In crop production, some method of weed control usually is needed to protect the crop. The purpose of weed control is to impede growth or to reduce the stand of weeds so that they do not imperil crop growth. A general aim is toward control the weed invasion in the crops.
Mechanical control includes hand weeding, hoeing, cultivation, mowing, clipping, and burning. These practices remove weeds or damage them suffiiently so that the crop has a competitive advantage.
Rotations of crops change environments in which weeds grow. Weeds often become established with a certain crop, and rotation of crops changes the scene in which weeds compete. Densely seeded crops or those with dense canopies have strong capacities to compete with weeds. Fertilization often helps crops to out compete weeds, and the competitive response of crops to fertilizers will vary, hence giving variable measures of control with crop rotations. Rotations of crops as a weed-control practice are addressed specifially later in this chapter.
Biological control involves introduction of an organism to destroy they weeds. Insects are the most common organisms used in this respect. Concerns always exist as to whether or not the insects introduced to eat weeds will turn to eating the crops after the weeds are eliminated. Weed-eating insects are not commonly available for
growers to utilize in crop production. Reclamations of range land from weed infestations in Australia and in western United States (see latter sections of this chapter) are often-cited examples of successful use of biological control. Farm animals also may be used in biological control. Weeds may be grazed by livestock after crops are
harvested. Sometimes livestock have been used in weed control in tree plantations. Geese may control weeds in strawberries.
Selective herbicides are used to control weeds in crops. The selection of herbicides available on the market is very large. An options for herbicides that are allowed in certifid organic practices. Some herbicidal soaps and organic acids are marketed and are certifible as organic, weed-control practices