Winter wheat response to climate change under irrigated and dryland conditions in the US southern High Plains

A rise in global temperature has been observed since the 1980s. The objective of the study was to understand the winter wheat (Triticum aestivum L.) responses and yield performances to the changing climate. The study was performed using growing degree day (GDD) model and regression analysis method. Wheat data (1940 to 2016) were obtained from the Southern Regional Performance Nursery (SRPN) experiments at Bushland,Texas. Wheat genotypes were divided into three groups: Kharkof as a check cultivar, the highest yielding cultivar for each year, and all other cultivars. Climate data were obtained from USDA Agricultural Research Service at Bushland and the National Oceanic and Atmospheric Administration. Temperatures between 1940 and 2016 showed a curvilinear trend with a significant rise since 1980. Mean temperature during wheat growing season (September 15 to June 15) increased at a rate of 0.35 degrees C per decade since 1980. Consequently, seasonal GDD and extreme degree days (EDD) increased at a rate of 69 degrees C d and 19 degrees C d per decade. From 1940 to 2016, wheat heading date has shifted earlier by 16 days for dryland wheat and 11 days for irrigated wheat. Maximum and minimum temperatures in March and April had a negative relationship with heading date, while precipitation had a positive relationship with heading date for both dryland and irrigated wheat. Early heading may have benefits for heat escape but also has the disadvantage of reducing precipitation prior to heading-a loss of 25 mm when heading shifted earlier by 16 days for dryland wheat. The five-year moving average yields increased steadily from about 1960 to 1980, plateaued until the late 1980s, and then declined significantly. However, average genetic yield gains were 505 kg ha(-1) under dryland and 1,671.4 kg ha(-1) under irrigated conditions for all new cultivars during 1940 to 2016. Yield trends for all three cultivar groups had similar patterns over the years. Increase in maximum temperature, frequencies of maximum temperature greater than or equal to 31 degrees C, and minimum temperature during grain filling period had significant negative effect on grain filling days and yield (except for minimum temperature under dryland conditions). Precipitation during the vegetative growth (November, January, and March) and grain filling (May) had a significant positive effect on dryland wheat yields, but only the January precipitation had significant effect on wheat yield under irrigated conditions. The study indicated that the rising temperature and shifting precipitation timings as a result of early heading are less favorable conditions for winter wheat production in the US southern High Plains.