Treating Soil as Living Organism Boosts Yields

Published online: Jan 23, 2017 Fertilizer, Potato Harvesting Anthony Brino
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When Eric Giberson was growing up on a potato farm in central Aroostook County, Maine, in the 1970s, “you grew potatoes in the ground,” he said.

“I didn’t grow up thinking that soil was a living organism—it is,” said Giberson, a conservationist with the USDA’s Natural Resource Conservation Service (NRCS) in Fort Kent, Maine, at the 32nd annual Maine Potato Conference.

The conference, held in Caribou, Maine, Jan. 18-19, kicked off with a series of presentations on soil health, something potato growers are paying more attention to in an effort to improve yields, reduce disease problems and prevent erosion.

“Soil health is the key for sustained economic yields. These are not new concepts. We’ve been talking about them for hundreds of years,” said Giberson. “The challenge is building soil quality in a potato system that’s relying on intensive tillage, and it’s very intensive tillage.”

Large-scale potato farming places a lot of stress on soil, with plowing and tilling to prepare rows for planting, tractors regularly making pesticide applications during the growing season, and heavy equipment and trucks driving through when the tubers are harvested.

Preparing soil for potatoes can lead to as much as a 2 percent reduction in organic matter, a crucial part of the soil ecosystem holding moisture, nutrients and microorganisms, said John Jemison, soil and water quality specialist with University of Maine Cooperative Extension.

“Soil health is really more than just organic matter, but organic matter is the best measure of trying to improve soil,” said Jemison.

For evidence of this, Jemison pointed to an unplanned experiment that happened last summer at the extension research farms in Orono, Maine, amid a drought that brought only about two-thirds of the region’s average rainfall.

The research team was growing Snowden potatoes, a chip variety, in two fields with almost identical characteristics, the only difference being that one had about 0.5 percent more organic matter. The field with higher organic matter had double the yields—likely due to the organic matter’s water retention, a trait that helped store moisture for the plants.

“Twice the yield, but with another half a percent organic matter in our soil, and I really can’t attribute [the yield] to anything else but that,” said Jemison.

Building organic matter should be a long-term effort, accomplished through natural amendments like compost, reduced tillage, growing cover crops after harvest and extended crop rotations, Jemison said. “Steadily and slowly, that’s the way to go.”

Many Maine potato growers rotate their fields on two-year cycles between potatoes and grains, although some use three-year rotations and the Maine Potato Board has been sponsoring research into crops that could be used to add another year to growers’ rotations and offer farmers something they could sell.

Jemison also suggested that potato growers could benefit from fields being rotated into pastures for cattle or other grazing livestock, which would add both additional organic matter from grasses as well as natural manure.

“I understand we don’t have enough animal agriculture up here,” he said. “We need more and that would certainly benefit us.”


Source: Bangor Daily News