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Title: Assessment of nitrogen losses to the environment with a Nitrogen Trading Tool (NTT)

Author
item Delgado, Jorge
item SHAFFER, M - USDA-ARS, RETIRED
item LAL, HARBANS - USDA-NRCS, PORTLAND, OR
item MCKINNEY, S - NRCS, PORTLAND, OR
item CROSS, C - NRCS, BELTSVILLE, MD
item COVER, H - NRCS, PORTLAND, OR

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2008
Publication Date: 5/16/2008
Citation: Delgado, J.A., Shaffer, M.J., Lal, H., Mckinney, S., Cross, C., Cover, H. 2008. Assessment of nitrogen losses to the environment with a Nitrogen Trading Tool (NTT). Computers and Electronics in Agriculture. 63:193-206.

Interpretive Summary: We defined the new concept of field-level reduced nitrogen losses as a function of improved N use efficiencies of field management scenarios that reduce the average N inputs and/or modify other management practices thus lowering N losses from a field. The newly released Windows XP version of the NLEAP-GIS was used to assess no-till systems from a humid North Atlantic US site, manure management from a Midwestern US site, and irrigated cropland from an arid Western US site. NLEAP-GIS and NMD can be used to quickly identify the best scenario that shows the greatest potential to maximize DNL at the field level and minimize N losses to the environment. This study suggests simulation model approach with the NLEAP-GIS tool can be used to assess how different scenarios impact N losses This approach can be used to assess the individual DNL via the equation: ' NO3-N + ' N2 + ' N2O + ' NH3 + ' Nst. We recommend that potential nutrient management users review the chapters from Shaffer and Delgado (2001), the chapters from Delgado and Shaffer (2006), and the details of the potential limitations of field N modeling. Our simulations with NLEAP-GIS (Shaffer et al., 2006) are in agreement with previous validation/calibration efforts conducted by Wylie et al. 1995, Xu et al. (1998), and Delgado (1998). The availability of a new NMD tool could allow nutrient managers to quickly estimate the potential gains and associated DNL . We recommend further research in this area. We also recommend communication and interaction between scientists and nutrient managers from the USDA-ARS, the USDA-NRCS, Universities, Extension Agencies, and others to develop a series of local and regional rules to apply a potential NMD approach to evaluate BMPs where nutrient managers can improve N management practices that reduce N inputs, improve nitrogen use efficiencies, reduce NO3-N losses, and reduce off-site transport at the farm level for these non-point sources. We are presenting a potential approach. If DNL will be assigned to users, there should be agreement at local, State, regional, and national levels on basic rules, approaches, and the interpretation and use of the ' NO3-N, ' N2, ' N2O, ' NH3, ' Nst, and ' Nt. In our approach, we interpret these DNL as reductions in farm N inputs and other management changes that improve nitrogen use efficiencies, as shown by reduced N losses and N transport to the environment.

Technical Abstract: Delta (or reduced) nitrogen losses (DNL) refer to potential downstream reductions in nonpoint source nitrogen (N) loading of streams or other water bodies and/or in reduced loading of the atmosphere with N-associated greenhouse gases from agriculture. Nitrogen credits as traded on the Communities Market commonly refer to discounted reductions in agricultural nitrogen losses that apply to a project downstream from an agricultural area. We defined a new concept of field-level DNL as a function of improved N use efficiencies of field management scenarios that reduce the average N inputs and/or modify other management practices thus lowering N losses from a farm field. We used a newly released Windows XP version of the Nitrogen Losses and Environmental Assessment Package (NLEAP) with a Geographic Information System (GIS) capability (NLEAP-GIS) to assess no-till systems from a humid North Atlantic US site, manure management from a Midwestern US site, and irrigated cropland from an arid Western US site. The new NLEAP-GIS and the Nitrogen Matrix of Differences (NMD) can be used to quickly identify the best scenario that shows the greatest potential to maximize field-level DNL and minimize N losses to the environment.