New Frontiers in Integrated Nitrogen and Crop Management Systems for Reduced N2O Emissions.

The imperative to reduce N₂O emissions per unit of grain yield grows ever stronger. Individual solution approaches abound, but have not achieved the expected mitigation results. The individual solutions range from a focus on N management alone (e.g. lowering N rates, better synchronizing N fertilizer applications with crop uptake, using enhanced efficiency N fertilizer sources, adopting precision N placement strategies, etc.) to consideration of superior crop management strategies designed to limit N₂O losses associated with nitrification/denitrification processes (e.g. using genotypes with higher N recovery efficiency, adopting no-till or strip-till,  planting cover crops, improving soil drainage, increasing corn plant density, timely irrigation, etc.). In this presentation, I will highlight examples of integrated N and crop management systems that have effectively reduced N₂O emissions in corn production much further than that which is possible with single-factor approaches. I will also encourage more collaborative research efforts that consider the complex management interactions that farmers face in making choices that increase crop yield and N efficiency simultaneously. The future science of N₂O emission reduction must incorporate better sampling methodologies (e.g. more frequent sampling of gas emissions and relevant soil properties, simultaneous measurement of other N gases like NH₃, etc.). However, impact of superior greenhouse gas science on crop agriculture will be limited unless such studies intentionally examine genotype by environment by management interactions to the maximum extent that is possible with available funding.