Influence of Forest-Pasture Conversion on the Erodibility of a Dystrophic Red Yellow Latosol with Different Deforestation Temporalities in the Southwestern Amazon

Abstract

The objective was to evaluate the erodibility of a Dystrophic Red Yellow Latosol from the Mutum Paraná River sub-basin to understand the influence of forest conversion and different pasture temporalities on its physical structure and the potential for sediment release after surface samples undisturbed were subjected to the Inderbitzen experiment. Tests of Mechanical Resistance to penetration and physical parameters under forest and pasture conditions were carried out. A simulation of surface runoff by water spraying (Inderbitzen) was carried out to analyze the disaggregation and transportability of particles. The erodibility equation (K factor) was applied, and the Limits of Consistency were defined to measure the Plasticity Index of the soil that qualifies its erodibility. The pasture samples submitted to the experiment indicated soils of low susceptibility to erosion, even under conditions of maximum slope of the area (17°) and under intense simulated flow (3 L and 6 L min-1) of sprinkler, not showing large losses of sediments or intense surface degradation. There was a relation between soil physical properties and the response of the sample in the experiment. Samples with higher total porosity (r = 0,89) and lower apparent densities (r = -0,88) showed higher disaggregation. There was a significant correlation between the simulated samples that showed lower sediment losses, with a higher percentage of clay (r = -0,65). Samples with a higher percentage of total sand indicated higher percentages of disaggregation (r = 0,68). Erodibility data obtained by the K-factor equation and Plasticity Index endorsed the low soil erodibility