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United States Department of Agriculture

Agricultural Research Service

Title: Nitrogen Management to Protect Water Resources

Authors
item Randall, Gyles - U OF MN, WASECA, MN
item Delgado, Jorge
item Schepers, James

Submitted to: Soil Science Society of America Special Publication Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 22, 2005
Publication Date: February 1, 2008
Citation: Randall, G., Delgado, J.A., Schepers, J.S. 2008. Nitrogen management to protect water resources. p. 911-945. In Schepers and Raun (eds) Nitrogen in Agricultural Systems. SSSA Monograph. 49. Madison, WI.

Interpretive Summary: Nitrogen (N) is one of the most important worldwide nutrients required for sustainability and economic viability of agricultural systems. Its global uses are large and projected to increase. Since N is the most dynamic and mobile nutrient, its inputs increase the opportunity for leaks from the N cycle via surface runoff transport, nitrate-nitrogen (NO3-N) leaching and gaseous pathways. Applying N at the proper rate and the proper time are the two N management practices having the greatest effect on reducing NO3-N loss from row-crop systems. Using the correct rate of N can reduce NO3-N losses about 20% compared to using a 30 to 40 kg ha-1 higher 'insurance' rate. Applying N in the spring can further reduce NO3-N losses approximately 15% compared with a fall application. For irrigated systems, irrigation scheduling is an important strategy to reduce NO3-N leaching losses. We have shown that crop rotations are tools to increase cropping systems N use efficiency (NUE) and reduce NO3-N leaching, especially rotation of deeper rooted crops with shallower rooted crops which can cut the net NO3-N leaching losses by 66%. We can use in-season tests such as the PSNT, petiole analysis, NRI, remote sensing, and others to better match the application of N with the times of higher uptake. This will significantly increase NUE and reduce NO3-N leaching losses by up to 85%. We can reduce the NO3-N leaching or even mine NO3-N from groundwater resources using rotations of deeper rooted crops and winter cover crops that act as scavenger crops.

Technical Abstract: Nitrogen (N) is one of the most important worldwide nutrients required for sustainability and economic viability of agricultural systems. Its global uses are large and projected to increase. Since N is the most dynamic and mobile nutrient, its inputs increase the opportunity for leaks from the N cycle via surface runoff transport, nitrate-nitrogen (NO3-N) leaching and gaseous pathways. Applying N at the proper rate and the proper time are the two N management practices having the greatest effect on reducing NO3-N loss from row-crop systems. Using the correct rate of N can reduce NO3-N losses about 20% compared to using a 30 to 40 kg ha-1 higher 'insurance' rate. Applying N in the spring can further reduce NO3-N losses approximately 15% compared with a fall application. For irrigated systems, irrigation scheduling is an important strategy to reduce NO3-N leaching losses. We have shown that crop rotations are tools to increase cropping systems N use efficiency (NUE) and reduce NO3-N leaching, especially rotation of deeper rooted crops with shallower rooted crops which can cut the net NO3-N leaching losses by 66%. We can use in-season tests such as the PSNT, petiole analysis, NRI, remote sensing, and others to better match the application of N with the times of higher uptake. This will significantly increase NUE and reduce NO3-N leaching losses by up to 85%. We can reduce the NO3-N leaching or even mine NO3-N from groundwater resources using rotations of deeper rooted crops and winter cover crops that act as scavenger crops.

Last Modified: 7/27/2014