N-source effects on temporal distribution of NO3-N leaching losses to subsurface drainage water

Understanding the temporal distribution of NO3-N leaching losses from subsurface drained 'tile' fields as a function of climate and management practices can help develop strategies for its mitigation. A field study was conducted from 1999 through 2003 to investigate effects of the most vulnerable application of pig manure (fall application and chisel plow), safe application of pig manure (spring application and no-tillage) and common application of artificial nitrogen (UAN spring application and chisel plow) on NO3-N leaching losses to subsurface drainage water beneath corn (Zea mays L.)-soybean (Glycine max L.) rotation systems as a randomized complete block design. The N application rates averaged over five years ranged from 166 kg-N ha(-1) for spring applied manure to 170 kg-N ha(-1) for UAN and 172 kg-N ha(-1) for fall applied manure. Tillage and nitrogen source effects on tile flow and NO3-N leaching losses were not significant (P < 0.05). Fall applied manure with CP resulted in significantly greater corn grain yield (10.8 vs 10.4 Mg ha(-1)) compared with the spring manure-NT system. Corn plots with the spring applied manure-NT system gave relatively lower flow weighted NO3-N concentration of 13.2 mg l(-1) in comparison to corn plots with fall manure-CP (21.6 mg l(-1)) and UAN-CP systems (15.9 mg l(-1)). Averaged across five years, about 60% of tile flow and NO3-N leaching losses exited the fields during March through May. Growing season precipitation and cycles of wet and dry years primarily controlled NO3-N leaching losses from tile drained fields. These results suggest that spring applied manure has potential to reduce NO3-N concentrations in subsurface drainage water and also strategies need to be developed to reduce early spring NO3-N leaching losses.