Interspecific root interactions increase maize yields in intercropping with different companion crops

Abstract Background Intercropping is assumed to increase food production while reducing fertilizer needs and environmental impacts of crop production. Aims We aimed to (1) investigate the effects of intercropping on yields and nutrient uptake of maize, and (2) determine the relative contributions of above‐ and belowground interspecific interactions (RC above/below ) to these effects. Methods We conducted a 2‐year, small‐scale field experiment with maize grown either in monocropping or intercropped with faba bean, soy, blue lupin, or white mustard as companion crop. We included a treatment in which interspecific root interactions were restricted due to barriers in the soil. Maize and companion crops were analyzed for yields, and maize additionally for nutrient uptake. Maize partial land equivalent ratios (pLER), partial nitrogen and phosphorus equivalent ratios (pNER, pPER), and RC above/below were calculated. Results Intercropping resulted in a similar productivity of maize as in monocropping on an area basis. Maize pLER, pNER, and pPER were larger than 1.0 in several species combinations, indicating a positive effect of intercropping on maize yields and N and P uptake. Interspecific root interactions accounted for 62–85% of the maize yield increase in legume/maize intercropping, but for only 22% in mustard/maize intercropping. Conclusion Our results indicate that intercropping is beneficial for crop production since it increases maize yields and N and P uptake of maize plants, and it also provides yields of a companion crop. A substantial part of these positive effects can be attributed to interspecific root interactions.