On-site effects of accelerated erosion on direct-physical soil quality indicators

Abstract

Accelerated soil erosion is a serious agricultural problem in South Africa limiting soil productivity and little it’s known about its effect on soil quality. This study aimed to provide a less laborious, less time consuming and inexpensive protocol of estimating the effects of accelerated erosion on the soil quality. An assessment was undertaken in sites showing threat of accelerated erosion using various direct physical soil quality indicators. Four sites with different soil types were identified at initial survey. In each of the sites, two areas were selected. These areas were then classified as Not Visibly Eroded (NVE) and Visibly Eroded (VE). Each measurement in all site was done in those area classified respectively. The most stable structure and consistency were observed in NVE areas. Medium and large stones were observed in VE areas in all soil types studied. The VE soils were lighter in colour compared to soil colour in NVE. Aggregate stability and moisture content were significantly higher for the NVE and VE areas. Difference in values of water stable aggregates between NVE and VE was clear which showed that stability of aggregates is important in determining soil susceptible to erosion. Bulk density values were slightly different for the two areas. However, there was no significant difference between the bulk density of NVE and VE. Differences between soil texture for NVE and VE areas are only apparent for the sand, clay and silt particles with no changes in textural class. For all soil types investigated, silt was vulnerable to accelerated erosion with respect to soil texture. The research has provided baseline protocol for using physical soil quality indicators to find out effects of accelerated erosion. Soil functionality is critical in the restoration process of soil quality, and the methods used here could be effectively applied in a broad range assessment of erosion impact.