Issue No. 6, Article 8/May 1, 2009
Thoughts on the Slow Start to Planting, Version 2009
The Illinois corn crop was 4% planted on April 26, the lowest percentage planted by this date since 1993 and only about a tenth of the acres planted by this date averaged over the past 5 years. On this date in 2008 we had only 5% planted, so we're not too far behind the pace set last year, which turned out to be a good year for corn in Illinois.
Unfortunately, the weather pattern seems to be different this year, with most areas of the state still wet at the end of April and more rain forecast for this week. Planting got underway fairly quickly in May 2008, with 28% planted by May 4, 60% by May 11, and 75% by May 18. There is almost no chance that we will be able to match that pace, at least in early May 2009, given the cool temperatures and slow drying rates, along with very wet soils in many areas now.
Can we do anything more than mope about this and hope that the forecasts are wrong and that it will turn warm and dry sooner? Not much (well, there may be little point to moping), though we can take some slight hope based on the fact that late planting did not hurt yields nearly as much in 2008 as we had predicted based on planting date studies done before 2008. But we also need to remember that 2008 was a most unusual year, with above-normal rainfall most months and temperatures that never got very high. There's no law that says that this can't happen again in 2009, but the chances aren't high.
We generally operate under the assumption that the drier the April the better, to allow planting to start early and proceed quickly. Darrel Good and Scott Irwin, ag economists here at the U of I, have been doing some work to see what weather factors correlate best with yield statewide. To my surprise, they found that April rainfall, at least up to amounts modestly above the monthly average, actually has a positive effect on yield. Even a very dry April typically has around 2 inches of rainfall, and I would have expected years with dry Aprils to have above-average yields and for more rain in April to translate into later planting and lower yields. This does not seem to be the case. That doesn't mean that the wetter the April the better, but we can see that other weather factors often override the effects of a wet April, even if a wet April means some delays in planting. A wet April that turns into a wet May could well be another story.
The question of switching from corn to soybeans as planting is delayed is a little complicated, given recent price moves in both crops. I would suggest using the guidelines regarding planting delays in corn published in issue 3 of the Bulletin (April 10, 2009) to estimate corn yield and using the guidelines for soybean in this issue, and basing the decision on costs and those (expected) yields for a given date.
Along with the question of switching from corn to soybean as planting is delayed into May will be the question of switching to an earlier hybrid. My quick answer? Don't. Most of the hybrids we will plant in Illinois have a growing degree-day "cushion" that means planting even in late May usually brings little danger of being frosted before physiological maturity.
There are few other adjustments we can or should make in preparation for, or in response to, delayed planting. It is clear now that planting should take priority over operations like N application, unless such operations can be done without delaying planting and without causing damage by driving on too-wet soils. On the plus side, planting into warm soils means that crops emerge faster and more uniformly than when soils are cool. We have accumulated only about the average number of GDD since the beginning of April this year--about 200 in central Illinois--so crops planted early have not emerged very quickly or made much growth yet.--Emerson Nafziger