SD yield potential deteriorated with hot dry weather

South Dakota had been expecting record corn and soybean yields. But a hot, dry August has dashed those hopes.

BURBANK, S.D. — South Dakota’s potentially record corn and soybean yields have been cut by hot, dry weather in August.

The state had some of the highest crop ratings in the nation for much of the season, and in the Aug. 10 U.S. Department of Agriculture Crop Progress report corn was rated at 83% good to excellent, with soybeans at 85%. However, conditions have deteriorated quickly as parts of South Dakota were hit by a flash drought receiving little or no precipitation in August, combined with above normal temperatures.

Keith Mockler with Bayer Crop Science said the crop has been under drought stress the last few weeks, especially in the southeast.

“I’ve never seen a crop that looked that good go south that fast,” he said.

This has cut yield potential on the corn crop by 10% to 15% in the southeastern part of South Dakota.


Dry corn .jpg
Corn in South Dakota dried up so fast in drought conditions that some producers found there wasn't enough moisture left to get it to keep for silage. (Michelle Rook / Agweek)

“As you move north up I-29 there’s a lot of that crop that’s probably lost 25% to 30%. There’s going to be a lot of corn in the 140s to 150s. You get into the southeast corn and there’s still going to be some 200-bushel plus corn but the big thing is it was 240 to 250 bushel per acre corn," Mockler said.

USDA had pegged statewide corn yields at 167 bushels per acre in the August World Agricultural Supply and Demand Estimates Report, and other private estimates had projected record yields for South Dakota. Mockler said it may still be one of the top five corn crops raised in the state, but the likelihood of a record statewide yield is no longer in the cards.

“We’re probably going to be in the upper 150s as a state average. There are some good spots in the state yet that received a little more rain through the month of July and got a little bit in August, but the majority of the state has had virtually nothing in August,” he said.

He said what was helping pull up the statewide average was the corn that was seeded into acres that were in prevented planting in 2019, because when farmers give the ground a rest it is usually followed by a big yield the following year.

The heat also hampered silage cutting efforts. Farmers got started when the crop was at the right maturity and moisture level, but within a matter of days the crop was too dry to ensile.

“We had some moisture way down into the low 50s and we like to chop that right at 70% moisture,” Mockler said.

He said many farmers stopped cutting silage and went to cutting corn for earlage.


The heat also pushed the crop so there will be some lighter test weight corn by one to two pounds, but it will be drier with moisture levels running 15% to 16%. Mockler said there may be some stalk quality and standability issues in the corn and he anticipates an early corn harvest.

“I think there’ll be a lot of corn being combined in mid to late September,” he said.

He thinks a third of the corn could be combined before Oct. 1 and before soybeans.

South Dakota’s soybean crop also started the year with the potential for record yields, especially as most farmers planted the crop early. In fact, Mockler said 2020 may be fastest he’s ever seen farmers in the western Corn Belt plant soybeans.

“I mean, we had a lot of producers that were done planting before May 1,” he said.

However, there is even greater concern about how much the dry weather has trimmed soybean yields, because their key reproductive stage is in August.

“To get optimum yields, you’d like to see an inch of rain per week every week in August,” he said.

Instead most areas were nearly dry or only received a few tenths of rain during the month. That will greatly reduce the size of the soybeans plus there were some pods that were aborted by the plants.


“It's kind of early to tell yet, but we’ve probably lost 15% to 20% of that soybean yield,” he said.

The yield ranges could be from 20 to 65 bushels per acre depending on the geography, but Mockler projects the statewide soybean yield will likely fall into the low 40s, which is well off the record yield estimates earlier this season.

Pests such as soybean aphids and spider mites were light this season, but fungicide applications were up as farmers were trying to prevent disease and preserve top end yield. He said the fields that were treated have held on longer than those untreated.

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