Saving water may not be the top reason farmers consider switching to reduced tillage systems. Most give top billing to saving money on fuel, labor and equipment maintenance.
But after they calculate those savings into their equations, they turn to improving the soil: making it more porous, increasing organic matter, reducing erosion (from wind and water) and improving moisture-holding capacity.
“We see some distinct advantages with moisture maintenance with conservation tillage,” says Doug Fairbanks, Ag Systems Manager with Monsanto.
“Reduced tillage, which leaves at least 30 percent coverage on the soil, helps reduce runoff, so more water percolates into the soil,” Fairbanks says.
He says residue also blocks sunlight from direct contact with the soil, keeping the temperatures down and reducing evaporation losses.
“Conservation tillage practices also keep moisture in the soil longer,” Fairbanks says. “Farmers don't plow the land and release moisture in the top 1 to 3 inches of the soil profile.”
He says during extremely hot conditions, when temperatures reach the 100-degree range, cultivation can easily cause soil loss of two-tenths to one-half inch for every cultivation trip across the field.
He says cotton plants, in particular, may pick up more moisture from light rainfall events in conservation tillage systems. “Without cultivation, we don't prune the feeder roots that grow into the middles. With even light rains, these roots can be more efficient in picking up available moisture.”
He says residue left on the ground after harvest helps the soil accumulate more moisture during winter. “We reduce runoff significantly, so the soil holds more moisture and stores it for the next crop.
“Also, organic matter begins to increase with reduced tillage systems, and, over time, the soil becomes more porous and helps water penetrate.”
Danny Davis, an Elk City, Okla., dryland cotton farmer who uses conservation tillage on his entire acreage, was Fairbanks' guest recently at a Monsanto Center of Excellence field day on Charlie Pribyla's farm near Seymour, Texas.
Davis says he started no-till in the late 1970s. “We didn't experiment,” he says. “We went strictly no-till on everything the first year. We had limited success, but the field did not wash or blow.”
He's experimented with a number of systems over the years and has adapted machinery to fit his needs.
Controlled traffic pattern, he says, makes a big difference in managing moisture.
“You have to be serious about traffic patterns,” he says. “After establishing the pattern, don't run machinery anywhere but in the hard middles. This is the most important thing to assure success in reduced till systems.”
Davis says farmers will see some advantages with conservation tillage the first year. “They will reduce wind and water erosion,” he says. “And they might reduce production costs.”
But the real advantages take years to develop, as organic matter begins to build up and the soil becomes more porous, mellow and fertile.
“After several years, no-till farmers will not see standing water in their fields,” he says. “The organic matter will increase and improved soil will soak it up. It's not something that happens right away, but begins to show up in the fourth or fifth season.”
He says organic matter increases slowly. “If we can get two-tenths to three-tenths of 1 percent per year, we're doing a good job,” he says. “If we can get the percentage up to 2 percent at an 8-inch depth, we've made a big improvement.”
He says for every year a farmer leaves residue on the field he's banking organic matter. Davis plants continuous cotton on most of his acreage and leaves stalks standing. “The old cotton stalk provides a route for the new plant roots to penetrate to moisture and nutrients,” he says. He emphasizes again that controlled traffic is essential to prevent that soil structure from collapsing.
Davis also plants a winter cover crop in row middles, usually before he harvests cotton. “I get a lot of questions about how much moisture we waste by making a cover crop,” he says. “It's a big issue. But I figure that every time a farmer goes to the field and breaks land or cultivates, he loses moisture from the soil.
“If he makes six or eight trips a year, he wastes a lot of soil moisture. We have to compare that loss to the amount we need to make a cover crop.”
Davis says old crop residue provides a good substitute for farmers who are not comfortable with planting a winter cover. Milo or corn stalks, he says, offer good rotation options and provide a lot of residue for conservation tillage.
Pribyla says planting in old cotton stalks appears to be the best option for his operation, after one year of experimenting with reduced tillage. “I think we have a bit of hardpan where we planted behind wheat and used the stubble for residue,” he says.
Pribyla says rain determines what farmers in the Texas Rolling Plains can do with a crop. “I think, after several years of reduced tillage, organic matter will build up and the soil will hold a half-inch rain longer. With better soil structure even a small rain will do more good.”