Possible Effect of High Temperatures During Wheat Grain Fill

Conner Raymond, Grain Crops Extension Associate, Princeton, KY
Dr. Lloyd Murdock, Emeritus Professor, Princeton, KY

In 2021, wheat producers across Kentucky saw record yields in one of the best wheat production years our state has seen in history. According to the National Agricultural Statistics Service the state average last year was 87 bu/A. This can be attributed to several factors including the near-perfect weather conditions we had throughout the growing season. As we near harvest, one concern to keep in mind would be the effect of higher than normal temperatures during grain fill that the majority of the wheat-producing areas of our state have experienced this year. In general, the ideal temperatures to have at flowering and through grain fill are between 66-72°F. When daytime temperatures exceed 72°F, dry matter accumulation reduces significantly as the temperature increases and stops when temperatures approach or exceed 92°F. The temperature at grain fill has an overall effect on yield in addition to diseases, insects, and other factors.

In 2018 the average state yield for wheat in Kentucky was reported to be 66 bu/A by the National Agricultural Statistics Service. The primary grain fill period that year was considered to be from May 25 through June 8. The average daily high temperature during this period was 84.4°F with seven days at or above 85°F and was one of the yield-reducing factors. Reported temperatures from May 25 through June 8 were taken from the Hopkinsville, KY Mesonet site.

In 2021, the year with the highest ever state average yield, the state average yield was 87 bu/A. The average daily high temperature from May 25 through June 8 was 76.5°F with only two days at or above 85°F.

In 2022, the state average yield will again be affected by the temperature. The average daily high temperature from May 25 through June 8 was 80.7°F with four days at or above 85°F.

Since so many other factors affect yield it is almost impossible to make accurate yield predictions based on this one factor. However, we can probably expect the state average yield to be in the lower 80s at the highest since growing conditions have been good prior to the grain fill period. The yield may also be affected by some disease factors.