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."