Fertilizer prices have declined substantially in the past 12 months, and are likely to stay low this fall. It’s the same for diesel prices, which have softened recently after pushing higher earlier in 2016.

Those breaks are a welcome sign for farmers looking at lower corn and soybean prices, according to Dave Miller, Iowa Farm Bureau Federation director of research and commodity services.

"Potash is down nearly 50 percent from its 2011 high, and is at the lowest prices seen in at least six years," Miller said. "DAP is down 18 percent from a year ago and MAP is down 17 percent, with both down more than 50 percent from the high prices of 2011-12."

Miller said nitrogen...