Effect of heat on grain fill
June 12, 2009
Winter wheat is a cool season crop, therefore it thrives in cool environments. Wheat does not do well in hot, dry and windy environments, especially during flowering and grain fill. The ideal temperature range during those critical stages of development is between 68 and 72 degrees F. At higher temperatures, wheat plants may abort flowers, which will result in fewer kernels per mesh.
If temperatures are very warm for more than three consecutive days during grain fill, plants will “senesce” (which means to age, develop or mature) early and speed through this critical stage. High temperatures in the grain filling stage will slow or stop formation of starch and protein. The kernel can be shriveled, resulting in lower kernel weight and lower yield. The kernels simply will not fill properly. This effect will be most pronounced if nighttime temperatures are in the 60’s or higher. If nighttime temperatures dip down into the low 50’s or lower, then wheat plants can tolerate high daytime temperatures better.
In addition to that, hot, windy conditions rapidly deplete available moisture and can result in heat scorch to the wheat plant. The result is often premature drying and bleaching of the heads. Even if there is soil moisture in the wheat field, high temperatures can “cook” the plant and force premature plant death.
Diseases can compound the heat stress effect and cause leaves to die even more quickly. Barley yellow dwarf and wheat streak mosaic are present in many fields this year.