Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/1996
Publication Date: N/A
Interpretive Summary: Soil erosion is a multifaced process involving detachment and transport of soil particles by rainfall and runoff. Each one of these subprocesses is influenced to different degrees by different factors. Rainfall is the most important erosive agent in interrill spaces on upland areas. It detaches soil particles, causes surface sealing, and transports through splash action soil material downslope and to the rill system where it is transported by concentrated flow. While these subprocesses have been recognized, little information is available about the relative role of the soil medium in these different processes. This study reports the findings of a study in which the composition of splash by rainfall and wash by surface runoff relative to the original textural composition is measured for two rainstorm intensity regimes and for two loess soils, one from Mississippi, the other from Saskatchewan. The results show that the clay size fraction in splash is similar to that of the original soil, but that preferential removal of clay size particles took place in surface runoff at least for the Saskatchewan soil which clay fraction is dominated by smectite. The more aggregated Grenada soil from Mississippi did not show preferential removal of clay. This information is helpful in interpreting sources and processes of soil erosion by different erosive agents.
Technical Abstract: Physical processes occurring during surface seal formation through a rainstorm are well understood, but limited information is available regarding the quantity and particle size distribution of splash and runoff at certain time intervals. In this study, we evaluated the quantity and particle size distribution of suspensions of both splash and interrill runoff in two loess soils with different mineralogy and aggregate stability, and somewhat different particle size distribution, but similar organic matter content. The soils were subjected to simulated rainstorms of approximately 40 mm h**1 and 100 mm h**1 intensities. the amount of splash was about four times higher for the Saskatchewan soil (Typic Haploboroll) with high smectite than for the Grenada soil (Typic Fragiudalf) which is rich in Fe-oxyhydroxides. The amount of splashed material and sediment load increased with increased rainfall intensity for both soils. Splash was decreased after wetting of the soil surface. The decrease in splash rate was more rapid with high rainfall intensity. The amount of clay size particles of the splash was similar to the original soil material. Microcorphologic observations confirmed the fluctuations in clay content with time, at the very surface. Soil materials splashed were much higher (10 to 20 times) than the interrill runoff losses. The later was controlled by the rainfall intensity. The soil material from Saskatchewan, produced more than 11 Mg ha**1 of interrill runoff with low rainfall intensity. High rainfall intensity produced 10 times more soil loss than low rainfall intensity. High amount of soil loss clearly shows that the Saskatchewan soil would benefit from erosion control measures.