Water infiltration influenced by agroforestry and grass buffers for a grazed pasture system

摘要

Agroforestry (AgB) and grass buffers (GB) are often adopted as alternative resource management tools in agroecosystems for environmental and economic benefits. The objective of this study was to compare the influence of AgB and GB systems under rotationally stocked (RP) and continuously stocked (CP) pasture systems on water infiltration measured using ponded infiltration and tension infiltration methods. Buffers were surrounded by a fence that prevented cattle from grazing within these areas. Soils at the site are Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Infiltration rates were measured using ponded ring infiltration units during 2 years for the four (AgB, GB, RP and CP) treatments with three replicates from two subareas within each treatment. Infiltration rate as a function of tension (at 50, 100, and 150 mm) was also measured using a tension infiltrometer. Water infiltration parameters were estimated using Green-Ampt and Parlange infiltration equations. Quasi-steady state infiltration rates (q _s ) and field-saturated hydraulic conductivity (K _fs ) for buffers were about 31 and 46 times higher as compared to pasture treatments, respectively. Green-Ampt and Parlange models appeared to fit measured data with r 2 values ranging from 0.91 to 0.98. The q _s (measured with ponded method) in the first year for the GB treatment was the highest (221 mm h−1) and for the CP treatment was the lowest (3.7 mm h−1). For both years, estimated sorptivity (S) and saturated hydraulic conductivity (K _s ) parameters were higher for buffer areas compared to the stocked pasture areas. Grazing reduced the infiltration rate for the pasture (RP and CP) treatments. Results show that the buffer areas have higher infiltration rates which imply lower runoff compared to pasture areas.