Effect of Corn and Soybean Canopy on Soil Detachment by Rainfall

Abstract

ABSTRACT RATES of detachment of soil particles by raindrop impact were measured in the field under corn and soybean canopies in ten minute simulated rainstorms of 40, 50, 75 and 100 mm/h intensity. The percentage of the rainfall volume reaching the ground surface decreased with increasing canopy cover only slightly until 50% cover was attained, and then more rapidly to reach about 40% of that in open ground with 90% cover. Detachment rates under corn increased with canopy cover and were 1.5 to 2.0 times greater at 90% cover than with no cover at all. A similar increase in detachment occurred under soybean at the lowest rainfall intensity, but detachment rates decreased at the other intensities so that at 90% cover they were 20 to 60% of those for bare soil. Inverse relationships were obtained between detachment and rainfall energy for all intensities under corn and at the lowest intensity under soybean; positive relationships were found for the other intensities under soybean. Existing approaches to modeling soil detachment under plants need to be modified to allow for cases where the volume and energy of the rain do not decrease in direct proportion to increases in effective canopy area and where the transformed raindrops are a more efficient detaching agent than the natural rainfall.