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Issue No. 13, Article 5/June 19, 2009

Still Wet, and Corn Not Planted?

While corn planting in Illinois was officially 96% complete by June 14, a considerable number of fields remain unplanted, especially in the southern part of the state, where less than 90% was planted. Wet weather continues in much of that region, though there are places where some progress has been made this week.

While I've tried to paint a realistic picture of what to expect with regard to late-planted corn, I've also emphasized that past observations are so variable that any estimate we make is a guess. Corn planted after June 15 in southern Illinois has yielded from zero to more than 200 bushels per acre, with an average of no more than 100 bushels. At this point in the season, we have no way to predict where in this range yields are likely to land. We still have a reasonable chance to get a corn crop planted this week (by June 20) to maturity with growing degree-days left in southern Illinois, but it would likely help now to shorten hybrid maturity by 10 days RM compared to hybrids normally used.

Prospects for corn planted the last week of June are not great, and it's likely that some acreage set for corn but not yet planted in such areas will be planted to another crop. The first choice for many will be to grow soybeans on these acres. Vince Davis has been covering late planting for soybean. Given that wet weather is starting to delay wheat harvest, it's likely that "full-season" soybeans will have little or no head start on double-crop soybeans in many areas this year. In fact, wheat dries out the soil as long as the wheat plants are still green, so fields following wheat harvest may in some cases be ready to plant sooner than those planned for a "full-season" crop.

One issue that has changed is the need to plant corn to recoup N applied earlier. Given how wet it has been for the past two months in fields not yet planted, a substantial portion of N applied early has likely been lost by now, especially if any of the applied N was in nitrate form (as in UAN). Most of the N from anhydrous ammonia and a considerable amount from urea applied in the past month is likely still present, but much of it is in the nitrate form by now and so subject to movement downward in better-drained soils and to loss by denitrification in fields where soils remain wet. In any event, the expenditure to apply N has diminished, and even though it's not pleasant to write off such an expense, it is likely that the value of yield loss from delayed corn planting will exceed the value of the N left in most fields, making the switch to another crop more logical.

Prospects for other crops planted this late are considerably less than prospects for soybean. One crop often mentioned for late planting in southern Illinois is grain sorghum. Grain sorghum is a true warm-season crop, with tolerance for high temperatures and some ability to withstand periods of low soil moisture. But its yields respond to the summer weather much like soybean yields do--because the flowering process in corn is not as sensitive to weather as is flowering in corn, and because grain sorghum flowers later than corn, it thrives on good conditions in August, much like soybean.

Still, planting grain sorghum in late June or early July diminishes its prospects considerably. One reason is that it flowers relatively late (the "days" attached to grain sorghum maturity are tied to flowering, not maturity) and so needs good late-summer weather to fill its grain well. Grain sorghum is also sensitive to cool weather; it can nearly stop filling if September is cooler than normal. It also has some insects that other crops don't, weed control is more difficult, and markets are spotty. Grain sorghum simply isn't a magic bullet as a late-planted crop. In the northern half of Illinois, its sensitivity to cool weather makes it generally unsuitable for late planting, at least as a grain crop.

Another possibility in the "desperation category" of late-planted crops is buckwheat. Buckwheat is an indeterminate crop, but it will usually produce some seed even when planted in mid-July. It continues to flower and set seeds up to frost in some cases, so late planting is not the way to get high yields, though in rare cases buckwheat might thrive if it survives through late summer and late September and October are cool and moist. More importantly, buckwheat is a cool-season crop, and hot, dry weather can mean no crop to harvest at all. Some people give it credit as a cover crop, but it does not fix N, and it would not be preferred as a soil-building cover crop over one like red clover.

There may be some market for buckwheat, but buyers look for large seeds, and buckwheat that comes under high-temperature stress will often not compete well in price.

If there is a market for forage crops, warm-season grasses like sorghum-sudan might be possibilities for late planting. Keep in mind that late planting of such crops may compromise their productivity, like it does for other warm-season crops. Most warm-season forage crops do not produce high-quality forage, so markets are often limited. It might even be better to plant corn as a possible forage crop than to plant sorgum-sudan, since corn might produce similar forage yields if it doesn't produce grain, and if the weather is favorable it might even produce grain for sale or feed. Some pests like corn rootworm are less likely to be a problem with corn planted very late, so it may be possible to use seed with fewer traits and a lower cost.

I learned this past week of some unplanted acres where the prevented-planting payment is expected to exceed the profit from a cash crop that could be planted this late. We would not normally give up on soybean until July in southern Illinois, but some unplanted (and still wet) fields in northern and central Illinois might be reaching the point where no crop will be grown for sale in 2009.

Planting a cover crop of some sort on such acres is often preferable to leaving it fallow. A cover crop will maintain microbes (VA mycorrhizae) that will help next year's crop to take up P better, thus preventing the "fallow" effect. A leguminous cover crop like red clover will provide some N to next year's crop. And cover crops usually help keep weeds down, thus reducing the amount of weed seed produced. Some producers may also choose to tile or haul manure on uncropped fields. While we would never wish for uncropped acres due to weather in Illinois, cover crops may in some cases be preferable to getting little income from very late-planted cash crops.--Emerson Nafziger

Author:
Emerson Nafziger

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