Denitrification is known as an important pathway for nitrate loss in agroecosystems. It is important to estimate denitrification fluxes to close field and watershed N mass balances, determine greenhouse gas emissions (N2O), and help constrain estimates of other major N fluxes (e.g., nitrate leaching, mineralization, nitrification). We compared predicted denitrification estimates for a typical c...

The nitrates (NO(3)-N) lost through subsurface drainage in the Midwest often exceed concentrations that cause deleterious effects on the receiving streams and lead to hypoxic conditions in the northern Gulf of Mexico. The use of drainage and water quality models along with observed data analysis may provide new insight into the water and nutrient balance in drained agricultural lands and enable...

ii ACKNOWLEDGMENTS I would like to acknowledge the following for completion of this thesis: God for giving me the patience, guidance and strength to succeed in this research. I am so grateful for everything I have been given and everything I was able to do. Without God I can do nothing. Dr. Nandita Basu for challenging and guiding me throughout graduate school and this research. I have grown an...

Methods are needed to quantify effects of land use and management practices on nutrient and sediment loads at the watershed scale. Two methods were used to apply a DRAINMOD−based watershed−scale model (DRAINWAT) to estimate total nitrogen (N) transport from a poorly drained, forested watershed. In both methods, in−stream retention or losses of N were calculated with a lumped−parameter model, wh...

of agricultural P to water quality. In Florida, FHANTM 2.0 (Field Hydrologic and Nutrient Transport Model, Pollution of surface waters by P from agricultural areas is a water version 2.0; Fraisse and Campbell, 1997) was developed quality issue in Delaware. The FHANTM 2.0 computer model can help identify areas with a high potential for P loss, but the model’s to simulate water and P movement fro...