SEAL FORMATION AND INTERRILL SOIL-EROSION

Interrill soil erosion depends primarily on soil detachment by raindrop impact (splash) and the transport capacity of thin sheet flow. Both splash and sheet flow erosion depend on soil surface properties. The purpose of this study was to investigate the effect of seal formation on interrill soil loss. Samples of three soil types - a Typic Chromoxerert, a Calcic Haploxeralf and a Typic Rhodoxeralf - with various naturally occurring exchangeable sodium percentage (ESP) levels were used. The soils were exposed to simulated rain using three different waters: distilled (DW), tap (TW), and saline (SW). The electrical conductivity (EC) of the TW and SW was 0.8 and 5.0 dS m-1, respectively. Seal formation was characterized by the final infiltration rate (FIR) and amount of runoff . Seal formation was enhanced with an increase in soil sodicity and a decrease in water salinity for each soil type. Nearly 70% of the variation in FIR (and seal formation) was explained by water salinity and soil ESP. Most of the variation in soil loss was explained by clay content, soil ESP, and water salinity. With the exception of samples with ESP <5 rained on with DW, soil loss increased linearly with an increase in soil clay content. Seal strength, as inferred from surface pitting by impacting raindrops, decreased with an increase in clay content, and was inversely related to soil erosion.