JACKSON, Tenn. — Grain sorghum plantings have increased in Tennessee this year, as growers found pre-season profitability projections better than corn.

Growers who have not raised sorghum lately, however, will need to manage carefully, especially if dry conditions after planting limited herbicide action. Dry weather in early May kept pre-emergence herbicides from activating in some grain sorghum ground, according to Larry Steckel, a University of Tennessee weed scientist based at Jackson.

"The challenge is, you’ve got to wait until sorghum gets to the three-leaf stage before you can spray it over the top," he said. Steckel addressed sorghum production issues in UT extension’s May video updates.

Richard Jameson said as of May 20 he was still waiting to apply atrazine on more than 600 acres of minimal- and no-till sorghum near Brownsville, in Haywood County. He got early-season control from a mid-April burndown on his no-till sorghum and applied the maximum rate of S-metolachlor at planting, starting May 3-4.

"So far, I’m happy with my weed control," said Jameson, who is working closely with a crop consultant to monitor his sorghum.

At the three-leaf stage, atrazine with oil is the best herbicide control in grain sorghum, according to Steckel, who said atrazine may be applied until grain sorghum is about 12 inches tall.

Rain in the forecast was keeping Jameson from applying atrazine. He is following University of Arkansas and UT guidelines for avoiding application to sorghum in wet conditions, when atrazine is more likely to damage young plants.

"After we’re done with the rain, and we get some dry weather, we’ll look at putting down some atrazine on the milo," Jameson said.

Palmer amaranth will be another challenge. Remember differences in sorghum and corn, cautions Steckel. "You can’t use rates (in sorghum) like you can in corn," he said. "It’s about half the rate as in corn."

He said a newer herbicide, like Husky, might be effective on later infestations of Palmer amaranth in sorghum.

A lack of rain in early May, especially toward Middle Tennessee, affected some grain sorghum stand quality. "Shooting for uniform emergence is where people need to be starting," said Angela McLure, extension corn and soybean specialist.

Replanting could be warranted in some fields. "Usually most people are planting in May," she said. "Usually June-planted sorghum yields less, and also you have a lot more insect problems with late-planted sorghum."

Milo and soybeans are the only field crops in Tennessee that projected positive returns above variable and land costs on non-irrigated ground, according to UT estimates published May 12. Returns for milo were $24 per acre, while soybean returns were estimated at $10.

Growers are watching sorghum fertilizer costs closely. Avoiding over-application of topdressed nitrogen could save some production costs. Many growers use liquid UAN applied behind the coulter at planting as their preferred option, according to McClure.

Tennessee’s grain sorghum acreage was last tallied by the Census of Agriculture in 2012. Growers harvested 11,496 acres for grain and another 1,104 acres of sorghum for silage or green-chop that year. Estimates of this year’s plantings are not yet available.