Although there are about 10,000 species of grasses and 12,000 legume species in the world, only about 40 are used for cultivation for hay, silage, and pastures. A forage manager must be familiar with the characteristics of these important grasses and legumes and a few miscellaneous forages that will be productive in his/her area. Following selection of a species, there is still another step to final selection - cultivar selection. The term cultivar originated from the phrase cultivated variety which means a variety that was purposely grown. Variety and cultivar are now mosty equivalent terms in the USA, with cultivar the more accurate term.
Forage breeders carefully choose plants showing strong characteristics, such as resistance to drought, winter hardiness, or shade tolerance, and selectively breed to produce seed that will provide advantageous traits in the resulting crosses. Since different farmers have different needs and locations have different characteristics, there are often many varieties of a single species. Forage breeding is more difficult than grain crop breeding. The diversity in forage crops: grasses, legumes, forbs or sedges; annual or perennial; warm or cool season; bunch or sod-forming; single species or mixtures; cross or self-pollinating characteristics all contribute to the complexities of forage breeding.
Advantages of Mixtures
Understanding the growth and regrowth habits of a forages species is an important aspect of making appropriate management decisions. However, when several species are growing together, management decisions are more complicated.
Advantages of mixing several species (grasses, legumes, and forbs) include:
extending the growing season,
improving forage quality,
reducing N fertilizer requirements with legume N2 fixation,
adapting to a wider range of climatic and edaphic conditions,
reducing susceptibility to insect and disease pressure,
reducing hay drying time with grass-legume mixtures,
increasing the organic matter content of the soil with extensive, fibrous grass root systems,
reducing weed encroachment,
producing higher yields.
Cool-season grasses limitations
Cool-season grasses (annual and perennial ryegrass, orchardgrass, tall fescue, etc.) grow well in spring and autumn temperatures but are less productive in hot summer temperatures. Utilizing another grass or legume species that grow more vigorously in summer periods will increase forage production and maintain high quality feed.
For hay or silage production, mixtures should have a similar developmental sequence so that they can be harvested at the same time. Including legumes in the mix will often increase the protein content of the final product. This is important since growing animals have a high protein requirement. Adding legumes to the mix can improve both palatability and digestibility.
Although planting a legume with a grass does not mean that all N fertilizer needs will be met, fertilizer requirements will be reduced since grasses will eventually benefit from being planted in soil where legumes fixed atmospheric nitrogen.
A mixture of species in a pasture can adapt to a wider range of conditions. Some species tolerate wet conditions, some dry, some acid, and some alkaline or sodic soils. Mixtures provide some insurance to unexpected conditions or a variety of conditions which may occur in a single pasture. A rule for mixtures is "remember simplicity". A large number of species in a mixture, sometimes called a "shotgun" mixture should be avoided, due to complicated management implications. Often a single grass and a single legume will best provide the benefits intended.
The proper selection of grass/legume forage species is more difficult than selection of many other crops. There are many different species and mixtures to consider. A thorough knowledge of forage species and their characteristics is required for optimal economical and environmental approaches to forage production. Proper selection is crucial because it will greatly influence yield, plant longevity, required management, and profit.
To begin the selection process, edaphic, climatic, geophysical and biotic stress limitations need to be determined. Then, limitations need to be categorized as either fixed or variable. Fixed limitations will exclude many species from consideration. Variable limitations may become fixed due to financial or management resources. Define the needs and purposes for establishing a forage crop. A wise selection can be made after considering the previous steps and the grower's personal predisposition. Any failures should be carefully evaluated before reselection begins to determine what step in the selection model was incomplete. The goal is to match prevailing conditions with species characteristics.