B.A. Stewart, S. Thapa, Q. Xue, and R. Shrestha (2018). “Climate change effect on winter wheat (Triticum aestivum L.) yields in the US Great Plains.” Journal of Soil and Water Conservation 73(6), 601-609. doi:10.2489/jswc.73.6.601
Abstract: Climate change, particularly rising temperatures, is occurring throughout the planet. Between 1980 and 2016, the five-year moving average global land and ocean temperature increased from about 14°C to 14.7°C (57.2°F to 58.4°F). For the United States, the increase was from approximately 11°C to 12°C (51.8°F to 53.6°F). This study was undertaken to determine how increasing temperatures are affecting winter wheat (Triticum aestivum L.) production in the US Great Plains. The overall study area consisted of North Central Texas, Oklahoma, Kansas, Nebraska, South Dakota, and North Dakota as subareas, roughly 1,500 km (932 mi) north-south and 400 to 600 km (248.5 to 372.8 mi) east-west directions. Yearly average grain yields at county level were obtained from USDA Quick Stats, and temperature data were obtained from the National Oceanic and Atmospheric Administration (NOAA) for the subareas. While grain yields steadily increased for all the subareas from the first year of record until the early 1980s, there were marked differences in later years, particularly beginning about 1990 and increasingly greater during the 2000s. Since 1990, the five-year moving average grain yields for North Central Texas decreased and Oklahoma remained somewhat steady. In contrast, Kansas average yields showed an upward trend, and Nebraska, South Dakota, and North Dakota showed significant increases. The average annual temperatures increased in all subareas but more in the northern than in the southern subareas. From 1939 to 2016, the heading dates of newly released cultivars were 2.3 and 2.9 days earlier every 10 years compared to 1.6 and 0.6 days for Kharkof at Bushland and Chillicothe, Texas, respectively. Since the amount of growing season precipitation is generally the most important factor affecting grain yield, earlier heading is likely to decrease grain yield due to shorter grain filling period. The increased yields were likely due to the warmer temperatures reducing winter killing and providing more growing degree days during critical growth stages in the northern areas where historically the climate was too cold for optimum winter wheat growth. The study clearly suggests that rising temperatures is making winter wheat production more challenging in the southern areas, but more favorable in the northern areas of the US Great Plains.