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Favorable growing conditions over much of Virginia during the early season allowed development of a good crop but many ears did not develop kernels all the way to the tip. This phenomenon is usually associated with environmental stress or nutrient deficiency because ear length (kernels per row) is heavily affected by stress. This year, however, most corn didn't experience much drought stress but some still exhibits poor tip fill.
One possible explanation is that very favorable conditions at the time when ear length was determined dictated the formation of unusually long ears. Silk emergence on a corn ear is sequential with silks near the base of the cob emerging from the husk first, and tip silks emerging last. It naturally takes more time for tip silks of long ears to emerge.
Pollen shed from an individual tassel may continue for up to seven days but the majority is shed on the second and third days after anther emergence. Pollen shed occurs in two peak "flushes" each day; once in mid-morning and once in late afternoon. Rainfall and dew also influence pollen shed because if anthers are wet, the pores will not open and pollen will not be extruded. It is likely that the inherently short pollen shed period for corn combined with several wet days created a situation where late emerging silks received no pollen, resulting in barren ear tips. Without pollen, the potential kernel is not fertilized and kernels do not develop. If a silk does not receive pollen it stays attached to the ovule until it decomposes so an easy way to check for grain pollination is to look for silks that have detached. Evidence for non-fertilization of an ovule exists when silks are still attached.
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