Soybean Damage Todd Spivey, LSU Extension
Soybean fields were flooded after Hurricane Harvey. Beans are most sensitive to flooding between R3-R5, says LSU Extension specialist, Todd Spivey.

Too much moisture hurts Louisiana cotton, soybean crops

Wet summer, Hurricane Harvey flooding limits Louisiana cotton and soybean production.

By the time Hurricane Harvey made its way through Louisiana, about all it could do to the state’s cotton crop was add insult to injury.

Soybeans and grain sorghum took a hit from bad weather, too. Corn yield, however, will be near a record.

“We had from 6 inches to 8 inches of rain from Harvey,” says Dr. Danny Fromme, associate professor at the LSU Dean Lee Extension and Research Center in Alexandria. “But most of the damage was done by then,” he adds. “We had a wet summer; we couldn’t catch a break, just continuous rain all summer long.”

Fromme says Louisiana farmers planted 215,000 acres of cotton last spring, up from 2016 and several years before that. “We will probably lose acreage next year after the trouble we had with this crop,” he says. Corn and soybeans likely will replace cotton acres.

He says 99 percent of the crop has been harvested. State yield will likely come in at 900 to 925 pounds per acre.  “That’s just an average crop,” he says. “But it takes more than an average crop now to make ends meet.”

MORE COTTON IRRIGATED

About 50 percent of the state’s cotton is irrigated, 105,000 this year, compared to 109,000 dryland acres. “That number has been inching up every year,” Fromme says. “When I got here four years ago, we had about 30 percent of the cotton irrigated.”

Adding corn and soybean acreage, he says, encouraged more irrigation. “We have a lot of water available, and 99 percent of irrigation is through furrow irrigation. That’s a viable option since we have a lot of water.”

Fromme works with cotton, corn and grain sorghum. “We have only about 12,000 acres of sorghum,” he says. Acreage at one time approached 100,000, but low price and sugarcane aphids have whittled it down.

Sorghum did not fare well this year, either. “We had a decent crop, but the rain hurt it, too. Grain sprouted in the head.”

Corn has been the exception. “This will be one of the best crops on record,” Fromme says. “I think 180 bushels per acre average yield is possible.” That’s from 500,000 to 600,000 acres.

He says soybean acreage ranges from 1.2 million to 1.3 million acres.

SOYBEANS HURT BY WEATHER

LSU assistant professor Dr. Todd Spivey works with soybeans and puts 2017 acreage at 1.24 million acres, and says soybean farmers had their share of bad luck, too.

“Yield estimate is 54 bushels per acre for a state total of 67 million bushels, but we’ve had problems.”

Spivey says farmers are reporting significant damage to beans when they take them to the elevator. “Rain hit the soybean crop at the absolute worst time. We had a lot soybeans at R7 and R8 stages when Hurricane Harvey hit.  That’s about mid-maturity. In mature beans, we saw a lot of sprouting, and some pod splits in the later beans.” He explains that the pod matures and will not expand more, but the bean is still capable of taking up moisture. The bean expands and blows out the pod. “We had a lot of beans exposed and rotting.”

STINK BUG INJURY

Stink bug infestation also hurt the soybean crop. “The red-banded stink bug typically overwinters only south of Baton Rouge,” Spivey explains. The mild winter, however, allowed the pest to overwinter much farther north. “We found active populations in alfalfa fields (north of its usual overwinter site) in February. They were feeding and reproducing. We did not get a typical winter kill.”

Disease pressure caused trouble, too. Spivey says stem blight and purple seed stain damaged soybean fields.

A University of Nebraska soybean disease webpage explains that purple seed stain (Cercospora blight) is also known as purple blotch, purple speck, purple spot or lavender spot. “Purple seed stain infection of the seed does not directly reduce yield. However, if a high percentage of stained seed is harvested, grain dockage may occur or seed certification may be denied,” according to the Nebraska report.

“We didn’t see much direct yield loss,” Spivey adds. “Some farmers made 60 bushels and up to 80 bushels per acre in some locations, but we hear reports of as much as 50 percent damage at the elevators. That’s an extreme case, but it is not uncommon to see 20 percent to 30 percent damage. Average damage two weeks before Harvey was 12 percent to 15 percent. The farther away we got from Harvey, the lower the damage — 5 percent damage rating is what we were most likely to see.”

GREEN STEM

Spivey says another issue, green stem, green bean, or green mold syndrome, caused yield reduction and harvest issues for soybean producers. Green stem syndrome, Spivey says, occurs when soybean plants maintain green stems and sometimes leaves long after they are normally brown and mature. “The beans dry down but the stems remain green,” he says.

That green vegetation creates harvest problems. Spivey says farmers may have to stop the combine, get off and unclog the machine frequently when working through sections with green stem syndrome. “This is not just a Louisiana issue,” he says. Research is ongoing across the country as well as internationally.

“We’re not certain of the exact cause,” he says. “A lot of factors may play roles, including stink bug feeding, which is a viable option this year. Regardless of the cause, green stem syndrome reduces the number of viable pods and seeds. Pods and seed die, and all the nutrients and photosynthates go into the stem. Seed quality is affected.”

He says farmers can do little to avoid problems with green stem issues other than let the plants wait and dry on their own time. Delaying harvest, however, also may result in quality loss.

Spivey says, in spite of the troublesome year, soybean acreage likely will increase in 2018. “A lot of growers did very well this year,” in spite of weather and other problems, he says.

He tends to agree with Fromme that soybeans likely will take some cotton acres in 2018.

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