Pea-barley intercrops

Research showing that intercropping field peas and spring barley can encourage more efficient nitrogen use.

Resource explained

While many plants rely on nitrogen (N) in the soil, leguminous plants such as peas and clover are able to convert atmospheric N into plant-accessible N, making them useful crops for replenishing soil N. This short academic paper (entitled ‘Pea-barley intercrops use nitrogen sources 20-30% more efficiently than the sole crops’) discusses data generated as part of an EU funded project on intercropping that was presented at a conference in Denmark in 2006. It contains interesting data and conclusions that still hold their relevance for farmers considering intercropping. It describes an experiment where the N use of different mixtures and sole crops of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L) were compared and N productivity determined in five sites across Western Europe that were managed according to organic principles.

Findings & recommendations

• When growing legumes as a sole crop, they will use soil derived ntirogen (N) even though symbiotic derived N is sufficient.
• Compared to a field pea or barley monocrop, a mixture of peas and barley used less soil N and more atmospheric N.
• Adding barley as an intercrop caused competition for soil N, and the peas took in more N from the atmosphere.
• Intercropping of legumes and cereals can help reduce soil N degradation and therefore the need for N fertiliser applications.
• None of the experimental mixtures led to an overall increase in soil N over the course of 3 years,  however intercropping offers the opportunity for organic cropping systems to utilise N without compromising total crop N yield levels.
• Across varying growing conditions, pea-barley intercropping showed that N sources were used 17-31% more efficiently by the intercrop than by the sole crops.

Header image photo credit: Natural England / R Harris (CC BY-NC-ND 2.0)