Narrow Grass Hedge Effects on Phosphorus and Nitrogen in Runoff Following Manure and Fertilizer Application

ing beef cattle feedlot manure under tilled and n-till conditions. This study was conducted on a steep (12% average slope) Monona silt loam (fine-silty, mixed, superactive, mesic Typic Hapludolls) soil near Treynor, Iowa. The experiment was a split-plot with no-till and disked systems as main plots and subplots of manure, fertilizer, and check with or without a grass hedge. A rainfall simulator was used and runoff was collected from both the initial and the following wet simulations. Only 38% of the no-till plots and 63% of the disked plots had any runoff during the initial 6.4 cm hr−1 water application. A single narrow grass hedge reduced runoff concentrations of dissolved P (DP) by 47&, to bioavailable P (BAP) by 48%, particulate P (PP) by 38%, total P (TP) by 40%, and NH4−N by 60% during the wet simulation on the no-till plots receiving manure, compared with similar plots with no hedges. The corresponding reductions in concentrations as a a result of a grass hedge for DP, BAP, PP, TP, and NH4−N on the disked plots were 21, 29, 43, 38, and 52%, respectively. Runoff NH4−N concentrations from fertilizer applied to the disked plots was reduced by 61%, NO3−N by 21%, and total N (TN) by 27% during the wet simulation when grass hedges were used. Grass hedges also reduced total quantities of DP, BAP, TP, and NH4−N during the wet simulation. The TP loss was 3.3% of applied P fertilizer and was 0.3% of applied manure P. Narrow grass hedges were effective in reducing P and N losses in runoff from both manure and fertilizer application.