A few months ago I linked to an article about how a four-year crop rotation involving alfalfa and small grains in addition to corn and soy could drastically decrease the use and toxicity of agrochemicals, while maintaining production and profit stable. I have just read this article more closely, and I have found a caveat. The authors of the report define profit on a per-acre basis, and by this measure, the more diverse, more sustainable rotations were indeed just as profitable as the two-year corn-and-soy orthodoxy. However, they also found that the more diverse, complex rotations require more work per acre to maintain, almost twice as much. This means that if the profit per acre is the same, but the hours worked are double, a farmer practicing the four-year rotation would either earn half as much as his chemically-addicted neighbor, or he'd have to work twice as much to earn the same amount.
This is not to say that more diverse rotations are not important or desireable, but it is necessary to be clear in what we're talking about. A farmer or any worker doesn't usually measure his wellbeing or productivity in terms of how much is produced by each acre or each unit of another resource input, but rather by what he earns for every hour he works. This is why we usually see intensive land use (high value created per acre but with low earnings per day of work) in places where there are a lot of poor people willing or obligated to work for little, while in places like Australia or the US we have high per-hour or per-day labor earnings, accompanied by relatively low profit per acre.
At any rate, this research was very interesting and important, and gives us a clear indication that it is possible to decrease fossil fuel and synthetic chemical inputs while maintaining the same level of food production and reducing environmental pollution. Now the key is to figure out how to do this while maintaining the same payoff for every hour the farmer works.