Hot & dry: Stress on the corn crop escalates
uestions and concerns about the potential of Indiana's corn crop are increasingly on the minds of growers throughout the state, especially in areas hardest hit by the current drought. Rainfall continues to be hit or miss as isolated storms rumble through the state, dropping decent amounts of rain here and there but missing large areas entirely.
The moderate temperatures enjoyed throughout the state since the end of May delayed the onset of severe drought stress symptoms in many areas, but those temperatures have recently climbed to above-normal levels and, coupled with excessively dry soil conditions, increasingly reveal the severity of the situation in field after field. Areas in the state have already "gone over the brink" to disaster status relative to yield potential.
Eighty-seven percent of the state is currently estimated to have subsoil moisture content that is rated short to very short and is higher for this time of the season than any year since 1988. Estimated crop condition continues to worsen; down to 27% good to excellent as of 24 June 2012 and is lower for this time of the season than any year since 1988.
For some, the effects of the drought began after planting in fields where seedbed moisture was simply inadequate for germination and emergence of the crop. Large areas in these fields are simply devoid of corn or soybean plants. With no rainfall after planting, many farmers elected not to attempt replanting knowing that the second attempt at establishing a crop would not be successful. The lost yield potential in such fields obviously cannot be recovered.
For other fields where initial stand establishment was satisfactory, the severity of the drought stress on crop development has slowly become worse and/or has escalated in recent weeks as the combination of drought and heat stress worsens. The severity of the stress is such in some fields that plants are simply dying. Some growers have already worked with their crop insurance adjusters to assess the yield loss potential of their damaged fields and have basically abandoned the crop for this year.
This early in the season, it is difficult to estimate the effects of the drought on the eventual statewide average grain yield because we cannot accurately forecast the weather for the remainder of the season. Trend yield with "normal" weather for corn in Indiana for 2012 would be 163 bushels per acre (bpa).
There is a moderate linear relationship between crop condition ratings (percent good and excellent) throughout June and grain yield at the end of the season that accounts for about 33% of the variability in historical grain yields. Based on that relationship alone, the predicted statewide average grain yield for corn as of the end of June would be 145 bpa or nearly 11% below the trend yield.
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