Effects of ecological intensification of agriculture on soil fertility and carbon and nitrogen stocks: An 8‐year study in southern Brazil

Abstract Ecological intensification (EI) of agriculture aims to optimize soil conservation, crop diversity and nutrient management. Despite growing interest in EI, its impact on soil properties, compared with conventional farming practice (FP), remains poorly understood as a result of limited field evidence. This study, conducted over eight seasons in southern Brazil as part of the ‘Global Maize Project’ of the International Plant Nutrition Institute, evaluated EI compared with FP, and FP with silage (FPS) using a split‐plot design. Four nitrogen application rates (0, 70, 140 and 210 kg ha −1 ) were applied to subplots with four replicates. Soil properties were measured to a depth of 1 m. The trial systems consisted of a maize–soybean rotation under no‐till during summer and cover crops and fertilizer application during winter. In the FP system, black oats and wheat were cultivated, while FPS utilized white oats and ryegrass. In the EI system, peas (without N application) and wheat were cultivated. In the 4‐years preceding the trial, the area was cultivated in a no‐till system with maize–soybean during summer and black oat–wheat in winter. Our results reveal distinct differences in soil properties among the systems, with FPS demonstrating greater soil acidity (pH of 4.4 at 0–5 cm) caused by higher N application than FP and EI systems. The lower soil pH altered soil nutrient dynamics, with decreased available Ca, Mg and K and increased Cu, Fe, Mn and Zn. Furthermore, nutrient availability varied, with EI having more inorganic N and DON at 0–40 cm compared with FP, but less in deeper soil (40–100 cm). Notably, EI system had more soil carbon (175 Mg ha −1 ) compared with FP (161 Mg ha −1 ), a relative annual increase of 1.8 Mg ha −1 year −1 over 8 years. These findings underscore the potential of EI to promote soil carbon, thereby contributing to climate change mitigation and soil health improvement.