WASHINGTON—Farmers fretting over a trade conflict sparked by President Trump’s tariffs may soon get more details on the $12 billion of aid that the administration has pledged, as their concerns mount over potentially plunging incomes and market losses.

“We certainly are appreciative of it but…we don’t know how it’s going to be determined,” Ryan Pederson, a North Dakota farmer who grows soybeans and canola, said of the proposed farm aid. “You can’t do any planning off of that because you don’t know what it’s going to be.”

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