Increases in agricultural yields are needed to meet increased demand for food due to rising global human population. Advances in technology and management have long been given credit for increases in production of major commodity crops (corn and soybeans) in the US Midwest. While weather accounts for the major fraction of year-to-year variation in yields, long-term trends generally are credited to improvements in technology and management. Lobell and Asner (2003) analyze trends in corn and soybeans in the US Midwest and find a negative correlation in yield trend with temperature trend after effects of technology and management have been accounted for. Regions showing a cooling over the period 1982-1998 have increased yields and regions with warming trends had decreased yields. For corn the yield dropped 19.5 bushels per acre per °C and soybean yields dropped 5.6 bushels per acre per °C. These results suggest that meeting future food demands will require technology and management enhancements that compensate for temperature increases due to global warming as well as increases due to rise in global human population. Interpreting the results of Lobell and Asner (2003) in another way, the projected warming trend (global climate model ensemble mean) of 3.5-4.0°C over the next 100 year would negate about 50% of the annual yield increase due to management for corn and about 30% for soybeans.
References
Lobell, D. B., and G. P. Asner, 2003: Climate and management contributions to recent trends in US agricultural yields. Science 299, 1032.