What does it mean when a climatologist slips on an icy sidewalk in early February and breaks his ankle? Does that tell us we're going to have more than the usual amount of spring rain because of freezing rain in winter? Iowa State University Extension climatologist Elwynn Taylor slipped on an icy sidewalk and broke his ankle last month. The accident occurred close to Ground Hog Day.
Is this a sign the drought of 2012 is broken? So far, it is not for Iowa and the western Corn Belt, as we move further into 2013. All it means is that Taylor has been hobbling around on crutches. The accident didn't slow him down much, by the way. He still attended most of his scheduled meetings and speaking engagements in February, talking to farmers and others about weather and crop prospects for 2013.
Western Corn Belt is heading toward 2013 planting season with dry subsoil
There is a lot of concern that we're entering planting season in 2013 with a very dry subsoil moisture supply -- not everywhere in Iowa and the Midwest -- but certainly low in many places. Any chance of totally replenishing soil moisture reserves before farmers get into the fields this spring? "We're not going to get this issue completely solved for Iowa, and the western Corn Belt," says Taylor. "It will take timely rains during the growing season to produce a big crop in 2013."
For much of Illinois and over into Indiana, they've already received enough precipitation since last summer's drought to pretty much correct their subsoil moisture situation. That's good news for the eastern Corn Belt. "But once you get into Iowa and our neighbor states to the west, we are still on the dry side," Taylor notes.
Official forecast says drought will likely keep its grip on Iowa at least through May
The latest three-month weather forecast from the federal Climate Prediction Center, issued in late February, holds little hope that Iowa's drought will ease soon. Forecasters say it's a coin flip whether the western half of the state will get more precipitation than normal through May. And there's a chance the weather might be warmer than usual, which would worsen the drought.~~~PAGE_BREAK_HERE~~~
Drought still covers all of Iowa, but it's most severe in the northwest quarter. The eastern third of Iowa has picked up more precipitation since last fall, recharging the subsoil moisture supply somewhat. If the eastern third of the state gets normal rainfall during the 2013 growing season, crops should do ok. But much of the rest of the state, especially northwest Iowa, has such a subsoil moisture deficiency that it'll need more than the normal amount of rain, says Taylor. For updates on the situation, visit this link.
Deep holes being dug for telephone poles show subsoil is still quite dry
Construction workers for electric companies in central Iowa have been digging deep holes in the ground, installing power line poles this winter. They are going down 10 feet or more and it's dry. They're not hitting the water table like they usually do.
"Typically in this part of the country, you hit at least the temporary water table when you get down below the field tile drains, or about 5 feet deep," says Taylor. "That's why corn and soybean roots are deep because they grow down to hit water and then they are done growing any deeper once they reach water. If there's full capacity of water in the soil there's not enough oxygen for the roots to grow, so they stop going deeper once they reach the water. In 2012 and 2011, crops used all the moisture they could get out of the top 5 feet of soil rooting depth, and the water just keeps draining down so the roots responded by growing down deeper than the usual 5 feet."
He adds, "The roots went down 7 or 8 feet and in some cases to 9 feet deep in 2012. And that's about as deep as corn and soybean roots have time to grow, during their growing season. So the crop roots pretty much used all the water out of the soil down to the 8 or 9 foot depth last year."
It'll take at least 16 inches of rain soaking into the ground to replenish subsoil moisture in many of the driest fields
Figuring each foot of soil profile holds 2 inches of water at field capacity it takes 16 inches of rain soaking into the top 8 feet of soil to get the tiles running again. "I asked a question at a meeting last week in Ames," says Taylor. "How many of you have looked at field tiles since Christmas? How many of you have found the tiles are running? Most of the people said they have checked their tile outlets, and there were a total of about 300 people present at this meeting—from farms, co-ops and FSA offices across Iowa."~~~PAGE_BREAK_HERE~~~
However, there were less than 10 people out of the 300 person audience who raised their hands to indicate they've seen tiles running somewhere in Iowa this winter. "So way less than 10% of the tiles in Iowa are running," says Taylor. "When I asked that question a year ago at this time, it was about 50%. And usually, in most years about 80% of the tiles are running at the end of February or beginning of March."
Looking beyond spring, what if subsoil moisture reserves aren't fully recharged going into 2013 growing season? What are the odds that Iowa and other dry areas in the western Corn Belt will get enough rain and get it on a timely basis during the growing season to make up for the lack of reserve subsoil moisture?
Without subsoil moisture, it'll be difficult to get a near-record crop yield in 2013
In other words, with low levels of subsoil moisture, what are the chances of getting enough timely rain events during the growing season to carry crops through to a good harvest? "That has happened before, as we look back at weather history in Iowa," says Taylor. "In western Iowa it's happened only once in 60 years. To receive enough rain as we go through the 2013 growing season to get a near record high crop yield without much soil moisture -- that would be very difficult to do in western Iowa especially. But in eastern Iowa it does happen more often."
You might not have much soil moisture in the driest one-third of Iowa, the situation a lot of places in western Iowa are in right now. And if they get timely rains during the growing season they end up with a fairly good yield, maybe 20% of the time, says Taylor. But they also end up with a crop disaster more than 20% of the time. "So this weather and crop yield outlook for 2013 is unsure for the eastern part of Iowa and just bad news for the western part of the state," he adds.
If Iowa has a dry spring, crops will need good, timely rains during 2013 growing season
"We can't say we're not going to get timely rains. But we are saying rains which occur on such a timely basis only happen rarely," says Taylor. "In Iowa, we rely on having a bank of moisture stored in the soil as a reserve for crops. So when that two week long hot dry period comes in summer, which it almost always does for a week or two, crops can draw moisture out of the subsoil reserve to carry them through the dry period. And if the moisture isn't there, crops can lose yield in a hurry when it turns hot and dry and they don't have reserve moisture to draw on from deeper in the soil."