Infiltration and Runoff for Variable Rainfall As Affected By Vegetative Buffers.

Due to climate change, more intense rainfall storms are anticipated in the future. A need exists for conservation practices which enhance infiltration to handle this challenge. The purpose of this study was to measure infiltration as affected by stiff-stemmed vegetative buffers (switchgrass, Panicum virgatum, L.) relative to row crop areas. Experiments were conducted on a well-drained Monona silt loam (fine-silty, mixed, superactive, mesic Typic Hapludolls). Row crop areas were in a corn (Zea mays L.)/soybean (Glycine max) rotation. Three landscape positions were monitored as affected by vegetative buffers: within the grass hedge, within a deposition zone (0.5 m upslope from hedge) and within a row crop zone (7 m upslope from the hedges). Treatment areas were monitored using ponded infiltration; the Green-Ampt and Kostiakov infiltration parameters were fitted to infiltration curves with coefficients of determination of 0.99 or higher. Comparisons among treatments were made using a constant rate storm of 25 mm/hr for 2 hours, and with a Type 2 variable rainfall storm with 125 mm rainfall in 24 hours. Significant treatment differences occurred: soils under grass hedges had saturated hydraulic conductivity 5.3 times higher than the row crop area and 36 times higher than the deposition zone. For the constant rate storm, no runoff occurred from either the grass hedge or row crop areas, however about 75% of the rain was lost as runoff for the deposition zone. No runoff occurred within the grass hedge area while more than thirty percent of the rainfall was lost as runoff for the row crop and deposition areas for the 125 mm storm. These results indicate vegetative buffers increase infiltration and reduce runoff for agricultural watersheds. Incorporation of conservation buffers in watersheds may reduce impact of high intensity climate-induced rainfall events.