Potato Conference puts soil in new light
County farmers urged to build up organic matter for better yield
CARIBOU, Maine — When Eric Giberson was growing up on a potato farm in central Aroostook County 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 in Fort Kent, at the 32nd annual Maine Potato Conference.
The conference, held at the Caribou Inn and Convention Center Jan. 18-19, kicked off with a series of presentations on soil health, something potato farmers 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 a new concepts. We’ve been talking about them for hundreds of years,” Giberson said. “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 creates a lot of stress for 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 dug up for the harvest.
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 the 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,” Jemison said.
For evidence of this he pointed to an unplanned experiment that happened last summer at one of the Cooperative Extension’s research farms in Orono, 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 exact 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 storing 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,” Jemison said.
Building organic matter should be a long-term effort, through natural amendments like compost, reduced tillage, cover crops after the harvest and extended crop rotations, Jemison said. “Steadily and slowly, that’s the way to go.”
Many Maine potato farmers 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 in the rotation and offer farmers something they could sell.
Jemison also suggested that potato farmers could benefit from fields being rotated into pastures, for cows 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.”