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Issue No. 24, Article 4/November 7, 2008

Observations from the Unusual 2008 Season

Soybean harvest is nearing an end for 2008 in Illinois, and corn harvest is finally making rapid progress, with some two-thirds or more of the crop harvested by now. To call this an unusual year seems like quite an understatement. The 2008 season in a nutshell:

  • The spring was cool and wet, and planting was delayed for both corn and soybean; corn reached 50% planted by about May 8, and soybean not until the end of May. Much of the crop was planted into less-than-ideal conditions.
  • Emergence and early growth of both crops was slow through late May, with emergence percentage lagging about two weeks behind normal.
  • In some parts of Illinois, many fields of both crops had to be replanted, in some cases more than once. Many fields of corn and soybean in south-central Illinois were planted (for the last time) in June, some in late June.
  • Rainfall was in plentiful supply in most areas in June and July, with monthly totals more than twice the average in some places.
  • There was little if any hot weather during the entire growing season, and growing degree day accumulation was below normal early in the season and fell further behind during the season, with deficits of 100 to 200 GDD from May 1 through the end of August.
  • Heavy rainfall fell in most areas during the first half of September, generated by hurricane remnants. GDD accumulations caught up slightly in September, but harvest started very slowly, with less than 10% of corn and soybean harvested by the end of September.
  • There was some light frost in northern Illinois the first week of October, but the first killing frost occurred only during the last week of October in most of the state.
  • Harvest of both corn and soybean dragged out through October, with delays due to late maturity in both crops, wet soils for soybean, and high corn grain moisture.

After a season of on-and-off, unevenly distributed poor conditions, yields of both corn and soybean will be among the highest on record, with soybean yield predicted at 45 and corn at 177 bushels per acre in the October estimate. There have been reports of very high yields of both crops in some areas, especially in parts of western, northwestern, and central Illinois. Soybeans and corn replanted in mid- to late June in south-central Illinois yielded in some cases 60 and 180 bushels per acre or more. The only reasonable explanation for such yields is that the season was much extended, with maturity occurring weeks to a month or more later than average, and a great deal of grain filling after September 1, during the weeks before maturity.

I had predicted back in the "troubled" days of May and June that a good September could bale us out of trouble, but the hope was that yields would not be less than normal for such late planting, and few were thinking about the possibility of above-average yields. Without doubt, the recovery from a late and poor start to the season was beyond anyone's hope.

The predictions I made in June about how crops would respond to late planting were completely inaccurate as a result of the unusual season. Averaged across plant populations, the last planting, on May 30, yielded more at Perry than did any of the earlier plantings, which ranged in date from April 7 to May 10. Such results represent a dilemma: if such a season will never happen again, then including it in the database means less accuracy in future predictions of planting date effects.

While yields in many fields are good to outstanding in many areas, problems in ear development, similar to those I discussed earlier in the season, became noticeable in some fields only during harvest, often only after yields were lower than expected. Some of these symptoms may be related to later-than-normal herbicide application and may in some cases be related to the use of certain additives, if not to the herbicides themselves. One symptom that has been reported from a number of fields is the presence of "empty" kernels, present only as the seedcoat, scattered on the ear among normal-sized kernels. We will study these cases and try to see if they have a cause in common. But it is possible that such unusual symptoms came about because of unusual interactions between practices and crop development as affected by unusual weather. If that's the case, we may never see such symptoms again.--Emerson Nafziger

Author:
Emerson Nafziger

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