Conservation tillage may seem like a relatively new concept to Southwest agriculture, but soil scientists have been testing systems to hold soil in place for much of the 20th century.
Folks developed a keen interest in farming methods that would reduce water erosion and, even more important to the Southern Great Plains, wind erosion, following the catastrophic Dust Bowl.
“The Dust Bowl claimed more than 100 million acres of land in the Great Southern Plains from 1931-1939,” says Paul Unger, a retired USDA-ARS soil scientist who worked at the Bushland, Texas, Research Center.
Unger discussed the history of conservation tillage recently at the Southern Conservation Tillage Conference in Oklahoma City.
Unger said the Southern Great Plains became a significant crop region in the late 1800s, during a period of exceptional rainfall. And from 1918 through 1929 good prices and demand for wheat resulted in a lot of native grasses being plowed under. That set the stage for disaster.
“Drought in the 1930s caused severe wind erosion,” Unger said. “Many families abandoned their farms.”
If there was a silver lining to the dark clouds of the Dust Bowl, it came from interest in conservation tillage practices that would reduce soil losses. Unger said the Hoeme cultivator, similar to the modern chisel plow, and the Noble blade plow, a forerunner of the stubble mulch plow, were developed in the 1930s to help control erosion.
Stubble-mulch tillage began in Nebraska around 1938. “They used blades or sweeps to undercut the surface of the soil to control weeds,” Unger said. “We use similar implements today with much wider sweeps.”
Unger said researchers at Bushland began testing conservation tillage methods using herbicides in the late 1940s and into the 1950s. “Results were not very good because of poor weed control,” he said. Kansas research with improved herbicides in the late 1950s showed more promise.”
Unger said atrazine and 2,4-D brought about renewed interest in reduced tillage system research at Bushland in the late 1960s.
“Researchers were looking at several tillage systems,” he said. “They also focused on amounts of residue left after harvest and showed increased yield with grain sorghum because of increased moisture holding capacity.”
Crop rotation and residue management were keys to increasing yields, he said.
“In the Rolling Plains researchers showed a significant yield increase with cotton on reduced tillage systems.”
He said Oklahoma cotton farmers began testing “lo-till” systems, in which a narrow seedbed was prepared in crop residue. The residue helped lower soil temperatures and hold moisture and the narrow bed improved seed-to-soil contact.
Unger said some studies also showed less greenbug infestation with reduced tillage.
“And over the long term, reduced tillage and residue management increased the amount of organic matter in the soil,” he said.
He also noted that farmers and scientists recognized that they must look at specific soil types to determine the best tillage method for a particular field.
“Today, farmers face more intense cropping systems,” Unger said, “and studies are ongoing to determine the best conservation tillage methods. We still need to increase residue for better moisture management.
“We hope to see more residue carryover in dryland production from one crop to another.” Researchers are currently looking at a stripper header for wheat. The machine strips the grain from the head and leaves the stalks standing,” Unger said.
“Stalks decompose slower and put more organic matter into the soil. We see a drastic change in wind erosion with standing stalks. It's also a cleaner operation with much less dust.”
Unger said acceptance of reduced tillage systems varies considerably across the Southern Great Plains. “No-till is limited,” he said. “But stubble-till is widely used, especially with winter wheat and grain sorghum.
“Conservation tillage in irrigated acreage will improve erosion control and water conservation.
“Moisture management is less critical in irrigated acreage now, but that may change. As aquifers deplete, we're likely to see more need to conserve water and more dryland production.”
He says cotton provides a unique challenge for reduced tillage systems, especially in a monoculture. Cotton stalk residue is not particularly heavy and provides less protection than grain sorghum or other grain crops.
“But cotton may be the best option, economically, for Southern Plains farmers.” he said. In some cases, winter cover crops help preserve soil. But farmers have to watch closely that the cover crop does not limit soil moisture for cotton.