CLIMATIC INFLUENCES ON CORN AND SOYBEAN YIELDS

The recent U.S. Renewable Fuel Standard calls for 36 billion gallons of ethanol production by 2022 with over half produced from plant biomass. Currently, the only feasible biomass based biofuels is ethanol derived from corn. The goal of our research is to assess the sensitivity of corn and soybean production to climatic change.

We used the US Department of Agriculture’s (USDA) National Agricultural Statistic Service (NASS) data on US county level yields of corn and soybean from 1970 to 2008. We developed county-level summaries of historical PRISM climate datasets from 1970-2008 and integrated them with historical NASS crop yield estimates to examine the relationship between historical crop yield and interannual climatic variability. We used PRISM climate data on minimum, maximum, and average temperature (tmin, tmax, and avgt) and precipitation (ppt) to model variation in corn and soybean yields as a function of climate. Climate data were averaged per month, two-months, and three-months. To determine the most relevant climate variables we performed independent second order polynomial regressions between yields and climate variables and determined their predictive power based on the coefficient of determination (R²). Using the climate variables identified in the previous step, we used a climate-envelope approach to model 1970-1989 corn and soybean yields as a function of climate and used 1990-2008 data to quantify how well yields actually matched the climate. June-Aug avgt and June-July ppt for corn and summer avgt and ppt for soybean yielded the models with the highest predictive power. Predicted corn and soybean yields for 1990-2008 matched relatively well the actual yield values, indicating that this approach has potential for use to model changes in corn and soybean yields as a function of climate.

Future modeling efforts will incorporate downscaled GCM data for future climate change scenarios from the Community Climate System Model (CCSM).to predict potential changes in corn and soybean productivity under climate change scenarios.