Purdue University agronomist Dr. Bob Nielsen says concerns about the success of the Indiana corn crop's pollination are "well grounded" because the success of failure of this important period greatly impacts yield potential.
"Severe drought stress can impact the pollination process in several ways," says Nielsen. "The effects are particularly likely to occur if the severe drought is accompanied by excessive heat and if corn fields have been subjected to drought stress in the days or weeks preceding the onset of the flowering period."
Nielsen explains that severe drought stress can delay the emergence of silks from the tips of the husks by slowing the elongation rate of the silks. "If the delay is too great, silks emerge after most or all of the available pollen has already been shed from the tassels. The result can be barren or nearly barren ears," he says.
"Another consequence of severe drought stress on the pollination process, especially if accompanied by excessive heat, is that exposed silks may desiccate and become non-receptive to available pollen being shed by the tassels," adds Nielsen. " Pollen "grains" cannot germinate on dried, exposed silks and, thus, will fail to fertilize the ovules connected to the silks. Again, the result can be barren or nearly barren ears.
Nielsen says even if pollination occurs successfully, severe drought stress that continues into the first week or two after pollination may cause newly-formed kernels to quickly abort. "Moderate stress often results in barren tips of ears because those kernels are usually last to form," he adds. "Severe stress may result in scattered kernel set throughout the ear or odd patterns of kernel abortion like the so-called 'zipper' pattern."