Agroforestry and grass buffer influences on water infiltration for a grazed pasture system
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Agroforestry and grass buffers are often adopted as an alternative resource management system in agriculture for environmental and economic benefits. The objective of the study was to compare agroforestry (AgB) and grass buffer (GB) systems under rotationally grazed (RG) and continuously grazed (CG) pasture systems on water infiltration measured using ponded infiltration and tension infiltration methods. Buffer areas were fenced which prevented cattle grazing in buffer areas. Soils at the site are Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs). Infiltration rates were measured using ponded ring infiltration units in 2007 and 2008 for the four treatments with six replicates. Infiltration rate as a function of tension (at 50-, 100-, and 150-mm) was also measured using a tension infiltrometer in 2007. Water infiltration parameters were estimated using Green-Ampt and Parlange infiltration equations. Quasi-steady state infiltration rates (qs) and field-saturated hydraulic conductivity (Kfs) for the buffers were about 30 and 40 times higher compared to pasture treatments, respectively. Green-Ampt and Parlange models appeared to fit measured data with r2 values ranging between 0.91 to 0.98. The infiltration rate in 2007 for the GB treatment was the highest (221.4 mm h-1) and for the CG treatment was the lowest (3.73 mm h-1). Estimated sorptivity (S) and saturated hydraulic conductivity (Ks) parameters were higher for buffers compared to the pasture treatments. Grazing reduced infiltration rates for the pasture (CG and RG) treatments. Results show that the buffer areas have higher infiltration rates which imply lower runoff compared to pasture areas.