weed

from Wikipedia, the free encyclopedia
Corn poppy and cornflower as undesirable weeds in cereals
Oat field with thistles

When weeds are called plants of spontaneous "accompanying vegetation" in crops of cultivated plants, grassland or gardens that are not there specifically grown and from the seed potential of the ground over root suckers come or Zuflug the seeds to develop. Alternatively, weeds or cultivated plant companions are often used today . The process of removing weeds using tools is called weeding .

In common parlance, the main criterion for designating a plant as a weed is that it is undesirable. Depending on the point of view of the person concerned, a feared economic damage as a result of competition or an aesthetic reason can be the trigger for the disorder.

These can be unwanted wild plants or crop plants that grow spontaneously. The term is not limited to herbs in the actual sense, but also includes grasses , ferns , mosses and woody plants. In the field of plant protection, undesirable grasses are also called “ weed ”.

Herbicide-resistant weeds are known as superweeds .

Disambiguation

The interpretation of the term weed depends heavily on subjective human perception. Some plant species are generally referred to as weeds. This is fundamentally wrong, as the same species can appear as weeds, useful plants , medicinal herbs , pointer plants, or in some other form. It only becomes a weed when it is perceived as "disturbing". Different views on this often lead to neighborhood disputes, sometimes even to political debates. It doesn't matter whether a “weed” is a herbaceous or woody plant species.

In the course of the environmental movement in the 1980s, there was a demand to replace the term “weeds” with “weeds”. However, "wild herbs" is already used to designate wild edible herbaceous plants, so that this requirement could not be enforced. The term accompanying growth is used in forestry , as both negative and positive side effects can be expected.

The ecological agriculture has a more nuanced perspective on the "weeds" that they do not exclusively as harmful plant, but also as an integral part of the ecosystem looks. Therefore, the negative occupied term "weed" is there rejected and the neutral name Beikraut preferred. The scientific name for arable weeds is segetal plants .

Plants are usually called weeds if they:

  • compete with a specifically cultivated crop for growth factors such as nutrients , light and water, so that the crop does not achieve the desired yield
  • complicate the management of an area by z. B. get into the crop and contaminate it (see seed cleaning )
  • have a massive distribution (through flight of seeds, extremely long root plexuses, displacement of competitors) and thus there is a risk that they will migrate to areas to be protected;
  • disturb the aesthetic perception of a person, for example in ornamental gardens, parks , on lawns or areas that are to be kept free of vegetation
  • make the yield of an area unusable due to their poisonous effect (example autumn crocus in hay )
  • to displace plants ancestral as neophytes from their locations

Herbology

The field of weed science has developed into an independent scientific discipline under the name Herbology in recent decades. The department deals with questions of weed biology, weed ecology and weed control and the resulting influences on the environment.

Arable weeds

Weeds naturally create problems for agriculture . The weed populations on an agriculturally used area are influenced by factors such as crop rotation , type of soil cultivation , mechanical care measures (e.g. with a tine weeder ) and others. The use of weed control agents ( herbicides ), which threaten the existence of many field weeds, is widespread today .

According to calculations of the herbicide industry-related Weed Science Society of America weeds could without weed control damage of up to 27 billion US dollars in corn and 16 billion US dollars in soybean in the US and Canada cause. Without weed control, the average harvests would be 52% (corn) and 49.5% (soybean) lower. In 1996 it was estimated that weeds caused a yield reduction of between 20% and 40%. If, on the other hand, mechanical care measures are used to control weeds, the respective yields decline only slightly.

history

The problem of weeds is as old as agriculture itself. In the Bible it is mentioned as God's punishment for the fall of man . In Genesis it says (chapter 3, 17-18): “So the soil is cursed because of you. You will eat of him with hardship all the days of your life. He lets thorns and thistles grow for you and you have to eat the plants of the field. "

Since the development of weeds is closely interwoven with that of agriculture, it probably originated in the area of ​​the fertile crescent moon . From there they advanced to Central Europe with agriculture. The first rural settlements date the beginnings of agriculture in Europe to 5000 BC. The weeds that came to Europe in this way are counted among the archaeophytes.

With the hook plow it was not possible to turn the entire field surface, the weed vegetation was hardly disturbed between the plow furrows. The fields were heavily interspersed with ruderal and pasture plants. Archaeological studies found that the species composition remained essentially the same from the Neolithic (around 4000 BC) to the Bronze Age (around 1250 BC) (with decreasing frequency: white goosefoot , knotweed , common kale , pigeon Trespe , small-fruited burdock bedstraw , dock species, tuberous timothy ( Phleum nodosum ), common bluegrass , flea knotweed and various vetches ).

During the Roman era , many types of weed that are typical of grain fields today were introduced with seeds from Mediterranean countries.

During the Middle Ages , most of the fields were tilled according to the three-field farming principle (winter grain - summer grain - fallow land ). During the fallow the cattle were driven into the fields. Even the young crops were grazed, which did little damage. The weed was more suppressed than the corn which only stronger through the grazing bestockte . Targeted weed control was carried out by weeding, the weed populations contained many pasture plants.

In the 18th century the improved three-field economy (winter grain - summer grain - root crops ) emerged. The typical ground and strawberry weed corridors emerged.

Competition from weeds

Due to weeds, up to 100,000 germinable seeds can be found on one square meter of arable land at the beginning of the growing season . B. with spring barley only a seed quantity of 400 m −2 is sown.

Annual seed production

Seed production of some weeds
botanical name German name Seed production
per plant
Veronica persica Persian speedwell 00.050 ... 100
Avena fatua Flight oats 00.100 ... 450
Galium aparine Burdock bedstraw 00.300 ... 450
Senecio vulgaris Common groundsel 01,100 ... 1,200
Capsella bursa-pastoris Ordinary shepherd's purse 03,500 ... 4,000
Cirsium arvense Field thistle 04,000 ... 5,000
Taraxacum officinale Common dandelion 05,000 (200 per capita)
Portulaca oleracea Purslane 10,000
Stellaria media Common chickweed 15,000
Papaver rhoeas Corn poppy 14,000 ... 19,500
Tripleurospermum maritimum
  subsp. inodorum 		Odorless chamomile 15,000 ... 19,000
Echinochloa crus-galli Chicken millet 02,000 ... 40,000
Chamaenerion angustifolium Narrow-leaved willowherb 80,000
Eleusine indica Indian finger millet 50,000 ... 135,000
Digitaria sanguinalis Blood-red foxglove 02,000 ... 150,000
Chenopodium album Goosefoot 13,000 ... 500,000
Triticum aestivum Common wheat 00.090 ... 100

Use value of weeds

Weeds encourage the soil to tine by rooting the soil between the cultivated plants and protecting it from direct sunlight. They can counteract erosion in fields that remain without vegetation for a long time (e.g. maize ) . The same applies to vineyards - in some cases, vegetation with low plants makes it possible to drive on.

Wild plants are an important gene reservoir that should be preserved if possible with a view to later use. Some crops, such as beet , lamb's lettuce and rye , were originally weeds. A number of weeds are important medicinal plants , e.g. B. Chamomile , ribwort and field horsetail .

As part of biological pest control , weeds in particular flowering provide parasitic wasps , caterpillar flies and other beneficial insects with nectar and pollen as food. Weeds infested with pests also enable beneficial insects to survive in the field as long as no infested crops are available.

Belonging to plant families

In Europe around 650 plant species can be counted among the field weeds. Half of them belong to the sunflower , cruciferous , carnation and sweet grass families . These families are also very species-rich outside of the weed communities. What is more striking is the disproportionate proportion of the goosefoot , foxtail and knotweed plants .

Weeds are often “seed weeds” with a short generation duration and sometimes several generations per year. The number of seeds per plant can be extraordinarily high, with the common shepherd's purse a vigorous plant can develop 90,000 seeds. If weed seeds get a few centimeters into the ground, for example through plowing, they can survive there for many years. In this context one speaks of the seed bank of the soil.

Perennial weeds are perennial plants that can regenerate quickly from their roots or rhizomes . These include creeping thistle , field bindweed , couch grass , goutweed , some dock TYPES and horsetail . These species can even be promoted by inconsistent mechanical control, since they also sprout from root and rhizome fragments.

In Central European forestry, for example, the common bird cherry ( Prunus padus ) or the black locust ( Robinia pseudoacacia ) are among the "unpopular" plant species.

Field weed societies

The composition of the weed populations in the fields depends on a number of factors. Even more important than the respective crop is the time of the last “radical” cultivation measure, be it through hoeing , plowing , harrowing , steaming or the application of a herbicide .

If the last tillage is in late autumn or early spring, a grain-weed community will arise even if no grain is grown in the field that year. If this last cultural measure takes place in May or June, a so-called hack weed society is formed . The reason for this are different dormancy and germination temperatures of the weed seeds.

The properties of the respective soil also have an impact on the weed population. The influences of the soil reaction , the nutrient and water supply and the soil type are particularly important . The climate and the existing seed bank at the respective location are also important.

The weed communities have been regrouped in the plant-sociological system over the last 80 years, for example by Braun-Blanquet in 1936 or Oberdorfer in 1957. The last comprehensive reorganization was in 1990 by Hüppe and Hofmeister.

In addition to the classification based on plant physiological systematics, there are also classifications according to growth, life form, diasporic spread, temperature optimum and an ecological sociological classification.

Conservation aspects

In Germany, one third of the approximately 270 plant species that are mainly found in field weeds and short-lived ruderal vegetation are regionally endangered or extinct. Preserving these species by maintaining traditional farming practices would be very expensive. Their conservation in botanical gardens is difficult because this plant almost inevitably read are those important (weeds) characteristics as the germ default missing.

In the 1980s , agricultural verge programs were introduced in several federal states with great success . Here, farmers undertake in return for compensation, not the edges of fields with pesticides to treat. In many federal states, interest in the field verge programs has decreased significantly from the 1990s to the present day. The risk situation for the Segetal flora documented in the Red Lists has not improved (more detailed description in the Karlstadt position paper). For this reason, the nationwide protective field project “100 fields for diversity” was launched in 2007. Switching to organic farming can also help preserve these endangered species. With special nature conservation standards, the effectiveness of organic farming for the protection of segetal species is optimized, especially in and on the edge of large protected areas. Another very effective way of protection are "field-internal nature reserves": These are very small areas within a field such as B. sandy knolls that create high quality living spaces and networking structures.

In addition to the plant species themselves, various animal groups are also affected by the decline in weeds, as these animals partially or completely feed on pollen , nectar , stems and leaves, roots or seeds of the weeds or use the weeds as habitat . The reduced availability of weed seeds has, among other things, contributed to a sharp decline in granivorous (seed-eating) bird species in the agricultural landscape in recent decades .

Species overview

The following table is the simplified version of a similar table in Wilmanns (1993). It is intended to provide an initial overview of which plant species occur on which arable sites (see also pointer plants ).

in all fields, but also in ruderal societies Common shepherd's purse , white goose foot , small cranesbill , common groundsel , vegetable goose thistle , chickweed , odorless beach chamomile
in fields and gardens, relatively independent of the nutrient supply Anagallis arvensis , Lamium Amplexicaule , Lamium purpureum , Myosotis arvensis , wild buckwheat , flea knotweed , field sow thistle , field speedwell , field pansy
on soils poor in base (acidic soil reaction , poor in nutrients) Field chamomile , field radish , annual ball , field spark , field cress , small sorrel in winter crops Common windstalk , cornflower , narrow-leaved vetch , wire-haired vetch
in root crop fields on sandy soils Blood-red foxglove , common heron-beak , hairy buttonwort , red-bristle millet , green-bristle millet
in root crop fields on clay soils Many-seeded goosefoot , hornwort , upright wood sorrel
on soils rich in bases ( calcareous , nutrient-rich) Dog parsley , blackgrass , oats , Geranium dissectum , poppy , mustard , Thlaspi arvense , speedwell in winter crops Ordinary field larkspur , Small spurge , Lathyrus tuberosus , Lithospermum arvense , Finkensame , Ranunculus arvensis , serrated lettuce
in root crop fields Solstice Spurge , Garden Spurge , Common Earth Smoke

Modern weeds

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.
Giant hogweed

In addition to the "classic weeds", "modern weeds" as invading plants ( neophytes ) cause serious problems due to the rapid spread of agriculture , forestry and nature conservation . On the one hand, they were introduced - rather unintentionally - through modern mobility (such as the giant hogweed ), on the other hand, they were imported according to plan, for example for limited greening purposes, and their spread could no longer be contained ( e.g. ornamental quince , vinegar tree , glandular balsam) or late bird cherry ).

See also

literature

Web links

Wiktionary: weeds  - explanations of meanings, word origins, synonyms, translations
Commons : Weeds (plants)  - Collection of images, videos and audio files
Wikiquote: Weed  Quotes

Individual evidence

  1. ↑ supporters and Prädidialmitglieder the Weed Science Society of America = WSSA .
  2. ↑ Left uncontrolled, weeds would cost billions in economic losses every year. at K-State Research and Extension News , May 16, 2016.
  3. ↑ Erich-Christian Oerke, Ulrike Steiner: Yield losses and plant protection. The cultivation situation for the economically most important crops. In: Series of publications by the German Phytomedical Society. tape 6 . Ulmer Verlag, 1996.
  4. ↑ Federal Office for Consumer Protection and Food Safety (Ed.): Position paper of the Advisory Board for Sustainable Crop Production . Dare to grow more weeds: A plea for a change of perspective in weed control in arable farming. October 9, 2019 ( bund.de [PDF; 71 kB ; accessed on November 20, 2019]).
  5. ↑ Ulrich Willerding: On the development of arable weed societies in the period from the Neolithic to the modern age in The prehistoric man and his environment. In: Forsch. U. Report prehistory and early history Bad.-Wütt. No. 31 . Stuttgart 1988, p. 31-41 .
  6. ↑ Ernst Burrichter, Joachim Hüppe, Richard Pott: Agricultural enrichment and impoverishment of vegetation in a historical perspective . In: Phytocoenologia . tape 23 , no. 1-4 , December 15, 1993, ISSN  0340-269X , pp. 427–447 , doi : 10.1127 / phyto / 23/1993/427 ( schweizerbart.de [accessed on March 14, 2019]).
  7. ^ A b Peter Zwerger, Hans Ulrich Ammon: Weeds - Ecology and Control; 105 tables . Ulmer, Stuttgart (Hohenheim) 2002, ISBN 3-8001-3846-8 .
  8. ↑ Thomas Eggers: Becoming and changing arable weed vegetation. In: Otti Wilmanns, Reinhold Tüxen (Ed.): Becoming and decaying plant communities. In: Reports of the International Symposia of the International Association for Vegetation Science. Volume 22, 1979, ISBN 3-7682-1218-1 , pp. 503-527.
  9. ↑ Andrew H. Cobb, John PH Reade: Herbicides and Plant Physiology . 2nd Edition. Wiley-Blackwell, Newport, Shropshire 2010, ISBN 978-1-4051-2935-0 , pp. 12 (English).
  10. ↑ a b Otti Wilmanns : Ecological Plant Sociology. 5th edition. 1993. In: Uni pocket books. Volume 269, Quelle & Meyer, Heidelberg, ISBN 3-8252-0269-0 , pp. 130-148.
  11. ↑ Heinz Ellenberg : Vegetation of Central Europe with the Alps in an ecological, dynamic and historical perspective (=  UTB for science. Large series . Volume 8104 ). 5th, heavily changed and improved edition. Eugen Ulmer, Stuttgart (Hohenheim) 1996, ISBN 3-8252-8104-3 .
  12. ↑ Joachim Hüppe, Heinrich Hofmeister: Syntaxonomic version and overview of the field weed societies in the Federal Republic of Germany. In: Reports of the Reinhold-Tüxen-Gesellschaft . Volume 2, 1990, pp. 61-81.
  13. ↑ Thomas van Elsen, Matthias Berg, Detlev Drenckhahn, Franz-G. Dunkel, Thomas Eggers, Eckhard Garve, Bernhard Kaiser, Hubert Marquart, Dietmar Pilotek, Dieter Rodi, Gisela Wicke: Wild herb protection - background, development tendencies and perspectives. Annex to the Karlstadt position paper. In: Nature conservation and landscape planning. Volume 37, 2005, No. 9, pp. 284–286, (PDF file of a draft version; 230 kB) .
  14. ↑ Thomas van Elsen, Matthias Berg, Detlev Drenckhahn, Franz-G. Dunkel, Thomas Eggers, Eckhard Garve, Bernhard Kaiser, Hubert Marquart, Dietmar Pilotek, Dieter Rodi, Gisela Wicke: Karlstadter position paper on the protection of wild herbs. In: Journal of Plant Diseases and Plant Protection. Special issue XX, 2006, pp. 527-533, Stuttgart, (PDF file; 230 kB).
  15. ↑ 100 fields for diversity .
  16. ↑ Frieben, B .; Prolingheuer, U .; Wildung, M. & Meyerhoff, E. (2012): Enhancement of the agricultural landscape through organic farming . Conservation and Landscape Planning 44: 108–114, 154–160.
  17. ↑ Gottwald F. & Stein-Bachinger K. (2015): Agriculture for biodiversity - A nature conservation standard for ecologically managed businesses . www.landwirtschaft-artenvielfalt.de, 208 pp .
  18. ↑ Werner, A .; Berger, G .; Glemnitz, M .; Stachow, U .; Platen, R .; Stein-Bachinger, K .; Hufnagel, J .; Wurbs, A .; Schröder, B. (2011): Importance of agricultural production for biological diversity in the agricultural landscape . - In: New ways for the conservation and sustainable use of agrobiodiversity: Effectiveness and perspectives of support measures in the agricultural sector; BMELV conference proceedings: 70-84; Bonn (IBV) .
  19. ↑ B. Gerowitt, E. Bertke, S.-K. Hespelt, C. Tute: Towards multifunctional agriculture - weeds as ecological goods? In: Weed Research. Volume 43, No. 4, 2003, pp. 227-235 doi: 10.1046 / j.1365-3180.2003.00340.x .
  20. ↑ EJP Marshall, VK Brown, ND Boatman, PJW Lutman, GR Squire, LK Ward: The role of weeds in supporting biological diversity within crop fields. In: Weed Research. Volume 43, No. 2, 2003, pp. 77-89, doi: 10.1046 / j.1365-3180.2003.00326.x .
  21. Jump up ↑ John R. Krebs, Jeremy D. Wilson, Richard B. Bradbury, Gavin M. Siriwardena: The second silent spring? In: Nature . Volume 400, No. 6745, 1999, pp. 611-612, doi: 10.1038 / 23127 .
  22. ↑ D. Moorcroft, MJ Whittingham, RB Bradbury, JD Wilson: The selection of stubble fields by wintering granivorous birds reflects vegetation cover and food abundance. In: Journal of Applied Ecology. Volume 39, No. 3, 2002, pp. 535-547, doi: 10.1046 / j.1365-2664.2002.00730.x .