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Grain sorghum aids cotton rotation

Crop rotation is one of those no-brainer practices that farmers know improves yield potential.

But when rotation options provide limited profit potential at a time when farmers struggle just to meet in-season production costs, delayed advantages often take a back seat to immediate economic necessity.

“We're working on that,” says Joe Ben Chote, field representative for the Lubbock-based Texas Grain Sorghum Association and the Texas Grain Sorghum Board.

Chote discussed the Sorghum PROFIT (Productive Rotations On Farms In Texas) program at the recent Southwest Crops Production Conference and Expo in Lubbock.

He says PROFIT efforts involve numerous agencies trying to “make grain sorghum more profitable for producers.”

“We hope to increase sorghum profitability by 20 percent,” Chote said. “We want to provide science-based data that will improve yields by 25 percent. We're making progress by examining production strategies and with variety research. The next goal is to get that information to producers.”

Poor growing conditions for the past few years have hindered yield goals, he said. “We also know that a sorghum rotation will improve cotton yields. Some studies indicate a 20 percent to 25 percent advantage for cotton that follows grain sorghum. Sorghum that follows cotton also shows yield increases.”

Chote says the organizations are “committed to producers. We hope to identify water, fertility and pest management needs.”

Dan Krieg, crop physiologist at Texas Tech, moderated the conference morning session and said Texas grain sorghum acreage at one time reached 7 million. “We are a grain deficit state,” he said. “And we have livestock and poultry industries that need the grain. The demand is there.”

Texas Extension agronomist Calvin Trostle outlined production techniques developed by Krieg and other researchers and specialists that may improve sorghum profit potential.

“Some of Dr. Krieg's work indicates that targeting plant populations to soil moisture conditions will improve profit potential,” Trostle said.

Recommendations include:

• A 30,000 to 35,000 seeds per acre planting rate provides good results under a wide range of conditions in west Texas. That's about two pounds of sorghum seed per acre (typically, 16,000 seeds per pound). That seeding rate is high enough not to limit yield but low enough that sorghum plants will not burn up during drought.

For late plantings into early July with little moisture available, lower targeted plant populations to as little as 20,000 seeds per acre and plant medium-early to early, drought-tolerant hybrids.

Store as much water as possible. It takes six to eight inches of available water to get a sorghum plant to the point of grain production. Once met, additional moisture has a significant effect on yield — 350 to 425 pounds per acre for each one inch of water.

Study after study shows that surface crop residue stores more soil water.

For full irrigation, Trostle says maximum yields will require 3.5 to 4.5 gallons per minute per acre.

“Some studies indicate a 20 percent to 25 percent advantage for cotton that follows grain sorghum. Sorghum that follows cotton also shows yield increases.”

“LEPA or low-set nozzles increase water efficiency. Critical irrigation periods are at mid-vegetative, boot, heading, flowering and grain fill stages.”

Trostle says work by Brent Bean, Extension specialist in Amarillo, shows that for maximum yield under full irrigation. 80,000 seeds per acre is adequate under most conditions. Bean recommends a medium to medium-late hybrid if planted before June 1.

For delayed planting, when less tillering occurs, he recommends an early-medium maturity hybrid with an increased seeding rate, near 110,000 seeds per acre.

“The highest return usually occurs if sorghum is irrigated at the boot stage,” Trostle says. Also, for higher yields, avoid moisture stress during the mid-vegetative stage (30 to 35 days after planting).

He says farmers can stretch limited water resources by dividing center pivot circles with different crops under each half-circle.

“For example, assume a 120-acre pivot at 1.5 gallons per minute. Plant half a circle in early to medium-early sorghum around May 5 in the South Plains. Plant the other half in cotton. That's about 3 gallons per acre for the 60 acres of sorghum.”

He says sorghum will nearly mature, with possibly one last watering, as cotton enters peak water demand.

“Farmers can then concentrate water to cotton. Allowing for a 10 percent decline in water capacity, they still have around 2.7 gallons per minute per acre for the 60 acres of cotton. Compare that to 1.5 or less gallons per minute if no sorghum is planted.”

Trostle says the rotation could work with other crops but sorghum is probably best for cotton because of the stubble it leaves. “Sunflowers planted early also could spread water usage.”

Trostle says sorghum rotation benefits to cotton have been known for some time, but scientists have not known exactly how much they gain.

“We know we break the cotton seedling disease cycle and the surface residue left by sorghum reduces wind erosion and increases water infiltration.”

He says a first-year study comparing four planting regimes — cotton following cotton; cotton following grain sorghum; grain sorghum following cotton, and grain sorghum following, grain sorghum — shows advantages.

The 2000 crop year yields in the two-year rotation study show: Cotton behind cotton, 641 pounds per acre.

Cotton following grain sorghum, 777 pounds per acre.

Grain sorghum following grain sorghum, 5,080 pounds per acre.

Grain sorghum following cotton, 6,224 pounds per acre.

“This is a first-year study and is not yet a conclusion,” Trostle says, “but it is in line with what we might anticipate.”

Trostle says nitrogen fertility also plays a role in sorghum profitability. “The rule of thumb is: two pounds of nitrogen per hundredweight yield goal. Even limited nitrogen on dryland sorghum will help subsequent dryland cotton to take better advantage of rotational benefits.”

Trostle says growers often look only at sorghum economics in the year they grow the crop. “Many feel they have to recover input costs in the year they spend it. Unfortunately, that precludes the long-term advantages.”

Those advantages include increased sorghum yield and higher residue amounts for improved erosion control and better moisture infiltration, which aids the subsequent cotton crop.

Trostle says farmers may have two new herbicides for grain sorghum this year. Aim is a broadleaf weed control, best used in a tank-mix with a non-ionic surfactant. Palmer ameranth control is weak if Aim is used alone.

Ally plus 2,4-D has been approved under a Section 18 for the Texas Panhandle and most of the south Plains (1/20 ounce of Ally plus 8 ounces of 2,4-d amine) for triazine-resistant pigweed.

Trostle and Chote both refer farmers to the website for more information on sorghum production practices and the Sorghum PROFIT program.


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