In the May 31, 2002 issue of the magazine Science, a 21-year study started in 1978 into production costs and output confirmed that, while organic agriculture produces somewhat smaller yields, it also required fewer resources than conventional farming. They discuss the tradeoff of short-term "rich harvests in exchange for polluting pesticides and fertilizers." The study concluded that: "The bottom line: Organic farms can be nearly as productive as regular farms for some crops, and leave soil healthier" " and are also more energy efficient. Organic crops were given less than half the nutrients, but still averaged 80% of the yield of "conventionally grown" plots. The study also found that "Because no synthetic fertilizer had to be produced or applied, growing organic crops also required less energy than conventional crops " up to 56% less energy per unit yield."
Source: Science, May 31, 2002.