Development of Technical Information for Use in Adaptive N Management.

Nitrogen management in humid regions is generally imprecise, inefficient, and results in high environmental losses.  Current approaches for estimating optimum nitrogen fertilizer rates are based on mass balances, average expected economic return based on field experiments, soil N tests, and crop leaf/canopy sensing.  However, N losses occur from dynamic and complex interactions among weather, soil organic matter mineralization and hydrology, crop water and N uptake, and management practices, resulting in variable annual crop N needs in corn production. Several studies have documented that weather impacts the early season soil N pool and greatly contributes to the variability in economic optimum in-season N rates for maize. For adaptive N management approaches to be successful, we need to understand and account for the processes that cause variability in N dynamics among farms, soils, climate and weather.  Weather and soil-mediated changes in early season soil N can be estimated by well-calibrated models that simulate soil and crop processes. Model output can then be used to adjust in-season N rates for corn resulting in more precise N management. We have developed such a model (Precision Nitrogen Management or PNM model) which simulates soil N transformations; soil N and water transport; and corn growth and N uptake. We also developed the Web-based Adapt-N tool, based on the PNM model, which utilizes newly-developed high resolution climate data to provide farm- or field-specific in-season N recommendations for corn. Adapt-N allows for more precise N management and also improved response to the effects of climate change.