Effect of Climate Change On Winter Wheat Production Systems: A Simulation Approach for Wyoming Conditions.

Dry land winter wheat, with an average area planted of 75,000 ha during the 2009 and 2010 growing seasons, is an important crop for Wyoming agriculture. However, dry land winter wheat production faces various challenges, such as climate change and variability. For instance, projections for future climate change call for warming in the Western central region of the United States where there are extensive areas of dryland winter wheat production. While warming would increase growing season length and contribute to fewer frost days, it would also lead to enhanced evaporation and plant water demand. This situation could eventually modify the soil-water balance which in turn could negatively affect winter wheat production. On the other hand, the growing conditions in Wyoming call for urgent need to use conservation cropping approaches if production is to be sustained in the long term. Among others, legume crops are suggested as options to traditional winter wheat-fallow system; however, the benefits of the adoption of this approach are not yet well known. The objective of this study was to determine the effect of climate change on the soil water balance of winter wheat production systems for conditions in eastern Wyoming. The CERES-Wheat model of the Decision Support System for Agrotechnology Transfer (DSSAT), previously calibrated with observed data from variety trials conducted in Torrington, WY, was used. The crop rotation tool of DSSAT was used to simulate two crop rotations and one climate change scenario, including traditional winter wheat-fallow and intensive winter wheat-spring legume for a period of 30 years. Daily outputs were analyzed focusing on phenology, yield, seasonal evapotranspiration, and average extractable water. Our results showed that for the traditional wheat-fallow rotation, the average simulated yield and total seasonal evapotranspiration were greater using the observed weather than those using the climate change scenario. The variability of the simulated yield was greater when using weather data corresponding to the climate change scenario. For the intensive rotation using both, observed weather data and climate change data, the average simulated yield of wheat was significantly reduced compared to the traditional wheat-fallow rotation; this was due to the negative effect of the legume spring-summer crop in terms of reduction of extractable soil water for the next winter wheat crop.