Evaluation of Soil Erosion Risk from Weathering Effects on K Factor of RUSLE in Cobija, Bolivian Amazonia

Abstract

Soil erosion by water is a serious problem in the Amazonia region of Bolivia. In the area of Cobija, Bolivia, around 8 Mg ha^-1 of Amazon soil is lost to the nearby watershed annually. The physical weathering of soils under natural conditions is one of the key processes for understanding structural changes in the soil. The soil erodibility (K) factor in RUSLE represents the susceptibility of soils to erosion, which can be measured with the standard unit plot experiment or through calculation with particle sizes and organic matter. Soil weathering affects soil particle distribution that is closely related to the K factor. Therefore, the purpose of this research is to evaluate and determine the change in the distribution of soil particles as well as the K value. The experiment was conducted in a laboratory setting. A total of 120 cans containing 1 g of soil each were used and treated with different periods and volumes of water added to represent weathering. The simulated weather conditions were set in line with conditions observed in Bolivian Amazonia. The pipette method was used to determine the distribution of soil particles. The results indicated slight changes in the distribution of the soil particles, reducing the percentage of fine sand and increasing the silt content, which affected the K factor as well as the estimate of soil losses based on RUSLE.