As expected with Indiana's waterlogged delay of serious corn planting, questions abound on the effect of delayed planting on corn grain yield. All things being equal, late planting of corn will result in yield losses of one to two bushels per acre per day of delayed planting relative to corn planted from late April to early May.
If things are not equal, delayed planting may have different effects. If you are comparing corn planted late under good conditions with corn planted early under poor conditions, the yield loss to delayed planting will likely be much less. If you are comparing late planted corn that experiences severe moisture stress during pollination with early planted corn that experiences excellent weather season long, the yield loss to delayed planting may be much worse.
What I am trying to remind you is that planting date is just one of many factors that determine grain yield in corn. In fact, numerous other factors are far more important in determining grain yield than is planting date. For example, rainfall and temperature during July and August are usually considered to be the most important yield-determining factors for corn in Indiana. In fact, the four 'disaster' years that Indiana corn growers have experienced statewide in the past 13 years (1983, 1988, 1991, 1995) were the result of mid- to late season hot, dry conditions.
So, while delayed planting may cause yield loss relative to early planting, excellent weather patterns subsequent to planting may result in a late planted corn crop that yields acceptably well. In fact, if you compare statewide average corn yields with the date by which 50 percent of the state's corn crop was planted, you will find little relationship between delayed planting and corn grain yield.
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