U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


Date of this Version



Published in Nitrogen in the Environment: Sources, Problems, and Management, Second edition, ed. J. L. Hatfield & R. F. Follett (Amsterdam, Boston, et al.: Academic Press/Elsevier, 2008).

“Copyright protection is not available for any work prepared by an officer or employee of the United States Government as part of that person's official duties.”
United States Code, Title 17, §105.


Nitrogen (N) from soil, fertilizer, and manure sources is generally inefficiently used (30-60%) in most crop production systems. As a consequence, unused inorganic N can move off crop fields and contaminate surface and groundwater resources. Local and national governments have responded with guidelines, standards, regulations, and in some cases fines when off-field losses of N have not been reduced. Along with these environmental pressures, soaring energy costs have resulted in commensurate increased costs for N fertilizers. These factors are real for crop producers and are compelling them to scrutinize their crop N management more closely than in previous decades. Numerous time-proven practices, established by research and in crop production settings, are available that will result in improved crop N use efficiency. More emphasis should be given to these practices on farms throughout the world. Additionally, recent advances in sensor technologies are playing an increasing role in shaping the future of crop N management. We highlight some of these technologies available to help producers make better N management decisions. Both soil and crop measurements are considered and compared. Nonetheless, "on-farm" implies that producers will be at the center of implementing change, and change means N management options will motivate producers to action. Prerequisites for grower adoption require that technologies and practices be reliable, incur minimal additional expense (time and equipment), and integrate with ease into current operations. When these criteria cannot be met, external incentives (e.g., regulation or cost sharing) may be necessary.