What livestock farmers need to consider when applying rangeland management principles
Compiled by Erastus Ngaruka, Technical Officer: Livestock in Agribank’s Agri Advisory Services Division.
Livestock (cattle, goats and sheep) have different foraging preferences and habits. Cattle and sheep are referred to as grazers because they predominantly depend on grazing, mainly on grass, and other herbaceous plants such as forbs. Goats are referred to as browsers because their diet is mainly from browsing on leaves and twigs from trees and shrubs.
However, all these animals can opportunistically adjust their foraging preferences and utilize any available forage resource present. For example, cattle browse or utilize trees and shrubs in times of grass scarcity, and goats have been observed to significantly utilize grazing material like cattle and sheep.
These foraging preferences have an influence of rangeland productivity.
In general, the main factors that influences rangeland productivity are; utilization or herbivory, plant competition and rainfall. Herbivory is also beneficial in stimulating re-growth, – when older tillers (stems) are harvested, new ones can emerge. On the other hand, if the grass is not used (grazed) for a long time, it becomes moribund or dies. Thus, the grass should be utilized sustainably. The most intense form of herbivory is grazing, and with poor management, overgrazing results.
Overgrazing is the common cause of degradation of rangelands or grazing areas in Namibia. It is the excessive use or harvesting of grass plants by the grazers (e.g. cattle). The impact of grazers is not only on grass utilization, but also on the soil status. Grasses have an important role of protecting and keeping the soil healthy and fertile. For example, the grass roots and the organic matter are critical to stabilize or keep the soil intact as they hold soil particles firmly together.
Overgrazing decreases grass density and cover, exposing the soil to adverse conditions such as erosion and extreme temperatures, amongst others. As a result, the soil loses its moisture holding capacity, the organic matter, its stability and its ability to support vulnerable plants, mainly grasses.
In addition, when grass is overused or is constantly grazed with no rest, it gradually loses its competitive ability with other opportunistic plants, such as the woody ones (trees/shrubs/bush). These woody plants take advantage, increase in density and aggressively invade the land. This is termed “bush encroachment”.
The encroacher bushes are characteristically efficient in utilizing a limited resource such as water. They have an extensive deep root system and can extract water and nutrients from any soil depth. Their canopy captures sunlight and intercept rain drops, thus depriving the vulnerable or weakened grass species of these resources.
Managing grazing may have varying approaches, but there are basic principles that farmers need to consider as set out in the National Rangeland Management Policy and Strategy (NRMPS-2012).
These are; Knowing your resource base, manage for effective recovery and rest, manage for effective utilization of plants, enhancing soil condition, addressing bush encroachment, drought planning, monitoring of the resource base, planning land use infrastructure, and ultimately putting all these principles together.
Further, the land’s carrying capacity is not solely based on its size. This judgement should be based on the available grazeable material versus the amount of grazeable material required by the animals over a defined period. On that, one critical consideration should be the “allowable grazing duration versus the allowable resting duration”. Here, the “graze shorter – rest longer” rule should apply together with a proper monitoring of the reaction of the grazing material and the soil. For that, view the grazing land not only from the “horizontal”, but from the “vertical” perspective as well.
In conclusion, the principles and rules may not universally apply to the varying grazing circumstances and practices of commercial and communal farmers but it is important that farmers understand the underlying forces in the process of rangeland degradation, and thus, explore appropriate and sustainable restoration practices.