Georgia cotton producers were expected to plant about 20 percent of their estimated 1.5 million-acre crop in some form of conservation-tillage this year. Some areas, like south Georgia's Coffee County, have becoming leading adopters of no-till or minimum-tillage practices.
“Fifty to 60 percent of the cotton in Coffee County is planted in conservation-tillage,” says Rick Reed, county Extension coordinator. “I encourage our new growers to network with farmers who have experience in no-till. Go to their fields, look at their equipment, and ask them what they've learned that has been successful, and what hasn't been successful.”
Reed advises his conservation-tillage growers to use cover crops. “We don't need winter weeds — we need a cover crop. A grower who is just starting out might want to start out with a small grain as a cover and move up to a rye cover.
“You must be patient with these systems. After three or four years, you'll notice an improvement in your soil quality. You'll see clods in the first year or two. But over time, those will work themselves out,” says Reed.
Most Coffee County growers who are new to conservation-tillage will start out with a wheat cover crop, he says.
“We know ultimately that rye is the best cover crop. But there's a fear that it'll get too big and you can't handle it or plant into it. That's a realistic fear. Growers have been very successful with rye, but you must work up to that level, and it usually takes two to four years to become consistent,” says the county agent.
Rye offers many benefits in the areas of disease and weed control, he adds.
Reed suggests that growers new to conservation-tillage begin by planting one half to three fourths bushel per acre of a small grain such as wheat for a cover crop. “You'll want to work your way up to one or 1.25 bushels per acre. And, eventually you can plant up to 1.5 bushels per acre on light soils.”
The early flowering stage would be the earliest recommended time for terminating a small grain cover crop, he says. “Preferably, we'd like to see it terminated at late dough stage. We want that head to be as fully developed as possible. With rye, we want to terminate when it's about chest-high.”
Growers must develop a conservation-tillage system that will hold residue in the field, notes Reed.
During this past winter's Georgia Cotton Production Workshop, Reed and members of the University of Georgia's Extension Cotton Team shared their thoughts on the use of conservation-tillage in cotton production. The following is a summary of that discussion.
Plan to succeed
Growers who choose to make the switch from conventional to conservation-tillage should begin planning well in advance, says Glen Harris, Extension soil scientist. “If you can get your soil into good shape prior to beginning a strip-till system, it'll make things easier when it comes to liming and fertilizing,” he says.
Harris advises growers to correct any nutrient or Ph problems throughout the plow layer before planting in a conservation-tillage system.
“In most cases, you'll be converting from a conventional, deep plowing system. If you're converting from a chisel plowing system, it'll be more difficult, but you can use that last opportunity to get some Ph and phosphorus and potassium incorporated into the soil,” says Harris.
Fertility and pH can be maintained in a strip-till system with surface applications if a grower starts off right, he adds. “You cannot correct problems later if you don't start off right. If you have a pH problem down to eight inches, throwing lime on top of the soil will not solve it.
“One of the hardest things for a grower to believe is that he can do a good job with pH by making surface applications. After you've been in a conservation-tillage system for about three years, we recommend taking a more shallow soil sample, at about two to three inches. A pH problem will develop on the top and work its way down.
“It's best if you can catch a problem with a shallow soil sample and correct it with a surface application of lime before it gets too deep. I've seen situations where growers have gone for five or six years, and the pH problem has gone too deep. The only option then is to plow or chisel in some lime. Once the problem gets too deep, it's difficult to correct with surface applications.”
Growers have several possibilities when selecting a cover crop for their strip-till cotton system, says Harris. Initial research focused on planting a legume crop in a conservation-tillage system, but this proved to be challenge, he adds.
“Most growers have gone to small grain covers or winter weed and old crop residue. About 95 percent of the cover crops in Georgia will be rye or wheat. But there's a renewed interest in legumes because of rising fuel and nitrogen prices.”
Harris advises growers not to fertilize their cover crops unless they want to work with a large amount of residue. Rye, especially, can become difficult to kill if it grows too large.
“How much residue should a grower make? I'd say as much as you can handle. But don't jump into strip-till for the first time with a lot of residue. Strip-till is a new game, and until you get used to it, you might want to consider starting with winter weeds and graduating to wheat, and then to rye with fertilizer.
If a grower plants cotton following a small grain cover, he should increase the nitrogen by about 25 percent, says Harris. “I'd like to see that nitrogen applied preplant to take care of the residue and make it more mellow. If a grower plants cotton following a legume, he probably can decrease the nitrogen rate.”
The most critical pieces of machinery for strip-tillage cotton production are a strip-till unit and a burndown sprayer, says Michael Bader, Extension engineer. Foam markers also can be helpful to prevent leaving strips in the field, he adds.
“If we stay with a conservation-tillage system year after year, and maintain the integrity of row patterns, we probably can eliminate subsoiling in our heavier soils,” says Bader. “In our sandier soils, we probably can eliminate subsoiling if we control our traffic. But it's difficult to control boll buggy and dual picker traffic, so it's probably best to continue subsoiling in sandier soils.”
More seedling disease
Southeastern producers probably will find a higher incidence of seedling disease in conservation-tillage cotton, says Bob Kemerait, Extension plant pathologist.
“Increased organic matter gives pathogens something to feed upon,” he explains. “The cooler soil temperatures and higher soil moisture associated with conservation-tillage also encourages soil-borne seedling diseases.”
But, he adds, there are benefits in conservation-tillage that should help to reduce the incidence of seedling disease. “Organic material in the ground will increase the microbial flora and fauna associated with the soil, and this will give us benefits. One of the best things we can do to reduce seedling disease is to encourage rapid, vigorous growth of the cotton plant. If conditions are warm enough, the increased soil moisture in conservation-tillage will help with rapid germination of the seed,” says Kemerait.
Before using an in-furrow fungicide in conservation-tillage, Kemerait advises growers to consider several factors at planting time. “Consider the history of the field, the soil and air temperatures at the time of planting and the projected weather forecast. Often times, it won't be economically beneficial to use an in-furrow fungicide.”
Strip-till insect pressure
Seedling insects, such as early season thrips, often are associated with conservation-tillage, says Phillip Roberts, Extension entomologist. “But a lot of data has shown that we have fewer thrips in strip-tillage versus conservation-tillage. But by no means would that allow us to stop using a preventative insecticide at planting,” he says.
Cutworms are a potential problem in cotton strip-tillage systems, notes Roberts. “The risk of having problems with cutworms definitely increases in strip-tillage. In conservation-tillage, cutworms can become established on winter weeds or covers, particularly legume covers.
“We need to burn down the cover crop in a timely fashion — at least three weeks prior to planting. Cutworms may linger until cotton emerges from the ground. And cutworms are more of a problem in legumes than in wheat or rye,” he says.
If a grower is in a high-risk situation where he suspects a cutworm problem, it might prove effective to band a pyrethroid behind the planter, says Roberts.
It can be said that beneficial insect activity is greater in conservation-tillage because there are more fire ants, says Roberts. “Fire ants are good predators, helping us with corn earworms and tobacco budworms. But we see aphids build more rapidly wherever we have fire ants. Fire ants protect aphids from other predators.”
Weed control strategies
Cutleaf evening primrose is a major problem in conservation-tillage cotton production because paraquat and glyphosate are not very effective in controlling the weed, says Stanley Culpepper, Extension weed scientist. Herbicides are available that will effectively control cutleaf evening primrose, but these materials have many restrictions, he says.
Wild radish and Florida pusley also are becoming major problems in strip-tillage systems, adds Culpepper. “Most growers who till their fields put out a DNA herbicide to control Florida pusley. If you're strip-tilling, and Florida pusley already has come up, there's not a consistent, effective, postemergence herbicide available to control the weed,” he says.
It's critical, says Culpepper, that a grower who has problems with cutleaf evening primrose, wild radish and Florida pusley, use 2,4-D in strip-till situations.
“We need to put out this application of 2,4-D 45 days prior to planting, which means late February or early March for most of our growers. You don't have to apply 2,4-D with Roundup or paraquat to take care of those weed species. If you use 2,4-D alone, it'll allow you more flexibility at planting.”
Culpepper says he would prefer using a small grain as a cover crop rather than winter weeds. “It's easier to kill a small grain than it is to kill winter weeds. I wouldn't recommend relying on winter weeds for a cover crop.”