Runoff nutrient transport as affected by manure application rate, residue cover, and flow rate

Little information is available concerning the effects of varying flow rate on nutrient transport by overland flow from areas on which manure was previously applied. The objective of this field study was to measure the effects of varying flow rate on nutrient transport following the application of varying amounts of beef cattle manure to plots containing either no-residue or a wheat residue cover. Beef cattle manure was applied and incorporated into the soil in May 2010 to meet zero, one, two, four or eight year corn phosphorus requirements. Three 30 minute simulated rainfall events, separated by 24 hour intervals, were applied each week for five weeks in June and July 2010 at an intensity of approximately 70 mm hr^-1 to 0.75 m wide by 2.0 m long plots. The effects of manure application rate, residue cover and runoff rate on nutrient transport were then determined using ANOVA. The presence of a crop residue cover significantly increased the transport of dissolved P, total P, NO_3-N, NH_4-N, and total N in runoff but decreased soil loss. Multiple year manure applications may be economically wise but can contribute to elevated nutrient levels in runoff, especially the four and eight year manure application rates. Increasing runoff rates, which simulated longer slopes, also increased nutrient transport in runoff.