I never expected to see "European" wheat yields in Illinois, but we have just finished a season in which the weather brought us very high yields. The yields in the University of Illinois variety trials, found at the Web site http://vt.cropsci.uiuc.edu, show that at the DeKalb location, one variety produced more than 150 bushels per acre. In the international metric system, that is more than 10 tonnes per hectare. I understand that in England there are "10-tonne clubs" that reflect the fact that this yield level is seen as a real achievement, even in the best climate for wheat in the world. We'll probably hold off on making application to start up such a club in Illinois, but it's an amazing thing nonetheless. I usually regard good wheat yields as equal to about half of good corn yields in an area. That would equate 150-bushel wheat with 300-bushel corn. They seem about equally likely.
Why such unusually high yields in 2003? Fall 2002 was relatively cool and dry, and wheat got off to a rather slow start, with less than average amounts of tillering and ground cover before dormancy. The crop came through the winter well, in part because it stayed cold, without repeated freezing and thawing cycles. Early spring weather was extremely favorable, with cool, dry weather in March and April. It was rainy and cool through much of May, with many wheat fields in southern Illinois saturated at times. Despite wet conditions, there were no serious problems with leaf and head diseases in most fields, probably because of cool temperatures and low inoculant loads. Fusarium head scab was an exception, but it was at high levels in only some fields in southern Illinois.
The weather in late May and early June remained cool, with enough good, sunny days to result in high grainfilling rates and high yields. The estimated yield on 780,000 acres harvested this year is 62 bushels per acre, which would be the highest ever in Illinois. Final yield figures will, I suspect, be even higher. Farmer field yields in the range of 120 bushels per acre were re-ported in central and northern Illinois.
I expect such high yields to be used as an opportunity to promote "intensive" wheat management. Without a doubt, better-managed wheat fields were able to take better advantage of the weather to produce high yields. But we need to be very careful about concluding that "intensive" (read "expensive") management was the real reason yields were high.
As an example, we conducted a study here at Urbana, in a field planted a little late following soybean last fall and where the stand this spring was not particularly good. It had 40 pounds of nitrogen applied at planting. In March, I applied rates of 0, 40, 80, and 120 pounds of nitrogen as ammonium nitrate. At heading, I applied 8 ounces of Quadris fungicide to half of each nitrogen plot. Table 1 shows the results.
There was no significant response to nitrogen rate in this study. Quadris produced a significant yield increase but of only about 5 bushels per acre, which would probably not have paid for the treatment. There were few visible foliar diseases on the crop, and no visible response to fungicide. In other studies, we saw significant yield increases from Gaucho seed treatment, mostly in the 3- to 5-bushel range, even though we do not think that there were many insects to manage.
In general, we found that pouring on extra inputs provided only small, if any, yield increases and often no return on investment. But with yields so high, many will feel that inputs they used really paid off, and others will wish they had used more inputs to raise yields even higher. We need to remember that most of what we hear on this topic tends to be testimonial in nature, with certain inputs used and high yields but no way to know if the inputs really paid their way. We also need to remember that getting another year like this past one is quite unlikely. It's not impossible, but it's the first such year I've seen in 22 seasons in Illinois, and I do not expect to see another one during my career. Sound management can keep us ready to take advantage of such a year if we get one without breaking the bank if we don't.
Sound management starts with variety selection (see the U of I variety trial results previously referenced). Plant close to the fly-free date for your area; the fly-free date ranges from mid-September at the northern edge of Illinois to mid-October at the southern tip. Make sure enough soil phosphorus is present or added, and apply 20 to 40 pounds of nitrogen to help get the crop started. Drill about 35 seeds per square foot, or about 1.5 million seeds per acre. Add topdress nitrogen during the winter or early spring to a total of 80 to 120 pounds of nitrogen per acre, and use herbicide if needed for wild garlic or other winter annuals. And hope for weather like we have had since last fall.--Emerson D. Nafziger