A prolonged slump in crop prices, combined with a more recent downturn in livestock revenues, are projected to drive U.S. net farm income in 2016 down for the third straight year, according to a new projection by the U.S. Department of Agriculture (USDA).

And the long-term farm income outlook beyond 2016 does not look promising, according to Iowa agriculture economic experts. Barring a major weather catastrophe or livestock disease outbreak that would force production cutbacks, there are no clear signs of a commodity price rebound that could fuel higher farm incomes, they said.

"It looks like it’s going to be a prolonged struggle," said Chad Hart, an economist for Iowa State University (ISU) Extension Service. "Global grain supplies are high, there is weakness in the global...