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More on Delayed Planting

May 17, 2002
The latest numbers show that we have 51% of the corn crop planted in Illinois (as of May 12), with a lot of progress over the past week in the northern part of the state. Heavy rains over the weekend have a lot of us wondering when we will ever get back into fields (or into them for the first time). It's a familiar refrain for this most frustrating planting season, especially in southern and southeastern parts of the state.

Where corn was planted, standing (or, in creek bottoms, moving) water is creating a lot of questions about the eventual need to replant. In most cases, seeds or small seedlings will not survive for the length of time that water is covering them. If the water went away within two days and only covered the surface one time, those plants should be showing signs of life, and they should revive reasonably well. In most cases, the water went down that quickly only at the edge of ponds and in some creek bottoms. Most other areas where water has stood will need to be replanted when they are dry enough. Overall, that's not a large percentage of planted acres, but it will mean more replanting than we have done in recent years. If it's any comfort, many crop watchers contend that drowned-out spots are more common in good corn years than in poor years, in that it's a signal that it rained.

While most stands in higher parts of fields appear to be good, they should be evaluated to make sure. Use the Illinois Agronomy Handbook or its Web version, http://web.aces.uiuc.edu/aim/iah, for guidelines on replanting. If you know you will have to replant drowned-out areas and think you may have to replant some higher areas due to poor emergence or seedling death, it would be a good idea to line up the amount of seed that you estimate will be needed. The practice of "repair planting" has become common, especially when low areas need to be replanted, and so fields will be driven on with planter and tractor. With wide planters, it is common for the operator to see reduced stands somewhere across the planter width and so to drop the planter down to plant, eventually planting more of the field than anticipated. If you have the ability to change seed drop rate on the go, such repair plantings would benefit from reduced seeding rates to avoid doubling plant population where the original stand is good.

More pressing questions continue to center on yield losses to be expected, as planting delays stretch out, and whether alternatives to corn should be considered. Duane Freder-king, of Pioneer, was kind enough to provide me with some information from research work done in the early 1990s by Dr. George Kapusta at Belleville. That data suggest that yield penalties from late planting are not as severe in south-central Illinois, including what I'll estimate approximately as the area between Benton and I-70. Duane suggests a yield loss rate for the last half of May to be about two-thirds percent per day of delay--roughly 1 bushel per day instead of 1 1/2 bushel per day of delay that we expect in the northern half of the state. The Belleville data project loss rates to accelerate, from 1 percent for the first week or so of June to 2 percent per day of delay by mid-June.

Questions also persist about the "last practical date" to plant corn in different parts of Illinois. This question probably has a different answer for every producer, depending on whether or not the corn is used directly for feed, whether it is to go for food grade, drying equipment, production equipment, alternative crop possibilities, expenditures already made (e.g., for N fertilizer), whether or not herbicides have been applied that will prevent alternatives, and just personal preference and outlook for this season. We can predict that the date by which our yield expectations for corn fall to about 50 percent of expected yield from early-planted corn will be approximately June 15 in northern Illinois, June 20 in central Illinois, and June 25 in southern Illinois. These dates are probably a week or two after the "latest practical date" for most producers who can sell the crop only as grain.

The question of whether or not to change hybrid maturity continues to come up, though with much of the crop planted in northern Illinois this is not as much of an issue. As I indicated before, there is little reason to switch to earlier-maturing hybrids in central Illinois before the end of May, and even then it makes sense only if the intended hybrid is fairly full season--say later than 112-day CRM or so. For most of the hybrids to be grown in southern Illinois, switching to an earlier one for delayed planting should probably never be done, at least not to one much earlier in maturity. One consideration, though, might be to change a less stress-tolerant hybrid for one that tolerates stress better. That might include switching to a Bt hybrid for protection against corn borer, which usually is more damaging to late-planted corn. Most people will need to check with their seed company to get an assessment of stress tolerance of corn they already have in the shed compared to alternatives that might be available.

Until we reach the end of May, a decision to change to another crop is premature for most producers. From a standpoint of marketing and equipment, the only choice for the majority of producers would be to switch from corn to soybean. We'll save discussion of that until next week or later, in hopes that the need to consider switching goes away as the corn crop gets planted. If persistent flooding already has some people making this switch, the maturity of soybeans lined up to replace corn should not be earlier than adapted full-season soybean varieties normally grown. Of course, expected soybean yield will also start to decline as we move to the end of May, but the decline, especially in southern Illinois, will not accelerate as fast as it will for corn.

For most people, switching to a crop like grain sorghum should be done cautiously, realizing that grain sorghum, while more tolerant to heat and dryness than corn and soybean, is also very sensitive to lower temperatures near the end of the season. Finding a market is also a concern in some areas, as is the need to monitor and control insect pests such as sorghum midge. Grain sorghum should seldom be considered for the northern half of Illinois due to cooler temperatures and lack of markets.--Emerson Nafziger

Author: Emerson Nafziger


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