Beyond extreme temperatures: soil water supply and yield variability

Tuesday, 16 December 2014: 9:45 AM
Daniel Urban, Stanford University, Stanford, CA, United States and David B Lobell, Stanford University, Los Altos Hills, CA, United States
Extreme weather events have profound consequences for both the mean and interannual variability of agricultural production, but while the role of extreme heat has been convincingly demonstrated, soil water supply has received less attention. In particular, there is debate over the extent to which damages attributed to extreme heat are confounded with drought conditions. In a pair of studies, we examine the effect of extreme moisture conditions, both wet and dry, on maize and soybean yields in the U.S. We find significant effects of waterlogging during the planting season, when crops are most vulnerable to excess moisture, as well as evidence for a strong interaction between high temperatures and low moisture during during the critical stages of the summer growing season. Using both precipitation and model-derived soil moisture data, our results suggest that considering temperature and moisture independently will underestimate yield damages during hot, dry conditions. Many warming scenarios project increases in both extreme summer temperatures and soil dryness, and considering these effects jointly can be important in estimating future yield variability.