The Omnivore's Dilemma: A Natural History of Four Meals

by Michael Pollan

Perhaps the greatest challenge to farming organically on an industrial scale is controlling weeds without the use of chemical herbicides. Greenways tackles its weeds with frequent and carefully timed tilling. Even before the crops are planted, the fields are irrigated to germinate the weed seeds present in the soil; a tractor then tills the field to kill them, the first of several passes it will make over the course of the growing season. When the crops stand too high to drive a tractor over, farm workers wielding propane torches will spot kill the biggest weeds by hand. The result is fields that look just as clean as the most herbicide-soaked farmland. But this approach, which I discovered is typical of large-scale organic operations, represents a compromise at best. The heavy tillage—heavier than in a conventional field—destroys the tilth of the soil and reduces its biological activity as surely as chemicals would; frequent tilling also releases so much nitrogen into the air that these weed-free organic fields require a lot more nitrogen fertilizer than they otherwise might. In a less disturbed, healthier soil, nitrogen-fixing bacteria would create much of the fertility that industrial organic growers must add in the form of compost, manures, fish emulsion, or Chilean nitrate—all inputs permitted under federal rules.