The fact less continuous cotton is being grown is a good thing, as rotations break up nematode and disease cycles. But the move to more rotation requires growers to consider several factors such as soil types, crop residue and time management, says Charlie Burmester, Auburn University Extension agronomist.
“From what I saw this past year, there are more things farmers need to consider about time management,” said Burmester at the recent Beltwide Cotton Conferences held in San Antonio.
In addition to nematode and disease problems, recent improvements in the prices of other crops also have led growers to try more rotations, he adds.
“There are many different ways to grow cotton and other crops, and I'm often asked which system is the best to use. That's a hard question to answer because I try not to promote one system over another,” says Burmester.
The options for cropping systems, he says, include conventional or inversion-tillage, no-till, strip-till and subsoiling, and ridge-till. “All of these are good systems that can be used successfully. But in many cases, the system you use will depend on your soil type.
“One of the main problems in some systems is soil compaction. You may have a compacted layer near the surface that'll cause restricted root growth early in the season. Or that compaction could be 12 to 18 inches down in the soil, causing a restricted taproot system. In both cases, you'll need some practices to alleviate those problems,” he says.
In Alabama, says Burmester, there are three major soils in the row-cropping areas of the state. The Coastal Plain soils are the same ones that run into Georgia, South Carolina and North Carolina, he says. “These are very sandy and productive soils, but they do have a tendency to have hardpans — 12 inches deep in some cases. They require some in-row tillage to alleviate that problem and give us a better root system,” he says.
These soils are very prone to drought, he says. “Sometimes, we say we're only three days from a drought immediately after receiving a rain. Cotton has done very well in these areas, but growers don't consider corn or soybeans as good rotational crops because of their drought sensitivity. The rotational crop of choice in these soils, especially in the southern part of the state, is peanuts.
“The nematode complex that attacks peanuts is not the same root-knot complex that attacks cotton. Since peanuts are an excellent rotational crop in these soils, many growers are going with two years of cotton and one year of peanuts. It's an excellent rotation, but you'll have to look at the soils in your area and determine which ones are best suited,” he says.
As you move north in Alabama, the Appalachian Plateau or Sand Mountain soils become more prominent, says Burmester. These are sandy soils but not as sandy as the Coastal Plain soils.
“As you go into this area, you see more no-till production. In many cases, you can no-till in these soils and be very productive. Most crops can be grown in rotation with cotton in these soils.
“But most of the fields in this region are small and sloping, and much of that is in pasture,” he says.
In the north and central part of the state are the Limestone Valley soils, he says. These are heavier, silt clay, red soils.
“These are very productive soils, and this area also has gone largely to no-till production.
“The biggest problem there is surface compaction. These soils have a tendency to form a small layer in the top 6 inches of the soil that can cause compaction problems. But we've found that rotational crops such as wheat or corn with fibrous root systems can actually break up this compaction layer and not require any type of tillage. Soybeans, with more of a taproot system like cotton, are not that effective.”
Soils, say Burmester, play a major role in which system a grower chooses to use. A lot of data has been collected in Alabama that shows the benefit of a good rotation to yields, he adds.
One test, conducted in north Alabama's Tennessee Valley, looked at one-year rotations of cotton with various other crops.
“One of the big things you'll hear about in rotations with other crops is building organic matter, and that's something we've seen in a lot of our trials,” he says.
A significant increase in organic matter was seen in six-year rotational plots that were planted no-till. The biggest problem seen in the tests, says Burmester, is that Tennessee Valley soils tend to have a compacted layer at the surface in no-till situations. No-tilling into old stubble wasn't successful in terms of yield, and wheat was needed to help break up the compaction.
“There are some unusual rotations out there,” he says. “In some areas of Alabama — in the southern part of the state — we can put in small grains and graze cattle, pull those off and still plant a crop.”
Residue management must be considered whenever a grower moves to these rotational crops, he says. “Whether you till or no-till will be a big factor in how much residue you'll have to handle.
“Row spacing also can be a problem. If you have cotton in one row spacing and corn in another, and you try to plant, you could be planting back into areas that have been compacted by tractor tires or pickers. You want to stay away from that if possible. In most cases, you'll be better off if you stay with the same row spacing.”
Planting dates also can be delayed when a grower is moving into rotational crops, says Burmester. “You have more residue on top of the ground and you'll have to delay a little before you get in the fields — the soils stay a little wetter.”
Planting equipment and modifications to existing equipment also might have to be considered, he says, depending on your soil types.
Time management became a very important factor for north Alabama growers this past year, says Burmester.
“We planted a lot of different crops this past year. Several of our farmers planted wheat in the fall and came back and planted corn in some fields in February. Then, in April, they planted some early Group 4 soybeans, and followed that by planting the rest of their fields in cotton. When wheat came off, they decided they'd plant all of those fields in double-cropped soybeans. At about mid-June or early July, the wheat was ready, and it was a very good crop. They harvested that and planted double-cropped soybeans.
“In early August, the corn was ready so they got in the fields with their combines. Before they could get out, early soybeans were getting ready, and early Group 4 soybeans won't wait on you. So they had to get the soybean heads on the combines and get everything done at once. In early September, I was telling them they needed to defoliate their cotton, which they weren't ready to do. By mid-September, we had some cotton being harvested. In early October, those double-cropped soybeans also were ready to harvest.”
The bottom line, says Burmester, is that you'd better be ready to manage your systems. “Some of our farmers had their tongues hanging out by the end of harvest. It turned out to be a very productive year for most of our crops, but we had not fully considered time management as much as we should have.”
Rotations, he says, offer many advantages for cotton producers, but growers need to think a lot more about management when they go to these systems.