DES MOINES, Iowa – The number of crop acres Iowa farmers are unable to harvest after the Aug. 10 derecho has climbed to 850,000, with severe drought conditions compounding the damage by expanding to most of the state, despite September rainfall.

That’s according to a new report by the USDA, which had estimated Iowa’s crop loss last month at 550,000 acres.

“The Aug. 10 derecho will go down as one the most significant weather days in state history – especially in terms of agricultural losses,” State Climatologist Justin Glisan said. “Damage estimates will become more refined as harvest activities are completed.”

The derecho, which packed over 100-mph winds (with gulf ball-size hail in some parts of the state), flattened fields, knocked over silos, and damaged livestock and machinery barns in its wake.

According to the Iowa Department of Agriculture and Land Stewardship (IDALS), Iowa corn fields were in the late stages of development and weren’t expected to fully mature or recover before harvest, leaving farmers to deal with yield losses, grain quality issues and limited marketing options.

The USDA said the storm may have impacted 8.2 million acres of corn and 5.6 million acres of soybeans in 57 of Iowa’s 99 counties.

Iowa Agriculture Secretary Mike Naig told the Associated Press he expects the number of lost acres to climb even more as farmers continue harvesting their crops. 

“Crops can deteriorate,” he said. “It’s a really dynamic situation.”

Glisan said one issue that will be difficult to address regarding the total loss of cropland is the combination of derecho damage through the drought region of west-central Iowa. 

“Because this part of the state was experiencing drought conditions when the derecho hit, it will be difficult to isolate how much crop damage and yield loss were caused by each event,” he said. “Drought conditions have eased across eastern Iowa over the last several weeks.” 

During the second week of September, the state saw more rain than during the entire month of August, which was the third driest in 148 years of Iowa records, he said. 

“Western Iowa – including the northwest corner – has seen some degradation as that portion of the state has been the driest part of Iowa for several months,” he said.

Glisan said outlooks through the end of October, however, suggested elevated probabilities of wetter-than-normal conditions. 

“Given the ideal conditions we’ve experienced statewide for harvest, timely rains would be welcome to help ease drought conditions, along with recharging the sub-soil moisture profile for next growing season,” he said.

The Iowa Crop Progress & Condition Report for the week ending Oct. 11 said topsoil moisture condition rated 17 percent very short, 34 percent short, 49 percent adequate, and 0 percent surplus. Subsoil moisture condition rated 21 percent very short, 37 percent short, 42 percent adequate and 0 percent surplus.  

Glisan said the first full week of October brought unseasonable warmth to the state, with positive departures of up to 10 degrees in western Iowa. 

“The statewide average temperature was 61.6 degrees, 8.2 degrees above normal,” he said. “Dry conditions prevailed across Iowa as well, with only a few stations reporting very light rainfall amounts. The lack of rain around the state led to weekly precipitation departures on the order of 0.50 inch to 0.70 inch.”

The report said Iowa corn reached 97 percent mature or beyond, over 3 weeks ahead of the previous year and 10 days ahead of the 5-year average. 

Corn for grain harvested in the state reached 42 percent, over three weeks ahead of last year and almost two weeks ahead of average, the report added, with moisture content of field corn being harvested for grain at 18 percent. Corn condition rated 44 percent good to excellent. 

Moreover, the report said soybeans dropping leaves or beyond reached 97 percent, just over two weeks ahead of last year, and nine days ahead of average. Nearly one-quarter of Iowa’s soybean crop was harvested during the week ending Oct.11, with 78 percent now harvested, over three weeks ahead of last year, and over two weeks ahead of average.

The USDA also said despite the derecho devastation and severe drought conditions, Iowa farmers harvested an estimated 12.7 million acres of corn by Oct. 11, a quarter of the state’s acreage. It was only the second time since 1990 that Iowa farmers had harvested so much corn this early in the season.

In addition, Iowa farmers are expected to harvest 9.3 million acres of soybeans, the report showed, unchanged from September, according to the Des Moines Register. 

In fact, the USDA boosted Iowa’s average soybean yield to 56 bushels per acre, up two bushels from September’s projection.

“Even with fewer acres, Iowa farmers still are expected to grow the most corn in the nation, harvesting 2.4 billion bushels this year,” the Register reported.