Polyculture

In agriculture, polyculture is the practice of growing more than one crop species together in the same place at the same time, in contrast to monoculture, which had become the dominant approach in developed countries by 1950.

Resources are used more efficiently, requiring less inputs of fertilizers and pesticides, as interplanted crops suppress weeds, and legumes can fix nitrogen.

Polyculture can yield multiple harvests per year, and can improve the physical, chemical and structural properties of soil, for example as taproots create pores for water and air.

Annual polycultures include intercropping, where two or more crops are grown alongside each other; in horticulture, this is called companion planting.

The cover plants help reduce soil erosion, suppress weeds, retain water, and fix nitrogen.

A living mulch, mainly used in horticulture, involves a second crop used to suppress weeds; a popular choice is marigold, as this has cash value and produces chemicals that repel pests.

[1] Regions where polycultures form a substantial part of agriculture include the Himalayas, Eastern Asia, South America, and Africa.

[3] The introduction of pesticides, herbicides, and fertilizers made monoculture the predominant form of agriculture in developed countries from the 1950s.

[6] The prevalence of polycultures declined greatly in popularity at that time in more economically developed countries where it was deemed to yield less while requiring more labor.

[1] Due to climate change, polycultures are regaining popularity in more-developed countries as food producers seek to reduce their environmental and health impacts.

[9] Its principal advantages, according to Adamczewska-Sowińska and Sowiński 2020, are:[3] A polyculture makes more efficient use of resources and produces more biomass overall than a monoculture.

[11] Interactions between crops are complex, but mainly competitive, as each species struggles to obtain room to grow, sunlight, water, and soil nutrients.

[6] This is an example of reconciliation ecology, accommodating biodiversity within human landscapes, and may form part of a biological pest control program.

Pests with more generalized preferences spend less time on a polyculture crop, resulting in lower yield loss (associational resistance).

If targeted by a specialized pest or disease, a crop in a polyculture will likely experience the same yield loss as its monoculture counterpart.

[16] The kinds of plants that are grown, their spatial distribution, and the time that they spend growing together determine the specific type of polyculture that is implemented.

[16] When two or more crops are grown in complete spatial and temporal overlap with each other, the approach is described in agriculture as intercropping, and in horticulture as companion planting.

These may be ploughed along the contours of a steep hillside, and are typically considerably wider than a single row of a cereal crop.

While strip cropping does not involve the complete intermixing of plant species, it provides many of the same benefits such as reducing soil erosion and aiding with nutrient cycling.

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.

Marigolds have a special place among weed-suppressing living mulches as they produce thiophenes which repel pests such as nematodes, and provide a second cash crop.

[3] For arable use, cereals such as wheat and barley, or broadleaved crops like rapeseed, can grow with living mulches of clover, vetch, or other legumes.

[1] Trees provide shade for the crops alongside organic matter and nutrients when they shed their leaves or fruits.

In addition to benefiting crops, trees act as commodities harvested for paper, medicine, timber, and firewood.

[21][22] A different polyculture system is used for coffee in Mexico, where the Coffea bushes are grown under leguminous trees in the genus Inga.

In seafood mono-species aquaculture, the greatest problem is the high cost of feed, more than half of which goes to waste, causing nitrogen release and eutrophication or algal blooms.

Integrated aquaculture uses plants both as food for the sea animals and for water filtration, absorbing nitrates and carbon dioxide.

[7] Regenerative ocean farming sequesters carbon, growing a mix of seaweeds and shellfish for harvest, while helping to regenerate and restore local habitats like reef ecosystems.

Pawpaw trees growing under mulberry trees, a forest gardening style of polyculture
A Central American polycultural "milpa" in 2011. Beans are growing among the drying maize; banana trees are in the background.
Excellent soil structure in land in South Dakota farmed without tillage using a crop rotation of maize, soybeans, and wheat accompanied by cover crops . The main crop has been harvested but roots of the cover crop are still visible in autumn.
Applying pesticides to crops in a monoculture : polycultures need lower inputs, reducing environmental harms.
Benefits of polyculture include fixation and provision of nitrogen by legumes and pest management. [ 9 ]
Companion planting of carrots and onions . The onion smell puts off carrot root fly , while the smell of carrots puts off onion fly . [ 17 ]
A living mulch planted to reduce weed growth between rows of maize plants.
A coffee farm in Colombia where coffee plants are grown under several tree species in imitation of natural ecosystems. Trees provide resources for the coffee plants such as shade, nutrients, and a well-maintained soil. [ 2 ]
Ducks with free access to rice paddies in Bali, Indonesia provide additional income and manure the fields, reducing the need for fertilizer. [ 25 ]