Cotton varieties currently available possess the potential to produce four to five times more than average yields, leading Texas Tech cotton plant physiologist Dan Krieg to conclude that environment rather than genetics exerts more influence on production.
Krieg examined the relationship between genetics, environment, yield and quality during the opening session of the Beltwide Cotton Conferences, held last week in Atlanta.
“The physical environment, including soil, rain, water supply and temperature, is the primary yield regulator,” Krieg said. “Management also plays a role in yield potential.”
Fiber quality traits, on the other hand, have a “strong genetic component, even though environmental factors do cause reduction in quality, especially with micronaire.”
Krieg said the interaction between yield and quality poses a significant challenge to cotton research. “We have no real solutions,” he said.
Yield potential has improved significantly over the past 50 or 60 years, Krieg said. “But the past 10 years created extreme concern as yields reached a plateau. We've seen extreme variability in yields.
“For instance, 1996 was a bad year for cotton. We had a better crop in 1997, but 1998 was bad across the Belt, and 1999 also was a poor year. And then 2000 was a killer.”
In 1999 and 2000, the Southeast had no rain from July through early August. In 2000, the Mid-South started out wet, but rainfall in June, July and August was less than 2 inches. North Arkansas was very dry.
“Texas has been dry forever, but was extremely dry in 1998, and 1999 started out with early rains but then had 60 days with none. And in 2001, Texas lost more than 1 million acres to drought.”
Krieg said Texas “is making progress in yield improvements, but for the last three years even irrigated cotton suffered because water supplies were limited. With irrigation, we still need rain to make a crop.”
He said Texas farmers plant some 2.5 million acres of dryland cotton. “Yields on this acreage has been flat for 30 years and that's a significant percentage of the U.S. cotton crop” and affects national yield averages.
Krieg said 11 years of data from 12 different research sites show environment to be the dominant factor in yield. “Varieties possess potential for high yields.”
He said boll number and retention affect yield. “The plant responds to environment and management to hold bolls,” Krieg said.
Fruiting position also plays a role. “We get 75 percent of our yield from the first fruiting position and 22 percent to 23 percent from the second. As yields increase, the percentage of plants with bolls on the key fruiting positions also goes up.”
Boll size, too, affects production. “The amount of lint per boll increases with yield.”
The number of seed per boll is a genetically controlled trait, Krieg said. But genetics cannot overcome extreme negative environmental conditions.
“Fiber quality relies more on genetics,” Krieg said, “but we also see an environmental link.”
Both length and strength are genetic factors. “We see an interaction between strength and micronaire, and temperature has a major influence on mike. Bolls set later in the season will have a lower mike because they grow under cooler temperatures.”