Disposal of swine lagoon effluent by overland flow for forage production

The application of animal manure or lagoon effluent to agricultural land to supply plant nutrients is a traditional means of waste management. The benefit is not only to provide nutrients for plant growth, but also to provide a place for waste disposal. However, since land areas for this use are limited, there has been an increasing interest in disposal of wastes at rates far in excess of the agronomic rates. High rates of lagoon effluent could adversely affect water systems, crops and soils. Swine lagoon effluent was applied using overland flow at rates of 560, 1120, and 2240 kg N ha{dollar}rmsp{lcub}-1{rcub}yrsp{lcub}-1{rcub}{dollar} and ammonium nitrate (NH{dollar}rmsb4NOsb3{dollar}) at 560 kg N ha{dollar}rmsp{lcub}-1{rcub}yrsp{lcub}-1{rcub}{dollar} to a 5% and a 10% slope on a Marvyn loamy sand (fine-loamy, siliceous, thermic, Typic Kanhapludults). Hybrid bermudagrass (Cynodon dactylon L. "Russell") and annual ryegrass (Lulium multiflorum) were established as cover crops. Total forage yields significantly increased with N applications compared to the control treatment (0 kg N ha{dollar}rmsp{lcub}-1{rcub}yrsp{lcub}-1{rcub}{dollar} application). Forage yield was not increased by lagoon effluent applications above 1120 kg N ha{dollar}rmsp{lcub}-1{rcub}yrsp{lcub}-1{rcub}{dollar} on either the 5% or 10% slope. At 560 kg N h{dollar}rmsp{lcub}-1{rcub}yrsp{lcub}-1{rcub},{dollar} {dollar}rm NHsb4NOsb3{dollar} and lagoon effluent produced the same forage yield. Lower rates of application resulted in more efficient N and P removal by the crop. Overland flow of swine lagoon effluent is an acceptable method of lagoon effluent management from a forage production standpoint. However, mean concentration of nitrate in deep seepage water reached and exceeded 10 mg NO{dollar}sb3{dollar}-N L{dollar}sp{lcub}-1{rcub}{dollar} with all three rates of wastewater application, and mean concentrations of dissolved P and total P in surface runoff on all occasions exceeded critical values associated with accelerated eutrophication. The steepness of the slope did not affect nitrate concentration in surface runoff. Higher nitrate concentrations in deep seepage water were found on the smaller slope. Ammonium-N concentrations were much higher in the surface runoff than in the deep seepage water and were unaffected by slope. Higher P concentrations were found during the early spring and summer seasons. Slope did not significantly affect dissolved P concentration but significantly affected sediment P concentration. Soil data analyses indicated that treatment had significant effect on soil NO{dollar}sb3{dollar}-N, extractable soil P and K, and pH. Nitrate-N leaching to groundwater through the soil profile and P loss to surface water via runoff pose a potential for water pollution, indicating a need to reduce application volume for this type soil.