The biological basis for nitrogen management in agroecosystems - Microbial Ecology in Sustainable Agroecosystems - page 111

chapter 6
The biological basis for nitrogen
management in agroecosystems
A. Stuart Grandy
University of New Hampshire
Cynthia Kallenbach
University of New Hampshire
Terry D. Loecke
University of Nebraska-Lincoln
Sieglinde S. Snapp
Michigan State University
Richard G. Smith
University of New Hampshire
Contents
6.1 Current challenges with nitrogen management ........................................................... 113
6.2 On-farm consequences of nitrogen management ......................................................... 114
6.3 Off-farm environmental impacts of nitrogen management ........................................ 114
6.4 Nitrogen use eficiency ..................................................................................................... 116
6.5 Synchrony ........................................................................................................................... 116
6.6 Nitrogen mineralization-immobilization....................................................................... 118
6.7 Temporal synchrony.......................................................................................................... 120
6.8 Spatial dynamics................................................................................................................ 121
6.10 Managing synchrony ........................................................................................................ 123
6.11 Conclusions......................................................................................................................... 126
References..................................................................................................................................... 127
6.1 Current challenges with nitrogen management
Nitrogen (N) inputs into agricultural systems are estimated to be in the range of 130-170
Tg N y -1 , and almost 90% of these inputs originate from inorganic fertilizers and other
anthropogenic sources (Smil, 1999). In general, crop recovery of fertilizer N is typically less
than 50% and often no more than 30% (Galloway and Cowling, 2002; Cui et al., 2010). The
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