The first decision a cotton producer makes each growing season also is the most important one, says Mike Jones, Clemson University Extension cotton specialist. “All of the seed technology, and all of the management practices you put into a field hinge on the selection of a variety, and the yield and quality of that variety,” said Jones at the recent Southeast Cotton Conference in Rocky Mount, N.C.
The art of selecting a cotton variety becomes more complex each year, he adds, especially considering the emerging biotechnology traits.
The most important criteria to consider when selecting a variety is yield potential, says Jones. “If a variety won't yield for you, it really doesn't matter which value-added traits are in that variety. You're going to lose money on yield and take discounts on quality, and that'll probably offset any advantage from value-added traits such as transgenic technology,” he says.
The second most important criteria in variety selection is yield stability, contends Jones. “You want a variety you can count on, and you want a variety that'll yield the same for you whether you have dry conditions, irrigation or plentiful rainfall. You want a variety that will yield in the top of the trials in every location you're considering.”
Growers also shouldn't forget fiber quality when selecting a cotton variety, he says.
In reviewing what growers planted across the U.S. Cotton Belt this past year, Jones says 39 percent of the cotton acreage was planted in varieties containing Bt technology. Southeastern growers, however, are planting much more of their acreage in transgenic varieties.
“South Carolina growers planted 70 percent of their 2002 cotton crop in varieties with Bt technology. Virginia growers planted 62 percent and North Carolina producers planted 60 percent of their cotton crop in Bt varieties,” says the agronomist.
U.S. cotton producers have enthusiastically embraced Roundup Ready technology, he continues. “About 73 percent of the U.S. crop planted this past year contained the Roundup Ready gene. This includes straight Roundup Ready and stacked gene varieties. Most states in the Southeast planted from 85 to 100 percent of their 2002 cotton crop in varieties containing the Roundup Ready technology.”
A look at the data, says Jones, reveals that U.S. growers haven't made much progress in the past 27 years in terms of increasing lint yields.
“A lot of folks talk about the yield plateau, and that's what we're seeing. We appear to have increased yields up until about the mid-1990s, then we reached a plateau.”
There are many theories, he says, as to what has caused this stagnation in U.S. cotton yields. “One theory that I'd like to put to rest is that we're getting a yield ‘drag’ from transgenic traits. From the information I've seen from our variety trials, it doesn't appear that we're getting any sort of yield drag from transgenic traits.
“All you have to do is go back and look at our university variety trials, where we test the current parents and their siblings all in the same trial. For example, we looked at the DP 5415 series in three states and across 46 sites. The transgenic version of this variety is holding its own. We've seen the same trend in other varieties.”
One of the primary causes of yield problems in recent years has been weather conditions, says Jones. “In the past five years, we've experienced extreme drought conditions in South Carolina, and that's a big reason we're seeing a yield drag.”
Another reason for poor yields, he adds, is that growers are not making good decisions when selecting cotton varieties. “It's amazing when you look at the percent of market of the top 10 yielding varieties from our university trials, and then look at how many of those top 10 varieties were planted by growers in the following year.”
In 1999, only 0.5 percent of South Carolina's acreage was planted in a top 10 yielding variety from the 1998 trials, notes Jones. That figure increased to 2 percent in 2000, 4 percent in 2001 and 22 percent this past year.
Growers can get variety selection information from several sources, he says, including official university variety trials. This past year, more than 60 cotton varieties were tested in South Carolina. Growers also can look at variety trials from neighboring states such as Georgia and North Carolina, especially where the varieties were grown in similar soil and environmental conditions, he says.
Seed companies also conduct numerous trials, says Jones, and growers also can rely on their own experience and that of their neighbors.
The varieties most cotton producers in South Carolina are choosing to grow are only average in lint yield, according to variety trials, says Jones.
“The problem we're seeing is that about 34 to 35 percent of our acreage is planted in straight Roundup Ready varieties, and they're not performing very well in our trials.”
Southeastern growers increasingly are seeing fiber quality problems each year, says Jones.
“Whenever you have a problem with fiber strength, you look first at the genetics of the variety you're planting. Eighty-two percent of the variations associated with fiber strength can be traced back to the variety. The same thing is true with fiber length. It's a different story, however, with micronaire, where environment is the dominant factor.”
If a producer plants a variety with low-quality characteristics, there's a greater risk of falling below the discount line in case of drought conditions, says Jones.
“If you plant a variety with good quality characteristics, there's a good chance — even under poor environmental conditions - that you'll stay above the discount line. Picking the right variety with a good fiber quality package is important.
“The majority of the varieties we're planting have lower fiber quality.”
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