1) Biological pest control 
Polyculture is agriculture using multiple crops in the same space, in imitation of the diversity of natural ecosystems, and avoiding large stands of single crops, or monoculture. It includes multi-cropping, intercropping, companion planting, beneficial weeds, and alley cropping. It is the raising at the same time and place of more than one species...
A system of pond aquaculture in which more than one species is raised. In China a type of polyculture has been developed over 4000 years in which different species of carp inhabit separate niches within the pond ecosystem, with beneficial results. 
polyculture Many diverse crops or species; also, multiculture.