Modeling Nitrogen Loss and Mitigation Potentials of Enhanced-Efficiency Nitrogen Fertilizers from Agricultural Soil System.

About half of the nitrogen fertilizer applied to crop production systems is lost to the environment via ammonia volatilization, nitrification and denitrification, and by leaching, erosion, and runoff. It is an environmental pollutant that effects air quality, human health, ecosystems, and contributes to greenhouse gas emissions. The rate of loss varies substantially by fertilizer types, application methods, soil types and environmental conditions mainly because of a mismatch between when the nitrogen is made available and when plants take up the supplied nitrogen. Evaluating losses on nitrogen from different sources of fertilizer and management options for mitigation potentials requires a predictive modeling framework. We are evaluating several sub-models within the DAYCENT ecosystem model for this purpose. Ammonia volatilization sub-models to predict ammonia loss due to application of synthetic fertilizer is being developed. In addition, enhanced-efficiency nitrogen fertilizers including urease inhibitors, nitrification inhibitors and slow-release fertilizers are also being developed. Hierarchical Bayesian inferences is being used for model formulation, calibration of model parameters, and model comparisons with field data. The new sub-models will provide DAYCENT with the capability to simulate the influence of various nitrogen fertilizer types and management practices, providing a robust, complete, and a reliable tool for decision support systems at various geographic levels from site to region and global scales.