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Shallow roots: Arkansas turns water on cotton crop

Jefferson County, Ark., cotton producers in early July were seeing their shallow-rooted crops wither from recent dry weather. Many producers were laying irrigation tubing or turning on center-pivot irrigation systems.

As a rule of thumb, farmers usually don't plan on irrigating cotton until after July 4, said County Agent Don Plunkett with the University of Arkansas Cooperative Extension Service.

“But everyone who waited until that date is now behind the eight ball and is scrambling to get their crops irrigated,” he said. Cotton grown around Sherrill, Ark., “is in a big-time stress.”

The problem is not just limited to Jefferson County but can be seen anywhere in Arkansas that hasn't had significant rains since June 17, according to Plunkett. Jefferson County has had only isolated rain in recent weeks.

Ironically, there's plenty of moisture in the soil. The problem is that plant roots are not deep enough to reach the moisture.

The early crops — planted in April and early May — received abundant rainfall from mid-May through mid-June. The frequent rains inhibited root systems, causing shallower rooting.

Plunkett said farmers have an old saying: “June dust is gold dust.” It means that cotton growers prefer dry weather in late May or early June to allow cotton roots to penetrate more deeply into the soil.

Because of recent dry weather, some farmers now have crops that are showing signs of moisture stress. Even cotton that appears to be holding its own may have gotten stressed to the point that it's nearly stopped growing, Plunkett said.

Another problem caused by June rains is that it delayed farmers in applying nitrogen fertilizer.

“Much of that problem has been corrected. We've had a few weeks of drier conditions, and farmers have been able go in and apply urea.” While farmers are waiting for the urea to go to work, Plunkett has recommended that they apply foliar fertilizer to severely stressed cotton where insecticides were being applied in an effort to “perk up stressed cotton and stimulate root systems that were not taking up soil fertility well.”

Another problem associated with the dry weather is that many farmers have a limited number of diesel units to operate wells, and the units are needed to water both rice and cotton fields at the same time, Plunkett said.

He said farmers can use Extension's cotton management program COTMAN to help predict stress in their crop and then use Extension's irrigation scheduling program IRRIG to tell them when to start irrigation. He said IRRIG can usually give a farmer a 10-day warning when irrigation needs to begin.

Compounding the problem for cotton farmers is the fact that they're entering a period in which insect numbers are going to increase.

He said private cotton consultants are reporting constant pressure from plant bugs around fields. Aphids and worms are a problem south of Pine Bluff, Ark., and stink bugs are “looming” in the background, the Extension agent said.

“It's about time for a large bollworm moth flight to occur, which will concern folks with non-Bt cotton,” Plunkett warned. “For the next two months, insects will be the major concern.”

The Extension Service monitors moth flights of cotton bollworm and tobacco budworms in an effort to alert consultants and farmers about impending problems from small worm hatch and feeding by the worms on cotton fruit. By knowing when eggs are laid, cotton scouts can be better informed about when to expect worms in fields, according to Plunkett.

Meanwhile, farmers need a little luck with the weather. “Send us a 1-inch rain every Friday night and we'll be happy,” Plunkett said.

Lamar James is an Extension communications specialist with the University of Arkansas.

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