Cotton growers may be leaving money on the table if they wait too long to begin irrigating their crop, says Darrin Dodds, assistant Extension professor of plant and soil sciences at Mississippi State University.

“A one week difference between initiating furrow irrigation can make a difference of 50 pounds in yield — at $1 to $1.50 cotton, that’s $50 to $75 per acre you’re potentially missing,” he said at the annual conference of the Mississippi Agricultural Consultants Association.

“In 2010, when weather was very dry during the bloom initiation period, University of Arkansas personnel saw a 120 pound difference between starting irrigation one week prior to bloom versus at or after bloom.”

 Water management is one of the most important aspects of cotton production — but one of the least understood, Dodds says.

“With concerns about drawdown of the Delta’s alluvial aquifer and increasing regulation of water use for crop irrigation, we need to use water as efficiently as possible to achieve maximum production.”

To do that, he says, it’s important to understand how cotton uses water.

“Once cotton reaches peak bloom, water use increases significantly. But commonly, producers wait until blooms have begun to appear to begin watering.”

Arkansas research in which irrigation was initiated two weeks prior to bloom, one week prior to bloom, and one week after bloom has shown the one week before bloom scenario to be the most efficient, Dodds says.

“Looking at three years of data, initiating irrigation one week before bloom was consistently higher in yield than initiating irrigation during the first week of bloom by approximately 50 pounds. Terminating irrigation at 5 percent to 10 percent open bolls also was the most effective over three years. If you continue to water beyond that point, added moisture under a lush canopy can increase the risk of hard lock, boll rot and other problems.

Capitalizing on cotton's horsepower

“We look at nodes above white flower as a measure of horsepower for producing cotton. If you go into bloom with 8 or 10 nodes above white flower, you know you’ve got a lot of horsepower in that plant and a lot of potential yield. If you delay irrigation until the first week of bloom, you’ve reduced the plant’s inherent horsepower and you’re potentially leaving yield on the table.”

A potential hangup with early irrigation initiation, Dodds says, is restriction of root growth that could cause yield loss. “But, in southeast Arkansas tests where irrigation was initiated one week prior to bloom, they saw no restriction of root growth.”

Irrigation also will increase plant height, he notes, “so you need to manage for that.”

Producers watering cotton with a center pivot system need to be particularly attuned to the crop’s water needs, Dodds says.

“With a pivot, you’re able to get only about half to one-third as much water to the crop as quickly as with furrow. And when it’s as hot and dry as it was in 2010, if you get behind with pivot irrigation, it’s awfully hard — sometimes impossible — to catch up to the crop’s need. It’s very important to protect deep moisture and to initiate irrigation prior to losing that moisture.”

The PHAUCET program for furrow irrigation, developed by Phil Tacker, former Arkansas Extension engineer, helps to determine the size of holes to punch in polypipe, calculates pressure changes along the length of the pipe, helps address different row lengths, calculates how many hours to pump in one set without problems, the length and slope of the pipe, row spacing, etc.

“Using this program can achieve water savings of as much as 25 percent,” Dodds says.

Variety selection is another important component of attaining maximum cotton production, he says.

“Growers have moved onto the technology highway en masse, and it’s obvious we’re going to continue to travel that road as companies put more genetic traits in their seed and more treatments on them.

“We’ve seen a lot of new varieties in the last two to three years — they’ve been coming more quickly than ever before. It has been somewhat of a challenge for those of us in the university community to get adequate data to put together for our growers and consultants, but we’re working closely with the seed companies to improve this situation.”

New traits in the pipeline

Among traits seed companies are working on that may be incorporated in future varieties, Dodds says, is drought tolerance — “I think we’ll see this first in corn varieties, but cotton probably will benefit from this research at some point in the future.

“There is also work going on developing transgenic lygus control in cotton; Bollgard III, the next generation of that technology, is also on the way; and we starting to see some work on dicamba/glufosinate-tolerant cotton.

“Research is also under way on nematode-resistant cotton. About 35 percent of our cotton ground has reniform nematodes; 10 percent to 15 percent has root knot nematodes, and where these problems exist, that technology would be useful.”

Closer on the horizon, Dodds says, are Glytol cotton and Glytol plus LibertyLink varieties from Bayer.

“Glytol plus LibertyLink was scheduled to become available last year in west Texas, but they had to pull back, and it’s my understanding it will be available this year.

“In the pipeline from Dow are varieties with additional nematode resistance and VipCot with the Syngenta developed Bt protein.

“The issue with many of the herbicide traits is that we’re recycling modes of action we’ve had for years. With dicamba cotton, for example, we’re recycling herbicide chemistry we’ve had for 30 or 40 years; with 2,4-D cotton, we’re recycling a chemistry we’ve had for 60 or 70 years.

“New modes of action coming into the market are virtually nonexistent right now. Industry is working on new chemistries, but it’s a very complex, very expensive, very time-consuming process — which makes it all the more important that we protect the modes of action we have, particularly the PPOs for soybeans.

“We really need to work hard not only to rotate modes of action, but to rotate crops in order protect these key chemistries as long as we can.”