Crusting, Runoff, and Erosion Response to Soil Water Content and Successive Rainfalls
- Yves Le Bissonnais and
- Michael J. Singer
Soil crusts reduce the water infiltration rate and may induce the erosion process by increasing runoff. We investigated the effects of initial soil water content and successive rainfalls on soil crusting, subsequent runoff, and erosion. Surface samples of Capay silty clay loam (fine, montmorillonitic, thermic Typic Chromoxerert) and Solano silt loam (fine-loamy, mixed, thermic Typic Natrixeralf) were packed into 0.37-m2 plots inclined at 9% slopes and subjected to simulated rainfall applied at 40 mm h−1 as 3.2-mm-diam. drops falling 2.5 m. Three successive 1-h rainfalls were applied to initially air dried or prewetted soils. Water splash, runoff, soil splash, and wash materials were collected at 5-min intervals. Post-rainfall photographs of crusted soil surfaces provided additional morphological evidence to support conclusions drawn from quantitative data. Prewetting reduced crust development, runoff, and erosion and the differences remained significant even during the third rainfall. For the initially air dry soils, erosion rates and runoff reached steady state after 25 mm of rain during the first rainfall, and were the same for the second and third rainfalls. For prewetted soils, runoff and erosion were lower, did not reach steady state during the first event, and increased during each subsequent rainfall. The infiltration rate for initially air dry soils was 20 times lower than for prewetted soils after 40 mm of the first rainfall, and remained 10 and 2 times lower after the second and third rain, respectively. The crust was still not completely developed on prewetted soils after 120 mm of cumulative rainfall.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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