STEMFLOW, RAIN THROUGHFALL, AND EROSION UNDER CANOPIES OF CORN AND SORGHUM

Modern soil erosion prediction technology, such as the Water Erosion Prediction Project, requires detailed information about plant status in the interrill and rill erosion processes. The total amount of rain that reaches the soil and is available for erosion under vegetated surfaces is a function of rain throughfall and stemflow. The objective of our research was to determine the effects, including the production of stemflow of canopies, of corn (Zea mays L.) and sorghum (Sorghum bicolor [L.] Merr.) on interrill soil erosion. A series of rainfall simulations of similar intensity (6.35 cm h-1) was performed in 1989 and 1990 on experimental plots of Cargill SX 383 corn and Garst 5503 sorghum grown on Cecil soil (clayey, kaolinitic, thermic Typic Kanhapludult). Runoff and sediment were collected at 5-min intervals over a 1-h period for two sets of treatments each under corn and sorghum: canopy and canopy minus stemflow. Stemflow, plant-height, and leaf-area data were collected from a total of 18 corn and 16 sorghum plants and used to estimate stemflow. Rain throughfall was estimated as the difference between total rainfall and calculated stemflow and was compared with observed runoff. Both corn and sorghum were observed to have high stemflow, the amount being highly correlated to total leaf area. Runoff under sorghum indicated that all the stemflow was potentially available for infiltration. Under corn, however, about one-third of the stemflow may have contributed to runoff. The average sediment concentration was not sensitive to canopy type. Erosion due to stemflow appeared negligible compared with that caused by throughfall.