Adventitious

An adventitious is, in Botanique, a vegetable species foreign with the indigenous Flore of a territory into which it is accidentally introduced and can settle.

In Agronomy, this term indicates a herbaceous Plante or woody undesirable at the place where it is. It is also used as synonym of Mauvaise grass .

Nature of the adventitious ones

Within the framework of the agricultural production, the adventitious ones can be not cultivated species installed in a field, but also push back them of a preceding culture:

  • pushes back cereals in a culture of colza,
  • pushes back potatoes in a cereal field or beets,
  • etc

The adventitious ones can be:

  • of the Hardy perennials, which reproduce in a vegetative way, or which remains in place several years: Grass, Laiteron of the fields, Bindweed, Tussilage, Thistle…
  • of the annual Plantes, generally, which reproduce by seed, with frequently a strong potential of reproduction: amaranth, Poppy, Chénopode, Sétaire, Wild oats, speedwell, Stellar…

Seeds

The seeds of adventitious are characterized by:

  • a great longevity, related to a resistance to the desiccation or asphyxiation during a major hiding, thanks to their more or less impermeable tegument with water and the air.
  • a large stock in the ground, about 20 to 400 million per hectare on 10 to 15 cm of depth, of which 5 to 10% would represent the flora of surface.

Periods of germination

The preferential periods of germination of adventitious vary according to the species:

  • germination of spring: Chénopode, Orache, Joined again…

Determination of the adventitious ones

The reasoned use of the Herbicide S requires the identification by the Agriculteur S of bad grasses present in their pieces, in order to avoid useless treatments.

In a coalfield given, the number of principal the Species S of bad grasses to be known is about thirty. In addition, some Espèce S are frequently associated with a given culture: Chénopode and amaranth in the Beet S, Gaillet and speedwell in the Cereal S, etc

Unfavourable actions on the cultures

The noxiousness of bad grasses arises in four forms:

  • competition with regard to the sunning, of water or the nutritive matters. The adventitious ones take their food with the detriment of the cultures. This competition is function of the nature of adventitious, the population density, the influence of the manure and the climatic conditions favorable to bad grasses.

  • the depreciation of harvests related to the presence of fragments of bad grasses which decrease the quality of the production, or of seeds the adventitious ones like the morelle one or the corn-cockle, which are likely to cause a bad taste or to induce a toxic effect. In the ensilage or harvest in dryness of pasture, the presence of Buttercup S, Prêle S, Fern S, Colchique S, or Mercuriale S can cause accidents, whereas they are not consumed in green by the animals.

  • the difficulty of collecting can be caused by the Gaillet or the Chénopode during the harvest of beets by the stuffing of the machines. The presence of Graminée S adventitious can support pours it Céréale S and thus affect the implementation of harvest.

  • the Devastating development of the S and the diseases can be favoured by the microclimate created by adventitious invading, or their role of tank or plants relay for the Virus, the Bactérie S, the Champignon S, the Acarien S or the Insecte S.

Harmful effect of the fight against the adventitious ones

In France like a great number of countries, the use of Weedkiller S to control the development of bad grasses involved a largely spread contamination of surface water and subterranean water by active substances of weeding, in particular of the chemical family of the Triazine S: Simazine, Terbuthylazine…

For this reason, the Herbicide S of the family of the Triazine S are the subject of measurements of prohibition in France.

The possibility of the development of cultures of transgenic Corn, presenting a tolerance to Weedkiller S, like the Glufosinate ammonium with the event of transformation T25, causes interrogations. Employees in the respect of the agricultural good practices, these GMO can reduce the consumption of Herbicide S. However, a not reasoned use of weeding can induce new water pollutions.

Means of treatment

The use of green Manure is a biological technique making it possible to limit the proliferation of the adventitious ones.

See too

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