The combination of inadequate rainfall and above-average temperatures is creating stress conditions in many cornfields across Ohio, and the mid-Corn Belt. According to the National Agricultural Statistics Service, 75% of the state is currently estimated to have subsoil moisture content that is rated short to very short.

During the past week, tassels began appearing in cornfields planted in April. The pollination period, the flowering stage in corn, is the most critical period in the development of a corn plant from the standpoint of grain yield determination. Drought effects on yield potential are greatest during the reproductive stage.

Yield losses to moisture stress can be directly related to the number of days that the crop shows stress symptoms. According to Iowa research by Claassen and Shaw on effects of drought, four days of stress (i.e. corn wilted for four consecutive days) at the 12th-14th leaf stage has the potential of reducing yields by 5-10%. The potential for yield losses to soil moisture deficits increases dramatically when plants begin to flower. During tassel emergence, four days of moisture stress has the potential to reduce yields 10-25%. Silk emergence is the most critical period in terms of moisture use by the plant. During this stage, leaves and tassels are fully emerged and the cobs and silks are growing rapidly. Four days of moisture stress during silk emergence has the potential to reduce yields 40-50%. Keep in mind that the stress conditions we are alluding to over these “four day periods” are severe and involve extensive leaf rolling (characterized by plants with “pineapple” like leaves) throughout much of the day. Fields with scattered plants exhibiting some leaf rolling late in the afternoon are probably not experiencing severe stress.