Chris Main, Extension cotton specialist with the University of Tennessee in Jackson, reported on a one-year study of variety responses to irrigation. Main cautioned the audience that the study was basically a one-year “fact-finding” exercise and that further research may show more differences.

“We want to find out if cotton varieties differ in response to irrigation,” Main said.

Weather was a factor. “Rainfall can be problematic with irrigation and variety response research,” he said. Rain may have accounted for some of the diverse results he found in the study.

He set up trials in Arkansas, Mississippi and Tennessee and planted 16 different varieties. Water application ranged from 21 inches to 29 inches for the season. He said heat units in Tennessee were about 300 less than average.

“We had a very positive impact on the crop in Arkansas,” he said. “We had a very negative impact on the cop in Mississippi. And we had little impact in Tennessee.”

Yield advantage in Arkansas, across all varieties, ranged from 32 percent to 110 percent. In Mississippi, yield was down by 280 pounds per acre. “In Tennessee we added a little on yield,” Main said.

He said a late rain and fruit shed likely affected Mississippi results.

“In Tennessee, we saw some varietal response to irrigation, about what we have heard from growers. But we detected no significant effect on gin turnout.”

He said overall, varietal differences were “hard to discern with some minor gin turnout variations. Rain patterns had an influence.”

He said one of the lessons learned is that more work is needed. Future studies may include adjusting irrigation scheduling “to build a better plant.”

He said monitoring the leaf area to find the detrimental point where irrigation application actually limits yield is an area of study. He also wants further study on when to turn off the water, do more soil moisture monitoring and identify where on the plant yield is made.