Now that conservation-tillage has become conventional among Southeastern farmers, what's next?
“Sod-based farming is, I think, the next step after conservation-tillage,” says David Wright, University of Florida Extension agronomist. “We have done a lot of good with conservation-tillage, but I think we have another step we can go to ‘turbo charge’ the system using perennial grasses.”
Conservation-tillage systems have been proven to be an improvement over conventional-tillage, says Wright. But even with conservation-tillage, there's still some soil degradation, erosion and a loss of organic matter.
“There are rotations across the country and all over the world that show essentially the same thing — over a period of time, whenever you have a loss of organic matter, you have a loss of nitrogen,” he says. “If you look at all of these locations in general, you'll see they were plowed up from native prarie grasses, especially when you get into the Midwest.”
One reason there were high organic matter levels to begin with was that the ground was in long-term perennial grasses, says Wright. They may have been native grasses, but they still were grasses, he adds.
“We have seen the adoption of many successful conservation-tillage programs,” he says. “Wheat and soybeans were very popular in the Southeast, and we have many other successful cover crop programs with cotton and corn. Recently, we've had more growers going with cover crops in peanuts. In addition, Roundup Ready crops greatly expanded the use of conservation-tillage across the country.”
There also have been many improvements in the equipment used with conservation-tillage, says Wright. “We have a long-term study at Florida, going into our 30th year, where we either have no-tilled the winter cover crop and strip-tilled the summer crop, using every crop you can imagine, and it is successful,” he says.
But, like a good marriage, conservation-tillage takes commitment, he says. “There is a lot of data comparing cover crops versus no cover crops. Soil moisture is better with a cover crop. And plants are likely to suffer less from stress due to high temperatures wherever there's a cover crop.
“There also has been a lot of data from the Southeast over the past two or three years looking at strip-tillage versus conventional-tillage.
“The peanut industry and peanut planting is now driven by tomato spotted wilt virus. In almost every case, we have half as much tomato spotted wilt virus in a strip-till farming system compared to a conventional system. In many years, we also have higher yields under strip-till conditions.
“Some peanut growers say they still can't make as high yields under strip-tillage, but there are reasons for that. The bottom line is that strip-tillage is cheaper, and that's why a lot of growers are converting to it.”
In some counties in the Southeast, there may be one farmer who started using strip-tillage and the entire county is now being strip-tilled, says Wright. But other areas are washed away because strip-tillage was never started, he says.
“One of the big reasons we see a lot of variability in the yields of conservation-tillage systems is the date when we kill the cover crop — that is critical,” says the agronomist. “There were several fields of corn and early planted cotton this year where moisture was depleted and insects moved in, causing replant situations. If you plant into a green cover crop, you had better be using soil insecticide. If the cover crop had been killed earlier, this wouldn't be a problem. I used to say that you should kill a cover crop three or four weeks ahead of planting. I think you may need to kill it a little earlier.”
Sod-based farming basically is the practice of using perennial grasses in a farming system, says Wright.
“You will find that using perennial grasses in rotations will make more difference than converting from conventional to conservation-tillage. That's in relation to soil health, yields, water quality, risk management and the economics of your farm. We're comparing conservation-tillage with annual cover crops to conservation-tillage with perennial grasses.”
There's currently a multi-state project, including Alabama, Georgia and Florida, where researchers are looking at the sod-based system, he says. “We have small plots, and in Florida we've dedicated a center pivot to this farming system. As far as growers are concerned, the profits drive this system.”
Cattle in such a system add diversity and help to reduce risks, he says. “Cattle don't mind being out in a hurricane. A cotton or peanut crop is not going to do very well in a hurricane during harvest. A lot of our best weather conditions occur from November until April. We have moderate temperatures, and we normally have good rainfall as we go into the spring planting season for cotton, peanuts and corn.”
The sod-based system, explains Wright, consists of two years of bahiagrass followed by a year of peanuts and a year of cotton.
“There's a lot of flexibility in this system in that if we don't need the grazing, we can take some of the winter cover crops to grain, or we can use it for hay or to feed cattle.
We have collected a lot of data from these small plots, and it has shown that you do have earthworms after perennial grasses.
“In everything we've looked at, the bahiagrass system far exceeds the annual cover crop system of cotton and peanuts with winter annuals and strip-tillage. We've witnessed better water infiltration, fewer soil nitrates, decreased leaching, less compaction and less soil bulk density. And there is less disease pressure with peanuts. With cotton, the root growth is 20 to 40 percent better behind these perennial grasses than in an annual cover crop.”
For years, plant pathologists said that land had to be turned for peanuts, says Wright. “We started working with strip-till peanuts in the late 1970s. But tomato spotted wilt virus is almost half in strip-till compared to where we turned the land. Many growers are planting twin-row peanuts now, and they want to know if they can have just one rip and plant peanuts. It does work. You can plant twin-row peanuts in an annual crop — such as rye, oats or wheat — or in a perennial grass crop.”
Penetrometer readings were made on spring-tilled versus fall-tilled bahaigrass, he says, and they showed much more decomposition from the fall tilled. “The root system of the crop has a major impact on that. We think the system will work whether you're using fescue, orchard grass, bahiagrass, bermudagrass or some of the native range grasses.
“With the sod-based system, we're adding more value over our conservation-tillage systems. When we plant cotton after peanuts after bahiagrass, we find eight times the earthworm numbers than in a traditional cotton/peanut rotation. Earthworms and bahiagrass leave a lot of channels, and that's where cotton roots go.”
Improved organic matter and increased soil productivity follow bahiagrass, says Wright.
“As far as economics, when we look at a conventional rotation with average yields on a 200-acre farm, there isn't very much money being made. But once you get fully into a sod-based rotation, adding cattle and increasing yields, there's a significant increase in profits. The income of that 200-acre farm can increase two to seven times over the conventional system.”
A conservation-tillage and bahiagrass system does work, says Wright. “We have seen reduced nematodes and diseases, increased yields, improved peanut grades, improved soil quality, and profits that are two to seven times greater. The key is that growers need to make the same commitment with this system as they did with conservation-tillage. This is the next step after conservationtillage.”