The 2012 drought was an example of the importance of agronomic management to achieve early optimum root development.
Emerson Nafziger, University of Illinois Extension agronomist, recommends a combination of soil management to encourage root depth and select hybrids and varieties with vigorous growth and good yield records.
“Faster growth in the spring means faster root growth, and that means a better way to tap the water that’s in the soil and that’s really about all we can do,” Nafziger said at the recent Corn and Soybean Classic.
Last year’s drought was another reminder that no two droughts are the same.
“We like to think that it’s drought, and that means this happened, this happened, this happened. No, that isn’t what happens,” Nafziger said. “We’ve had some of our best yields in years when the annual rainfall was way less than normal in some areas.
“It’s usually not a question of the quantity of water and did it rain enough for the year. I know that’s how some people like to summarize it, and we were 10 inches down or 8 inches down. Just forget about that. It isn’t very meaningful.
“Our corn crop needs about 22 to 23 inches of water to produce a good crop, and our rainfall averages through central Illinois is 35, 36 inches, so we get more rain than we need. And typically some of that water goes out the tile lines or runs off the field if it rains really hard and we don’t get that much into the soil necessarily, but generally we have enough for the crop.
“With our central Illinois soil, it takes a pretty good drought to do the damage that we had done this last year. The timing has to be right. It has to do with how well the crop was set up to take it and so on. That’s what I mean by kind of drought.”
Rainfall was below normal in nearly all of Illinois in every month from April through July, and total rainfall over this period ranged from 6 to 12 inches or about half of normal.
July’s average high temperatures were six to 12 degrees above normal. Rainfall and temperatures returned to normal in mid-August.
“Drought and heat always go together, and we don’t separate them in our mind very much, but we would have had a really serious problem in 2012 even if the temperatures hadn’t been above normal,” Nafziger said. “If the crop doesn’t have enough water, it’s not going to do well.”
The average corn yield in Illinois was 105 bushels per acre, nearly 70 bushels below trend line.
“Our 2012 soybean yield is 43 for Illinois, so that doesn’t make it a terrible soybean year,” the agronomist said. “The big scare still as we head into 2013 is: Are we going to have enough water in the soil when we start the season?
“It can still rain. I think we’re pretty close to full recharge through much of central Illinois. It’s important to get the soil back to moisture capacity, which is pretty much where we were last spring.
“It’s important to do that, but in Illinois it’s kind of a moot issue. I think in 1989 we didn’t fully recharge in every part of the state. That’s been the only year that we weren’t at field capacity heading into the spring.”
Planting began at record pace in 2012 compared to the previous year’s slow pace.
“If we would have had a spring in 2012 like we had in 2011, we would really be singing the blues because there is no way that crop would have tolerated what we took and still yielded 50 bushels in some fields like it did,” Nafziger said.
“Dry springs have great advantages. We like dry springs every year if we could get them. There was virtually no loss of spring-applied nitrogen, good uniform stands, almost no drowned-out spots.
“May and June were warm. There is also a lot of sunshine when it’s not raining, and that’s a good thing, as well, and we had very low disease pressure.
“Silking came early, and normally we would say that is great, but by the time we got through silking, our crop condition had deteriorated way down because of no rain.
“Soybeans were still planted at near record pace. They started to bloom early. That’s an advantage, and when we don’t harvest them early after an early start to bloom, normally that’s a really good sign for soybeans.
“The soybean crop was really set to be excellent. The corn crop was, too, but by the middle of summer we knew that it wasn’t going to be. The soybean crop also looked bad by the end of July, but that rain came along and it helped it out.”
With the early planting and deep roots, the corn crop was in “really good shape to take the drought that it got,” the agronomist said.
A dry June also helped the corn develop.
“Historically, dry Junes are good for corn yield as long as it remembers to rain after than,” Nafziger said.
“The dryness developed very steadily. There wasn’t a drowning flood, and then it was really dry after that. It kept getting drier and drier and drier, and that’s an advantage with a corn crop. It can take some little adjustments there.
“High temperatures were not a huge issue. Yes, we would have liked lower temperatures, but that probably wouldn’t have helped the crop a whole lot.
“It would have delayed its development a little, but if it wasn’t going to rain until mid-August, which was the case for most of us, it didn’t really matter if that crop tried to pollinate the first or second week of July.
“The high temperatures moved it along a little bit faster, but realistically our night temperatures weren’t much above normal and that’s typical of very low humidity in summer weather.
“The growing degree days actually didn’t increase as much as we would have expected when it got up to 100 degrees.
“Our cutoff temperature is 86 degrees, so growing degree-wise, if it’s 90 in a day or 95, it all gets the same growing degree days. But by some point in July, roots simply couldn’t extract any water.
“The relief in August came too late for corn, and it helped soybeans. Corn is efficient in its use of water, but it’s very sensitive to drought stress as we saw this last year around the time of pollination, and it can switch off yield and it did.
“Soybeans just are different. They’re not as efficient in their use of water, but they’re more resilient because the rainfall will rescue them. We do not expect the amount of water used to produce a bushel in either crop to change much, and we can expect water to be a limitation.”
Root systems matter, particularly in a drought and anything that keeps nodal roots from developing rapidly and going deep creates problems for the plant.
“No-till in some cases did that,” Nafziger said. “No-till was tough to get done in some places because it had dried out enough that you couldn’t get penetration, and most places it didn’t rain after it was done, and for no-till, that brings on some problems that we don’t expect.
Tom Doran, Field Editor
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