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Corn and Soybean After a Tough Planting Season

June 21, 2002
Corn and soybean planting is finally coming to an end for 2002, except of course for double-cropped soybean. And, in areas where excessive rainfall during the past two weeks has resulted in drowned crops in lower parts of fields or in bottomland, some producers are still hoping to plant soybean. A few still may be hoping to plant corn, but yield prospects for corn now are low enough that another crop should be planted if that is feasible.

Double-cropped soybean producers are accustomed to planting this late, but those hoping to replant in the northern half of the state face unfamiliar challenges. For almost everyone, the maturity of the varieties for planting in late June should be the same as that of varieties planted in May. In the northern tier or two of counties, producers who like to use late-maturing varieties (early group 3) for planting full-season soybean might want to drop back to a shorter-season (mid- or late group 2) variety in order to reduce the chance of the crop's not maturing before frost. Those who normally plant early-season varieties might even consider moving to slightly later-maturing ones. Late-planted soybeans tend to stay short, and if earlier varieties are used, they stay very short, especially if there is dryness during vegetative development. Shorter-season varieties also tend to be less able to withstand short periods of dry weather than longer-season varieties.

Probably more important than changing variety for replanting this late is using narrower row spacing. Because of the reduced vegetative growth--plant height and leaf area--that we expect when planting is delayed, soybean planted late in wide rows often will not form a complete canopy, and yield will suffer as a result. Any soybean planting after June 15 should, therefore, be done at a row spacing of 20 inches or less. Late planting in narrow rows probably should be done at a seeding rate of at least 200,000, keeping in mind that warm, moist soil conditions usually result in good emergence. On the other side of the coin, seed that has not been stored in very good conditions might be losing germinability by now. Last year was a good year for production and seed quality, so this should not be a problem unless seed was stored unprotected. But germination has been known to start dropping by the end of June, so some care is warranted to make sure replanted seed is good.

Most of the corn is growing well now, due to favorable temperatures and good soil moisture. Corn planted in early April at Urbana is now about waist high, with 11 or 12 leaf collars visible, while that planted in late April has reached the 9- to 10-collar stage. Even corn planted late will start its period of rapid upright growth soon, and its appearance will improve rapidly after that. Some of the "improvement" will come from the larger plants' making it difficult to see the problems that exist in some fields, however. We have had reports of poor stands due to the May frost, from hail, and from crusting and poor emergence, as well as from standing (and "restanding") water. Stands in 2002 will not be as good as those in 2001, but they're probably at least "average" in most fields.

If normal temperatures prevail, we're looking at tassel emergence being a week or so later than it was last year in the fields that were planted on time. Growing degree-days lost due to delayed planting or just cool temperatures are starting to accumulate now, but we can't expect corn planted in late May or early June to pollinate before mid-July. The key to successful pollination will be, as always, the weather. We need moderately warm temperatures and some early July rainfall to prevent yield-reducing stress in the crop. In general, the corn crop this year will have a smaller, shallower root system than we would like, meaning that it will be more affected by any stressful weather conditions. If we ever needed the "gentle inch of rainfall per week," it's this year. On the positive side, stored soil water is plentiful at this point, so our deep Illinois soils will help provide the water that the crop needs. Let's hope for the best.

Wheat harvest is just beginning in southern Illinois. The crop there headed at the normal time, and the fact that it was filling grain up to the time it reached maturity recently is a good sign for yield, though there may be grain quality questions in many areas. I did have one report of "decent" yields, but where water stood in fields we probably can't expect miracles. For those who will be double-cropping, soil moisture supplies should be adequate for soybean establishment, at least in most areas.--Emerson Nafziger

Author: Emerson Nafziger

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