Chemical attributes and fractionation of soil organic matter in integrated and conventional agricultural production systems in the Midwest, Brazil

Abstract

Replacing conventional management with conservation practices, like crop-livestock integration and agroforestry, can boost soil organic carbon. However, humic fractions are more sensitive to management changes. This study evaluated the impact of conventional and integrated systems on soil quality, focusing on fertility and organic carbon content in the Atlantic Forest biome. Samples were collected at depths of 0–5 cm and 5–10 cm, with 5 replicates per treatment, and each replicate consisting of 5 sub-replicates collected randomly. The analysis included soil organic carbon, chemical attributes of the soil, chemical fractionation, stocks of carbon in chemical fractions of soil organic matter, and variations in carbon stocks for each chemical fraction. The treatments evaluated were Agroforestry in the pasture phase; Agroforestry in the crops phase; Crop-livestock integration with pasture; Crop-livestock integration with crops; Cultivated Forest; Conventional tillage system; No-tillage system; Permanent pasture, and degraded pasture. The results obtained were analyzed for normality and homogeneity of the data using the Shapiro-Wilk and Bartlett tests, respectively. Subsequently, the data was subjected to analysis of variance using the F test, and the mean values were compared with each other using the Scott-Knott test, both at 95% confidence level in a completely randomized design. Lower pH values were found in the degraded pasture, reaching 3.8. The conventional tillage and no-tillage systems had higher phosphorus levels than the other evaluated systems. Agroforestry systems showed statistical differences based on the crops grown between the rows. The highest soil organic carbon contents at 0–5 cm depth were found in pasture and crop-livestock integration areas. There was a 28.7% increase in organic carbon in the agroforest with pasture compared to that with crops. The pasture phase of the agroforestry system exhibited positive variations in labile carbon fractions compared to the crop phase. Both crop-livestock integration and permanent pasture systems significantly improved the quality, content, and stock of the organic soil fraction, showing higher quality indexes than the other systems.