Did you buy “organic” food at the supermarket in 2006 — say, one of those clam-shell boxes of spinach? If so, there’s a strong chance you got hoodwinked.

Get this, from the Sacramento Bee: For years, a California organic-input company was passing off synthetic fertilizer as organic and selling it widely to the state’s organic farms (including nationally distributed giants like Earthbound Farms). The offending company, California Liquid Fertilizer, owns about a 33 percent market share among the state’s organic farmers, the Bee reports.

Using an open-records request, the newspaper found that state regulators uncovered the mess in June 2004, but didn’t force the product off the market until January 2007.

The question of fertilizer lies at the heart of organic production. Industrial agriculture leaches nutrients from soils, replacing them with synthetic and mined fertilizers. These substances create all manner of ecological trouble.

Ideally, organic agriculture recycles nutrients into the soil through on-farm composting and cover-cropping. As I’ve argued before, creating truly closed-loop, sustainable soil-fertility regimes is the key challenge for organic agriculture going forward.

The kind of intensive monocropping that holds sway on California’s industrial-scale organic farms — the ones that supply our nation’s supermarkets much more than the ones that supply the state’s celebrated farmers markets — generally ignore that challenge. They practice instead what’s known as “input substitution” — merely looking for a relatively benign replacement for industrial inputs like fertilizer and pesticide.

That’s how they found themselves buying fertilizer spiked with ammonium sulfate, a byproduct of the industrial steel-making process.

“Organic agriculture is becoming very dependent on these amendments,” one grower told The Bee. “If you don’t use them, and your competitor is using them, you’re going to suffer.”

Funny — that’s the same mentality that’s driven conventional farmers to grow more and more dependent on agrichemical and farm-equipment manufacturers over the past half-century.