Qualidade do solo em diferentes sistemas de uso e manejo no bioma Pampa

Abstract

Land use directly influences the soil's ability to provide ecosystem services. Conservation management practices help maintain this capacity by stimulating or inhibiting characteristics that promote soil sustainability. This study aimed to identify the impact of different land use and management systems on soil physical attributes, along with variables representing sustainability, such as total organic carbon and microbial biomass carbon. The study area is located in the Campanha region of Rio Grande do Sul, in the Pampa biome, with the predominant soil being Haplic Luvisol and a subtropical climate. Five land use systems were evaluated: monoculture cropping (LE), integrated crop-livestock (LP), pasture with improved native field (PC), pasture with Tifton (PT), and legal reserve (RL). Twelve sampling points were selected, with four replicates randomly allocated in each third of the terrain. The predominant soil textures were silty-loam (66.6%), sandy-loam (20%), and clay-loam (13.3%). Attributes assessed included density, macroporosity, microporosity, total porosity, total organic carbon, carbon stock, organic matter percentage, and microbial biomass carbon. Statistical analyses were performed using RStudio, where data were tested for normality and homogeneity of variance using the Shapiro-Wilk and Levene tests, followed by Kruskal-Wallis/Dunn, ANOVA/Tukey HSD, and Welch’s ANOVA/Games-Howell, as appropriate. Principal Component Analysis (PCA) was conducted to identify the interactions between soil attributes and land uses. Soil density and microporosity did not differ among the systems in the 0.0-0.2 m layer. In the 0.0-0.05 m layer, total porosity, total organic carbon, and carbon stock showed no significant differences across systems. The system under Pasture – Tifton and improved native field had the highest macroporosity values in the 0-0.05 m layer, with the former showing the highest averages across all evaluated layers. Total porosity in the 0.05-0.10 m layer was higher in the Pasture-Tifton and Legal Reserve systems (0.45 and 0.44 m³ m⁻³, respectively), and in the 0.10-0.20 m layer, the Legal Reserve system had the highest value (0.42 m³ m⁻³). Extreme Cropping had the highest total organic carbon and carbon stock in the 0.05-0.20 m layers. Microbial biomass carbon was higher in the Pasture-Native Field (0.0-0.10 m) and Legal Reserve (0.0-0.20 m) systems. Principal Component Analysis revealed correlations among the evaluated attributes, with soil density negatively correlating with microbial biomass carbon and total porosity, and a positive relationship between macroporosity and total organic carbon in the Pasture-Tifton system. Monoculture Cropping stood out for its total organic carbon content but had lower physical and biological attributes compared to other systems. Principal Component Analysis, relating density, microporosity, and macroporosity, suggested that soil compaction might be reducing soil functionality. Microbial biomass carbon proved to be the most sensitive indicator of management and environmental conditions.