Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/18/2007
Publication Date: 7/25/2007
Citation: Johnson, C., Corwin, D.L., Shanahan, J.F. 2007. Site-Specific N Management in an Intensified No-till Dryland Cropping System. Soil and Water Conservation Society. Interpretive Summary:
Technical Abstract: Traditional uniform N application is inefficient. Nitrogen is over-applied in low-producing parts of a field and under-applied in areas with high-production potential. The result is lost income for farmers, diminished carbon sequestration, and negative environmental impact (soil acidification, toxin accumulation, and water contamination). While variable-rate fertilizer applicators are currently available, prescription maps for their use are lacking. Our Conservation Innovation Grant funds a 5-year 610-ac demonstration project in northeast Colorado to evaluate soil electrical conductivity (EC) as a basis for site-specific N management (SSN) in dryland winter wheat. We are assessing SSN for economic feasibility (profit, risk, and yield), soil conservation effects (N-use efficiency), and grain quality impact. Each year, eight N treatments are applied in strips (120 ft by ½ mile) across each of two 80-ac wheat fields to traverse EC zones. Crop biomass, grain, and pre-plant/post-harvest soil samples are collected to assess soil/crop response within each N-rate/EC-zone combination. Using GIS technology, yield, EC, and N-treatment maps are compared to identify economically and ecologically optimum N rates within EC zones. A clearly-defined procedure and cost-benefit analysis for SSN will be produced. Farm publications, extension bulletins, and a Field Day will heighten producer awareness of the: (i) soil factors contributing to yield variability, (ii) importance of pre-plant soil testing, (iii) problems associated with uniform fertilization, and (iv) potential benefits of SSN. The impact, significance, and transferability of this project are bolstered by its regional scope, the on-farm large-scale approach, and the partnerships involved (producers, scientists, financial consultant, industry, and extension).