"Iowans are in the future business," Clinton told about 200 people in a hall at the Des Moines Area Community College. "Just look at the way you have seized opportunities from wind energy to biofuels."
About 36 percent of Iowans live in rural areas, according to census data, and agriculture is a major driver of the state's economy.
Clinton pledges to invest in rural business and infrastructure by expanding tax credits and grants. Money to help farmers starting out and to promote farmers markets and local foods would double under her plan. Clinton's campaign did not say how much her proposals would cost or how she would pay for them.
Iowa is the nation's leading producer of ethanol, a fuel additive made mostly from corn. Future federal support for renewable fuels is a leading concern for proponents. The Environmental Protection Agency has proposed reducing the required volume of renewable fuels in US gasoline. Clinton said she will seek to strengthen the renewable fuel standard, but she did not provide specifics.
Clinton said the country must "expand the overall contribution that renewable fuels make to our national fuel supply."
On family farming, Clinton said that too often, "the deck is still stacked against small farms." She said she would ensure that crop insurance and disaster assistance go to farmers who need it the most.
While she remains the front-runner in the Democratic primary contest, Clinton has struggled with questions over her use of a private email account and server as secretary of state. Seeking to focus the debate on her policies, she interrupted her New York vacation for the campaign trip, which will also take her to the Democratic National Committee meeting in Minneapolis this week.
Later in the day, at a winery in Baldwin, Iowa, Clinton spoke about the promise of renewable fuels to power air travel.
"I think it holds the promise for not only more fuel for automobiles, but for aviation," Clinton told about 200 people gathered outside a rustic barn. "Think about it. If we do this right, and I've talked to people at the Pentagon, if we do this right, for commercial airlines and for military aircraft, we could be fueling so much air traffic with biofuels. We have just begun to explore what we can do."
Clinton also spoke about the importance of expanding rural broadband Internet, saying that "we have to do for Internet access what we did years ago for electricity."
"She's right on," said Virginia Anderson-Larson, 63, of Canton, who said she appreciated the rural message. "As I listened to her, I felt like she knew us,"
Gary and Kathy Wosoba, who farm in nearby Monmouth, said Clinton was right on the issues.
"There's a lot of issues in rural America that people in Washington don't recognize," said Kathy Wosoba, 66. "Particularly the Republican Party has lost touch with reality."
The AP contributed to this report.