NC218: Assessing Nitrogen Mineralization And Other Diagnostic Criteria To Refine Nitrogen Rates For Crops And Minimize Losses
Statement of Issues and Justification
Nitrate enrichment of ground water and surface waters and their impacts on drinking water quality and hypoxia in the Gulf of Mexico are important water quality issues. Nitrogen (N) use in cropping systems in the North Central Region is one of the major sources of nitrate entering natural waters. To address concerns about Gulf hypoxia, the National Science and Technology Councils Committee on Environment and Natural Resources issued a report identifying a 20% reduction in N loss from farmlands as a component of a strategy to ameliorate the Gulf of Mexico hypoxic zone. Studies to identify the source of nitrate that may contribute to Gulf hypoxia suggest that states within the North Central region are major contributors (Bratkovich et al., 1994; Rabalais et al., 1995; Burkart and James, 1999). Concerns with nitrate enrichment of groundwater continue to grow and are a legitimate public health concern because many municipalities and rural residents depend on groundwater as their primary source of drinking water.
The need to understand and elucidate the role of active carbon (C) and N pools in cropping systems continues to be critical for predicting N mineralization and availability in cropping systems. Jarvis et al. (1996) concluded that better quantification of the N mineralization contribution in cropping systems would help minimize N losses to the environment and allow more accurate recommendations for crop production. If N mineralization can be predicted more reliably, more precise guidance can be provided so that sufficient supplemental N can be applied to optimize crop production without the risks of over application.
Improved understanding of active C and N pools is especially important in view of current efforts to sequester C in agricultural soils as a means of lowering greenhouse gas emissions and minimizing the influence of these emissions on global warming (Rosenberg et al., 1999; CAST, 2000). Specifically, very little information is available on the effects of soil C buildup on N mineralization and the supplemental N needs of crops grown on these soils. Conversely, little is known about changes in C and N mineralization in cropping systems where soil C content is being depleted.
Surveys indicate that farmers are reluctant to adopt improved N management practices that could lower the frequency of excess N application because they perceive a high risk of economic loss if these practices are implemented (Shepard, 2000; WDNR, 2000). Educational programs and materials are needed to illustrate for producers and agricultural professionals the agronomic and environmental impacts of adopting various N management practices. This information should aid producers in making sound research-based decisions about the impacts of adopting improved practices instead of relying on perceptions that may not have a valid research basis.
The members of the NC-218 committee and the projected participants of the proposed project have the range of technical expertise and the appropriate facilities to conduct the proposed research. The regional and cross-regional perspectives and the range of experimental environments provided by the various participants will lead to broad applicability of the findings from the research. In addition, use of a core experiment approach plus the centralized, collaborative arrangements for analytical determinations, data analysis, and interpretation are advantages of the regional research approach.
Impacts from successful completion of the proposed work include improved diagnostic capability to predict crop N needs in the North Central region and in other areas represented by the committee membership. Communication of improved N management techniques to agricultural professional and farmers will lead to more efficient use of N from all sources and a reduction in excess N applications in crop production. This communication will be facilitated by the N management guidance document to be prepared as a part of this proposal and by the substantial Extension and outreach efforts planned by project participants (See Appendix E). Implementation of improved N management, especially avoiding excess N use, will reduce N losses and avoid water quality problems associated with nitrate enrichment.
Back to Top