Complementary Use Of Native And Introduced Pastures In Grazing Systems
A Combination Of Native Pastures And Introduced Forages In Grazing System Can Benefit Both Plants, Animals
Pasture and grazing management is an integral part of land stewardship for landowners with livestock, whether the property is big or small. Understanding how plants and animals interact in grazing systems is a critical component of sustainable land management and using a combination of native pastures and introduced forages can be beneficial to both the plants and animals across the landscape.
Grazing animals make foraging decisions as a result of several interacting factors. As animals harvest forage for nutrients, they respond to plant availability, accessibility, and palatability (i.e., how good something tastes), as well as interactions with other animals on the landscape. Preference for specific plants is exhibited by animals when they choose some plants over others, which is influenced by plant abundance, stage of plant growth (which is directly tied to palatability), and the array of plant species available. One factor that plays a role in many of these decisions is season of growth of various plant species, whether they are native plants in a rangeland setting or introduced forages in an improved pasture.
Characteristics of Native & Introduced Pastures
Native rangeland is comprised primarily of native grasses, forbs, and shrubs. These perennial-dominated systems are generally very diverse and offer grazing animals a heterogeneous selection of forage species. Native rangeland provides land managers a system that can be less intensively managed, requires very low input costs, and is relatively drought tolerant when managed correctly. Native rangeland species are well-adapted to site conditions such as soil type and annual precipitation because they evolved on these landscapes.
In contrast, introduced pastures (i.e., pastures planted with non-native forage species) generally offer a more homogeneous selection of either perennial or annual forage to grazing animals. Many land managers often choose to plant perennial grasses or perennial grass/ legume mixes. These systems generally require more intensive management and higher input costs for establishment and/or maintenance (e.g., seeding, fertilizer, fencing, etc.) than native rangeland. Depending on the species, they can also be somewhat less drought tolerant. Land managers often choose to use introduced pastures because of their potential for higher yields than native rangeland; their ability to offer higher quality forage at specific times of the year than native rangeland can provide, specifically in the spring and fall in Montana; their resiliency to grazing; the flexibility they offer managers in grazing systems; and their ability to withstand greater grazing pressure.
Seasonality of Forages
When considering how to best use a combination of native and introduced forages, an important factor to consider is the seasonality of the forage (i.e., the season of active growth of the plants). Using a combination of forages that offer highquality feed at various times of the year can benefit grazing animals.
Cool-season species dominate most Montana landscapes and can offer year-round forage if managed correctly. These plants, whether native or introduced, initiate growth in the spring and generally complete their life cycle by mid-summer. Introduced grasses generally start growing earlier in the spring than native grasses and, therefore, can provide grazeable forage before native rangeland is ready to be grazed. If fall precipitation is adequate, coolseason, perennial grasses will green up again in the fall, offering additional high-quality forage for grazing animals at that time of year.
Examples of cool-season, introduced grasses that offer early spring forage and are adapted to early spring grazing are crested wheatgrass, Siberian wheatgrass, and Russian wildrye. Russian and Altai wildrye and crested wheatgrass all have the potential to regrow in the fall when conditions are favorable. All three species provide highquality forage in the fall and both wildrye species provide high-quality winter feed.
Warm-season species, which are less abundant in Montana due to our climate, begin growing in summer when temperatures are higher and can provide high-quality forage in summer and fall. Warm-season species can be used in areas suitable for their growth when management objectives include summer and fall grazing. Examples of warm-season species in parts of Montana include little and big bluestem and prairie sandreed. Management Considerations
When choosing introduced species to plant in pastures, it is important to consider the available moisture characteristics on the site, driven by annual precipitation and soils, and match species accordingly. In areas that are subirrigated (i.e., where water naturally occurs just below the ground’s surface) or where irrigation is available, species with higher moisture requirements can be considered (e.g., smooth brome, orchardgrass, meadow brome). For dryland pastures, the mean annual precipitation of the site should match the requirement of species that can grow and thrive with lower available moisture, such as crested wheatgrass, Russian wildrye, and pubescent wheatgrass.
In a complementary grazing program where native and introduced forages are used, timing of grazing is of primary concern to benefit both the forage and the grazing animal. Graze cool-season, introduced forages early in the spring while native rangeland is still maturing. It is important to consider that some cool-season species tolerate early spring grazing better than others. For example, crested wheatgrass, and Russian wildrye are very tolerant of early spring grazing, while Altai and basin wildryes and pubescent and intermediate wheatgrasses are less tolerant at that time of year. Graze pastures with species tolerant to spring grazing first in the spring and remove livestock early enough that there is sufficient soil moisture for those plants to regrow. This will offer an opportunity for fall grazing on these pastures.
Due to the differences in timing of growth of native and introduced forages, it is advised to fence native rangeland separately from introduced pastures. This strategy is especially important to sustain native rangeland plants where spring grazing occurs. It is well documented that grazing animals will preferentially graze native species over introduced species in the spring, potentially damaging the native plant community if grazed moderately to heavily for consecutive years.
