Influence of Agroforestry and Grass Buffers on Infiltration for a Grazed Pasture System.

Agroforestry and grass buffers have been adopted as an alternative resource management system in agriculture for environmental and economic benefits. The objective of this study was to measure infiiltration as affected by agroforestry (AgB) and grass buffer (GB) systems relative to rotationally grazed (RG) and continuously grazed (CG) pasture systems. Pasture and GB areas included red clover (Trifolium pretense L.) and lespedeza (Kummerowia stipulacea Maxim.) planted into fescue (Festuca arundinacea Schreb.) while AgB included Eastern cottonwood trees (Populus deltoids Bortr. ex Marsh.) planted into fescue. Soils at the site were Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalfs). Soil infiltration rates were measured using ponded ring infiltration and tension infiltration units with six replicates.  Treatments included AgB, GB, RG and CG.  For ponded infiltration, a single steel infiltration ring (25 cm diameter and 30 cm length) was vertically driven 15 cm into the soil. A 5-cm positive hydraulic head was maintained inside the ring for 180 minutes using a Mariotte system during data collection. Tension infiltrometer measurements were made at 5, 10, and 15-cm soil water tension. Infiltration data were fit to the physically-based Green and Ampt infiltration model.  The quasi-steady ponded infiltration rates for the buffer treatments were about 10 times higher compared to the rotationally grazed and continuously grazed pasture treatments.  Reduced infiltration was attributed to increased soil bulk density from cattle traffic in the pasture areas.  This study illustrates the benefit of enhanced infiltration in non-grazed buffer areas which will reduce runoff and nonpoint source pollution from grazed sites.