EFFECT OF ANTECEDENT SOIL-MOISTURE ON SPLASH DETACHMENT UNDER SIMULATED RAINFALL

Antecedent soil water content is an important variable affecting soil erosion processes and may be responsible for much of the variation in splash and wash erosion rates. The purpose of this study was to determine the effect of antecedent water content on splash detachment and on soil and hydraulic variables that control splash. Five soils ranging in texture from sandy loam to clay were exposed to simulated rainfall with an intensity of approximately 64 mm h−1for 1 h. Wash, splash, runoff, and infiltration were measured for near-saturated (−0.5 kilopascal) and air-dried soils in 0.14 m2Al erosion pans. Changes in the soil surface were monitored with a fall-cone device. Prewetting significantly reduced runoff occurring over a 60-minute rainfall period for the Heiden clay only. Prewetting reduced splash detachment rates for all soils except the Miami silt loam, with the greatest reduction for the Heiden clay. Total splash for the air-dried and prewetted Heiden clay was 770.1 and 169.4 g in 60 minutes, respectively. Prewetting increased soil shear strength following 60 minutes of rainfall for all soils. Development of a surface seal controlled the amount of soil detached from the Miami silt loam. Miami silt loam had the highest final shear strength values for air-dried and prewetted soils and the highest difference between initial and final shear strength (Δτ) among prewetted soils. Prewetted wash and splash sediment size was larger than that for air-dried sediments. Antecedent soil moisture conditions prior to rainfall influenced the amount of splash detachment and the physical processes that control amount of splash. © 1990 Williams & Wilkins.