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Loose Soil Keeps Potatoes Healthy

For potato growers whose plants are under stress, the message seems to be “loosen up.” Soilwise, that is.

Stressed potato plants are more susceptible to disease, which in turn reduces yield and can make the tubers more likely to rot during storage. To help farmers address this issue, a University of Wisconsin-Madison research team has determined that managing soil compaction can help keep potato crops healthy and stable during storage. That means a better bottom line both for farmers and processors.

Potatoes are big business for Wisconsin, pumping $200 million into farmers” pockets. And that”s just part of the vegetable”s economic impact as the state”s numerous processing plants turn spuds into chips, fries or other processed potatoes. But with storage losses of up to twenty percent in a bad year, crop scientists are trying to find ways to improve overall health so that the harvest can hold up until it”s needed by processors.

“By looking at subsoil tillage, we”re in effect treating the symptom of the problem,” says A.J. Bussan, a professor of horticulture in the UW-Madison College of Agricultural and Life Sciences. “Potatoes are stressed by warm conditions and sudden rainy periods can saturate the soil which deprives the roots of oxygen. Potato tubers in this condition are susceptible to a disease called pink eye, which breaks down the protective waxy coating around cell walls. We wanted to see if deep tillage that breaks up and loosens the soil would help water drain away from the roots more quickly and alleviate pink eye.”

Bussan and his graduate student Mike Copas, a Wisconsin native who grew up on a vegetable farm near Plainfield, partnered with processing companies to study compacted soils in several fields across the state. Compacted soil is caused by heavy machinery traffic, and while it doesn”t affect the quality of the crop itself it does keep water from draining away – which means in very wet conditions the plant roots can be deprived of oxygen, contributing to pink eye.

“We found that deep tillage does tend to alleviate pink eye,” Bussan says. “In subsoil-tilled fields we found less rotting during storage than in conventionally tilled fields. Since eighty percent of Wisconsin”s potato crop is stored after harvest – so that potatoes can be provided to processors on a year-round basis – this is an important result.”

Bussan notes that subsoil tillage equipment is expensive, and with the added fuel costs farmers might also want to consider finding ways to reduce compaction by managing their wheel traffic or using different crop rotations.

He and Copas have been publishing their results in the Wisconsin Potato and Vegetable Growers Association newsletter and meeting with state farmers at annual conferences. They also have requests to present their work elsewhere in the nation and in Canada.