Also, species with the potential to reduce pest populations should be chosen, while those that harbor diseases or arthropod pests of the cash crops should be avoided. Common cool-season legumes used as cover crops in annual rotations include vetches, winter pea and bell bean. For similar reasons, cereal grains are usually preferred over other grass species, such as bromes, in annual rotations. In choosing warm- season cover crops, the ability to perform well with minimal irrigation is often of primary consideration. Legume species in this category include cowpea, hyacinth bean and sunnhemp.
Typical grass cover crops for warm conditions include sudangrass and sorghum.
Using these species can reduce or eliminate the costs associated with purchasing and sowing seed each year. Although many of these species compete effectively with weeds if properly managed, in some cases the reseeding cover may revert back to resident vegetation within a few years. It may be necessary to resow the cover crop in 3 to 5 years. With some cover crops, self-reseeding can fail if insufficient moisture is available in the spring to mature the seed for the next year s cover crop. This problem will most likely occur if the row middles cannot be irrigated, such as when using drip irrigation.