Nutrient Transport as Affected by Rate of Overland Flow

Little information is currently available concerning the effects of varying flow rate on nutrient transport by overland flow. The objective of this study was to measure the effects of overland flow rate on nutrient transport following the application of beef cattle or swine manure to plots containing 0, 2, 4, or 8 Mg ha-1 of corn residue. After addition of residue materials to 0.75 m wide by 2.0 m long plots, beef cattle or swine manure was added and the plots were then either disked or maintained in a no-till condition. Three 30 min simulated rainfall events, separated by 24 h intervals, were applied at an intensity of approximately 70 mm h-1. The transport of dissolved phosphorus (DP), particulate P (PP), total phosphorus (TP), NO3-N, NH4-N, total nitrogen (TN), and soil loss was measured. Nutrient load from the plots on which manure was applied was not significantly affected by the amount of corn residue on the soil surface. Transport of DP in runoff was greater under no-till than till conditions. Rate of overland flow significantly affected PP and TP load. The transport of NO3-N and TN was affected by runoff rate but was not significantly influenced by tillage. Both tillage and runoff rate were found to affect the transport of NH4-N in runoff. Soil loss was significantly influenced by the amount of residue on the soil surface and runoff rate. Tillage condition and runoff rate should be considered when nutrient transport from land application areas is estimated