Influence of soil texture and organic matter on the erosion resistance of sloped agricultural soils of the Peruvian Amazon

Abstract

Soil erosion is a major driver of soil degradation in the Peruvian Amazon, compromising the productivity and sustainability of agricultural systems established on sloping terrain. This study evaluated the relationship between soil texture, soil organic matter (SOM) and relative erosion susceptibility, expressed through the comprehensive soil erosion resistance (CSER) index, across 48 plots distributed among four sites representing contrasting land-use systems: oil palm in Lamas (LA-OP), primary forest in Picota (PI-FO), coffee in Alto Saposoa (RM-CO) and rice in Yurimaguas (YU-RI). The CSER was calculated using principal component analysis and membership functions based on structural, textural and erodibility indicators. The results revealed positive correlations between CSER and clay content, elevation and SOM, whereas sand content was negatively correlated with the index. Redundancy analysis showed that land use, soil texture and SOM jointly explained 90.34% of the variation in the evaluated indicators, with clay content accounting for the largest independent contribution (32.58%). Generalised linear models indicated that a one-standard-deviation increase in SOM was associated with a 0.04-unit increase in CSER, whereas an equivalent increase in silt content was associated with a 0.04-unit decrease in CSER. In contrast, clay exhibited a positive nonlinear relationship with CSER. These findings suggest that clay and SOM act as protective factors by enhancing soil erosion resistance, whereas higher silt contents are associated with greater soil vulnerability to erosion.