Adapt-N On-Line Tool for Site-Specific and Weather-Adjusted Nitrogen Management in Maize: On-Farm Strip Trial Results.

More efficient nitrogen (N) management in maize production systems in humid regions is a priority, because of the well-documented negative environmental impacts of N on water quality and greenhouse gas emissions. Nitrogen management tools to improve maize N use efficiency need to account for the dynamic, complex and locally-specific interactions among weather, soil and management that affect crop-available N in the soil, and crop N uptake. The web-based Adapt-N tool uses field-specific management, soils, and crop information supplied via a web-interface by users, and newly-developed near real-time high resolution climate data, as inputs for a dynamic simulation model. The tool calculates in-season N fertilizer needs by simulating daily soil C and N transformations, soil water storage and transport, and N and water uptake by the maize crop. The Adapt-N web-interface provides a sidedress N recommendation and graphs visualizing seasonal dynamics over time of soil N, crop growth, temperature and precipitation for a user’s location. New York (NY) and Iowa (IA) growers, in collaboration with consultants and extension staff, beta-tested the Adapt-N tool in replicated on-farm strip trials in grain, silage and sweet corn in 2011, with additional trials planned for the 2012 growing season. Adapt-N recommendations were compared with grower N applications in 17 replicated strip trials in NY and 9 in IA. On average, N application rates were reduced by 65 kg/ha (60 lb/ac) in NY and 50 kg/ha (45lb/ac) in IA.  Yield losses from reduced N rates were negligible, except in a few cases where the tool was improperly used or model adjustments were needed. Yield gains from a few cases with higher Adapt-N-based recommendations were significant. Overall, Adapt-N use increased grower profits by about $85/ha ($35/ac) in NY and $60/ha ($25/ac) in IA, and significantly reduced estimated N leaching and denitrification losses. Revisions made to the Adapt-N tool for the 2012 season will be presented. Initial testing shows potential for Adapt-N to improve N use efficiency in maize, increase grower profits, and reduce environmental impacts of N use in maize production.