Interrill Erodibility Affected by Cropping Systems and Initial Soil Water Content

Abstract

The effects of continuous soybean and continuous corn cropping systems and initial water content (IWC) of the soil on runoff, soil loss, and interrill erodibility were studied in the laboratory. Samples of a Mexico silt loam (Udollic Ochraqualf) were packed in 0.3-m-wide 1.0-m-long soil beds and subjected to a series of simulated rainfall events. Differences in measured runoff and soil loss between the cropping systems were less than 1.0%. The IWC did not affect soil loss during the initial event, but it had a significant effect (p < 0.05) during the following event where an increase in mean IWC from 4 to 15% decreased mean soil loss from 12.9 to 10.7 g min1 m2. Cropping did not influence interrill erodibility (Ki) calculated from a power relationship with rainfall intensity. There was a negative linear relationship between Ki and IWC. Calculating Ki from rainfall intensity and runoff rate improved the relationship between Ki and IWC. Our results indicate that interrill soil losses and erodibility are sensitive to IWC and need to be considered in interrill erosion research and modeling, particularly for silt loam soils. Our results also indicate that including a runoff rate term in the equation used to predict interrill erosion will improve its prediction accuracy.