Avaliação dos atributos físicos da qualidade do solo em sistema de uso no sul do Amazonas, Brasil

Abstract

The physical attributes of the soil play a fundamental role in determining the quality and capacity of the soil to provide ecosystem services such as water retention and nutrient supply in different land use systems. With this in mind, we aimed to assess whether different land use systems affect the soil physical attributes. Four land use systems (LUS) were selected in Humaitá, Amazonas, Brazil: Natural Forest, Pasture, Cassava, and Acai. A transect with fifteen sampling points was carried out in each LUS. At each point, disturbed and undisturbed soil samples were collected in the 0-5 cm, 5- 10 cm, 10-20 cm, and 20-40 cm layers, dried in the shade, and crushed to obtain aggregates and fine soil. In the laboratory, the following attributes were analyzed: soil density, soil penetration resistance, granulometric analysis, soil porosity, geometric mean diameter, weighted mean diameter, aggregate class, volumetric soil water content, and soil organic matter. The results were subjected to statistical analysis, verifying the assumptions of normality and homoscedasticity at a 5% significance level (P≥0.05). ANOVA was then carried out; if significant, the Tukey test was conducted at a 5% significance level (P<0.05). It was found that the pasture showed an increase in soil density of 26% in the 0-5 cm and 5-10 cm layers, compared to the areas under natural forest, cassava, and acai. Soil penetration resistance varied significantly (P<0.05) between pasture and natural forest, with an increase of 34%. The total soil porosity for the areas under acai, cassava, and pasture was similar (P≥0.05) in the 0- 5 cm and 5-10 cm layers. However, the pasture in the 0-5 cm and 5-10 cm layers showed significant differences from the natural forest, with a 7% and 8% reduction in both layers (P<0.05). We conclude that the conversion of natural forests into LUSs, such as pasture, cassava, and acai, causes changes in the physical attributes of the soil, affecting soil quality.