Seal Formation, Runoff, and Interrill Erosion from Seventeen California Soils
1993
Soil surface crusts and seals reduce soil infiltration rate, increase soil strength, and may increase erosion by increasing runoff. Among the most important factors determining amounts of erosion are the soil chemical and physical properties that determine soil sealing and erodibility. Soil splash and wash erosion, runoff, and splash volume were measured for 17 soils, which ranged in clay content from 80 to 360 g kg⁻¹, exchangeable sodium percentage (ESP) from <1 to 56%, and organic C from 4 to 70 g kg⁻¹. The experiments were performed on 30 by 30 cm plots on a 9% slope using simulated rainfall applied at a constant 40 mm h⁻¹ as 3.2-mm-diam. drops falling 2.5 m with a kinetic energy of 24.5 J mm⁻¹ m⁻². Water splash and runoff and soil splash and wash materials were collected at 5-min intervals during each 1-h rain. Soils that had 31 to 70 g kg⁻¹ organic C and 2.4 to 10.7% citrate-bicarbonate-dithionite (CBD) extractable Fe plus Al did not form seals, infiltration rate remained high throughout the rainfall run, and neither runoff nor erosion occurred. Soils with < 200 g kg⁻¹ clay, 30 g kg⁻¹ organic C, and 2.0% CBD-extractable Fe plus Al readily formed seals that reduced the infiltration rate and the total volume of water infiltrated and increased the volume of runoff water and mass of soil eroded. These data suggest that the formation of soil seals increases runoff and erosion through the early stages of seal development.
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