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

Surface sealing is determined by aggregate disintegration and clay dispersi on, which in turn depend on aggregate wetting rate, and soil sodicity and t exture. We hypothesised that soil susceptibility to seal formation increase s 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 infilt ration rate (IR) and runoff, in cultivated soils varying in clay content an d 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 simulate d 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. I n soils with low clay content (8.8%), the effect of WR on seal formation wa s negligible, whereas effect of ESP was significant. Conversely, in clay so ils (>52.1%), WR had a predominant effect on IR and runoff, while the effec t of ESP was notable yet secondary to that of WR. The soils with intermedia te clay content (22.5-40.2% clay) were the soils most susceptible to seal f ormation, with WR and ESP having moderate effects on seal formation. Effect s of WR on aggregate disintegration and seal formation increased with incre asing clay content and aggregate stability. Conversely, the role of ESP in determining sealing decreased with an increase in clay content and in WR.