Providing a cotton production system that minimizes input costs while maximizing yields in an environmentally sensitive manner might sound like pure fantasy, but that's the goal of University of Florida researchers.
“We're putting together a regional team to begin testing a farming system that should be viable, even under today's tough conditions,” says James Marios, University of Florida plant pathologist.
“We've come up with a sod-based rotation system, where you're planting bahiagrass or bermudagrass for at least two years, and then you're using that grass as an alternative crop for hay or forage. We're finding that in some areas of the Southeast, we can sell a lot of 50-pound square bales of bahiagrass for $2.50, which is a very decent return if you have good grass yields,” says Marios.
Grass roots, he explains, can greatly improve soil conditions in row-crop situations. “We hear a lot about compaction problems in the Southeast. Remember that two-thirds of a grass biomass system is below the ground. The roots penetrate the soil and can very quickly take apart the hardpan. In two or three years, you may completely remove a hardpan,” he says.
Hardpans a problem
Most soils in the Southeast, says Marios, have a hardpan that is about six to 10 inches deep. This hardpan, he adds, has a significant impact on water, fertilizer and crop roots.
“After fields are planted in bahiagrass or bermudagrass, crop roots will follow the channels left behind by the grasses, allowing deeper penetration. Research conducted in the 1970s showed that you can get a 500-percent increase in cotton roots that go down five feet, and that offers tremendous potential for filling your water profile when rainfall does occur. The sod-based rotation will have a significant impact on soil compaction,” he says.
A sod-based rotation system also will improve fertilizer use, notes Marios. “Numerous studies have shown more efficient uptake of all of the important nutrients whenever you have a larger root system. You'll have a healthier plant, and it'll be able to withstand all of the year's stresses in better condition.”
In addition, water use will be more efficient, he says, as the larger roots fill the soil profile. “And this will reduce plant stress, not only from other pests but also from the plant itself, because of the increased root system.”
Studies from the 1970s in the Southeast showed that rooting depth affects plant water stress, says Marios. “If you're in a non-irrigated system, you can go only about four or five days if you're rooting depth is only 15 centimeters, and that's where our hardpan is located in the Southeast. If you have an evaporation rate of about .2 inch to one-fourth inch per day, you'll very quickly run out of water.
“Even if you have irrigation, you'll have to water a field every three to five days if your hardpan is at six inches or 15 to 20 centimeters. On the other hand, if you could get your root system to go down to 150 centimeters, you could go up to 30 days before watering.”
The impact of pests on cotton or other row crops can be affected significantly by a bahiagrass rotation, says Marios.
“The nematodes will be reduced directly by bahiagrass. And, in some studies, bermudagrass also can be effective. Insects will be shifted dramatically because you don't have a continuous cotton situation. Instead, you have a good rotation. Weeds will be forced to compete not only in a row-crop system but also in a pasture system, and there aren't many weed spectrums that can do very well in both systems.”
Dramatic shifts also will be seen in pathogens, he adds, as grass crops affect diseases such as rhizoctonia and pythium.
Florida researchers have developed a management model to help explain how a sod-based cropping system can be a viable alternative, says Marios.
“The first thought of many farmers to such a system is that they can't afford to put half of their land in grass, and that's a reasonable response. In looking at cotton, we estimated that it would cost about $400 to produce a cotton crop. We also looked at the cost of establishing bahiagrass.
“If you're producing 650 pounds of cotton and selling it at 68 cents per pound, you're basically farming for your inputs. On a 50-acre plot, you're making about $1,700 or $26 per acre. We feel like we can increase that yield by about 50 percent. Then, you'll go to 975 pounds per acre, bringing a return of about $10,000 on 50 acres or $200 per acre.
“If you go into a four-year rotation, rather than growing 200 acres of cotton and making about $7,000 per year, you can go to only 100 acres of cotton at 965 pounds per acre and earn more than $30,000 on your 300-acre farm. If you just leave the bahiagrass, you still can have a return of more than $20,000 per acre. Even though you're producing less cotton acreage, you'll have a much better economic return because you're increasing yield.”
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