Iowa Crops Starting to Show Serious Heat Stress

High temperatures and lack of rain is beginning to take a toll on corn and soybeans statewide.

Published on: Jul 10, 2007

Iowa is losing some potential on its 2007 corn crop. The continued dryness combined with the hotter than normal temperatures is hitting just as the corn is entering its critical pollination stage. "It's July 9 and the dryness and hot temperatures are causing both the corn and soybean crops to show considerable stress, and it is starting to shave off some yield potential, especially for corn, says Iowa State University Extension climatologist Elwynn Taylor.

Normally June is the wettest month for Iowa. This year, the precipitation total statewide for the month of June was below normal. "We had a wet spring in Iowa, then a dry June. Now as we move into the critical corn pollination period in July, both the corn crop and the soybean crop need rain," says Taylor.

The heat is on for 2007 corn crop

As Iowa's summer heats up, crops are showing signs of stress from hot temperatures and low moisture. Leaves are curling from dryness as few areas of the state have received significant rainfall recently. Many areas receiving measurable rainfall in the past month dealt with flooding and soil erosion as the rain fell in a very short time frame.

In the weekly crop and weather survey report issued by Iowa Ag Statistics Service on July 9, topsoil moisture rates 15% very short, 39% short, 44% adequate and 2% surplus across the state. Subsoil moisture rates 7% very short, 22% short, 68% adequate and 3% surplus. The survey results were gathered on July 8, then compiled and released July 9 by the government agency.

Iowa corn crop 37% tasseled on July 8

Oats turning color are at 66%, 7 points behind last year's 73% and one point behind the 5-year average. Condition of the oat crop is unchanged from last week at 4% poor, 22% fair, 60% good and 14% excellent.

Corn tasseled, at 37%, is 3 days ahead of last year's 18% and 6 days ahead of the 5-year average of 13%. The percentage of Iowa corn silked as of July 8 is at 18%. That's also 3 days ahead of last year and 5 days ahead of normal. Average corn height for the 2007 Iowa crop is 65 inches, an increase of 14 inches from the previous week. Corn condition is rated at 2% very poor, 5% poor, 21% fair, 53% good and 19% excellent.

Half of Iowa soybean crop is blooming

Soybeans blooming are at 52% for Iowa, ahead of last year's 47% and the 5-year average of 39%. About 7% of soybeans are setting pods. Soybean condition is 1% very poor, 5% poor, 22% fair, 57% good and 15% excellent.

About 29% of the second cutting of alfalfa hay is complete. That is behind last year's 58% and the 5-year average of 39%. All hay condition is 3% very poor, 12% poor, 38% fair, 40% good and 7% excellent. Alfalfa fields are being affected by large leafhopper populations.

Pasture condition as of July 8 rates 2% very poor, 11% poor, 37% fair, 41% good, and 9% excellent. Pastures are having a hard time keeping up with grazing. Livestock are also showing signs of stress due to heat. Fly populations continue to pester livestock.