The most telling Cabinet nomination that Barack Obama will advance once he assumes the presidency on January 20 — and from a long-term standpoint perhaps the most meaningful one — will not be his selection for secretary of State, secretary of Defense, Treasury secretary or attorney general. Obama, constrained by circumstance and the demands of official Washington, is set to fill those positions with predictable players from the usual D.C.-insider lists.

The pick that offers the most insight into where Obama will lead the country is his selection the most misunderstood position in the Cabinet: secretary of Agriculture.

The Department of Agriculture is, to be sure, misnamed. Ever since Abraham Lincoln evolved what had been a subdivision of the Patent Office and then a section of the Department of the Interior into an independent federal agency that the 16th president referred to as “the people’s department,” the department has been about much more than just farming. And that is only more so today, as the agency deals with everything from food safety and the spread of organic farming to buy-local food initiatives, rural development, food and nutrition programs in urban areas, and overseas aid.

The USDA is a key player when it comes to energy policy, both because of the rise of biofuels and because of the increasingly adventurous grant-making by its Renewable Energy Systems and Energy Efficiency Improvements Program.

The USDA’s Forest Service administers almost 300,000 square miles of national forests and grasslands.

The secretary of Agriculture is, as well, often a definitional player in trade debates — as the question of how the United States supports farmers remains an essential one when it comes to forging trade agreements and engagement with the World Trade Organization.

With a $97 billion annual budget and roughly 110,000 employees — more than the departments of Health and Human Services, Housing and Urban Development, and Energy combined — it is one of the largest non-defense agencies in the federal government. And its hand is everywhere, with thousands of county extension offices spread across every state.

Bill Clinton and George Bush made what might best be described as “hack” appointments to the Department of Agriculture, naming political pals with limited real-world experience in contemporary farm and food debates. In Bush’s administration, in particular, the job of the secretary of Agriculture has been to promote the agenda of corporate agribusiness with regard to trade policy and the lowering of food safety standards. As such, there is a lot of repair work to be done.

The question for weeks after the election was whether Obama would nominate someone who was ready to do the work.

Now, that question has been answered.

Unfortunately, the answer is not a bold one.

Obama plans to nominate former Iowa Gov. Tom Vilsack, who was briefly a contender for the 2008 Democratic presidential nod before dropping out to back first Hillary Clinton and, finally, Obama.

Vilsack is a capable administrator with the right partisan credentials.

But he only moved to the top of the list of Agriculture secretary prospects because he is a prominent Democrat who comes from what Washington insiders know as a “farm state.” As governor of Iowa, Vilsack had to engage with farm issues. But that embrace was anything but inspired. Family farm activists, fair-trade campaigners and advocates for organic foods were regularly disappointed by the stands he took. The Organic Consumers Association was blunt, declaring: “Vilsack has a glowing reputation as being a schill for agribusiness biotech giants like Monsanto.”

Early on, reviews like that one seemed to lead Obama’s transition team, and Vilsack himself, to recognize that the Iowan was not the best choice. But as the timeline for filling Cabinet chairs accelerated, Vilsack moved back into contention.

Obama could have done better, much better.

Some activists suggested a radical break with recent Agriculture Department appointments. They wanted to see Obama select a genuine change agent: writer Michael Pollan, whose books — “In Defense of Food: An Eater’s Manifesto” and “The Omnivore’s Dilemma: A Natural History of Four Meals” — have reframed the debate about food production, food safety and eating. Pollan would have been a bold choice, somewhat like Franklin Roosevelt’s selection of Henry Wallace as his Depression-era secretary of Agriculture. But the author admitted he was an unlikely pick.

More competitive — and still quite appealing — was Tom Buis, the president of the National Farmers Union, who was an early and wise counselor for the president-elect. Buis, an Indiana farmer who has also served as an aide to top Democrats in the Senate, has over the past several years been in the thick of every major debate about farm and food policy. He knows the issues and, for the most part, he has been on the right side of them, although critics of ethanol initiatives will find fault with his advocacy on that front.

Unlike the Farm Bureau, a conservative grouping that has historically aligned with corporate agribusiness interests and Wall Street, the Farmers Union has for a century represented working farmers and Main Street. In recent years, Buis and the NFU have emerged as key players in advancing fresh thinking about farm and food issues: supporting the development of organic farming, backing the development of farmers’ markets and local food programs, promoting country-of-origin labeling and other food safety initiatives, and battling the commodities speculators that have driven up global food prices.

Emblematic of the broader view taken by Buis and the NFU is the group’s embrace of fair-trade thinking; some years ago the NFU broke with other major farm groups to recognize that free-trade agreements such as NAFTA have failed working farmers in both the United States and the rest of the world.

There were, to be sure, other prospects for secretary of Agriculture.

The president-elect could have picked a sharp state official with a record of leading on agriculture issues, such as Wisconsin Secretary of Agriculture Rod Nilsestuen or North Dakota Commissioner of Agriculture Roger Johnson. Even more impressive would have been former North Dakota Commissioner of Agriculture Sarah Vogel, an always-ahead-of-the-curve advocate for food safety and fair trade. The same can be said for Minnesota Secretary of State Mark Ritchie, a former policy analyst in Minnesota’s Department of Agriculture who co-founded and for many years led the Minneapolis-based Institute for Agriculture and Trade Policy.

Vogel, Ritchie and Buis are different players with different strengths. But each had a record of commitment to approaching farm and food issues from the perspective of those who grow and eat this nation’s bounty — as opposed to the agribusiness conglomerates and speculators that profiteer off America’s and the world’s fields of plenty. As such, each would have been “change” choice.

Vilsack is, at best, a cautious pick.

We can only hope that the new secretary of agriculture will break with some of his old friends in agribusiness — and that, as he fills powerful posts withing the department that he will consider the likes of Vogel, Ritchie and Buis.

He will need the help.

As Buis noted in a gracious statement recognizing Obama’s pick, “Rural America is facing many challenges – the farm and rural economy have changed dramatically for the worst over the last few months as a result of the worldwide economic recession, the rules for the 2008 Farm Bill have not been finalized nor implemented, more people are seeking food assistance, and commodity prices have fallen dramatically while farmer input costs remain high.”

Translation: America is going to need more than an old-fashioned Department of Agriculture to meet the challenges of the 21st century. Vilsack must recreate the department as a smart, activist farm and food agency. And he should surround himself with those who have gotten farm and food issues right in recent years — not the hangers-on who have so frequently been on the wrong side of the fence.