By Rich Pope, Department of Plant Pathology
In a season that started with weather tumult fouling up the planting season in many areas, we have done pretty well in getting the corn and soybean to reproductive stages. Degree days remain behind long-term averages as of August 17.
But now the focus is on grain fill. The cooler than normal weather of the last two weeks are potentially beneficial, as the cool nights tend to stretch out the grain-fill period. The longer the plants stay functioning, the more dry matter can be stored in the grain. That is, as long as plants avoid an early killing frost. Normal killing frost dates in Iowa are around the first of October in northern Iowa and about the 10th of October in the south. Two weather factors that will help enhance corn yields in the next six weeks are ample sunshine and rain, to avoid moisture stress.
For the fun of it, I prepared a chart of base-50°F degree-day accumulations through the 2008 growing season to date for central Iowa. Our degree-day deficits have pretty consistently lagged the long-term average by about 7 to 8 degrees per week. Of course, it bears mention that degree days gained when the seed was in the bag don’t count. In some areas this accounts for a considerable share of the acres and explains much of the variability in crop development.
Rich Pope is an Extension specialist working in the Corn and Soybean Initiative
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