Читать книгу Herbicides and Plant Physiology - Andrew H. Cobb - Страница 16

The most obvious problem caused by weeds is the reduction of yield through direct competition for light, space, nutrients and water. Weeds can have many further effects on the use of land, as illustrated in Table 1.2.

Table 1.2 Problems caused by weeds.

Source: Naylor, R.E.L. and Lutman, P.J. (2002) What is a weed? In: Naylor, R.E.L. (ed.) Weed Management Handbook, 9th edn. Oxford: Blackwell Publishing/BCPC. Reproduced with permission of John Wiley & Sons.

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