Cover crops effects on subsequent soybean yield in Brazil: A meta-analysis

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Context Brazil is the world's leading soybean producer, facing the challenge of sustainably intensifying its production systems while preserving soil health and ensuring resilience under increasing climate variability. Cover cropping is a proposed strategy to enhance soil health and yields, but its quantitative impact across Brazil's diverse agroecosystems is not well synthesized. Objective This study quantified the cover crops effect on subsequent soybean yield in Brazil and identified the environmental and management factors that moderate this response. Methods Data from 53 peer-reviewed field studies conducted across Brazilian agroecosystems were synthesized using a random-effects model. The natural logarithm of the response ratio (lnRR) was used as effect size. Heterogeneity was assessed by I² and Q statistics, publication bias by the rank correlation test, and confidence intervals were estimated by bootstrap resampling (10,000 iterations). Categorical moderators (control type, cover crop functional group, climate zone, soil texture, soil organic matter, P and K fertilization, baseline yield quartiles) and continuous moderators (cover crop biomass and surface soil wetness index) were analyzed by subgroup analysis and meta-regression. Results Overall, cover crops increased soybean yield by 8.72% (95% CI: 6.40–11.15). Yield gains were larger when cover crops replaced fallow (10.60%) than a previous cash crop (4.77%). Single-species grasses (16.97%) and legumes (16.06%) produced the largest increases. Benefits were greatest in low-yield environments (19.91% and 20.62%), tropical climates (17.14%), and under drier conditions, and were amplified by higher phosphorus fertilization rates. Higher biomass from grass cover crops increased soybean yield by up to 33%. Conclusion Cover crops are an effective tool for increasing soybean yields in Brazil, although the largest gains are achieved through aligning cropping system, cover crop functional composition, and environmental context. Implications These findings identify the management and environmental factors associated with cover crop performance in Brazilian soybean systems, including cover crop functional group, cropping system context, and phosphorus fertilization, providing an evidence base to guide cover crop selection as part of broader sustainable intensification and climate resilience strategies.