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Polycultures in Practical Plants

Practical Plants allows users to create Polycultures (or guilds) and displays these under each plant in that polyculture.
Create a new polyculture in the box below


Benefits of polycultures

Polycultures leverage beneficial associations between plants to increase crop yield, prevent pest damage, improve soil health, maximise crop yield by area by interplanting crops which can co-exist spatially, and suppress weed growth.

Pest suppression and trap crops

Some plants function as a pest confuser, secreting from their roots or dispersing aerially chemicals which act to mask the presence of the primary crop. Other plants can perform as a trap crop, which draw the pest from the primary crop by being more attractive to the pest, and acting as a sacrificial crop to lure them away from the more valuable primary crop. By interplanting with plants that perform these functions, severe damage from pests can be avoided without requiring additional inputs of organic or chemical pesticides. See lists of pest confusers and trap crops

Improvements in soil health

Plants which function as a nitrogen fixer are able to fix atmospheric nitrogen into the soil to be used by other plants. Planting nitrogen fixers as a primary crop (beans and peas, for example) or a dedicated soil improving crop (eg. clover) prevents nitrogen depletion of the soil, and reduced the need to leave fields to lie fallow. SOme nitrogen will be made available to other plants growing close by, but the majority will enter the soil when the nitrogen fixing plant dies and decays. Likewise, some plants function as a mineral accumulator drawing nutrients from deep in the soil and bringing those nutrients to the surface to be released when the plant dies and decays. By interplanting with plants that perform these functions, nutrient levels in the soil can be maintained without requiring the additional inputs of organic or chemical fertilizers. See lists of nitrogen fixers and mineral accumulators[1]

Spatial and temporal interactions

Plants have different preferences for sunlight, and interplanting can allow sun loving crops which grow tall and provide dappled shade to co-exist with plants which grow lower and prefer or tolerate partial shade. In this mannor, two crops can co-exist in the same space. Similarly, by carefully timing for the various growth stages of plants, one is able to sequence crops temporally. Perhaps interplanting a quick growing crop with a slow growing crop, allowing for a full harvest before the slower growing crop needs the space and light. See examples of Spacial interactions and Temporal interactions.

Beneficial Habitats

Beneficial habitats?sometimes called refugia?are another type of companion plant interaction that has drawn considerable attention in recent years. The benefit is derived when companion plants provide a desirable environment for beneficial insects and other arthropods?especially those predatory and parasitic species which help to keep pest populations in check. Predators include ladybird beetles, lacewings, hover flies, mantids, robber flies, and non-insects such as spiders and predatory mites. Parasites include a wide range of fly and wasp species including tachinid flies, and Trichogramma and ichneumonid wasps. Agroecologists believe that by developing systems to include habitats that draw and sustain beneficial insects, the twin objectives of reducing both pest damage and pesticide use can be attained. For detailed information on establishing beneficial habitats, request the ATTRA publication Farmscaping to Enhance Biological Control.

Security Through Diversity

A more general mixing of various crops and varieties provides a degree of security to the grower. If pests or adverse conditions reduce or destroy a single crop or cultivar, others remain to produce some level of yield. Furthermore, the simple mixing of cultivars, as demonstrated with broccoli in University of California research, can reduce aphid infestation.


Polycultures in history

Polycultures precede modern agriculture, and were much used throughout history to maximise crop yield on plots of land small enough to be managed without modern machinery. In Italy there is evidence that the practice of intercropping grape vines and Acer campestre (Field Maple) dates back to the late medieval period[2]. The Native Americans were known to grow a polyculture of beans, corn, and vine squash known as The Three Sisters: the corn providing structure for the beans to grow up while offering partial shade, the beans fixing the soil with nitrogen, and the vine squashes forming a dense ground cover[2]


References

  1. ? Beyfuss, R; Pritts, M [Companion Planting: Ecogardening Factsheet #10] Cornell University (2012/05/27)
  2. ? 2.02.1 Zachary Nowak Looking Back to the Future: Historical Polycultures in Central Italy Agroforestry News Vol 19 No 4 (2011/08/01)