FILE: Chickens gather around a feeder at a farm on August 9, 2014 in Osage, Iowa. (Scott Olson/Getty Images)

Just six weeks after they assembled for their first Iowa cattle call of the 2016 election cycle, the Republican presidential candidates are back again here this weekend, this time to show how much they know — or don’t know — about American agriculture.

A forum on agriculture in Iowa might seem like the political equivalent of sending coals to Newcastle. But to the organizers of Saturday’s day-long talkfest, it is an opportunity to force a conversation about a topic they believe is both misunderstood nationally and rarely talked about in any depth by presidential candidates when they campaign here.

The weekend will mark the first time that former Florida governor Jeb Bush has appeared in Iowa since he began his aggressive march toward full-fledged candidacy. The other rising Republican, Wisconsin Gov. Scott Walker, will be here, too, along with at least nine others who say they are seriously thinking about seeking the GOP nomination.

The group includes the former agriculture commissioner of Texas, Rick Perry (who also served a record 14 years as governor). New Jersey Gov. Chris Christie will be here, as will Sen. Ted Cruz of Texas, Sen. Lindsey O. Graham of South Carolina and the two immediate past winners of the Iowa GOP caucuses, former Arkansas governor Mike Huckabee and former senator Rick Santorum of Pennsylvania.

Saturday’s forum is only one of a string of political events designed to keep the candidates focused on the state with the first caucuses on the presidential calendar. Six weeks ago, they were here to speak to conservative activists. In the future they will be drawn by religious conservatives, social conservatives and local party committees.

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In June, newly elected Sen. Joni Ernst (R-Iowa) will host a “Roast and Ride” fundraiser and pig roast. Then in August, the Iowa Republican Party will put on its quadrennial straw poll, an event that has drawn considerable criticism for the time and expense it demands of candidates given its apparent minimal returns on caucus day.

The attention showered on Iowa, a state whose population is not representative of the nation at large, has rankled politicians in other states. But the caucuses have survived many challenges and Iowa activists defend the state’s status, arguing that this is one of few places where candidates must spend time in conversation with average voters.

The agriculture summit, which will take place at the Iowa State Fairgrounds, won’t look and feel like the typical presidential cavalcade. The candidates won’t get the chance to deliver set speeches. Instead they will sit in a comfortable chair on a stage in a cavernous room before an audience numbering around 900 people and submit to questions by Bruce Rastetter, a wealthy agribusiness executive and political donor.

Rastetter said he came up with the idea while tailgating at an Iowa Hawkeyes football game last fall with a friend, Nick Ryan, a conservative activist and strategist.

“He said, ‘What wasn’t talked about the last two presidential cycles in Iowa?’ ” Rastetter said Friday in the arena where the candidates will appear on Saturday. They agreed there was too little discussion about agriculture policy and hatched the plan for this weekend’s summit.

Rastetter has another goal, which is to demonstrate that agriculture policy is more than a special interest to a segment of Iowa’s population. He said he has been asked repeatedly by reporters heading here this weekend, why is there a need for an agriculture summit?

“My flippant response is that every American has to eat every day,” he said. “But in thinking about it in a more thoughtful way, I don’t think that there is any industry in the U.S. that touches people’s lives more every day than agriculture does.”

The candidates have been given an idea of the topics, and they go well beyond issues of crop payments and aid for the ethanol industry, which for years few presidential candidates were willing to oppose. Sen. John McCain (R-Ariz.), campaigning in 2007 and 2008 here, always joked that he started each day with a glass of ethanol.

There, of course, will be questions about the future of the Renewal Fuel Standard, which requires that gasoline must include minimum level of renewable fuel. But Rastetter intends to cover other topics, including the issue of immigration and what policies are needed to assure the farm community has a steady and reliable work force.

He wants the candidates to talk about international trade, about food labeling and food safety in the context of genetically modified foods, about wind energy and about conservation programs and the Environmental Protection Agency.

“Let’s make sure we have a substantive discussion on issues like this, rather than just retail politics where they don’t get on the record on these things,” Rastetter said.

Rastetter is more than a disinterested interlocutor. He has been one of the nation’s leading pork producers, one of the nation’s leading ethanol producers and runs an operation now that encompasses those products and more.

A generous philanthropist, Rastetter also is a political player, a friend and contributor to Iowa Gov. Terry Branstad (R). He was co-chair of Branstad’s finance committee in 2010.

Branstad for one is thrilled at the prospect of the GOP candidates devoting their weekend to a discussion of agriculture. “Foreign policy and agriculture are going to be the most important issues that candidates need to address in the 2016 election,” he said in a telephone interview.

He was sharply critical of the Obama administration, saying it has “failed miserably” and complained that the president hasn’t mentioned ethanol in more than three years.

“His EPA is recommending a reduction in renewable fuel standards,” Branstad said. “When we strongly protested it — there was strong bipartisan protest in the heartland of America — they didn’t do anything.”

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Iowa more than most states has been able to sustain and grow its economy in recent years thanks to a strong agricultural sector that kept the unemployment rate lower than most as the economic downturn began in 2008 and through the recession of recent years. But with the costs of commodities slipping, there is concern that Iowa’s farmers could begin to suffer considerably.

Farm incomes are projected to drop by 33 percent, according to the Agriculture Department. Corn prices — a key commodity in the state — are below the cost of production, and farmland values are slipping for the first time in more than three decades, with a 7 percent drop last year, according to Branstad.

“Agriculture, which has been a real strength in the national economy and Iowa, is beginning to hurt,” he said. “So it’s important for these presidential candidates to share their vision and their plan to revitalize agriculture.”

Adding to the atmosphere on Saturday will be the knowledge among all the candidates that the person asking the questions could become one of their supporters and key contributors before next year’s caucuses.

Rastetter said he has tried to make clear that the forum “is not about my support,” but rather for Iowans who care about agriculture and presidential politics. He said he does not intend to make an endorsement “any time soon. Asked if he would endorse before next year’s caucuses, he said, “I think I will.”