Service plants are a group of plant species that are cultivated in order to improve agroecosystem functions. They are not meant to be harvested or grazed. This term usually refers to sown herbaceous species, but can be extended to hedges and trees, which can then be considered part of agroecological infrastructures.
Service plants can be planted between two crops (multi-service cover crop) or intercropped with the main crop as a companion plant. They can cover the plot perennially (e.g. alfalfa), or temporarily (e.g. gelatinous fabaceae).
They are chosen for the ecosystem services they provide during their development and/or after their destruction:
- Improvement of the nitrogen cycle (“nitrate trap” or “green manure” function).
- Pest control (weed competition, biofumigation, allelopathy or push-pull strategy: repelling pests to direct them to an area where they can be controlled).
- Encouraging pollinators and crop auxiliaries (reservoir plants, flower strips, nectariferous plants, etc.).
- Preservation and improvement of the soil fertility: physical fertility (improved structure), chemical fertility (nutrient supply) and biological fertility.
- Reduction of the risk of water pollution (leaching of plant protection products) and of net greenhouse gas emissions (carbon sequestration via photosynthesis and storage in biomass, and increased albedo effect).
- Contribution to landscape diversity and aesthetics.
The quantity and quality of these services depend on the objectives set and the pedoclimate under consideration. There may be constraints (financial or technical) and potential disservices (attraction of pests, competition with the following or associated crop). For example, a faba bean decompacts the soil thanks to its taproot and provides nitrogen for the following crop, but destroying it too late can dry out the soil and adversely affect the following crop development.
The use of service plants in crop rotations is a valuable agroecological lever for building up farm resilience and promoting ecological continuity at the landscape level.