Highly drought tolerant

For farmers looking at crop options, sunflowers could provide an energy and water-efficient alternative to corn.

“With energy costs up, farmers are looking for options,” says Calvin Trostle, Texas Extension agronomist at Lubbock. “The sunflower is one of the most drought tolerant plants available, comparable to cotton.”

Trostle discussed sunflowers and other “alternative” crop options during the recent Southwest Crops Production Conference and Expo, a Southwest Farm Press-sponsored event.

“Growers can achieve more efficient production and economic returns with the first five to 10 inches of water applied (at the optimum time) to sunflower than with other crops. Limited irrigation in most years can produce yields similar to full irrigation.”

He says sunflower, because of an extensive root system, likely will produce more in moderately dry soils than under wet conditions. Sunflowers need adequate soil moisture, however, just before, during and after flowering.

“During these growth stages, one or two good rains or irrigation applications can double yields,” Trostle says. “Also, oil content increases with good soil moisture.”

Moisture is critical at 20 days prior to flowering (bud stage) to 20 days after flowering (petal drop). “High water demand begins at bud stage and peaks at flowering, about six weeks after emergence. With confectionery varieties, farmers may irrigate to ensure good seed size and quality.”

Trostle says overwatering early will limit rooting depth and diminish drought tolerance. “Kansas and Colorado data suggest about 150 pounds of yield per one inch of irrigation after the first seven inches of water,” he says. “At optimum timing, expect 100 to 200 pounds of yield for every one-inch of irrigation water.”

Trostle says preplant irrigation for sunflower may have longer benefit than for other crops,

“Optimum irrigation should include two mid-season applications, the first at bud swelling and the second at full bloom. For limited pivot irrigation, with less water available per pass, the first primary watering should be at bud stage, followed by two subsequent applications seven to ten days apart.”

Trostle says sunflower does better with less frequent heavy irrigations (two inches to four inches). “We see reduced opportunity for disease development,” he says.

Fertility also makes a difference. “Many west Texas farmers neglect adequate fertility,” Trostle says, “although potassium and phosphorus will normally not be problems unless soil test information indicates a need. Sunflower will need 3.6 pounds of potassium and 1.5 pounds of phosphorus for each 100 pounds of yield goal.

“The most common fertilization error is nitrogen deficiency, which may be hard to recognize. Watch for reduced growth, then lighter green to yellow leaves.”

Trostle recommends five to six pounds of nitrogen per acre for every 100 pounds of yield goal. He recommends a preplant or sidedress (when plants reach eight to 16 inches) treatment. “Do not apply at planting except between rows.”

Seeding rates for west Texas are lower than suggested for other areas, Trostle says.

“Less seed means more money,” he says, “since larger seed is more valuable in confectionery markets. For confectionery, plant 17,000 seeds per acre in irrigated fields, 11,000 to 12,000 in dryland conditions. For oilseed varieties, plant 20,000 to 23,000 per acre irrigated; 12,000 to 15,000 dryland. Oilseed rates may be revised slightly upward.”

Soil moisture and seed size also may affect planting rate. With good grade, smaller seed can reduce seeding costs $2 to $4 per acre. Seed size can mean a difference of up to 3,000 seed per pound.

Trostle recommends an air/vacuum planter. “It's particularly important with confectionery varieties. Also, calibrate carefully to assure proper seed drop.”

Planting dates vary according to temperature. “Don't plant more than two weeks before the last average spring frost date to capitalize on adequate germination conditions. Minimum average daily temperature should be 50 degrees.”

He says early plantings through mid-May show the highest yield potential and best oil content, but also have the highest potential for head moth and stem weevil infestations.

“The last recommended planting dates with shorter maturity hybrids are: Panhandle, July 5; Lubbock to Amarillo, July 10; south of Lubbock, July 15.

Trostle recommends firm seedbeds and planting depth of 1.5 to 2 inches.

Trostle says under good conditions, sunflowers tend to respond to more narrow row spacing, with 30 inches optimum. Seeding rate would be the same for 30-inch rows or 40.

Plant orientation also is important. “Plant rows in a north-south orientation. Before flowering, heads follow the sun but at bloom they face east and droop downward. The north-south orientation reduces rubbing of heads, which can led to disease or shattering.”

Head moth infestation is another potential challenge for sunflower farmers, Trostle says. “Timing insecticide applications properly is critical. Spray moths, not worms; the moth is fertile only when pollen is available.”

He recommends scouting early in the morning with early evening as a fallback. “Pay particular attention around bud swelling. Some of the newer varieties may open sooner than older ones.”

Trostle says if scouts report even scattered head moths, farmers should initiate controls. “Make spraying decisions as early as possible, 5 percent bloom (yellow is visible).”

He says early planting may require a second application about five days after the first to avoid egg lay. Occasionally a third application is necessary.

“Check with your county Extension agent, integrated pest management agent or crop consultant for insecticide recommendations.”

Trostle says some farmers have complained that sunflowers are hard on soil and that subsequent rotation crops do poorly. “Sunflowers remove moisture and nutrients from deep in the root zone. They require nutrients similar to a 40 bushel per acre wheat crop.”

He says nitrogen levels in cotton following sunflowers is the main concern, but phosphorus also could be low.

Farmers should test soil following sunflowers, but if that's unavailable, Trostle recommends increasing nitrogen rate by 30 to 40 pounds per acre and phosphorus by 20 pounds per ace in irrigated cotton. For dryland, increase nitrogen rate by 20 pounds.

He also recommends planting sunflowers early (by early May) to allow soil moisture to recharge from September to October, when rainfall is usually abundant in west Texas.

“Fall-seeded small grains after sunflower will be an iffy proposition.”

Potential disease problems in sunflower crops may include: rust, if conditions are cool; downy mildew, but usually not an economic problem; black stem, which can be limited with rotation.

“Sclerotinia is usually not a problem due to the warm, dry climate, but watch out for it if conditions turn cool and wet.”

Sunflowers may offer viable, economic crop options for west Texas farmers in 2001

Some tips on production

Timely, efficient harvest will improve profit potential for sunflower producers, says Calvin Trostle, Texas Extension agronomist.

“Sunflowers are physiologically mature when the back of the head is yellow,” he says. “Bracts turn from green to yellow and brown.”

Birds can take a toll on sunflower yields if the crop remains in the field past optimum maturity. “Early harvest at maturity is the best remedy,” Trostle says.

Desiccation also may promote early harvest and reduce potential for shattering. Paraquat applied when sunflower seed reach 28 percent to 30 percent moisture may help with quick termination.

Growers also should pay attention to harvesting equipment.

An all-crop header, with little modification, may be the best choice to harvest sunflowers. A small grains platform may work, but “only if inexpensive catch pans are installed to cut losses (shattering seed falling to the ground).”

Trostle says a corn head can work but is not the best choice. He recommends installing stationary knives to cut the stalks.

“Regardless of the equipment, make certain to check for inefficiency and harvest losses.”

Over-threshing, he says, is the most common problem. “Broken heads overload the cleaning shoe with small pieces of seedhead and trash.”

Trostle also recommends a slow cylinder speed, 250 to 450 rpms, and concaves well open.

“Harvest at a reasonable speed when seed moisture is in the low teens, less than 15 percent. Use a minimum amount of air. And it is usually better to decrease concave clearance than to increase cylinder speed to improve threshing.”

Trostle says volunteer sunflower may cause problems in rotational crops. He recommends leaving residue on the soil surface so birds can clean up the seed. “Roundup Ready crops following sunflowers also offer good control options.”

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