MIXTURES
Selection criteria
The problems related to the choice of mixtures involve defining the number of components and therefore indicating the species and varieties to be associated based on environmental adaptation, associative behavior, and methods of utilization (haymaking, grazing, etc.).
In more favorable areas (plains with fertile soils), it is advisable to reduce the mixture to only two components (one grass and one legume). In more disadvantaged areas (less favorable climate and poorer soils), mixtures of 3-5 species are recommended. Only in particular situations (hilly and mountainous areas or less fertile soils) may the use of more complex mixtures be justified.
The aggressiveness of the components (which should be similar to avoid one prevailing over the others) is a very important agronomic characteristic but is not easy to identify.
Other important selection criteria include persistence and growth rhythm. For these two requirements, one can adhere to two opposing principles: that of similar characteristics for longevity and development rates, and that of complementary characteristics.
The criterion of behavioral similarity is advisable when the mixture is bifid and when one wants to achieve all the advantages of association. The criterion of complementarity is valid when the number of constituents is high and when operating in difficult environments where the needs for balance prevail over productive ones.
A different longevity of the components can be useful in anticipation of a succession, as in the case of red clover, which, being less persistent, will later be replaced by other legumes such as bird’s-foot trefoil or white clover; or in the case of using Italian ryegrass to increase productivity in the first year and allow slower but more persistent grasses (Dactylis glomerata, Festuca arundinacea, Poa pratensis) to take its place.
Different earliness, which translates into a lack of synchronization of phenological phases, can also be advantageous when anticipating less timely utilizations.
However, the choice and proportion of species to associate must be primarily linked to the planned methods of utilization (cutting or grazing) and the type of animals for which the mixture is intended.
The table below shows the associative behavior of some species during the establishment phase and in established swards in Italian environments.
For mowing, the choice of the components of the association should fall, depending on the areas, on: Lolium multiflorum, Festuca arundinacea, Dactylis glomerata, Phleum pratense, Bromus spp, Medicago sativa, Trifolium repens (Ladino), Red clover, Hedysarum coronarium, Onobrychis viciifolia.
For haymaking purposes, it is preferable to choose species that dry more quickly, such as Festuca arundinacea, Dactylis glomerata, Festuca pratensis, Phleum pratense and, among the legumes, which are slower to dry, Trifolium pratense and Medicago sativa.
In view of grazing uses, the species to be used to form the associations must be chosen, depending on the environments, from: Lolium perenne, Trifolium repens, Dactylis glomerata (some cultivars), Poa pratensi (fresh areas), and Lolium rigidum, Dactylis glomerata (some cultivars). Medicago polymorpha, Trifolium subterraneum for Mediterranean areas.