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Weather endangering Corn Belt’s row crops

By Staff | Jul 18, 2012

Although Iowa’s row crops are suffering with day-after-day record heat and little or no rain for relief, north central Iowa’s corn and soybeans are still hanging on, although just barely.

Rain is needed, very soon.

The U.S. Department of Agriculture’s National Agricultural Statistics Service released Monday said that north central Iowa’s topsoil moisture is rated as 95 percent short or very short, and that 94 percent of subsoil is rated short or worse.

According John Holmes, an Iowa State University Extension crop field specialist, based in Clarion, “it’s still too early to tell” what impact weather has had on row crops yields.

Bob Streit, a crop consultant in Ames, said if the region receives adequate rain this week, the potential for 160 to 200 bushels per acre still exists for corn, except for those areas that were on sandy or shallow soils, or on top of hills. He said aerial flyovers over the weekend showed that “those areas are generally gone. There was quite a color change in the week’s time with the crop being much yellower.” That is compared to conditions a week earlier.

In general, Holmes agreed with the assessment.

He said the early planted corn tasseled earlier, ahead of the bulk of the intense heat, “and pollinated well. It seems to be holding on well, except for the sandy spots.”

He said early planted corn is already in late-blister to early dough stages, an indicator of kernel development.

However, later-planted corn, he said, is under intense pressure to produce. That corn is struggling to pollinate in the current heat wave, he said. “The hot conditions are hard on it.”

Holmes said he’s done several soil probes this week and found some moisture at the 2- and 3-foot level. “It’s not wet,” he said, “but it is moist and the plants are living on that right now.”

The big question for late-planted corn: when will it mature and the plants die?

“It needs 60 days after pollination,” he said. He estimated most corn will die around September 5 to September 10. “Will it die too early?”

Other questions farmers need to be considering is the potential for high nitrates in corn that develops in dry conditions and is a hazard when fed to livestock.

“We’re going to be looking at storage issues with lighter test weights,” he said, “Maybe some aflatoxin.” Aflatoxin is a naturally occuring mycotoxin that can invade grain when in stressed conditions such as high humidity or drought. They are listed as some of the most carcinogenic substances known.

Concerning soybeans, Holmes said most fields “are just holding their own” and guessed most plants won’t be setting pods until late-July or early-August. And in this heat, there’s always the threat of plants aborting pods.

Spider mites, a sap-sucking, plant-ruining pest that flourishes in drought because the bugs that kill them die off, have been reported in Rockwell City this week, Holmes said.

Soybeans are showing a slow progress, struggling to fill in their rows, Streit said, “and in some of the worse areas, seem to be shrinking.

“Several good rains could help hold the late flowers and unfilled pods, so they still have potential.”

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