Characterizing Water Dependent Soil Repellency with Minimal Parameter Requirement

Abstract

Soil water repellency varies nonlinearly with soil moisture, describing a repellency versus water content curve. Despite this water dependence, soil repellency is usually characterized by repellency indexes measured at fixed soil water content. We provide a statistically robust yet simple method to determine water repellency at a range of soil water contents, by proposing alternative water-dependent soil repellency parameters derived from the molarity of an ethanol droplet (MED) test. Useful correlations are found between some of these proposed repellency parameters, such is the case of'the integrated area below the repellency curve, which is found to be strongly correlated with the soil water content at minimum repellency, Consequently, an efficient strategy for describing the repellency versus water content curve is designed based on a combination of parameter interdependence and a minimum number of determinations necessary. Following this strategy, only 27 samples are sufficient (p < 0.05) to characterize the water-dependent repellency of the studied soil. The integrated area below the repellency curve is proposed as the key Index for repellency characterization. Furthermore, a new combined parameter IRDI (Integrative Repellency Dynamic Index) is defined as a measure of the average water dependent repellency. This allows simple comparisons of the whole water repellency behavior among different soils by coalescing the repellency curve into a single characteristic value.