Double gains: Boosting crop productivity and reducing carbon footprints through maize-legume intercropping in the Yellow River Delta, China.

The increasing demand for environmentally friendly agricultural practices has driven the need for diversified crop cultivation to optimize crop productivity while minimizing carbon footprints (CFs). However, the impacts of crop diversification on crop production and environmental benefits are still poorly understood. In this study, conducted at two sites in the Yellow River Delta, China, we investigated the effects of legume intercropping, specifically maize/soybean (M/S) and maize/peanut (M/P) systems, on crop productivity, economic return, ecosystem economic budget (NEEB), CF, and carbon sustainability index (CSI) in comparison to conventional monocrops. Crops were grown in replicated field plots and fertilized in their strips according to common practice for monocrops. Compared to the expected averages of monocrops, maize/legume intercropping demonstrated higher crop yields, with M/S achieving a 37% and 43% increase at the two sites, respectively, and M/P achieving an 11% and 20% increase. The higher overyielding in M/S was attributed to stronger selection effects, i.e., interspecific facilitation. However, the complementarity effects induced by the competitive dominance of maize were similar in both intercropping systems. Additionally, M/S exhibited greater potential for improving net revenues compared to M/P. Life cycle assessments revealed lower CFs in the intercropping systems compared to monocultures. M/S reduced CFs per unit of area by 26.8% at both sites, CFs per unit of maize equivalent energy yield by 25% and 33%, and CFs per unit of revenue by 20% and 25% at the two sites, respectively. M/P also resulted in reduced CFs, albeit to a lesser extent. Intercropping enhanced the CSI, with the highest values observed in the M/S system. However, both intercropping systems showed limited effects on soil C sequestration. Overall, our results highlight that maize/legume intercropping is a feasible approach to enhance crop productivity while reducing CFs. The M/S system outperformed the M/P system in terms of crop yields, economic benefits, and CF reduction. However, the intercropping systems showed limited effects on SOC storage. This study provides important implications for sustainable agriculture by appropriate crop diversification.