Waiting for those last two or three cotton bolls in the top of the plant to mature can cost you more than they're worth, according to research from the University of Georgia. The findings, from a study on harvest timing conducted in 1999 and 2000, were discussed by Craig Bednarz, associate professor, University of Georgia, during the Engineered Fiber Selection Systems Conference in Memphis.

The study was designed to determine optimum harvest timing as well as the impact of weathering on the yield, quality and profitability of a cotton crop. Researchers compared 12 to 13 stages of crop maturity at which researchers applied harvest aids, then machine-picked the plots.

“In 1999 we had an open fall,” Bednarz said. “We maximized yield and adjusted gross income when we applied harvest aids at 75 percent open bolls and machine-picked the cotton two weeks later.

“For every week we waited after 75 percent open bolls, the harvested crop lost 13.8 pounds of lint per acre and $6.74 in adjusted gross income. The majority of the loss in adjusted gross income was due to losses in lint yield.”

In 2000, a rainy harvest season, “We maximized yield and adjusted gross income when we applied our harvest aids at 85 percent open bolls and machine-picked the cotton two weeks later. For every week we waited after 85 percent, we lost around 57 pounds of lint per acre and $28.32 in adjusted gross income.

“In 2000, the reductions in adjusted gross income were due primarily to reductions in lint yield, but also to reductions in fiber quality. Specifically, the losses were due to declines below base grade in strength and uniformity, which hurt our price per pound.”

The researchers conducted an economic analysis by cotton fruiting position to determine any benefit of waiting for top bolls to mature.

“In our part of the world, the biggest money positions are main stem nodes 9, 10, 11 and 12. Based on our research, when the cotton crop is 65 percent open, the plant is going to be open all the way to node 13, which means our biggest money positions are already going to be open before we apply harvest aids.

“If we wait until the crop is 85 percent open, obviously our big money positions are still open, and have been open a week longer, and our crop is open all the way up to node 16 or 17.

“At 85 percent open bolls, researchers observed that there were two or three unopened bolls in the top of the plant per 10 feet of row. At 65 percent unopened bolls, there were four to six unopened bolls in the top of the plant per 10 feet of row.

“Our studies showed that if we waited to pick at 85 percent open bolls versus 65 percent open bolls, we increased yields 1 to 3 percent and we assumed that the yield came from the top of the plant.”

On the other hand, “If we waited one week after 85 percent open boll, our study showed we decreased lint yields by 9 to 11 percent. The majority of that reduction came on the bottom of the plant. That's the oldest fruit on the plant.

“The take-home message from the research is that if you apply your harvest aids and harvest your crop in a timely fashion, you're going to have some unopened bolls in the top of the plant, but they are worth very little to you.”