in livestock feed  

• Select the most suitable legume to match your soil type, climate and market opportunities. For example: peas thrive on lighter land and beans perform better on heavier soils
• Refer to the Processors and Growers Research Organisation (PGRO) Pulse Descriptive List to choose a variety suited to your soil, location and end market. Research market demand, buyer specifications, and price trends before planting
• Check and manage soil pH. Grain legumes require soils with a pH between 5.5 and 6.5. Soil testing is vital before sowing. If pH falls outside this range, take corrective action (e.g. liming) to optimise conditions

• Legumes could be introduced as a break crop within arable rotation, helping to disrupt pest and disease
• They can also be intercropped or intersown with other arable crops to improve system resilience and nitrogen use efficiency
• They also offer scope for use as a wholecrop silage to reduce a mixed farm’s dependency on imported protein feeds
• Be aware of how often they can be included in a rotation. For example, beans should only be grown once every 5–6 years
• Identify buyers and processing options early. Many types of high-quality peas and beans are suitable for a range of premium markets, but all types are suitable for animal feeds