Long-Term Crop Diversification Improves Soil Biological Functioning and Sustains Grain Productivity in the Brazilian Cerrado

Long-term crop diversification can alter soil functioning and crop performance in the Brazilian Cerrado, but the extent to which these responses persist across cropping systems remains unclear. This study assessed four soybean-based systems maintained under no-tillage from 2017 to 2025: soybean–maize, soybean–millet, soybean–palisadegrass, and soybean–maize + palisadegrass. Soil was sampled once after the 2025 harvest at 0–0.10 m, with four field replicates per system, and evaluated for chemical attributes, enzyme activity, and soil quality indices using the BioAS framework. Soybean and maize grain yields were evaluated annually, and cumulative yields were calculated over eight growing seasons. Soil P and K were higher in the maize-based systems, whereas organic carbon was greater under palisadegrass and maize + palisadegrass. β-Glucosidase activity was 27% higher under palisadegrass and 42% higher under maize + palisadegrass than under sole maize. IQS Biological was also higher in the palisadegrass-based systems, while IQS Chemical did not differ among treatments. Annual soybean yield differed among cropping systems and growing seasons, but the system × season interaction was not significant. Cumulative soybean yield was 6.8% higher under palisadegrass and 6.5% higher under maize + palisadegrass than under soybean–maize. Maize yield did not differ between sole maize and maize + palisadegrass. These results indicate that including palisadegrass in soybean-based systems was associated with improved biological soil quality and greater soybean productivity, while intercropping maize with palisadegrass maintained maize yield.