Bianca Nadine Moebius-Clune
Cornell University

Nitrogen (N) management in maize production is often imprecise and inefficient in humid regions due to dynamic, complex and locally-specific interactions among weather, soil and management variables. In the eastern U.S.A., large N leaching losses from areas of intensive maize production have contributed to seasonal development of hypoxia zones in the Gulf of Mexico and Chesapeake Bay, while nitrous oxide from denitrification makes up the largest fraction of greenhouse gas emissions associated with U.S. agriculture. Such losses primarily occur in a wet spring/early summer, but can also occur following the cropping season if excessive N was applied, or if drought limited crop N uptake. Adaptive N management accounts for the temporal and spatial variability in N dynamics to allow for more efficient use of applied N. This will be particularly important for adaptation of agriculture to climate change. We developed the web-based Adapt-N tool for adaptive N management in maize production, and are validating its use for on-farm applications during the 2011 and 2012 growing seasons. Adapt-N simulates locally-specific daily soil C and N transformations, water transport and N uptake during maize growth, to calculate in-season N fertilizer needs. Adapt-N has three important components: 1) the well-validated Precision Nitrogen Management (PNM) dynamic simulation model, 2) newly-developed high resolution climate data (daily precipitation and temperature) available on a 4x4 km grid, and 3) a readily accessible web-interface, that is also mobile enabled, allowing farmers to define field-specific management and soil test information to run simulations based on location-specific weather patterns. Farmer inputs and climate data are accessed by the interface as inputs for the PNM model. The ‘Results’ page of the interface provides users with in-season N recommendations together with graphs of key soil, crop and climate simulation results. In replicated on-farm strip trials in New York State and the state of Iowa (U.S.A.) in 2011, grower applications of N to grain and forage maize, and sweet corn were 17 – 146 kg/ha higher than rates recommended by Adapt-N in almost all cases. In a few locations where excessive rainfall occurred, Adapt-N recommended higher rates. Harvest data are still being collected. Access to this tool promotes lower N applications in average years when less is needed, but provides justification for higher in-season N applications after wet springs.