Disturbing the soil is a no-no when building soil health, but it’s basically impossible to grow potatoes without moving dirt.
Growers may need to take a step backward when they grow a high-disturbance crop, but they can take two steps forward in the other years of their rotation, says Marlon Winger, a soil health specialist for USDA’s Natural Resources Conservation Service (NRCS) in the Mountain West.
Reduced tillage methods and cover crops are primary tools for improving the soil, but Winger has been frustrated by the shortage of appropriate implements in the West.
“We don’t have very many (no-till) drills,” Winger said during a July 11 webinar.
What they lack in equipment, growers have made up for with ingenuity. A North Dakota grower has figured out a garden-scale way to produce no-till potatoes. The seed pieces are placed on the ground and covered by a rolled-out round bale of grass hay and alfalfa.
“When they harvest these potatoes, they just pull the straw back away from the vine and pull up your potato with very little soil disturbance,” Winger said.
A grower of another high-disturbance crop, sugarbeets, no-tilled a test field of the crop and cut the water supply to the field by 20 percent. The sugar company said it would cover the farm if the yield cratered, but the decline turned out to be minimal, Winger said. An armor of plant material, living or dead, improves soil health by trapping moisture and reducing erosion.
“I love the word ‘armor’ because it’s aggressive. It feels like you’re protecting it,” Winger said.
In the West, the short growing season leaves little time after harvest to plant a cover crop, and the need for irrigation makes it difficult to plant soil-protecting bushes or trees. Growers can still break up the unsheltered stretches in their fields with strips of tall grasses, Winger said.
Wheat harvesters are making increasing use of stripper headers. These combine heads pluck the grain heads and leave the straw standing. In addition to protecting the soil from wind erosion, the straw traps some of the snow, Winger said.
One farmer in Saskatchewan plants two crops, such as mustard and lentils, in separate rows but harvests them together. The crops are separated at the bin.
Living roots anchor a community of soil microbes that build the soil structure. As proof, Winger recalled the time he tried unsuccessfully to knock soil off the roots of a plant. He realized he was looking at the rhizosphere, in which the plant, microbes and soil essentially become one.
By contrast, dead soil can reduce a crop’s nutrient uptake. Winger once met a grower trying desperately to get phosphorus into his potatoes even though there was plenty of it in the soil.
Livestock can add another layer of diversity to cropland, but confinement-oriented farmers in the West have not always thought to graze their fields. Winger was initially concerned about grazing sudangrass, which releases poisonous prussic acid when it freezes. But farmers told him that they did not have problems as long as they used sudangrass in mixes.
“The animals can kind of self-regulate,” Winger said.
Like many farmers, Winger admits he was slow to accept the new ideas of soil health.
“As a county extension agent, I used to teach thousands of people a year the best way to improve your garden soil is to till in your organic matter,” he said.
For farmers, adopting new practices can be socially risky. Minimal-till fields look messy compared with tilled fields, but that is by design, Winger said. But the message is getting through. Almost all the sugarbeet growers in the Owyhee district of western Idaho are now using some combination of strip till, no-till and cover crops.
Like other Pennsylvania farmers, potato growers have jumped on the cover crop bandwagon, said Bob Leiby, a crop consultant for the Pennsylvania Co-Operative Potato Growers.
Growers are selecting cover crops that provide a variety of soil services, including nitrogen-building legumes and the hardpan-busting daikon radish, Leiby said in a phone interview.
Some mustards appear to be biofumigants, meaning they have pesticidal effects when they break down. Growers are trying mustards in the West too, Winger said. They plant the crop after wheat and then disk or plow the mustards into the ground. Winger wants growers to add some carbon-rich cover crops to this mix so the fields have some protective residue in the spring.
Pennsylvania researchers tried to grow no-till potatoes a few decades ago, but the yield was terrible. Nevertheless, some growers continue to experiment with ways to minimize soil disturbance and build the soil, Leiby said.
One grower recently told Leiby he was going to till under his wheat straw because he needed the organic matter and the price of straw was down.
“I thought, ‘Okay, that’s a good attitude to have,’ ” Leiby said.
Source: Lancaster Farming