Plant species richness as a strategy to improve soil quality and increase forage yield in a tropical ecosystem

Abstract Background and Aims Plant species richness can provide a range of benefits to the soil, since mixtures of species with contrasting functional traits enhance soil organic carbon (SOC) stocks. However, there is still limited information on the impact of increased plant species richness on tropical forage systems. This study evaluated whether increasing plant species affects soil quality attributes and forage yield in a tropical ecosystem. Methods The experiment consisted of five treatments: 1) very low—single grass ( Urochloa brizantha ); 2) low – grass intercropped with cowpea; 3) medium – MIX with grass intercropped with cowpea and buckwheat; 4) high – MIX with grass intercropped with cowpea, buckwheat and forage radish; and 5) very high – MIX with grass intercropped with cowpea, buckwheat, forage turnip and sunflower. Results Increasing species richness altered root mass without reducing forage yield. Compared with the very low richness treatment, the very high richness significantly increased microbial biomass carbon (C) (130%), total organic C (19%), soil aggregate stability (60%) and the C management index (BMI > 86%), with no clear influence on occluded carbon in aggregates or on the arylsulfatase. The total organic carbon occurred mainly as particulate organic matter. Higher levels of total, particulate and microbial carbon, together with changes in metabolic and microbial quotients, were associated with greater species richness effects on soil quality in the short term. Conclusion Forage species richness played an important role in soil quality attributes, promoting SOC sequestration without compromising forage yield. These findings advance the understanding of species-diverse production systems as a strategy for sustainable intensification.