A farm in the Palouse region, which includes parts of Eastern Washington.
Gary Wegner first noticed the problem in 1991, when a field on his family’s farm west of Spokane produced one-fourth the usual amount of wheat. His father and grandfather attributed the problem to farming on shallow soils, but Wegner decided to dig deeper. Lab tests revealed a surprising result: the soil had become acidic.
Wheat farmers are now seeing this problem across the inland Pacific Northwest. The culprit, as far as anyone can tell, is the abundant use of synthetic nitrogen to increase crop yields, a practice that has otherwise revolutionized production over the past half century. Over time, however, it has contributed to a soil health problem that has farmers worried about the future of farming in the Palouse.
“We’re riding the edge of a crisis,” says Paul Carter, an agronomist and the director of WSU Extension in Columbia County. “We can pretty well nail it down to the addition of nitrogen to our soils for crops. In 1940 or 1950, nitrogen was applied at five pounds per acre. Now, in some areas, we're up to 100 or more pounds per acre.”
Pullman-based USDA soil scientist David Huggins agrees with Carter, describing soil acidification as a “quiet crisis.” Quiet, because it can be masked by other types of problems and because farmers haven’t tended to look for it. Quiet also because most people aren’t aware of the soil health challenges that farmers face today as a result of increasing pressure to produce more food.
But it is nonetheless a crisis. At stake is the sustainability of wheat farming in Washington. As the state’s third largest commodity crop, wheat represents $1 billion of the state’s $10 billion agriculture sector.
A race to the bottom
Soil pH, Huggins says, is a “master variable” that affects almost everything: soil microbes, plant diseases, the ability of plants to access nutrients in the soil, the effectiveness of herbicides and how long they take to break down in soil—all of which can have an effect on crop yield.
“We farmers have used lots of ammonia fertilizer and that use has increased faster than the yields have,” Wegner says. “Some farmers say it's a race to the bottom. The more you put on to raise yields, the more you have a pH [acid] problem.”
If it gets bad enough, soil acidification can render land unsuitable for growing crops altogether. Farmers near Rockford, Wash., south of Spokane, have a hard time growing an economically sustainable crop of wheat because the soil there has become too acidic.
Thirty years ago, Bob Mahler, a soil scientist at the University of Idaho, decided to map the extent of the problem in northern Idaho and eastern Washington over time. He found that since the Green Revolution—which transformed the agricultural industry, resulting in greater wheat yields but requiring more ammonia-based nitrogen fertilizers—soil acidification had dramatically accelerated. Between 1960 and 1985, 65 percent of the soils in that region’s farmland became acidic.
Evidence unearthed by Carter in Columbia County suggests the issue has continued to get worse.
Sylvia Kantor is Seattle-based freelance writer and formerly a science writer at Washington State University in the College of Agricultural, Human, and Natural Resource Sciences. You can follow her journey through the U.S. National Park system at 59x59blog.wordpress.com