Late-season dry weather raises concerns
The 2013 corn growing season has had its share of ups and downs, with late planting due to early rainfall, more rain in June, and temperatures that were at or below normal most of the season until recent weeks.
Pollination conditions were good in most places, with adequate soil moisture and generally good temperatures. By late July most fields were in good shape, with good kernel counts and good canopy color and leaf health.
Much of the crop reached the middle part of August in good shape, helped along by continued cool temperatures. But rainfall became infrequent or stopped at some point in July or August, depending on location. At Champaign, July rainfall was slightly above average, with 5.03 inches at the airport, more than half of which fell on July 21. Many areas received much less than this.
Temperatures continued to be part of the weather story, with growing degree day accumulations well below normal during the last week of July (with barely more than 100 GDD at Champaign) and again the third week of August. That changed to above-normal temperatures the last week of August, and since then, weekly GDD accumulations have been above normal, with the total for the first 10 days of September 234 GDD, nearly half the normal total for the month.
Despite the hot, dry weather of recent weeks, corn in many fields has retained some green color, at least in the upper canopy, and it appears that kernels continue to fill. That may not be the case in some of the drier parts of the state, where the crop either ran out of water earlier in August or where canopy color wasn’t very good even before that.
Many have commented on the poor leaf color in some fields, even in areas where there has been some rainfall. Some have reported that adjoining fields with the same hybrid, planted and treated alike, show differences in canopy color and crop condition. Reasons for this are often not clear, but might be related to soil condition at planting, differences in how well nitrogen stayed in the soil and available to roots, or root damage due to flooding or insects. I think that root-related problems are more likely to be issues than loss of N. As is sometimes the case when roots have issues, corn following corn may not perform as well as corn following soybean again this year.
The high temperatures of recent weeks along with drying soils have acted to move the crop toward maturity faster than we had expected.
In most areas this is the result of high temperatures rather than of lack of water. At Champaign, GDD accumulations from May 1, May 15, and May 30 through September 10 totaled 2,760, 2,590, and 2,310, respectively. Mid-season hybrids used in central Illinois typically need 2,700 to 2,750 GDD from planting to maturity, so early May plantings should be at or near maturity by now. Those planted in mid-May should mature by September 20 or so, while corn planted in late May or early June is still be several weeks from maturity, unless dry soils bring on early maturity.
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