Of all the potential hazards that a journalist can expect to confront when embarking on an interview with one of the world's bestselling novelists, being sexually molested by a turkey is not one of them. But here we are, standing in the middle of a field talking about literature, the environment and the future of America, and all the while Tom, a pumped-up male who must weigh well over 20lbs, is orbiting me in progressively smaller circles. His tail feathers are fanned out, he is making an alarming noise similar to a police siren and is shaking his blood-red proboscis at me - all classic signals, so I'm told, that he's hitting on me.

This particular beast belongs to Barbara Kingsolver, a writer famous for her love of nature and of all things rural, whose connection to the land is one of the qualities that so endears her to her millions of readers. We are at her farm in deepest Virginia, coddled within a U-shaped mountain ridge in the Southern Appalachians. There's a stream - or hollow as they call it in these parts, pronounced "holler" - running down the middle of the smallholding. The view is of rolling woodland and lush pasture, and in all directions chickens, sheep and a donkey are milling about. I'd like to report that it was a place of profound tranquillity, but with all the braying, cock crowing and turkey sirens blasting it was more like Times Square on a Saturday night.

Kingsolver, 52, has acquired an enviably long list of bestselling books, mainly novels but with a sprinkling of poetry and essay collections. She is best known for The Bean Trees, Pigs in Heaven and, above all, The Poisonwood Bible, a towering novel set in the Congo that has gained her a massive global following. It has sold more than two million copies, bears the imprimatur of Oprah Winfrey, and was recently voted by members of British book clubs as their favourite novel of all time.

I have travelled down to the Kingsolver farm on the eve of publication of her latest volume, Animal, Vegetable, Miracle. The book marks something of a departure for her as a writer, as it is her first work of narrative non-fiction.

To get a sense of what the book is about, think of Super Size Me, Morgan Spurlock's film in which he spent a month doing nothing but consuming McDonald's fast food. Now imagine its opposite, and you are getting close to Animal, Vegetable, Miracle. Like Spurlock, Kingsolver and her family set themselves a time-limited task - a year in their case - but instead of plumbing the depths of America's fast-food culture, their ambition was to shun it completely. While Spurlock set out to record the damage that would be inflicted on his own body by eating the equivalent of nine Big Macs a day, Kingsolver wanted to explore the positive impacts - physical, spiritual and environmental - of a diet that was wholesome, seasonal and local.

Part of the motivation of the book was repulsion at America's advanced state of what Kingsolver calls "alimentary alienation", where food is mass-produced and has little or no bearing on the lives of those who eat it. With the help of her husband Steven Hopp, an environmental studies lecturer, she lays out in the book the shocking scale of the crisis. The average food item on the American shelf has travelled 1,500 miles - further than most families go on annual holidays. The US consumes about 400 gallons of oil a year per person for agriculture, a rate of guzzling second only to the car. And here's a fact straight out of Alice in Wonderland: the US exports 1.1m tonnes of potatoes, and imports 1.4m tonnes.

The side-effects of America's fast-food culture are legion: global warming caused by high food airmiles; obesity due to the poor diet, particularly among American children, who are predicted to be the country's first generation with a shorter life expectancy than their parents; the destruction of farming habitats to clear the way for mass cropping of corn and soya beans; the detachment of millions of Americans who have absolutely no inkling of what they are consuming or where it comes from. As Kingsolver sums it up: "Woe is us, we overfed, undernourished US citizens. We are a nation with an eating disorder, and we know it."

But there is also a positive narrative to the book, a desire to scratch her itch for earthiness that is rooted, she says, in her childhood in rural Kentucky. She has hung on to that link with the soil of her formative years ever since, through college in Indiana, where she studied biology, and almost three decades living in Tucson, Arizona, a city of a million people plonked in a desert. "I've never really lost contact with the land," she says, her words interrupted periodically by bursts of Tom's lustful siren. "The real places for me were always outside the concrete. I've never been able to go for a day without thinking that I'm an animal, and an animal is dead without its habitat and food chain."

So in 2005 Kingsolver and crew - her husband and two daughters Camille, 19, and Lily, 10 - upped sticks from Tucson and moved to Virginia, where Steven already owned a small farm of about 100 acres, most of it woodland and steep hills.

They drew up a plan for a year living as "locavores" - eating food that they had either grown themselves or had bought from the surrounding area. "We weren't rule bound, we didn't draw a line in the map," she says, keen to avoid any impression of preaching or fanaticism. "We wanted to do something that almost everyone could relate to at some level - to take the approach of a normalish American family and see what they could do. Not to be heroic or explore a human extreme, but to show that this was doable."

They were on a trip to find a "real" American culture of food, and the book is the chronicle of that journey. Some of it is about the deprivation they endured - the foregoing of bananas and pineapples, for instance, which are banned on the grounds that exotic fruits are the Humvees of the food world.

But most of the book is devoted to the joys of what they experienced, as the year unfolded. March, when the "project", as Kingsolver calls it, began, was the month of asparagus, eaten the very day it was cut. April was for baby lettuces and greens; June for cherries, the first sweet taste of fruit after months of abstinence from exotics. With July came an outpouring of new potatoes, cucumbers and aubergines; and August saw them drowning in tomatoes of many different varieties, her favourite being the Dolly Partons. On Thanksgiving, the dining table was piled high with food that was grown or reared on the farm - including one of Tom's progeny roasted for the occasion - with the exception of cranberries, which they allowed themselves to purchase from further north. Even in the depths of January they got by, with kale and chard, frozen pesto and cans of tomatoes prepared before winter set in.

There was no slump into winter madness, like Jack Nicholson in the Shining. If anything, Kingsolver says she felt rather guilty that it all went so smoothly. "One of the challenges constructing the book was that it was almost too easy. Where is the suspense?"

Yet reading the book, you could not accuse the locavore of leading a bland or dull life. Even on the morning we come to the farm, Kingsolver has been up since 4am, woken by the harrowing sounds of a racoon breaking into the chicken coop and killing two birds. Later, we stumble on the bones of a turkey - the dug-up remains, it transpires, of Mother Number One, their first breeding turkey and Tom's original mate, who came to a sticky end last week in the jaws of a coyote.

If abundance was the over-arching theme of their year, death was never far away either. They were careful not to give their animals names, so that when the day came to "harvest" them they could do so without squirming. (A few cherished animals slipped through that injunction: notably Sally the donkey and Opal the Icelandic sheep.) Kingsolver describes in the book with almost clinical detachment the process of cutting off a rooster's head, and the way the wings flap afterwards with the body spewing blood.

It is hard to imagine this globally renowned novelist splattered with chicken blood, particularly on the day we meet when she reveals no trace of the farmyard in her personal appearance. She is dressed in a sky-blue shirt with matching earrings, and I notice that her fingernails are perfectly trimmed and clean. That puzzled and impressed me in equal measure: how someone so evidently seeped in the grit and dirt of her surroundings could be so spotlessly turned out when she chose to.

But over a few hours spent in her company, the quality that stood out most was precisely this ability to straddle different worlds with apparent ease. Barbara Kingsolver - bestselling writer, eco-campaigner, farmer, mother.

The year of the "project" was in part for her an exploration, and a celebration, of all those facets of her life. In the book there is a passage that some women readers will relate to, others may find hard to swallow, in which she says that she has finally, after many years, come to accept as a compliment the idea of being a "housewife". She argues that women of her generation made a "devil of a bargain" when they traded homemaking for careers.

"We lost a lot - we traded our aprons for the minivan and the Lunchable, and the result was children with health problems because we pick up junk food on the way to the soccer game. That's the great hoodwink of my generation."

Over the span of the year of the project she found she gained some of that homely comfort back, without jeopardising her job as a writer. She is unabashed about her desire for domesticity, insisting her ability to talk about it now is a sign of how far women have come, a mark of confidence "that my cooking will not overshadow my other work".

Kingsolver's literary work is infused with the themes developed in Animal, Vegetable, Miracle. Most obviously, her latest novel, Prodigal Summer, is set in the Southern Appalachians and describes in fictional form the very same landscape and love of nature.

But there are also clues to her interest in nature in Poisonwood Bible, though they are harder to find. The novel, first published in 1999, is a magnificent portrayal of a dysfunctional American family. It is told through the voices of the wife and four daughters of a crazed evangelical Baptist who has taken them to the Congo on a mission to save African souls. At face value the harsh jungle setting of the novel, where even the trees are toxic - the poisonwoods of the title - is as far from the rich and gentle Appalachians as you could imagine, as is Nathan Price and his warring family from Kingsolver's own brood. During the course of their locavore year, the Kingsolver family if anything grew closer and more harmonious, in contrast with the discordance displayed by her characters. "People in my novels always have terrible problems. If they are not terrible, I make them more terrible," she says.

Yet several of the themes pursued by Kingsolver in her non-fiction are present in nascent form in Poisonwood Bible. The mad Baptist struggles in vain to grow crops in the Congo because he stubbornly refuses to listen to the local experts. His daughter Leah has difficulty making sense of her home country to her African friend: "How could I explain to Anatole about soybean fields where men sat in huge tractors like kings on thrones, taming the soil from one horizon to the other?" Leah's twin sister, Adah, describes the sensation on returning to the US of walking down a supermarket aisle stuffed with produce that nobody really needs.

And there's an underlying link between the two books that goes to the core of Kingsolver's power as a writer. Beneath their deceptively humanist surfaces, both Poisonwood Bible and Animal, Vegetable, Miracle are intensely political books. You can read Poisonwood Bible as a simple tale of tragedy in the rotten heart of one family; but equally it is an allegory for the damage wrought by US foreign policy, which sought to uphold the interests of big corporations by frustrating Congo's early bid for independence - a morality tale that seems to become more relevant with every passing day.

It's the same with her new book. You can read it as a straightforward chronicle of a year spent eating locally garnered food; but equally it is a caustic portrait of the wounds inflicted on America's own landscape by the government-backed corporate drive for profits.

When I put this to her, she pauses, with the inward look of someone who likes to choose her words carefully, and then she says: "What was done in my name in the Congo was a presumption that what works in one culture should be forced upon another, the agenda of course being to go in and get the goods. Farming has become an extractive industry, like mining. It used to be about the American dream, with families working hard to enrich themselves and their communities; now it's about large powerful corporations pulling out the good stuff and leaving behind a mess. So yes, there is a similarity."

The locavore year technically came to an end several months ago, though the family has largely stuck with the regime. They eat out a little more frequently than they did, and occasionally buy wild Atlantic salmon, though they regard such treats as splurges rather than entitlements. Kingsolver is working on a new novel, which she describes as "a fictional secret history revealed in a surprising way".

Before we part, I ask her what change the year has had on her. "Physically, not much. But I really have connected with this place. To eat of this place helped me to become of it, to belong." And as we drive away down the farm's dust track, Tom's love call fading into the distance, I admit to myself that I got it wrong. There is a profound tranquillity here after all.

· Animal, Vegetable, Miracle, by Barbara Kingsolver is published on July 5 by Faber & Faber price £16.99. To order a copy for £13.99 with free UKp&p go to theguardian.com/bookshop or call 0870 836 0875