GRAZING MANAGEMENT FACTORS
Length of the grazing period is a powerful tool in stopping overgrazing and improving land health. By reducing grazing periods to a minimum number of days, livestock are denied the opportunity to regraze or browse plants that are still recovering from a previous defoliation episode (See definition of overgrazing, Chapter 6). During conditions of rapid vegetation growth when soil is moist, temperatures are moderate, and light is abundant, short grazing periods are necessary to prevent a recovering forage plant from being grazed again. When plant growth slows or when plants are dormant, grazing periods can be much longer without the risk of overgrazing. Along with stock density, manipulation of the length of grazing periods has given managers an important new tool in improving and protecting range condition.
Plants, soils, and riparian areas must be periodically protected from herbivory and other impacts of livestock and/or big game. Plants need sufficient time to recover from the effects of grazing or browsing and to store food reserves for winter and other times of dormancy. Rest periods allow replacement of senescent plants by new seedlings and tillers. Soils also must have time to be relieved of compaction incurred through trampling, to accumulate new litter reserves, and to recharge with water. Riparian areas require time to re-armour, to rebuild filtering systems, and to recover habitat values for other uses. By controlling the length of rest periods, managers can ensure that plants, soils, and riparian areas receive sufficient rest, but not excessive rest. When rest periods become too long, vegetation may stagnate and offer less desirable forage, cover, and habitat conditions for diverse plant and animal populations.
Depending on the riparian area objectives, finances, and the time prescribed to reach objectives, non-use (rest) will at times be the best alternative for achieving rapid results on some types of rangeland. This is especially true in non-brittle environments.
Class of Livestock
Sheep, goats, cattle, and horses all have behavioural characteristics and diet preferences which make them more or less suited for particular environments and circumstances on rangeland. Age, breeds, and gender also influence animal behaviour and grazing characteristics. By knowing and understanding these varied animal characteristics, managers have added flexibility in applying grazing management as a tool. For example, some weedy plants that would be avoided by cattle will be readily consumed by sheep. Thus plant succession can be desirably altered by using a particular class of livestock. Because cattle nowadays are the primary type of livestock in use, the tool is more limited than it has been historically. (See Figure 6.?, Feeding Niches of Wild and Domestic Ungulates.)
Season of Use
Vegetation and soils respond differentially to grazing use depending on when they are exposed to livestock impacts. Managers have the option of selecting when livestock are introduced into a pasture and when they leave. This determines the season of use. When growing conditions for forage plants are very good - that is, when soil moisture is abundant, soil and air temperatures are warmer, days are long, and plants are growing rapidly, plants can recover very rapidly from grazing events. Later in the season, as growing conditions are less favourable, plants need longer recovery periods. While the start of the growing season may be as early as April, managers may choose to wait until May or June to begin the grazing season. Or they may choose to take an early short grazing harvest, let recovery occur in the favourable conditions that follow, and then harvest the regrown forage during the ensuing dormant period. This kind of management flexibility can favour the livestock producer as well as the forage plants.