Crop Weed Competition

Crop Weed Competition

Weeds appear much more adapted to agro-ecosystems than our crop plants. Without interference by man, weeds would easily wipe out the crop plants. This is because of their competition for nutrients, moisture, light, and space which are the principal factors of production of crop.

Competition for Nutrients

Weeds usually absorb mineral nutrients faster than many crop plants and accumulate them in their tissues in relatively larger amounts.

Competition for moisture

    • In general, for producing equal amounts of dry matter, weeds transpire more water than do most of our crop plants. It becomes increasingly critical with increasing soil moisture stress, as found in arid and semi-arid areas.
    • As a rule, C4 plants utilize water more efficiently resulting in more biomass per unit of water.
    • In weedy fields soil moisture may be exhausted by the time the crop reaches the fruiting stage, i.e. the peak consumptive use period of the crop, causing significant loss in crop yields.

Competition for light

    • It may commence very early in the crop season if a dense weed growth smothers the crop seedlings.
    • Unlike competition for nutrients and moisture, once weeds shade a crop plant, the increased light intensity cannot benefit it.

Competition for space (CO2)

Crop-weed competition for space is the requirement for CO2 and the competition may occur under extremely crowded plant community conditions. More efficient utilization of CO2 by C4 type weeds may contribute to their rapid growth over C3 type of crops


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