Increasing acid soil levels are starting to have a serious impact on yields and profitability among no-tillers in the Pacific Northwest. Continuing to apply more nitrogen (N) seems to be the problem.

Both growers and agronomists in the area feel that it’s getting close to what might be called a serious crisis.

“We can pretty well nail it down to the addition of N,” says Paul Carter, a Washington State University agronomist and educator in Columbia County. “Back in 1940 or 1950, our wheat growers were applying N at a rate of 5 pounds per acre. In some areas, we’re now up to 100 or more pounds per acre.”

Masks Other Concerns

USDA soil scientist David Huggins says soil acidity issues are often masked by other problems. The Pullman, Wash., researcher says soil pH affects soil microbes, plant disease, the ability of plants to access nutrients from the soil, the effectiveness of herbicides and the time it takes pesticides to breakdown in the soil.

Bob Mahler, a University of Idaho soil scientist, says soil acidification has increased dramatically in both northern Idaho and eastern Washington over the past half century. Between 1960 and 1985, he says 65% of the soils in the region turned acidic.

Carter collected data from 76 fields across several rainfall zones in his county and found acid soil conditions were widespread. Some 97% of these fields tested acidic with a soil pH below 6. In 89% of the fields, the soil pH in the top 6…