Issue No. 3, Article 8/April 9, 2004
The Season Gets Under Way
While we have had fewer warm days this year in late March and early April than in 2003, soils are drying well in many parts of the state, and both planting preparation and planting are starting to get under way. Although some producers in the northern part of Illinois wait to plant until after the middle of April, many in central and southern Illinois start to plant as soon as soil conditions are good for planting. Some may even do so before soil conditions are good. Others may plant in good conditions, but chances for weather-related problems are greater with earlier planting. In fact, some of the corn planted in March this year is struggling with the wet and cool weather in the past weeks, and some may need replanting.
Our data suggest that corn planted in the first half of April will on average yield less than corn planted in late April, but this effect will vary with weather. Can we guess whether this will be a year when very early planting helps or hurts yields? Not very well, though one key to gaining from early planting is to wait to plant until soils are in good shape to plant. "Good shape to plant" tends to be interpreted by individuals differently, but most of us know it when we see it. Taking a spade and turning over soil to 4 or 5 inches deep will often show how well the soil crumbles, indicating how ready it is to plant. If you prefer not to look too closely at whether or not you are bringing up wet soil, then it is probably not very fit.
As I have said before, the first half of April is no time to do "foolish" things to get corn planted. If it turns wet and cold after early planting, we may feel that early planting was valuable because it meant not planting late, but corn planted into soils when they are too wet will often fail to thrive. We generally need a little better "luck" for corn to emerge and grow well when it's planted very early. This doesn't mean we shouldn't plant early, but we should do so only when conditions are good.
Even if a lot of acres need to be planted in the next month, history tells us not to get too agitated even if rainfall in April is normal and we aren't able to plant exactly when we would like. The last week of April is considered the ideal time to plant, but yield losses for planting up to 10 days on either side of the ideal date are not large. On the other hand, one of the real benefits of planting early is that replanting, in the event it is needed, can be done closer to the optimum planting time.
Does anything change with planting date? It is often considered best to plant full-season hybrids first, followed by midseason and shorter-season hybrids. In fact, the maturity range utilized by most producers is not that large: Even "full-season" hybrids have a fair cushion of growing degree-days for a given area, and growth rates for all hybrids are slow when growing degree-days accumulate slowly early in the season. This means that, except to make sure that fuller-season hybrids don't get planted late, managing crop development and maturity through planting date won't usually make large differences. By the same token, getting the crop up and growing by early May often has limited benefits, both because growth is slow under cool conditions and also because an emerged crop is more subject to frost injury, and sometimes to other problems.
One question this spring is whether varietal maturity and planting date can be used to ensure early harvest, which this year can mean a considerably higher selling price of the crop. Due to the photoperiod effect on flowering and the slow growth of soybeans during cool temperatures, planting very early does not mean a much earlier harvest, though there is some effect, perhaps a day earlier maturity for every 5 days or so earlier planting. This is expected to vary a lot with the year. Varietal maturity is a more effective method of moving up harvest date, but this often comes at a cost of lower yields. In northern Illinois, a mid-September harvest by early planting of early varieties (groups 1.8 to 2.0) may not be able to ensure a yield great enough to negate higher prices. Early-maturing varieties can yield with later ones if the weather is good, but they usually have less ability to survive periods of dry weather without losing yield.
Chances of managing maturity and planting date for mid-September harvest are much better in central Illinois and are good in southern Illinois, though there will often be some yield penalty when soybean seed has fewer days to fill. Planting an MG 2.8 to 3.0 in early May in central Illinois might work, but cool temperatures in August will sometimes prevent early harvest. Trying to ensure harvest by the end of August will likely be counterproductive in most years because of large expected yield losses. In general, it may work to try to make small changes in hopes of harvesting early, but be prepared for these changes not to work as planned.
Our research has shown that the first 20 days or so of May in northern and central Illinois are the best time to plant, and any time in May is good for southern Illinois. Planting in early April and late May results in yield losses of about 10%, though this varies from year to year. Dropping about 150,000 to 175,000 seeds usually results in optimum stand numbers. We did not find much reason to change seeding rates for different planting dates. Serious stand loss can occur regardless of planting date, usually as a result of heavy rainfall before emergence and, when planting is very early, of frost. But even with good stands, soybean planted before mid-April tends to yield less than that planted in late April through mid-May.
Wheat is generally in good shape, benefiting from the gradual warm-up and general lack of flooding and freeze injury. If it turns warm and wet, there could be some nitrogen loss, but the crop should remain in good shape if cool, relatively dry weather holds through the next weeks.