Variety selection, planting dates still basic

Cotton farmers have an unprecedented number of variety choices available for a wide range of growing conditions and production systems. But choosing the right variety for the right system, even the right field, may mean the difference between success and failure, says Texas Extension cotton specialist Randy Boman, Lubbock.

And with some of the newer value-added options, and accompanying higher seed costs and technology fees, growers need to take a hard look at seeding rates, to make certain they get the most value for their investment.

“Many good varieties are currently available to High Plains producers” Boman says. “But be careful when selecting a new one.”

Boman says yield potential and fiber quality should be the top two consideration for variety selection.

“Producers sell pounds of lint and fiber quality dictates how much each pound is worth.”

He recommends farmers examine university performance tests over multiple years and multiple sites.

“Unfortunately, many transgenic varieties show up without multi-year university testing,” he says.

Adaptability is extremely important. Boman says in recent years some High Plain growers have tried full-season picker-type cotton “that's sometimes better adapted to other regions. Weigh the benefits of yield, fiber quality and vigor,” he says, “but don't forget boll type. Stormproof bolls can be extremely important with stripper harvest and meteorological events that are common to the High Plains.

“Check for stormproofness of new varieties. Often we can produce the lint but can we harvest it?”

He says open bull, full-season types have been popular for the past few years, especially under irrigation. Warm September weather permitted growers to make late-set bolls. Proper irrigation, termination and timely harvest-aid application are crucial, he says.

“Do not leave an open boll cotton to condition for harvest with a freeze. There Is a high probability of significant pre-harvest losses.”

Boman says farmers should consider value-added traits such as herbicide and insect resistance in variety selection but should look closely at higher seed costs and technology fees in relation to weed species present and the likelihood of budworm/bollworm pressure.

“We know the value of a transgenic herbicide program in foul fields,” he says. “And if producers traditionally spend a lot of money on budworm/bollworm control, the technology can be a bargain. Economic benefits of subthreshold worm control are still being studied in the High Plains, where bollworm problems tend to be lighter than in other cotton production regions.”

Boman says farmers should consider disease-tolerant or -resistant varieties in fields with histories of verticilium wilt or fusarium wilt/nematode problems.

Plant Density

Boman says plant populations can be adjusted to reflect various field conditions and yield potential. In 40-inch rows, optimum planting rate is two to five seed per foot of row. “Target the low end for dryland and the high for irrigated cotton.

“Use good quality seed and plant for seed per foot of row instead of pounds per acre. Depending on seed size and variety, the number of seed in a pound can vary as much as 1,500.

Boman says germination should be at least 80 percent (required in purchased seed). Also consider vigor.

“Seed treatments can increase seedling survivability during stand establishment if environmental and disease pressures occur,” Boman says. Survivability may run as low as 50 percent during cold, wet periods but as high as 80 percent under more ideal planting conditions, warm soils with no environmental stresses.

Boman says farmers can predict a seedling survival rate of 60 percent to 70 percent. “Consequently, target stands for the upper range of optimum production to provide a cushion for stand loss. For a target stand of five plants per foot of row, plant six seeds per foot if you expect 80 percent germination. If environmental conditions result in a one-third stand loss, there are still four plants per foot. Half-stand losses result in 3 per foot.

Boman says higher rates may be justified for planting early in marginal soil temperatures; lower rates may be justified In later planting into warmer soils.

“Dryland fields likely perform better with lower plant populations than irrigated fields,” he says.

Planting too thick also may delay maturity. “Excessive populations increase node location of the first fruiting branch on the mainstem” Boman says, “causing a possible shift from nodes 5 or 6 up to 7 or 8. Each increase in one node may delay maturity by three to five days.”

Excessive plant populations also increase the number of barren plants per acre. A barren plant functions as a weed, robbing fruiting plants of sunlight, moisture and nutrients.

Reducing seeding rate also cuts costs, especially with transgenic varieties. Roundup Ready seed, for instance, costs about $35 per bag, plus the technology fee, $20.30, for a total of $55.30 per bag of seed. At 10 pounds per acre, a grower will spend $11.06 per acre for seed. At 15 pounds per acre, the cost jumps to $16.60, and at 25 pounds, the cost is $27.65.

Boman also recommends high quality and fungicide-treated seed that scores high (160 or above) on the Cool Warm Vigor Index (CWVI). The CWVI is a combination of the germination percentage plus survival rate in a warm and cool germination cycle.

“The test is available from the Texas Department of Agriculture facility in Lubbock,” Boman says. “Knowing the CWVI value allows growers to segregate seed into vigor rating lots. High vigor seed can be planted in cooler soils; lower vigor rating seed can be planted as soils warm. High vigor lots also may justify lower seeding rates, Boman says.

He says fungicide treatments may be justified. “Stay with basic treatments for rhizoctonia, pythium, fusarium and thelaviopsis (black root rot). Other seed treatments may not pay dividends.

“Fungicides generally enhance stand establishment, Minimize stand losses, help maintain healthy roots and vigorous plants, possibly reducing the potential for replanting expenses.”

Boman says several fungicides are available to control diseases. Farmers should select the one best suited to a specific disease.

Apron is a good pythium material. Nu-Flow M, Vitavax-PCNB, Demosan and Baytan or Nu-Flow M at 1/2 ounce per hundredweight are effective for rhizoctonia. For black rot, recommendations include Baytan or Nu-Flow at 1 ounce per hundredweight.

Boman says recent research indicates black root rot may be a more significant factor in yield losses than once thought.

“The combination of high quality seed and chemical seed treatments reduces risk and results in plants more tolerant to early season stresses. They also show stronger emergence when planted deeper and produce a more uniform stand. Early plant growth is more vigorous.”

Planting Time

Soil moisture availability often dictates when farmers plant throughout much of Texas, but temperature also is a factor.

“Research shows that cotton plants require more than 100 hours above 64 degrees Fahrenheit at the seed level to emerge,” Boman says. “The optimum target is a 10-day average minimum soil temperature of 65 degrees at eight inches deep. With poor quality seed, 70 degrees is a better target.”

Boman recommends soil temperatures in the seed and root zone exceed 60 degrees and the five-day forecast calling for overall temperatures on the upswing. Low air temperature forecast should be above 50 degrees.

“During critical germination periods, soil temperatures below 50 degrees can result in chilling injury and malformed seedlings, reduced vigor, poor stand establishment, and Increased likelihood of seedling disease,” Boman says.

“Emergence usually occurs after accumulating 60 to 80 DD60 heat units after planting. If as few as 25 heat units are forecast for the next five days, farmers should delay planting.”

e-mail: [email protected]

Editor's note: Part. two of the Southwest Farm Press Exclusive series Cotton 101 looks at variety selection and seeding rates. Related articles in this issue will deal with early season Insect control.

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