Charles Mitchell is no stranger to sustainable farming practices. He grew up drinking milk from dairy cows that were fed on locally grown corn and grass on his family farm — about as close to sustainable and organic as one could get back then.

On the sustainable farming issue, he considers himself an optimist, albeit a qualified one. He points with a sense of pride to the headway row-crop producers have made in the last quarter century introducing sustainable practices on their farm — an effort to which he has contributed as an Alabama Cooperative Extension System agronomist and as a professor in Auburn University's Department of Agronomy and Soils.

Likewise, within the last decade, aspiring organic farmers have made great strides developing specialized markets for their produce.

But this is precisely the point at which qualified optimism yields to hard-bitten realism.

Like many of his other Extension and university colleagues, Mitchell remains entirely unconvinced that large-scale farming practices will ever be 100 percent environmentally sustainable.

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Yes, sustainability practices will continue to make steep inroads in row-crop farming — Mitchell has no doubt about that — but he doesn't see anything approaching full sustainability in the foreseeable future.

As the global population approaches more than 9 billion people by mid-century, there are simply too many mouths to feed. Consequently, the concerns associated with large-scale farming will be as much about efficiency as sustainability.

"On a global scale, I really don't think there is anything that will be fully sustainable," Mitchell says. "Something else has got to happen."

Whatever farming model emerges certainly will incorporate sustainable practices, though farming, at least the large-scale farming essential for feeding the world, will not be 100 percent sustainable, Mitchell says.

If that is the bad news, Mitchell says the good news is that sustainable practices nonetheless comprise a significant part of large-scale farming in the 21st century.

He cites conservation-tillage, which was developed as an incentive for farmers in the 1985 farm bill, as one of the more laudable advances in production agriculture over the past century.

Conservation-tillage, or reduced-tillage as it's also known, reversed the appalling loss of topsoil that characterized previous generations of row-crop farming. Before these reduced-tillage practices were introduced, some row-crop farms were losing as much as 20 tons of topsoil an acre annually.

"We have brought those erosion levels down to the level at which the soil is able to tolerate cultivation and still remain productive," Mitchell says.

In some cases, farmers have managed to go a step further with high-residue conservation practices, which safeguard the soil against erosion.

While there is still plenty of room for improvement, Mitchell says considerable progress has been made, with about 60 to 70 percent of Alabama cropland operating within some form of conservation-tillage system.

Organic farming practices are also making steep inroads in Alabama and throughout the South. While encouraged by this trend, Mitchell says consumers and aspiring organic farmers alike should see this practice for what it is: One that will comprise only a small part of commercial farming in the future.

"Even if the all the cropland in the United States were committed to organic production, you wouldn't manage to feed even the population of this state," Mitchell says. "It won't work because we simply don't have the land resources to do that."

Even so, Mitchell sees a future for organic farming, if only on a small scale.

"On a local scale, it's very attractive, and specialized markets are springing up everywhere," Mitchell says. "We're still a wealthy nation and many people still have the disposable income to spend on these specialized products."

Likewise, Mitchell says there are plenty of opportunities for other organically grown products, such as milk and grass-fed cattle, especially in Alabama, which, because of its warm climate, is able to grow forage grasses for longer periods during the year.