Crop diversification shapes soil multifunctionality under common hydroclimatic extremes

Rising extreme climate events threaten agricultural production and food security. Climate adaptation strategies that enhance soil health are key to strengthening the stability and resilience of agricultural systems. This study reveals how crop diversification influences soil health functions and yield stability, by combining soil, yield, and climate data from thirteen farmer-led experiments in southern Brazil, a region highly exposed to climate variability. Twelve soil health indicators were integrated into four latent functions via factor analysis (79% of total variance explained) and linked to crop diversification, soil texture, and crop yield through structural equation modeling (~76% of variance explained in crop yield). Crop diversification, particularly combined crop rotation and cover crop mixtures, were positively associated with soil water storage independently of soil texture (β = 0.41). Among the four soil health functions, biochemical regulation of soil processes was the most significantly linked to crop yield ( R ² m = 0.31). Yield instability was the strongest direct predictor of crop yield (β = −0.61). On average, systems integrating crop rotation with multispecies cover crops achieved yields 1.76 times higher than the state average, and with markedly lower instability (24%) than conventional or single-practice systems (1.08 times the average; 33–39% instability, respectively). These findings identify yield stability as a key component of climate adaptation, and support integrated crop diversification as a promising strategy for regenerative agriculture and climate policy in Brazil.