Sugarcane yield response to legume intercropped: a meta-analysis

Intercropping with legumes has attracted much attention worldwide, regarded as a sustainable alternative to chemical N-fertilizer. Many studies have investigated the effects of introducing legumes into sugarcane systems. However, how agro-environmental conditions influence the effect of legumes on sugarcane yield is still unclear. Thus, we performed a meta-analysis to i) quantify the effect of legume intercropping on sugarcane yield, ii) assess how agro-environmental and management conditions influence the response of sugarcane yield to intercropping, and iii) assess the influence of legumes in interaction with weeds on sugarcane yield. We combined data from a systematic literature review and experimental data from a network of trials conducted in the tropical island of La Réunion. 315 observations (one-year x site x intercropping treatment) were analyzed with mixed effects models to assess the effect of legume intercropping on sugarcane yield and factors influencing the response of sugarcane yield. Intercropping with legumes resulted in lower sugarcane yields compared to the monoculture treatment in 63% of cases. Our study highlighted how resource availability (e.g., annual temperature, global radiation, soil organic carbon content) influenced sugarcane yield response to legumes. Late sowing and early destruction date of the legume mitigated the negative effect of legumes Viaud et al., preprint 2022 on sugarcane yield. Our study also showed that the negative impact on sugarcane yield increased over years of intercropping, raising questions about legumes' actual contribution to soil fertility. Further studies are needed to optimize legume sowing and destruction dates to find a trade-off between expected services (N enrichment and weed control) and disservices (yield loss, costs, and labor time) in sugarcane agrosystems according to the climate and soil context