Wetting rate, sodicity, and soil texture effects on infiltration rate and runoff

Surface sealing is determined by aggregate disintegration and clay dispersion, which in turn depend on aggregate wetting rate, and soil sodicity and texture. We hypothesised that soil susceptibility to seal formation increases when the aggregate wetting rate (WR) is increased, and that the effect of WR depends on soil texture and soil sodicity. The objective of this study was to investigate the effects of WR on seal formation, by observing infiltration rate (IR) and runoff, in cultivated soils varying in clay content and exchangeable sodium percent (ESP). Effects of 3 wetting rates (2, 8, and 64 mm/h) on IR and runoff from 6 Israeli soils exposed to 60 mm of simulated rain of deionised water were studied in the laboratory. The soils ranged in clay from 8.8 to 68.3% and ESP levels from 0.9 to 20.4. Effects of WR on soil infiltration rate and runoff depended on soil texture and soil ESP. In soils with low clay content (8.8%), the effect of WR on seal formation was negligible, whereas effect of ESP was significant. Conversely, in clay soils (>52.1%), WR had a predominant effect on IR and runoff, while the effect of ESP was notable yet secondary to that of WR. The soils with intermediate clay content (22.5–40.2% clay) were the soils most susceptible to seal formation, with WR and ESP having moderate effects on seal formation. Effects of WR on aggregate disintegration and seal formation increased with increasing clay content and aggregate stability. Conversely, the role of ESP in determining sealing decreased with an increase in clay content and in WR. am. ai L SR 029 W t ci s in A . et .