Planting two or more species in the same field in the same year. This general term describes a multiplicity of systems that are as complex as agriculture itself. The first conscious planting by early people consisted of mixtures of cereals, grain legumes, roots, and tubers that were located near permanent dwellings. Perhaps this system of planting was patterned after the natural combinations of trees, shrubs, and other plants from which food was gathered in the wild, or resulted from the unintended growth that originated from seed contained in kitchen refuse that germinated and thrived in early fertile garbage dumps.