Polyculture

In agriculture, polyculture is the practice of growing more than one crop species in the same space, at the same time. In doing this, polyculture attempts to mimic the diversity of natural ecosystems. Polyculture is the opposite of monoculture, in which only one plant or animal species is cultivated together. Polyculture can improve control of some pests, weeds, and diseases while reducing the need for pesticides. Intercrops of legumes with non-legumes can increase yields on low-nitrogen soils due to biological nitrogen fixation. However, polyculture can reduce crop yields due to competition between the mixed species for light, water, or nutrients. It complicates management as species have different growth rates, days to maturity, and harvest requirements: monoculture is more amenable to mechanisation. For these reasons, many farmers in large-scale agriculture continue to rely on monoculture and use crop rotation to add diversity to the system. Other forms of polyculture can be found in permaculture and integrated aquaculture. Polyculture has traditionally been the most prevalent form of agriculture. A well-known example of historic polyculture is the intercropping of maize, beans, and squash plants in a group often referred to as "the three sisters". In this combination, the maize provides a structure for the bean to grow on, the bean provides nitrogen for all of the plants, while the squash suppresses weeds on the ground. This crop mixture can be traced back several thousand years to civilizations in Mesoamerica and is representative of how species in polycultures sustain each other and minimize the need for human intervention. Integrated aquaculture, or the growing of seafood and plants together, has been common in parts of Eastern Asia for several thousand years as well. In China and Japan, for example, fish and shrimp have historically been grown in ponds with rice and seaweed. Other countries where polycultures have traditionally been a substantial part of agriculture, and continue to be so today, include those in the Himalayan region, Eastern Asia, South America, and Africa.