From an ecological standpoint, the fundamental problem with U.S. farm policy dating back to the ’70s is that it rewards farmers for maximizing yield at all cost.

Encouraged to produce as much as possible, all the time, farmers have few incentives to conserve resources or protect water, air, or soil quality. The federal government’s dizzying array of biofuel subsidies — which have propped up crop prices and encouraged yet more production — only exacerbates the situation.

I don’t think greens fully appreciate the ecological troubles associated with these policies. Peter Donovan’s recent post showed how agriculture has vast — and presently, largely untapped — potential to mop up a significant amount of carbon from the atmosphere. And I recently posted about how the biofuel boom is unleashing a cascade of chemicals onto farmland, both domestically and globally.

And now we get this. Researchers at the University of Illinois have shown that nitrogen fertilizers, when applied at levels currently common in the Midwest, severely deplete the soil’s ability to store carbon. The consequences are dire. As one of the researchers put it:

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The loss of soil carbon has many adverse consequences for productivity, one of which is to decrease water storage. There are also adverse implications for air and water quality, since carbon dioxide will be released into the air, while excessive nitrogen contributes to the nitrate pollution problem.

Essentially, the boom in corn production now underway in the Midwest is a subprime mortgage on our cropland’s future productivity — and a drain on the Midwest’s water resources. Since fertilizer-lashed soil loses its ability to hold water, farmers need to irrigate their land at higher levels, taxing the Midwest’s water table — to speak nothing of all the carbon that could be stored in soil, which is now drifting into the atmosphere, doing its bit to warm the planet.

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