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Physical and Chemical Crusting Processes Affecting Runoff and Erosion in Furrows

Surface sealing and soil crusting increase runoff and erosion dramatically on many soils. The rate of this increase may depend on the extent and predominant processes of soil crusting. The objective of this study was to evaluate the effects of soil crusting processes on infiltration and erosion, particularly rill erosion. Six field plots (3.5 by 0.9 m) with V-shaped furrows with sideslopes of 0.2 m m -1 and gradients of 0.11 m m -1 were established on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Kanhapludult). Treatments included control, gypsum (surface-applied, 5 Mg ha -1 ), screen cover, and the combination of cover and gypsum. Two consecutive rains at an intensity of 90 mm h -1 were applied to each treatment, and soil surface was allowed to dry between rains. Statistical analyses showed the main effects of cover and gypsum, as well as their interaction, significantly increased final infiltration rate (FIR) on this soil. During Event 1, FIRs were increased by 26% for either cover or gypsum treatment and by 132% for the combined treatment. Although the effectiveness of all treatments was reduced during Event 2, the combined treatment still showed 56% increase over the control treatment. As a result of runoff reduction, overall soil loss from the two events was reduced by 64, 28, and 88% for the cover, gypsum, and combined treatments, respectively. Minimizing seal formation by either cover or gypsum delayed rill formation and reduced rill erosion to a similar extent, but the combination of the two was much more effective. For this soil, both chemical (dispersion) and physical (raindrop impact) forces, as well as their interaction, are critical in crust and seal formation.