Effect of conservation agriculture practices on soil organic carbon and maize yield in vertisols

Abstract:

Over 56% of Brazil's vertisols suffer from declining soil organic carbon, and maize productivity in these heavy clay soils has plateaued at 3.2-3.8 t/ha for more than a decade. This research evaluated five tillage and residue management treatments for their impact on Soil Organic Carbon (SOC) and maize grain yield in vertisols at Uberlandia, between June 2021 and April 2024. Treatments were Conventional Tillage (CT), Reduced Tillage (RT), Zero Tillage (ZT), zero tillage with residue retention (ZT+R), and zero tillage with residue plus cover crop (ZT+R+CC), laid out in a randomised block design with four replications. SOC in the 0-15 cm layer rose from a baseline 0.52% to 1.04% under ZT+R+CC after three maize cycles, against 0.58% under CT. Maize grain yield followed the same order: ZT+R+CC (5.42 t/ha) > ZT+R (4.87 t/ha) > ZT (4.13 t/ha) > RT (3.76 t/ha) > CT (3.47 t/ha). Bulk density, infiltration and microbial biomass carbon all improved under conservation treatments. Net carbon sequestration reached 2.18 Mg C/ha/yr and the benefit-cost ratio touched 2.14 for ZT+R+CC. The combination of reduced soil disturbance, surface residue and cover crops appears to be the most promising path to rebuild SOC and raise maize productivity in vertisol-dominated tracts.