Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 8/5/2010
Publication Date: 2/15/2011
Citation: Scharf, P.C., Kitchen, N.R. 2011. Use of GIS-based site-specific nitrogen management for improving energy efficiency. In: Clay, D. E., Shanahan, J. F., editors. GIS Applications in Agriculture. Volume Two: Nutrient Management for Energy Efficience. Boca Raton, FL: CRC Press. p. 359-384. Interpretive Summary: Nitrogen (N) fertilizer is a crucial input for crop production but contributes to agriculture’s environmental footprint via CO2 emissions, N2O emissions, and eutrophication of coastal waters. The low-cost way to minimize this impact is to eliminate over-application of N. This is more difficult than it sounds. Weather interacting with terrain has a huge influence on N loss, N mineralization, and crop yield potential (therefore N demand). Optimal nitrogen fertilizer rate varies widely from year to year, field to field, and place to place within a field. Precision N management technologies are the only way to address within-field variability, and some may help to address year-to-year or field-to-field variability as well. In this analysis we examine recent case studies for corn in Missouri and cotton in Texas using Geographic Information System (GIS) software tools. We examined the energy returns (including the outputs, fuel, and feed) to N fertilizer using site-specific technologies compared to blanket N fertilizer approaches. In most of our case studies, energy was saved using site-specific technologies for corn production. In cotton, energy was saved only with high-yielding drip-irrigation systems. This analysis will help land managers see how GIS tools are crucial in quantifying the impact of management options on agriculture's footprint on the landscape.
Technical Abstract: Nitrogen (N) is a significant energy component of in support of crop production but it can be highly variable within fields. To our knowledge, no efforts have been made to employ GIS-based site-specific N management (SSNM) to assess and improve energy costs and efficiency. We examine recent SSNM case studies for corn in Missouri and cotton in Texas using GIS tools. Specifically we addressed the energy returns (including the outputs, fuel, and feed) to N fertilizer, particularly SSNM compared to blanket N fertilizer recommendations. These SSNM approaches tested included grid soil sampling, management zone strategies, aerial photography, and canopy reflectance. In irrigated cotton, positive energy returns to N fertilizer and to SSNM were achieved in high yielding drip-irrigation cotton, but not in lower yielding center pivot cotton. In the four corn case studies in Missouri, SSNM yielded more energy than conventional N management.