100% Organic Farming Not Realistic?

According to an article by the Economist, they argue that organic/local farming is only useful in some circumstances. On the argument of the energy efficiency of organic farming the article has this interesting snippet -

"What of the claim that organic farming is more energy-efficient? Lord Melchett points out for example that the artificial fertiliser used in conventional farming is made using natural gas, which is “completely unsustainable”. But Anthony Trewavas, a biochemist at the University of Edinburgh, counters that organic farming actually requires more energy per tonne of food produced, because yields are lower and weeds are kept at bay by ploughing. And Mr Pollan notes that only one-fifth of the energy associated with food production across the whole food chain is consumed on the farm: the rest goes on transport and processing.

The most environmentally benign form of agriculture appears to be “no till” farming, which involves little or no ploughing and relies on cover crops and carefully applied herbicides to control weeds. This makes it hard to combine with organic methods (though some researchers are trying). Too rigid an insistence on organic farming's somewhat arbitrary rules, then—copper, a heavy metal, can be used as an organic fungicide because it is traditional—can actually hinder the adoption of greener agricultural techniques. Alas, shoppers look in vain for “no till” labels on their food—at least so far."