Early Freeze Poses Risk For Late Planted Sorghum

Post on September 15, 2025

early freeze poses risk for late planted sorghum

Brent Bean, Sorghum Checkoff Director of Agronomy

Unusually wet weather in late spring delayed grain sorghum planting across many regions this year. At the same time, good soil moisture following wheat harvest created opportunities for double-cropping sorghum in some areas. The length of time from planting to harvest-ready grain depends mainly on the maturity of the hybrid planted, accumulated heat units, and, to a lesser extent, day length and night temperatures. As with other summer crops, late-planted sorghum carries the risk of reduced yield and grain quality if an early freeze occurs before the crop reaches maturity.

Once sorghum has flowered, it typically requires approximately 45 days to mature under normal conditions. This timeline can speed up or slow down depending on heat unit accumulation, and drought stress may further delay maturity. The impact of a freeze depends heavily on the growth stage of the crop. At the soft dough stage-when kernels can still be crushed between the fingers-only 30-50% of the final grain weight has developed, so a freeze at this point can cause severe yield loss. By the hard dough stage, however, about 75% of final weight is present. From this stage, sorghum usually reaches full maturity within 10-14 days. Yield losses from a freeze during hard dough range from 2-27%, depending on how close the grain is to maturity. Each day of favorable growing conditions during this period significantly improves yield potential.

Not all freezes cause the same level of damage. A light freeze may kill leaves but leave stalks intact, allowing the plant to continue filling grain. More severe freezes often result in low test weight, producing shriveled kernels that are difficult to thresh. Test weight reductions stem from an increase in broken kernels and foreign material. Grain that falls below 55 pounds per bushel cannot qualify as U.S. No. 2 grade sorghum and will be subject to price discounts, which vary with the degree of test weight reduction.

Fortunately, research indicates that sorghum with test weights between 40-60 pounds per bushel has similar feeding value for livestock. For this reason, growers facing discounts in commercial grain markets may find it more profitable to sell directly to livestock feeders. Another option is to improve test weight by adjusting combine settings or cleaning the grain after harvest to remove light and broken kernels. While these practices reduce total yield, they can improve the grain's marketability.

For additional guidance, growers can consult the Kansas State University publication Harvesting Grain from Freeze-Damaged Sorghum, which outlines management strategies for dealing with freeze-damaged crops.