Evaluating agronomic performance and environmental benefits of conservation practices in subtropical pasture systems

Abstract

Sustainable agriculture is key to global food security and ecosystem services, including climate mitigation. However, the benefits of conservation practices in grassland systems remain poorly understood. This 2-year field study evaluated the effects of conservation practices on subtropical perennial grass pasture productivity, soil health indicators, and greenhouse gas (GHG) emissions responses. Treatments included cover crop (overseeded annual and perennial legumes), nutrient management (organic or inorganic nitrogen [N]), and soil amendments (biochar and basaltic rock). Nitrogen fertilization increased forage productivity, while other treatments showed limited agronomic benefits. Establishing annual or perennial legumes in grass-dominated systems proved challenging, indicating that improved establishment strategies are needed for successful integration. Most practices had limited short-term effects on soil carbon (C), soil health indicators, and GHG emissions. Biochar had the greatest impact, increasing soil C stocks (82 vs. 26 Mg C ha⁻¹) and soil water retention (0.30 vs. 0.06 m³ m⁻³) at the 0- to 10-cm depth. However, elevated soil phosphorus (P) following biochar application may pose environmental risks in soils susceptible to P losses. Overall, environmental conditions were the primary drivers of GHG fluxes. These findings indicate that conservation practices in subtropical pastures require long-term, site-specific implementation before improvements in soil health, agronomic performance, and environmental outcomes can be expected.