GHG Emissions and Strategies to Mitigate and Adapt: Nitrogen Management for Controlling N2O Emissions and NO3 Leaching Losses.

Mitigation and adaptation to climate change are increasingly important because impacts are currently being observed and are expected to increase in the future.  Improved N management is an important component of an overall mitigation and adaptation strategy because N is an essential plant nutrient that contributes to climate change by via N2O emissions and eutrophication of aquatic systems from nitrate leaching. Methods to mitigate N losses from cropped systems include: use of improved efficiency fertilizers, applying fertilizers while plants are growing, and use of cover crops to scavenge N during the non-growing season. Observations from GRACEnet sites show that enhanced efficiency fertilizers are typically effective in reducing N2O losses from dryland and irrigated systems in the western US, but results are inconsistent for systems in the central and eastern US. Observations and model simulations show that cover crops decrease NO3 leaching, but have mixed effects on N2O emissions. Cover crops are both a mitigation and adaptation strategy because they can be grown in northern areas as temperatures warm. Switching from fall to spring application of fertilizer is expected to reduce both N2O emissions and NO3 leaching, particularly in years when planting is delayed due to excessive spring moisture. Local environmental conditions interact with economic and policy incentives to determine which management decisions can be feasibly implemented to mitigate N losses.