The powerful derecho windstorm rolling across a large section of Iowa on Aug. 10 took its toll on corn and soybeans growing in fields in the storm’s path. USDA’s weekly crop report issued Aug. 17 shows the damage resulted in a 10% decline in Iowa’s statewide corn rating. Iowa’s corn crop is now 59% in good-to-excellent condition, versus 69% on Aug. 9.

USDA estimates the derecho contributed to a 2% drop in the national corn condition rating as of Aug. 16, with the U.S. corn crop now 69% good-to-excellent compared to 71% the previous week.

Dwayne Gerlach, farming near Nevada in central Iowa, says there’s a lot of corn blown down or leaning badly in his area. “In some fields it’s nearly 100% flat. In most fields there’s at least some corn standing, a lot of it leaning over and some blown down. Some stalks are snapped off in areas of fields,” he says. “The wind exceeded 100 mph here.”

Farming with other family members, Gerlach says they had some grain bins destroyed — one blown down and another blown a half mile across a soybean field. An older barn was destroyed by the strong wind. There was some wind damage to his house.

“Soybean plants in fields that were bent down by wind have generally straightened back up. There is leaf damage to some soybeans. But it’s the corn that’s really taken a hard hit,” Gerlach says. “A lot of it is tangled, and it will be difficult to harvest this fall.”

“It’s been one week since the catastrophic derecho hit Iowa. There were 57 counties in the path of the storm, with 36 counties experiencing severe crop damage. There was also significant structural damage to grain storage facilities,” says Iowa Secretary of Agriculture Mike Naig. “Cleanup continues and farmers are working with their crop insurance adjusters and agronomists to gain a better insight into the yield impact of the storm.”

The complete weekly Iowa Crop Progress and Condition report is available on USDA’s site at nass.usda.gov/ia.

Crop report

A derecho blew across a large area of Iowa on Aug. 10, but farmers still had 5.7 days suitable for fieldwork during the week ending Aug. 16, according to USDA’s National Ag Statistics Service. Dry conditions continued to be a concern for most of Iowa. High winds experienced on Monday caused considerable damage to on- and off-farm grain storage in their path as well as other structures. The level of crop damage reported varied widely depending on location and wind strength.

Topsoil moisture is rated 20% very short, 36% short, 42% adequate and 2% surplus. The state’s topsoil moisture remains over half short to very short although it improved slightly. Subsoil moisture condition is rated 17% very short, 36% short, 46% adequate and 1% surplus. Iowa’s subsoil moisture also remains over half short to very short.

Corn is 81% in the dough stage or beyond, almost two weeks ahead of last year and five days ahead of the five-year average. Just over one-quarter of Iowa’s corn crop is in or beyond dent stage, 11 days ahead of the previous year and three days ahead of average. Corn condition is rated 59% good-to-excellent, a drop of 10% from the previous week and the lowest level this crop season.

Soybeans are 97% blooming or beyond, three days ahead of average. Soybeans setting pods are over two weeks ahead of last year and one  week ahead of average at 90%. Soybean condition fell again last week, and the crop is now rated 62% good-to-excellent, the lowest level so far this season. Only 3% of oats remain to be harvested for grain, two days ahead of both last year and the average.

Alfalfa hay second cutting is 97% complete, four days ahead of last year but one day behind the five-year average. Just over half of the third cutting is complete, 10 days ahead of last year. Pasture condition fell to just 33% good-to-excellent.

Weather

A powerful line of severe thunderstorms, known as a derecho, brought widespread agricultural and structural damage across rural and urban areas of Iowa on Aug. 10.

“Moderate to heavy rain also fell along the path of the derecho with scattered thunderstorms over the next few days,” reports Justin Glisan, state climatologist at the Iowa Department of Agriculture. “However, dryness persisted in much of the state with deficits on the order of an inch.”

Sections of central Iowa reported receiving up to an inch of rainfall with locally higher amounts last week. Slightly warmer conditions were also observed across much of Iowa with the statewide average temperature of 72.9 degrees F, 1.1 degree above normal.
Weekly precipitation totals ranged from no accumulation at several stations in southwest Iowa to 2.4 inches in Story City (Story County).

The statewide weekly average precipitation was 0.67 inch, while the normal is 0.96 inch. Burlington Municipal Airport (Des Moines County) reported the week’s high temperature of 94 degrees on Aug. 10, which is 9 degrees above normal. Spencer Municipal Airport (Clay County) reported the week’s low temperature of 48 degrees on Aug. 15, which is 11 degrees below normal.

U.S. ratings decline

The condition of the U.S. corn and soybean crops declined last week, according to USDA. The two crops’ good-to-excellent ratings fell back slightly.

In its report issued Aug. 17, USDA’s estimate of corn with a good-to-excellent rating is 69%, versus 71% a week ago. The report says 76% of the nation’s corn is in dough stage, versus a 69% five-year average. USDA pegs the U.S. corn crop as 23% dented, versus a five-year average of 24%.

The 2020 Iowa corn crop, following the Aug. 10 derecho windstorm event, has a good-to-excellent rating of 59%. The Illinois corn crop is rated as 76% good-to-excellent.

USDA says 96% of the nation’s 2020 soybean crop is now in the blooming stage, ahead of the 94% five-year average. They estimate 84% of the U.S. soybean crop is setting pods, versus a 79% five-year average. USDA estimates the U.S. soybean crop as of Aug. 16 has a good-to-excellent rating of 72%, versus 74% a week ago.