Newer cotton varieties require different approach with PGRs

Higher yielding cotton varieties are coming fast and furious from the major seed companies. Along with these rapid changes comes a need for a closer look at a number of production strategies, including the use of plant growth regulators.

Clemson University Cotton Specialist Mike Jones says, “A lot of the varieties we grow now, like 555 are extremely tall, and our growers have been well trained to hit these varieties hard with plant growth regulators.”

The old reliable triple nickel, DPL 555, will no longer be available to growers after this September. Other standard varieties are being replaced with higher yielding varieties, with advanced genetic traits included.

“Though we did not see any significant statistical differences in lint yield between these new cotton varieties and DPL 555, several of these look like good alternatives for South Carolina cotton growers,” Jones says.

Jones' research team looked at five current commercial varieties, including DPL 555BR, DPL 143BR, ST 4554B2RF, DPL B2RF, and DPL 0935B2RF and five experimental varieties including, DPLX 07X440DF, DPL 0912B2RF, DPL 0949B2RF, MCS 0711B2RF and MCS 0702B2RF.

In 2008, the 10 varieties were sprayed with no, high (40 ounces total applied three times) and standard rates (24 ounces total applied twice) of a plant growth regulator (Pentia). In a year with high yield potential, and on land with high yield potential (three bales per acre), the high rate of PGR actually reduced yield on the new varieties by 6-7 percent, compared to no PGR and standard rates of these materials.

Looking at the same tests in 2009, Jones says the PGR-treated cotton plants appear to be responding similarly to the 2008 tests. In some varieties, we got slightly higher yields with more PGR and in other varieties we got less yield from more PGR.

There is no question that all the cotton varieties responded to PGRs. The plants in the higher rate plots appeared to be shorter and greener than the standard and no treatment plots. PGRs generally cause cotton leaves to thicken, giving them a darker, greener color and a healthier appearance, Jones explains.

More importantly, he says, is what happened internally when we sprayed different varieties with different rates of a PGR.

“With these PGR treatments we were changing the internal portioning of dry matter within the boll. High rates of PGRs decreased gin turnout and decreased the micronaire fairly consistently over these new varieties,” Jones says.

Fiber length can be a critical marketing factor in U.S. cotton exported to China and other Asian markets. Jones says there was a consistent increase of fiber length.

Taking advantage of newer, high yielding, high quality cotton varieties is critical if Southeast cotton growers are to survive projected hard times in 2010 and meet expected lint demand increases from 2011 to 2015.

The USDA says upland cotton exports are projected to decline through 2010/11, reflecting a reduction in acreage and production and diminished availability of stocks.

Exports then grow moderately, accounting for over three-fourths of U.S. cotton use by the end of the projection period.

As a consequence, while the U.S. cotton trade share initially falls below 30 percent, it then rebounds to nearly 34 percent by the end of the projection period.

Cotton stocks decline in the first several years of the projections as some acreage shifts to other crops. As projected cotton prices strengthen after 2009/10, improved net returns provide economic incentives for cotton acreage to rise, and stocks increase through the end of the projections.

High rates

“Our growers have been conditioned to stay on top of these older, proven varieties, and as a result many have gone to some fairly high rates of PGRs. It appears, from our tests, that we are going to have to look at some new strategies on PGR use to take full advantage of the new varieties that are coming rapidly from a number of seed companies,” Jones says.

Across the entire test in 2008, cotton varieties not treated with a PGR produced an average of 1,560 pounds of lint per acre. High, or aggressive levels of a PGR reduced average yields to 1,467 pounds per acre. The standard treatment produced the highest yields of 1,568 pounds per acre.

Cotton seed production also was highest in the standard treatment — 4,040 pounds per acre. The high PGR treatment had the lowest (3,869 pounds per acre) and the check plots had 3,957 pounds of seed per acre.

Micronaire across all the varieties ranged only from 4.1 to 4.3 and fiber length varied from 1.12 to 1.14 inches. Fiber strength and fiber uniformity had similarly minor variations across all varieties.

Compared to DPL 555BR, the newer varieties had only slight advantages. The triple nickel plots produced an average of 1,532 pounds per acre. The new varieties as a group had slightly higher yields, though not all out-yielded DPL 555.

Seed cotton production was the major difference among varieties and PGR treatments. Seed cotton was reduced by 21 percent on DPL 0935B2RF and 15 percent on DPL 143B2RF, both commercially available varieties, using the high rate of a PGR.

In contrast, DPL 555 and DPL 0935 both had a 14 percent yield increase from standard rate application of a PGR.

There are exciting changes coming in cotton varieties in the next few years and Jones urges growers to evaluate data from multiple locations and multiple years when possible. He stresses that the experimental varieties used in the tests at the Pee Dee Agricultural Research and Education Center are not yet available to growers.

TAGS: Cotton
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