Biochar amendments increase the yield advantage of legume-based intercropping systems over monoculture

Biochar soil amendments are receiving increased attention as one strategy to improve soil quality and crop productivity. However, studies about how biochar affects crop productivity so far have mainly focused on single cropping systems. Few have examined the effects of biochar additions on intercrops. We conducted a field experiment that investigated the effects of biochar amendments on yield and nutrient uptake in an intercropping system where maize (Zea mays L.) was intercropped with either soybean (Glycine max L.) or peanut (Arachis hypogaea L.). The relative advantages of both yield and total nutrient content were calculated as land equivalent ratios (LER). Biochar amendments significantly increased the yield advantage in both maize/soybean and maize/peanut systems over the single crops. Similarly, they significantly enhanced the relative N and P uptake advantage. Using the 15N isotope dilution method, we examined the effect of biochar amendments on peanut N2-fixation and subsequent N transfer from peanut to maize in a root-box experiment. Biochar amendments of 10 and 20 g kg−1 soil increased peanut N fixation by 15.52% and 14.11%, and increased N transfer from peanut to maize by 32.66% and 36.07%, respectively. These results indicate that amending soil with biochar can amplify the benefits of legume-based intercropping by enhancing legume N fixation and facilitating N transfer from legume plants to co-existing cereal crops.