Why do weeds cause problems?
Weed control is important for both the direct effects that weeds have on yield and production costs as well as the indirect effects they can have on grain quality. Specifically, the weeds
(1) decrease yields by direct competition for sunlight, nutrients, and water and/or by allelopathy.Allelopathy is the production of chemicals by the plant that inhibit the growth of surrounding plants.
For example, weed seeds in grain can cause the buyer price to be reduced. This effect is known as dockage.
Weed seeds in grain can also cause uneven moisture gradients in the grain causing loses in grain quality due to the formation of molds and/or due to cracking losses during milling.