Assessing interrill erosion rate from soil aggregate instability index, rainfall intensity and slope angle on cultivated soils in central Greece

In order to develop a new formula for assessing interrill erosion rate by incorporating the soil aggregate instability index, β, erosion plots at seven sites in central Greece were used to measure interrill erosion rate under natural rainfall conditions during a 39-month period. Soils classified as Alfisols, Inceptisols and Entisols with slopes 7-21%, moderately well to excessively drained, clay to loamy textured, were studied. Runoff and total sediment were collected after each ponding rainfall event. The equation Ei=0.628βSt1.3e0.0967I30 was finally proposed (R2=0.939,P<0.001) to describe interrill erosion rate. The term, St represents the tangent of the slope angle, and I30 represents the maximum rainfall intensity in 30 min. The addition of the aggregate instability index to improve existing methodologies provide was considered to provide an easy to determine and reliable measure of soil erodibility. Validation with independent data showed that the model predicted interrill erosion well (R2=0.766, P<0.001). Therefore, the proposed model based on the aggregate instability index, β, has the potential to improved methodology for assessing interrill erosion rate.