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Northern Idaho farmers concerned about acidic soils

Crop soils in north-central Idaho are becoming more acidic, possibly because of the repeated use of ammonium-based fertilizers, scientists say.
Robert Sandlund of the Natural Resource and Conservation Service in Grangeville said some farmers have started to notice a reduction in crop yields.
“We’ve been tracking this soil pH for a while,” Sandlund told the Lewiston Tribune. “No two soils are the same. All kinds of factors affect pH. But we do know one thing, and that is that the application of ammonium-based fertilizer will change the pH of a soil. It will lower it.”
He said farmers in the Craigmont-Winchester-Reubens area in particular have seen changes.
“These guys have to apply fertilizer in order to get the production, and most apply it in a very responsible amount because it’s very expensive,” Sandlund said. “They’re not over-applying, but over years and years and years of applying, it’s affecting the pH.”
Sandlund said a new trend of minimum tillage that limits how much soil is stirred up also could be causing the drop in pH by not allowing the fertilizer to spread out.
“If farmers start seeing their pH getting down in that low five region, we’re kind of waving the flag of, ‘OK, be careful and start monitoring your soil tests, and if you see yields suffering then pH might be an issue,'” Sandlund said.
Farmers do have ways to improve the soil by adding calcium amendments.
“Basically you’re adding calcium carbonate to the soil,” Sandlund said. The process is effective, but it’s expensive, time-consuming and difficult, “usually involving tons per acre.”
“It’s spread on as a fine powder and worked into the soil and it will move the pH back up,” he said.

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