Impact of Climate Change on Yields and Components of the Water and Nitrogen Budgets of Dryland Wheat Systems in the US Pacific Northwest

As part of the Regional Approaches to Climate Change (REACCH) project (funded by USDA-NIFA), a regional assessment of historical and future yields and greenhouse gas (GHG) emissions of dryland wheat-based cropping systems in the US Pacific Northwest is being conducted. Two issues of interest in the region are changes in the water footprint and nitrogen use of wheat-based systems as a result of climate change. These two are related to the interaction between crop performance and the partitioning of water and nitrogen budget components. They also inform the tradeoff between crop production and environmental services and the sustainability of wheat systems in the future. Computer simulation-based assessment is being done using the CropSyst cropping systems simulation model and daily weather data downscaled to a 4x4 km grid. Future weather is projected using 12 general circulation models (GCMs) and two representative concentration pathways of future atmospheric CO2 (rcp 4.5 and rcp 8.5). The study region is divided in 3 agro-ecological classes (AECs): grain fallow, grain fallow transition and continuous cropping classes. The following rotations were included by AEC: WW - SF, WW - SW - SF and WW - SW - SP, where WW is winter wheat, SW is spring wheat, SP is spring peas, and SF is summer fallow. A typical conventional tillage (CT) cropping system in each AEC is evaluated as a baseline.