Oregon wheat growers were in their second week harvesting a bumper crop when the Substation fire broke out Tuesday afternoon, burning 70,000 acres in the state's wheat basket in Sherman and Wasco counties.

Agricultural experts estimate the fire has burned 1 million bushels of wheat, more than $5 million in crops, and it is still just 15 percent contained.

The loss represents a small share of the Northwest's annual wheat production, 260 million bushels. But for individual growers it is potentially devastating – with losses totaling $250,000 or more per farm.

"Some of these farmers got wiped out, most of their crop if not all," said Tana Simpson, associate administrator, Oregon Wheat Commission.

Most farmers had insurance, Simpson said, but policies typically cover the average value of a crop – not the premium from this year's hearty harvest, which was bolstered by favorable moisture conditions. And if the fire turns out to have a human cause – authorities say they have opened a criminal investigation into the cause – then some damage may not be covered.

Sherman and Wasco counties are Oregon's second- and third-largest wheat-producing regions, respectively. Nobody knows yet just how much wheat has burned.

That's because only a portion of the fire zone had wheat. Farmers in that region typically leave half their fields fallow each year to accumulate moisture, and the region also includes sagebrush and canyons that are not cultivated.

No one has stepped back to tally up just how much has burned.

"A lot of growers have stopped what they're doing, and everyone's fighting this fire," said Brian Tuck, a professor in crop and soil science with Oregon State University and director of the university's agricultural research extension center serving the mid-Columbia River.

Farmers were about a quarter of the way through this year's harvest, according to Tuck. Fortunately, he said, the weather has been warm and dry – which means crops that haven't burned should be in good condition.

In areas that have burned, Tuck warned that the fire could have damaged the soil and burned up the stubble that ordinarily protects the soil through the winter by guarding against erosion and preserving moisture. Tuck said agricultural experts were meeting in The Dalles on Friday afternoon to begin discussing strategies for recovering.

Meanwhile, farmers who lost crops to fire will begin tallying their losses. Ben Thiel, director of risk management with the U.S. Department of Agriculture in Spokane, said most farmers will have had federal insurance that covers loss due to fire and suggests farmers file a claim within 72 hours.

The federal insurance applies only to losses when "the ignition source of the fire is due to a natural cause or natural disaster." If the fire turns out to be have deliberately set, or caused by human actions, losses may not be covered.

Sometimes, Thiel said, damage from a fire that didn't start naturally will be classified nonetheless as a natural disaster. That's because wind, drought or other factors may have exacerbated it.

-- Mike Rogoway | twitter: @rogoway | 503-294-7699