Polyculture

Polyculture is a form of agriculture in which more than one species is grown at the same time and place in imitation of the diversity of natural ecosystems. Polyculture is the opposite of monoculture, in which only members of one plant or animal species are cultivated together. Polyculture has traditionally been the most prevalent form of agriculture in most parts of the world and is growing in popularity today due to its environmental and health benefits. There are many types of polyculture including annual polycultures such as intercropping and cover cropping, permaculture, and integrated aquaculture. Polyculture is advantageous because of its ability to control pests, weeds, and disease without major chemical inputs. As such, polyculture is considered a sustainable form of agriculture. However, issues with crop yield and biological competition have caused many modern major industrial food producers to continue to rely on monoculture instead. Polyculture is a form of agriculture in which more than one species is grown at the same time and place in imitation of the diversity of natural ecosystems. Polyculture is the opposite of monoculture, in which only members of one plant or animal species are cultivated together. Polyculture has traditionally been the most prevalent form of agriculture in most parts of the world and is growing in popularity today due to its environmental and health benefits. There are many types of polyculture including annual polycultures such as intercropping and cover cropping, permaculture, and integrated aquaculture. Polyculture is advantageous because of its ability to control pests, weeds, and disease without major chemical inputs. As such, polyculture is considered a sustainable form of agriculture. However, issues with crop yield and biological competition have caused many modern major industrial food producers to continue to rely on monoculture instead. 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 ago to civilizations in Latin America and Africa 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 polyculture has traditionally been a substantial part of agricultural and continues to be so today include those in the Himalayan region, Eastern Asia, South America, and Africa. Because of the development of pesticides, herbicides, and fertilizers, monoculture became the predominant form of agriculture in the 1950's. The prevalence of polyculture declined greatly in popularity at that time in more economically developed countries where it was deemed to produce less yield while requiring more labor. Polyculture farming has not disappeared entirely though as traditional polyculture systems continue to be an essential part of the food production system today. Around 15% to 20% of the world’s agriculture is estimated as relying on traditional polyculture systems. The majority of Latin American farmers continue to intercrop their maize, beans, and squash. Due to climate change, polyculture is returning in popularity in more developed countries as well as food producers seek to reduce their environmental and health impacts. The kinds of plants that are grown, their spatial distribution, and the time that they spend growing together determines the specific type of polyculture that is implemented. There is no limit for the types of plants or animals that can be grown together to form a polyculture. The time overlaps between plants can be asymmetrical as well, with one plant depending on the other for longer than is reciprocated, often due to differences in life spans. When more than two crops are grown in complete spatial and temporal overlap with each other, it is referred to as intercropping. Intercropping is particularly useful in plots with limited land availability. Legumes are one of the most commonly intercropped crops, specifically legume-cereal mixtures. Legumes fix atmospheric nitrogen into the soil so that it is available for consumption by other plants in a process known as nitrogen fixation. The presence of legumes consequently eliminates the need for man-made nitrogen fertilizers in intercrops. When a crop is grown alongside another plant that is not a crop, the combination is referred to as cover cropping. If the non-crop plant is a weed, the combination is called a weedy culture. Grasses and legumes are the most common cover crops. Cover crops are greatly beneficial as they can help prevent soil erosion, physically suppress weeds, improve surface water retention, and, in the case of legumes, provide nitrogen compounds as well. Strip cropping is a form of polyculture that involves growing different plants in alternating rows. While strip cropping does not involve the complete intermixing of plant species, it still provides many of the same benefits such as preventing soil erosion and aiding with nutrient cycling. Permacultures are polycultures of perennial plants. Legume-grass mixtures and wildflower mixtures are common forms of permaculture, popular in Europe and more temperate climates. Permacultures increase soil fertility through nitrogen fixation, decrease soil erosion, regulate water consumption, and decrease the need for tillage thereby conserving soil nutrients. Permacultures require even less human intervention than other forms of polyculture because of lower harvest and tillage rates. In many Latin American countries, agroforestry is a popular form of permaculture as well where trees and crops are grown together. Trees provide shade for the crops alongside organic matter and nutrients when they shed their leaves or fruits. The elaborate root systems of trees also help prevent soil erosion and increase the presence of microbes in the soil. In addition to benefiting crops, trees act as commodities themselves for use in paper, medicine, firewood, etc. Growing coffee plants alongside other tree species in Mexico is a common practice of agroforestry.