P. Lawlor

Nitrogen Application Rate Effect on Nitrate-Nitrogen Concentration and Loss in Subsurface Drainage for a Corn-Soybean Rotation

Matthew J. Helmers, James L. Baker, Stewart W. Melvin, 2008 .

Effect of different land covers on nitrate-nitrogen leaching and nitrogen uptake in Iowa

Z. Qi, M. Helmers, P. Lawlor, 2008 .

Nitrification Inhibitor and Nitrogen Application Timing Effects on Yields and Nitrate-Nitrogen Concentrations in Subsurface Drainage from a Corn-Soybean Rotation

M. Helmers, P. Lawlor, J. Baker, 2004 .

Subsurface Drainage in Iowa and the Water Quality Benefits and Problem

M. Helmers, W. Crumpton, P. Lawlor, 2004 .