Submitted to: Soil and Water Conservation Society
Publication Type: Book / Chapter
Publication Acceptance Date: January 23, 2007
Publication Date: November 1, 2010
Citation: Sadler, E.J., Bausch, W.C., Fausey, N.R., Ferguson, R.B. 2010. Water management: a key to reducing nitrogen losses. In: Delgado, J.A., and R.F. Follett, editors. Advances in Nitrogen Management for Water Quality. Ankeny, IA: Soil and Water Conservation Society. p. 38-60. Technical Abstract: Improving yield per unit water applied has probably always been the goal of irrigators. This ratio of yield per unit water was some 40 years ago named water use efficiency (WUE). This emphasized obtaining the maximum yield for a given irrigation amount, often by increasing fertilizer applications, usually of nitrogen (N). The implications of this approach were examined from the theoretical standpoint of water and N balances and in case studies. Examination of the water and N balances shows points of interactions where mobile soluble N species can migrate with moving water, or relatively less mobile species can transform to more mobile species because of the prevailing water content. These considerations were applied to the case studies. Experiences in the South and Central Platte River valley with continuously irrigated, intensively managed maize showed elevated groundwater nitrate-N levels and illustrated some means to reverse the historical trend. Intensive management of maize under rainfed conditions in the US Corn Belt was shown to cause losses of nitrate-N from tile drains. Again, a management practice has been shown to substantially reduce these losses. A case study in the Southeast Atlantic Coastal Plain documented spatial variation in both WUE and N use efficiency, suggesting that while yield patterns were somewhat predictable, spatial variation in N use was not. Results from these case studies lead to a conclusion that simultaneous optimization of both inputs will be required for economically and environmentally sustainable agriculture.