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UT survey of boll maturity

Farm Press cotton-bolls-staff-dfp-5591.jpg
Tyson Raper surveyed 44 agronomists, growers, consultants, experienced sales consultants and specialists.
Boll survey shows lowest development level for opening bolls with ethephon.

Tyson Raper, University of Tennessee's cotton and small grains specialist believes that we can learn a great deal by comparing notes. In the case of boll maturity specifically, he believes that slicing bolls and comparing maturity is one of the best ways to time defoliation.

"When it comes down to it, there is a large amount of variation in what each of us consider to be a boll that can be opened with ethephon," he says. "With cool temperatures in the forecast on what remains a late crop, many are trying to figure out which bolls might be opened with an application and when to start." 

Raper wanted to know what agronomists, growers, consultants, experienced sales consultants and specialists thought was the earliest boll stage that could be opened using the defoliant, ethephon. He numbered stages of boll development one through 12. 

He emailed several dozen individuals in the Midsouth and Southeast and several working outside of the region including North Carolina.

University of Tennessee Institute of Agriculturebollmaturitychart.jpg

This image includes a few notes on the observed differences as numbers progress from immature (Boll 1) to mature and cracked (Boll 12). Note the breaks of no jelly within the seed at Boll 6, faint seed coat color at Boll 8, difficulty cutting Boll 9 and completely mature seed at Boll 11.

 Raper said the vast majority of respondents immediately stated a range followed by conditional statements pertaining to sunlight, temperatures, or harvestability.  

"In hindsight, I could have probably worded the question better," he said.  "When pressed, I often clarified the question with something along the lines of, ‘what number boll would be the lowest you think you could harvest?’"

He analyzed 44 responses and charted them.

University of Tennessee Institute of Agricultureboll_maturity_poll_survey_w_pic-1024x612.jpg

"The most impactful presentation of this data, in my opinion, requires a conversion to percent of respondents," he said. 

The graph shows the percent of respondents that believed they could open the corresponding boll with ethephon graphed by boll number.

University of Tennessee Institute of Agricultureboll_maturity_poll_survey_perc_pic.jpg

Raper noted a number of things regarding the survey:

  • 100% of the respondents – all 44 - believed they could use ethephon to open a boll that was difficult to cut, had a dark seed coat color, and had no jelly within the seed (Boll 11).
  • 70% of the respondents believed they could use ethephon to open a boll that had faint seed coat color, no jelly within the seed, but the boll was still easy to cut (Boll 8).
  • Less than 40% of respondents believed they could use ethephon to open a boll that had just lost all jelly within the seed but was easy to cut and lacked seed coat color (Boll 6).
  • Less than 25% of respondents believed they could use ethephon to open a boll which had jelly within the seed (Boll 5). 

"If the calendar will allow, don’t defoliate until the uppermost boll you intend to harvest has lost all jelly within the seed and the seed coat is beginning to show faint color," Raper said.  "If you can wait until this point, the majority of participants in this poll believe you’ll be able to open that boll."  

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