Submitted to: Soil and Water Conservation Society
Publication Type: Book / chapter
Publication Acceptance Date: 8/24/2010
Publication Date: 12/10/2010
Citation: Gross, C., Delgado, J.A., Shaffer, M., Gasseling, D., Bunch, T., Fry, R. 2010. Chapter 15. A tiered approach to nitrogen management: A USDA perspective. p. 410-424. In Delgado, J.A. and R.F. Follett (eds) Advances in Nitrogen Management for Water Quality. SWCS, Ankeny, IA. Interpretive Summary: Computer simulation models are very useful tools for: • assessing the potential for farm management practices to impact natural resources; • quantifying the potential for conservation practices to prevent or mitigate those impacts; and • targeting conservation practice application to the most vulnerable acres in order to prevent nutrient losses to the environment. The NRCS continues to use computer simulation models such as NLEAP-GIS, APEX, and NTT technologies to help assess and protect natural resources for a healthier environment. Tier One risk analysis tools such as the Nitrogen Index are being developed as field-based or first level tools that can consistently and systematically assess nitrogen status across various landscapes and cropping systems. Continued development and use of Tier One technology tools, coupled with the scientific underpinnings of computer simulation models such as NLEAP and APEX for verification, will be instrumental to applying sound nutrient management strategies with NRCS conservation planning technical assistance and conservation programs.
Technical Abstract: The USDA Natural Resources Conservation Service (NRCS) has developed policy and conservation practice standards for planning and implementing nutrient management as part of an overall conservation plan that addresses soil conservation including soil, water, air, plant and animal natural resource concerns. The nutrient management planning component of a conservation plan includes the rate, timing, form, and method of application of all forms of nutrients to specific fields. Over eight million acres of cropland and grazing land undergo nutrient management planning annually in the U.S.A. The planning process involves working with landowner objectives and resources to develop the proper rate, timing, form, and method of application of nutrients for their climate and cropping system based on land-grant university nutrient recommendations and soil and tissue testing. Environmental risk analysis tools can play an important role in nutrient management planning. A tiered approach utilizing quick and easy Tier One tools when they are adequate, followed by the use of more precise Tier Two and Tier Three tools when necessary, is an efficient way to address the environmental risks of nitrogen losses in the conservation planning process. With input from the landowner, a Tier One tool such as the Nitrogen Index (Delgado et al., 2006a; 2008) or a Tier Two tool such as the Nitrogen Losses and Environmental Assessment Package with GIS capabilities (NLEAP-GIS) (Shaffer et al., 2010; Delgado et al., 2010) can be used to analyze the risk of nitrogen loss and predict nitrogen use efficiency. These tools can help assess the impact of irrigation practices, timing of nutrient applications, form of nitrogen being applied, and the placement of the nutrients on the field. Planning scenarios can then be adjusted using adaptive management techniques to maximize nitrogen use efficiency.