Worsening dry conditions afflict southern Iowa crops

Drought conditions are likely to develop over the southern half of Iowa in August as the month starts with a string of abnormally hot days with little chance for rain, according to the U.S. Drought Monitor.

The portion of the state that is abnormally dry or in varying degrees of drought expanded last week to more than half of the state. It’s the first time the dry area has been that large since April, when persistent rains delayed corn planting.

The latest Drought Monitor report released last week showed an expansion of severe and extreme drought in northwest Iowa and the extension of abnormally dry conditions across much of southern Iowa.

“In all honesty, we are kind of at a pivotal point this week, depending on what our temperatures do,” said Aaron Saeugling, an Iowa State University Extension field agronomist who monitors southwest Iowa. “Our water demand just grows exponentially.”

He said farmers’ worries about their crops have worsened as available soil moisture has quickly deteriorated in the past two months. The area’s total rainfall ranged from a half to 1.5 inches of rain for the entire month of July, he said, compared with the normally expected amounts of more than 4 inches.

Southwest Iowa previously led the state in available soil moisture, according to U.S. Department of Agriculture reports. In early June, about 96 percent of its topsoil and subsoil had adequate or surplus moisture. As of Sunday, about 27 percent of topsoil and 36 percent of subsoil had adequate water for crops to grow.

The stress on the corn is most apparent in the afternoons, Saeugling said, when the plants roll their leaves to retain moisture.

“They are basically shutting down photosynthetically,” he said. “And they’re in the reproductive phase, so that affects grain yield.”

Over the past two weeks, the swath of southern Iowa in abnormally dry conditions has swelled, the Drought Monitor shows, but the portions of Linn and Johnson counties in that zone have remained largely unchanged in that period — the southwestern tip of Linn and the western portion of Johnson. Neither of the counties currently is classified in a drought condition.

The National Weather Service issued a heat advisory for Tuesday afternoon for most of the state. Actual temperatures were expected to approach or exceed 100 degrees, and high humidity will make it feel much warmer.

“We’re in a pattern that essentially is causing warm air to get pulled in from the south,” said Dylan Dodson, a meteorologist for the National Weather Service. “It’ll cool off a little bit — relatively speaking — but it will stay hot through the end of the weekend. … The eight-to-14-day outlook keeps us hot.”

The “relative” cooling happens after Tuesday, when there is a chance of scattered storms across the state and a reduction in high temperatures Wednesday of 5 to 10 degrees. But that still means much of the state will reach the high 80s or 90s.

Justin Glisan, state climatologist for the Iowa Department of Agriculture and Land Stewardship, said he expects the dry conditions to expand in the early part of August but said the month has been trending wetter in the past decade.

“The law of averages, that’s how I’d like to see things,” he said. “We have the hot snap and then maybe see below-average temperatures and more rainfall.”

Last week, the state averaged temperatures of about 3 degrees cooler than normal with abysmal rainfall, Glisan wrote in his weekly report for the U.S. Department of Agriculture. Much of the south had no rain, and the highest reported rainfall accumulation was .89 inch near Churdan.

Crop conditions suffered as a result: The state’s corn was rated 76 percent good or excellent, down from 80 percent the previous week. Soybeans were rated 73 percent good or excellent, down from 75 percent.

This article first appeared in the Iowa Capital Dispatch.