Expect soil drought to continue in 2013
Unless corn and soybean farmers of the Corn Belt have exceptional rain and snowfall that soaks into the soil between now and next planting season, 2013 crop yields could be negatively affected, according to Elwynn Taylor, Iowa State University meteorologist. He said there are reasons to expect a prolongation of the drought that began in late 2011 and hit hard in 2012.
Elwynn Taylor “We are still going to be at risk in a lot of places to have the drought continue next year because the soil moisture is still less than usual,” he said, during a presentation at the Farm Progress Show at the end of August in the DuPont Pioneer tent.
Agricultural ground could be water recharged completely if a drought area were to receive 18 inches of moisture that soaks into the ground between Oct. 1 and spring planting when crops start using water next year, Taylor said.
WATER YEAR BEGINS OCT. 1
“We assume that the crops don’t use any significant amount of water after Oct. 1; therefore, Oct. 1 in the world of a hydrologist, is New Year’s Day. The water new year begins Oct. 1, and any moisture that falls after Oct. 1 is considered as water for the coming year,” he explained.
Taylor used rainfall expectations for Iowa, which has similar rainfall expectations as other high-yield producing Corn Belt areas. He said the normal expectations for rainfall is two inches for both October and November, then December, January and February are the driest months of the year at one inch of snowfall moisture (one foot of snow equaling about one inch of moisture), and then the averages climb from two inches in March, three inches in April and four inches in May. That only totals 16 inches through the end of May after all the corn and soybeans are normally planted.
“This is the expected moisture, but all those expected amounts don’t add up to 18 inches by planting time next spring. And we hope all the rain doesn’t come right at planting time,” Taylor added.
NEED FOR COMPLETE SOAKING
Corn growing in high-quality soil in drought areas drained the soil of moisture up to nine feet deep during 2012. It would take a really abnormal year for 16 inches, let alone 18 inches, to soak into the top seven feet of soil during the coming months. First of all, some rains come as downpours with a lot of runoff instead of soaking into the soil. Second, snowfall often melts while the ground is still frozen so that the moisture cannot infiltrate the soil. If 10 inches of snow were to be evenly spread across frozen ground for an extended period of time in late winter, the average soil temperature of 50 degrees at five feet would move its way up to thaw the ground and allow infiltration of melted snow moisture into the ground.
“We have reason to believe that this drought will be going on for some people next year because it will take an amazing amount of fall rain and early spring rain to get the soil moisture back up to a level we consider ideal, which is essentially full of water so that field tiles are running and getting rid of excess moisture.
“How much water will it take to do that? Each foot of our better agricultural soils holds two inches of plant-available water. If there is more than two inches of water in the soil, it will drop out the bottom if it can, out the tiles if they are there.
“For five feet, the average rooting depth for corn and soybeans in Iowa, that is 10 inches of water. This year, the roots went deeper than usual,” Taylor explained. In generalities, with 20 inches of moisture necessary to produce an average corn crop, it means that 10 more inches of rain is normally needed during the growing season, but it didn’t occur this year, and the soil, up to even nine feet deep in some fields, was drained of every ounce of moisture by roots going deeper and deeper.
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