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High Yield Team: In the zone
Above: Bill Darrington, Persia, Iowa, shows the root channels that result from his deep zone tillage system. He normally deep-tills new ground twice with this tool.
Soybean farmers in arid regions often salivate at the mention of Iowa. All you have to do is throw seeds on top of that rich, black ground and let timely rains do the rest, isn't it?
Tell that to Bill Darrington. Sure, he farms in Iowa. But the land near his hometown of Persia has more in common with drier Nebraska than Iowa.
"We deal with the Rocky Mountain high that comes across Nebraska and Kansas," says Darrington. "It makes it a fourth of the way into southwest Iowa to about Highway 71, and the eastern part of the state gets the moisture."
Yet, Darrington has found a way to make the best of what moisture he has through deep zone tillage.
"We needed a way to increase water infiltration in the sidehills of where we farm in western Iowa," says Darrington. "We chose a straight-leg deep- tillage tool to do that. It runs deep and lifts the soil gently, and sets it down without exploding and destroying the soil structure. It leaves a nice layer of residue while leaving the soil profile intact to help reduce the risk for severity of erosion."
Darrington uses the deep zone tillage along with addressing soil balance issues during the first two years of new land he farms. He first digs holes in a field to determine hardpan depth. Depending upon the hardpan level, he then deep-tills 14 to 21 inches.
"You don't have to make the slots each year," he says. In the second year, he tills down the center of the previous year's 30-inch rows. Slots 15 inches apart are the end result.
"Be prepared for a hard pull," he warns. "Running the tool above the hardpan pulls easier, but it gives no results." Tractor power requirements will be 50 to 100 horsepower per shank.
"After that, we scout annually for problem areas, such as field areas where trucks or grain carts go," he says. Darrington plants corn in a strip-till system and seeds soybeans into cornstalks.
Right: Water infiltration is also aided by earthworms that thrive under Darrington's deep zone tillage system. The earthworm channels transfer oxygen, water, and nutrients to the roots.
The slots enhance water infiltration by providing a smooth path for soybean roots to penetrate the soil profile. They also attract earthworms that feed upon the surface residue and are attracted by the increase in oxygen that accompanies the deep zone tillage system. These free employees carve channels that ferry water through the soil.
"The earthworm tunnels are an IV for the plant," says Ray Rawson, a Farwell, Michigan, farmer and High Yield Team expert panelist who's promoted the deep zone tillage program for several years. The slots also enable oxygen to work into the soil, says Rawson. "Where there is oxygen, you see more nodulation on soybeans," he adds. This ultimately leads to higher yields, he says.
Typically, oxygen resides in the top 4 to 8 inches of the soil surface, Darrington says. By relieving compacted soils, deep zone tillage creates the potential for more nodules that can go down 30 to 42 inches on the roots.
Darrington says the program has enabled him to cope with dry weather.
"It gives us a huge root system, and that's a way to deter stress," he says. "We are able to survive a little longer with this system in a drought."