Multi‐Decadal Analysis on the Impact of Climate Change, Genetic Gain, Cultivar Type, and Harvest Timing on Main and Ratoon Rice Yield and Quality

Thirty-three years of climatic and commercial rice yield and quality data were used to estimate the impact of climate change, genetic gain, cultivar type, and harvest timing on main and ratoon crop grain yield and quality for the Texas Gulf Coast rice production region. Major climate change has occurred since 1991, with cumulative annual degree-days (°D) and atmospheric [CO₂] increasing 11.6% and 18.4%, respectively, and precipitation, irradiance, and relative humidity decreasing by 22.0%, 2.3%, and 3.3%, respectively. Daytime °D > 10°C and ≤ 30°C, daytime °D > 30°C, nighttime °D > 10°C, atmospheric [CO₂], irradiance, relative humidity, and precipitation significantly affect several main and ratoon crop traits, with increased nighttime °D > 10°C consistently reducing grain yield and two of the four measured grain quality traits. Hybrid rice outyields inbred cultivars and produces slightly higher total milling yield for both the main and ratoon crops but consistently produces lower head rice yield and more broken grain. Had the positive effect of increasing atmospheric [CO₂] on grain yield not been incorporated into the analyses, a large part of the increase in grain yield over time would have been incorrectly attributed to inbred and hybrid genetic gains. Several quality traits worsened the later the rice main crop was harvested, due to increased temperatures during grain fill for later produced rice, and possibly due to increased insect and disease pressures. The negative effects of climate change on rice grain quality can be partially mitigated by shifting seeding dates earlier and by focusing rice cultivar development on incorporating high temperature and high CO₂ resistance traits.