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
Competition for light
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