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Sod-based rotation provides multiple benefits

Jim Marois University of Florida
<p> Jim Marois, University of Florida</p>
Research has shown that a comprehensive rotation program, coupled with reduced or no-till systems, provides far-reaching benefits. Perennial grasses push roots deep into the soil and build organic matter. Cattle play an important role in the sod-based system.

Farmers have known for ages that crop rotation provides benefits beyond a yield bump. Advantages include improved pest control, opportunity to switch herbicides and other crop protection materials and the potential to tap different commodity markets to spread financial risks.

Now, research has shown that a comprehensive rotation program, coupled with reduced or no-till systems, provides far-reaching benefits that go beyond the farm gate.

Jim Marois, University of Florida, says a sod-based rotation and no-till production system that includes perennial grasses offers significant benefits to farmers and the environment.

“It pays to get grass and animals back to where farmers grow crops,” Marois said during the No-till Oklahoma Conference held recently in Norman.

He said environmental conditions in the Southeast may be significantly different from those in Oklahoma and other Southwest areas. Some of the plants may not be as adaptable to the region and rainfall differences can be considerable. But the principles will apply.

“We see a lot of interest in water in the Southeast,” Marois said. Developing production systems that utilize water efficiently is becoming a priority. Building soil organic matter is a key, he said.

“Two-thirds of the biomass of perennial grasses is below ground,” he said. “One-third of annual grass biomass is below ground.”

He said perennial grasses push roots deep into the soil and build organic matter. “Going from 1 percent organic matter to 2 percent can mean a lot to a farmer,” said Marois. “After 10,000 years of agriculture extracting from the soil, we are now able to enrich it.”

He said integrating perennial grass into a rotation system can increase crop root growth by 50 percent. He said a sod-based rotation increases water penetration, plant water use potential and nutrient cycling.

Economic diversity

“It also increases economic diversity by adding cattle, hay and grazing options.  The system also reduces the amount of time producers spend on certain (seasonal) activities.”

He explained that rotations that include perennial grasses spread risks by dividing center pivots into quarter circles. “With just 50 acres of cotton, for instance, producers face less stress to plant in a limited time. They also have greater flexibility and can respond to commodity market changes.”

He’s worked with a no-till, sod-based system that included: cotton, bahiagrass, bahiagrass and peanuts. A conventional-till rotation system included: peanuts, cotton, cotton and peanuts. “We used a winter oat cover crop in both systems.

“One acre of bahiagrass,” he said, “produces 20,000 pounds of root mass in the soil, mostly in the second year. Oats produce from 3,000 to 4,000 pounds of organic matter. Sod-based rotation also sequesters an amount of carbon equal to 100,000 gallons of gasoline burned.”

He said the organic matter and soil moisture relationship is linear. “The more organic matter the more water in the soil.”

Leaching can be a problem in sandy Southeastern soil and is a particular concern near Florida’s many springs, Marois said. Sod-based rotations near those springs help protect the pristine waters.

He said no-till production “preserves what we have. Sod-based rotation restores what’s been lost—organic matter—by rotating perennial grasses through cropland.”

Cattle play an important role in the sod-based system. “We’re looking at the effect of cattle on compaction and nutrient extraction,” Marois said.  Researchers are weighing such factors as: nitrogen uptake, earthworm populations, soil compaction, crop yield and quality, organic matter content, economics, the impact of cattle on the soil, soil respiration and other issues.

“We’re also looking at the possibility of reducing nitrogen demand significantly with this system.”

He said cotton typically requires 50 pounds of nitrogen to make one bale of cotton. “We’re looking at growing three to four bales of cotton with just 60 pounds of nitrogen.”

A bahia, bahia, peanut and cotton rotation could be a key. “Bahia roots punch through the compaction layer and earthworms then push through. Cotton roots follow and go deeper (than usual).”

He said water infiltration increases significantly with a bahiagrass rotation. “Hard rains soak in quickly,” he said.

Deeper roots make a significant difference in avoiding water stress. Marois said roots that penetrate to six inches will need water every three days. Roots that probe to 60 inches can go without water for 30 days without moisture stress.”

Cattle advantages

He said cattle actually help nutrient management and may add as much as $120 per acre with nutrient cycling in the top six inches of soil. Cattle manure and urine contribute to nutrient levels.

Compaction is not a big deal. “Cattle compact soil a lot less than farmers feared,” Marois said. “Peanuts following grazed land were not difficult to dig.”

Typically, farmers place cattle on the land in June and keep them on until first frost, Marois said. In some cases, with overgrowth for instance, cattle may stay on longer or be put on for additional short periods to manage vegetative growth.

Farmers may seed fields while cattle are on and “let the cattle punch the seed into the soil.”

Aflatoxin is also less of a problem in peanuts with sod-based rotations. “With high temperatures, dry soils and plant stress we found no aflatoxin in either irrigated or non-irrigated peanuts. Soil moisture retention is better.”

He said they don’t see nematodes in bahiagrass.

Oklahoma State University Extension agronomist Chad Godsey said organic matter averages about 1 percent in much of Oklahoma’s cropland. “A 1 percent increase in organic matter means a lot of bushels of wheat or other crop,” he said.

Marois said farmers using strip-till in this system may rip the soil down to 10 inches to 12 inches so “the root system will go deeper, especially in heavier soils and with peanuts—not so much for cotton. We want to disturb the soil as little as possible.”

Marois said perennial grass options for the Southwest likely will differ from those suited to Florida, but he said the principles still hold.

“Start the program on the worst part of the farm,” he recommended. “If it works there it will be beneficial across the farm.”

Sod-based rotation research has widespread support throughout the Southeast, he said. Cooperators include Auburn University, National Soil Dynamics Laboratory, National Peanut Laboratory,  University of Georgia, Virginia Tech, Nature Conservancy, Natural Resources Conservation Service, Cotton Incorporated, Florida Water Management Districts, USDA, Florida Department of Environmental Protection and others. He said Coca Cola has also worked with the project on sustainability issues.

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