Herbicides and Plant Physiology. Andrew H. Cobb. Читать онлайн. Newlib. NEWLIB.NET

Автор: Andrew H. Cobb
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Биология
Год издания: 0
isbn: 9781119157700
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Problem Mechanism
Reduced crop yield Interference with access to light, water and nutrients
Reduced crop quality Admixture of contaminating seeds in arable crops Contamination of vegetable crops
Delayed harvesting Conservation of moisture may delay ripening and increase moisture level when harvested
Interference with harvesting Climbing plants making combining more difficult Vigorous, late‐growing weeds interfering with harvesting of potatoes and sugar beet
Interference with animal feeding Plants with spines or thorns inhibiting animal foraging
Poisoning Poisoning either through ingestion or through contact
Tainted animal products Imparting an undesirable flavour, e.g. to milk
Plant parasitism Competing for nutrients and water
Reduced crop health Acting as an alternative host for crop pests and diseases Increasing the amount of vegetation at the base of the crop, increasing moisture and disease
Reduced animal (and human) health Acting as an intermediate host or a vehicle for ingestion of pests and parasites Photosensitivity Teratogens Carcinogens
Safety hazard Reducing vision on roadsides Causing a risk of fire under electricity lines and on garage forecourts
Reduced wool quality Hooked seeds reducing the value of fleece
Water flow prevented Plant mass blocking ditches and irrigation channels
Allelopathy Releasing substances toxic to the growth of crop plants
Impacted crop establishment Vegetation preventing the establishment of young trees Competing for space with establishing crops

       1.4.1 Yield losses

      In the tropics, parasitic weed species from the genera Cuscuta (dodders), Orobranche (broomrapes) and Striga (witchweeds) can have a profound effect on a range of crops. They absorb nutrients directly from the crop plant, which may not set seed at all in the case of cereals such as sorghum.

      Weed control techniques are therefore aimed at the reduction in the competitive ability of weeds in a crop and the prevention of weed problems in a future crop. The former is increasingly based on chemical use, and the latter also requires suitable cultural and agronomic practices.

      Source: Lacey, A.J. (1985) Weed control. In: Haskell, P.T. (ed.) Pesticide Application: Principles and Practice. Oxford: Oxford University Press, pp. 456–485. Reproduced with permission of Oxford University Press.

Crop Yield loss (%) Country
Cassava 92 Venezuela
Cotton 90 Sudan
Groundnuts 60–90 Sudan
Onions 99 UK
Rice 30–73 Colombia
Sorghum 50–70 Tanzania/Nigeria
Sugar beet 78–93 Texas, USA
Sweet potatoes 78 West Indies
66 UK
Yams 72 Nigeria

      Source: Oerke, E.C., Dehne, H.W., Schonbeck, F. and Weber, A. (eds) (1995) Crop Production and Crop Protection: Estimated Losses in Major Food and Cash Crops. Amsterdam: Elsevier.

Estimated loss owing to weeds (%)
Africa 16.5
North America 11.4
Latin America 13.4
Asia 14.2
Europe 8.3

e-mail: [email protected]