If perennial polycultures are such a good idea, why haven't they been developed before now? Certainly the polyculture part has been explored and developed to some extent. One source suggests that "humans have produced food from integrated polycultures for approximately 98.5% of farming history."26 Modern farmers use a wide variety of techniques today that emulate aspects of a perennial polyculture. They use crop rotations to reduce the need for pest control and fertilizer; use cover crops to improve soil quality, prevent soil erosion, and minimize weed growth; use no-till and low-till farming to minimize soil erosion and increase retention of water and nutrients; practice soil management to improve fertility; employ diversity to protect against monoculture vulnerabilities; use integrated pest management to reduce the need for pesticides; and employ rotational grazing to prevent soil erosion and contribute to soil fertility.27
Using perennials, however, has been virtually absent from modern experiments in agriculture primarily because the goal in agriculture has generally been to achieve high yield and everyone knows that annuals put their energy into producing seeds while perennials put their energy into producing roots and rhizomes. There have been some past attempts to investigate perennial grains, particularly wheat. As long ago as the 1920s, the Russians had a large perennial wheat breeding program, and there have been sporadic efforts since then. It was not until the mid-1970s, however, that Wes Jackson argued for perennial polycultures, founded The Land Institute, and introduced the notion that perennial polycultures could be developed into
25 This program won its developer, Dr. Norman Borlaug, the Nobel Prize in 1970, and the story about the program has been recounted in many places. See, for example, The Nobel Foundation Web site biography of Norman Borlaug, 1970. As of April 13, 2007: http://nobelprize.org/nobel_prizes/peace/laureates/1970/ borlaug-bio.html.
27 Leo Horrigan, Robert S. Lawrence, and Polly Walker, "How Sustainable Agriculture Can Address the Environmental and Human Health Harms of Industrial Agriculture," Research Review, Center for a Livable Future, Johns Hopkins Bloomberg School of Public Health, Vol. 110, No. 5, May 2002, pp. 445-456. As of April 13, 2007: http://www.jhsph.edu/clf/PDF%20Files/Sustainable_Ag_Horrigan.pdf.
"an agricultural system with the ecological stability of the prairie and a grain yield comparable to that from annual crops."28
More recently, people have begun to pay more attention to the potential of perennials in agriculture. In a study on the economic benefits of the Earth's biota, David Pimentel and colleagues concluded that:
Cultivating perennial cereal grains that can be harvested continuously for 4 to 5 years without tilling and replanting—in place of annual grains whose energy-intensive spring and fall tilling exposes soil to wind and water erosion—could reduce erosion as much as 50 percent, saving $20 billion worth of soil and $9 billion in tractor fuel every year in the United States. . . . Genes for perennial cereal grains already exist in wild plant species.29
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