SEAL FORMATION AND INTERRILL SOIL-EROSION

Interrill soil erosion depends primarily on soil detachment by raindro p impact (splash) and the transport capacity of thin sheet flow. Both splash and sheet flow erosion depend on soil surface properties. The p urpose of this study was to investigate the effect of seal formation o n interrill soil loss. Samples of three soil types - a Typic Chromoxer ert, a Calcic Haploxeralf and a Typic Rhodoxeralf - with various natur ally 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 conductivit y (EC) of the TW and SW was 0.8 and 5.0 dS m-1, respectively. Seal for mation was characterized by the final infiltration rate (FIR) and amou nt of runoff . Seal formation was enhanced with an increase in soil so dicity and a decrease in water salinity for each soil type. Nearly 70% of the variation in FIR (and seal formation) was explained by water s alinity 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 wi th an increase in soil clay content. Seal strength, as inferred from s urface pitting by impacting raindrops, decreased with an increase in c lay content, and was inversely related to soil erosion.