(FORTUNE Magazine) – Do the words ''organic farming'' remind you of Aquarian health fanatics? Think again. The highly respected National Academy of Sciences has just published Alternative Agriculture, a book that demands to be taken seriously. The publication features case studies of 14 American farmers who have enjoyed crop yields up to 40% greater than average though they use little or no synthetic pesticide, herbicide, or fertilizer. Even more important than increased crop yields is the fact that natural farming avoids adding any more chemicals to the nation's water supply by way of runoff from fields. Pollution from sewage plants, factories, and other industrial waste is down impressively, but agricultural pollution continues virtually unchecked. At present at least 90% of American farmers rely heavily on chemical pesticides and fertilizers. A small dip in that figure could mean big money for a number of biotech companies that produce alternatives. In 1990, Mycogen of San Diego will introduce a bacterial pesticide that is not only natural but longer lasting than similar products already being sold by pharmaceutical companies. Farmers could spray with the new pesticide on a biweekly basis rather than every other day or so. By 1992, Calgene of Davis, California, may have something for farmers not ready to go all natural but who would try something less damaging to the environment. Among other things, the company is designing bacterial genes that can be implanted into cotton. This will enable the plants to break down synthetic weedkiller into harmless components.