Prewetting rate and aging effects on seal formation and interrill soil erosion

Seal formation and interrill soil erosion are affected by antecedent soil water content. We hypothesized that other time-dependent variables, such as prewetting rate and aging duration, would also affect seal formation and interrill soil loss. Aggregates (4-9.5 mm) from a Calcic Haploxeralf and a Typic Chromoxerert were packed in 400 x 200 mm pans, placed under a rainfall simulator, and prewetted by either (i) a matrix potential of -0.2 kPa, or (ii) 5 mm of rain at rates of 1, 6, or 30 mm h(-1). After prewetting, the aggregates were left to age for 15 min or 18 h, then subjected to 60 mm of distilled water simulated rainfall of moderate (12.4 kJ m(-3)) kinetic energy. Final infiltration rate increased from 5.0 to 26.6 mm h(-1), percent runoff decreased from 59.1 to 2.5, and soil loss decreased from 302 to 5.4 g m(-2) as prewetting rate decreased from 30 to 1 mm h(-1) in the Typic Chromoxerert; similar results were observed in the Calcic Haploxeralf. For aggregates from both soils, aging increased the final infiltration rate and decreased runoff, only when partial slaking was achieved by slow and moderate prewetting rates. Conversely, 18 h of aging also effectively decreased soil loss in the fast prewetting rate in the aggregates of both soils. Surface sealing was enhanced by aggregate slaking and breakdown. Slaking was reduced by slow prewetting and cohesive forces. Aging increased the cohesion forces between soil particles and reduced the latter's susceptibility to sealing and erosion.