Wheat Strip Effects on Nutrient Loads Following Variable Manure Applications

Abstract

Vegetative filters have been found to significantly reduce nutrient loads in runoff. This study was conducted to: (1) evaluate the effects of a narrow wheat strip, varying manure application rates, and different overland flow rates on runoff nutrient loads following application of beef cattle manure; (2) determine the upper capacity of a narrow wheat strip to reduce nutrient loads by applying excessive amounts of manure; and (3) compare the effectiveness of narrow wheat strips and grass hedges in reducing runoff nutrient loads. A 1.4 m wide strip of actively growing winter wheat was located at the bottom of selected 0.75 m wide by 4.0 m long plots. Three 30 min simulated rainfall events, separated by 24 h intervals, were applied at an intensity of 70 mm h-1 to the plots. The wheat strips were effective in reducing runoff loads of NO3-N, NH4-N, and total nitrogen (TN). Runoff loads of dissolved reactive phosphorus (DP), particulate phosphorus (PP), total phosphorus (TP), NH4-N, and TN were significantly influenced by manure application rate. The application of manure to meet a 2-year rather than a 1-year corn P requirement did not significantly increase DP, PP, or TP loads. However, application of manure to meet a 4-year P requirement resulted in DP, PP, and TP loads that were significantly greater than those obtained for a 2-year P requirement. Runoff rate significantly affected each of the measured water quality parameters. The actively growing wheat strips were much less effective than grass hedges in reducing runoff nutrient loads.