Agroforestry and Grass Buffer for NPSP Reduction From Row Crop Watersheds.

Three decades after the implementation of the Clean Water Act in the 1970s, nonpoint source pollution (NPSP) remains a major challenge in protecting and restoring water quality.  Despite improvements in soil conservation practices, crop rotation and nutrient management programs, significant concerns still exist regarding soil erosion and nutrient runoff from agriculture.  The objective of this study was to examine NPSP reduction as influenced by agroforestry and grass buffers in watersheds under row crop management.  A paired watershed study consisting of agroforestry, contour grass buffer, and control treatments with a corn-(Zea mays L.)-soybean [Glycine Max (L.) Merr.] rotation in MLRA 113 Central Claypan Areas was used to examine treatment effects on runoff, sediment, and nutrient losses.  Runoff samples were collected after each measurable runoff event using ISCO samplers and composite samples were analyzed for sediment, total nitrogen (TN) and total phosphorus (TP) for the 2004 to 2008 period.  Buffers reduced runoff by 19% compared to the predicted value by the calibration equation.  The three watersheds on average lost 17.9 kg sediment ha^-1 yr^-1.  The agroforestry buffer treatment reduced sediment, TP, and TN losses by 30, 11, and 26% compared to the predicted value.  The reduction in the grass buffer treatment was 28, 13, and 22% for respective parameters.  Results indicate that agroforestry and contour grass strip practices effectively reduce NPSP loss from corn-soybean watersheds.  Findings from this study can be used to design improved agroforestry practices for ecosystem services by minimizing the amount of land taken out of production while optimizing environmental benefits.