Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 1/20/2002
Publication Date: 4/20/2002
Citation: Huggins, D.R., Pan, W.L. Key indicators for assessing nitrogen use efficiency in cereal-based agroecosystems. Journal of Crop Production. 2003. v. 8. p. 157-186. Interpretive Summary: Worldwide applied N use efficiency is about 33% and improvements in N use efficiency can be realized in virtually every cropping system. Unfortunately, evaluating how or where efficiencies in N use can be achieved is complicated by the many crop, environmental and economic factors that control N use. We demonstrate key indicators of nitrogen use that enable crop, environmental and economic assessments of nitrogen management strategies. Use of nitrogen efficiency indicators was demonstrated for two field studies, one in Minnesota and one in Washington that included different tillage, crop rotation and applied N rates. The nitrogen use efficiency indicators identified key areas where improvements could be made in nitrogen use that were unique for each cropping system. Use of these indicators will aid monitoring of cropping system nitrogen use, assessment of nitrogen management strategies, and identification of key areas where improvements in nitrogen use efficiency can be obtained. Improvements in N use efficiency will lead to less N contamination of surface and ground waters and greater financial returns to producers.
Technical Abstract: Improving N use efficiency (NUE) is an important objective of agroecosystem management. We demonstrate key indicators of NUE that enable a broader assessment of N management strategies. Nitrogen efficiency components were defined to assess soil and crop physiological processes, and agronomic factors related to N use. Measurements of grain yield, grain N, aboveground plant N, applied N, and post-harvest root-zone soil N were used to assess available N efficiency, available N uptake efficiency, N utilization efficiency, N harvest index, N yield efficiency, N reliance efficiency, and grain N accumulation efficiency or N harvest efficiency. Use of N efficiency components was demonstrated for two field studies: (1) hard red spring wheat with four N levels and two tillage treatments: no-tillage (NT) and conventional tillage (CT); and (2) corn in crop sequences of continuous corn (C-C), corn-soybean (C-S), two years of corn following alfalfa (ALF-C-C), and two years of corn following perennial grass (CRP-C-C). Tillage, crop rotation and applied N had large and variable effects on different N use efficiency components. The N efficiency component analysis was useful for monitoring cropping system N use, assessing N management strategies, and identifying key areas for improvements in N use efficiency.