Grass-based diversification of cotton production systems improves soil health and multifunctionality balance in tropical sandy soils.

Crop diversification is widely used in agroecosystems to improve soil health and sustain food and fiber production while protecting the environment. However, its benefits remain poorly documented in the Brazilian savannah, a major cotton-producing region characterized by sandy soils. This study assessed the long-term (i.e., 12-year) effects of crop diversification on soil multifunctionality in cotton-based systems on sandy soils in the Brazilian savannah. Five cropping systems were evaluated: cotton monoculture under conventional tillage (CT) (control), millet-cotton succession under CT, and three crop rotations under no-tillage: cereal, legume and grass. Fourteen indicators were evaluated to represent five soil functions: nutrient supply, water regulation and aeration, plant growth support, erosion control, and carbon sequestration and cycling. Soil multifunctionality was evaluated using the soil health index (SHI) and the coefficient of variation among functions. Their interaction was interpreted using the Soil Health Interaction Functional Trends (SHIFT) approach. Diversifying cotton production with grass cover crops improved soil health more effectively than the use of legume cover crops. Cropping systems incorporating cover crops improved soil functional balance by 38% relative to systems relying only on cash crops. The SHIFT approach improved the understanding of the effects of cropping systems on soil multifunctionality compared with the soil health index alone. According to SHIFT, millet-cotton and grass rotation were classified as healthy and balanced, whereas monoculture was classified as unhealthy and unbalanced. These results demonstrate that grass-based cotton systems improve soil health and functional balance in sandy soils of the Brazilian savannah.