Farmers should understand the various attributes that are key to determining the grazing value of an area.
07 July 2021 | Agriculture
Livestock farming in Namibia is dominated by grazing livestock, mainly cattle and sheep.
These animal species mainly depend on grass for their nutrition, Agribank's technical advisor for livestock and rangeland Erastus Ngaruka said.“When one describes a grazing area, there are several attributes that should be key to determining the grazing value of that area. These are grass species composition, frequency, abundance, density, and soil cover amongst others,” he said.
Basically, the quality of the grass plant can be attributed to its species, growth structure and life cycle.
According to Ngaruka, farmers commonly use the term palatability as an assertion of the quality of the grass. However, grasses have different levels of palatability.
A palatable grass is one that an animal is attracted to or selects amongst others to graze, and this is influenced by its smell, taste, nutrients and digestibility.
Therefore, Ngaruka said selective grazing becomes dangerous especially when species' diversity or composition is narrow, thus, leading to local extinction of extremely sensitive valuable grass species.
Grass life cycle
“One of the important attributes that farmers should understand is the grass life cycle or lifespan.”
According to him, there are two different lifespans under which grasses can be classified - annual and perennial. The annual grasses refer to grasses that have a lifespan of less than a year. They grow fast, produce seeds quickly and shed seeds for reseeding, and then the mother plant dies. Usually, annual grasses emerge with the first rainfall or are only seen during the wet season but disappear during the dry season, by August.
Ngaruka said many grazing areas in Namibia are dominated by these types of grasses as their dominance increases with rangeland degradation.
“On the other hand, perennial grasses have a longer life span or last for more years. “Unlike annuals, they do not die after shedding seeds, but only undergo a dormancy period during the dry season to conserve nutrients for regrowth from the same stump in the next rainy season.”
He said there are many different species of perennial grasses, however, not all are palatable or well utilised by grazing animals.
According to Ngaruka, the most valuable perennial grasses are more sensitive to continuous grazing; thus, their dominance decreases with overgrazing or rangeland degradation, which - in turn - gives rise to aggressive establishment of annual grasses.
“To make informed grazing management decisions, farmers need to know and understand the impact of the prevailing ecological perturbations, including herbivory, climate and intra-and inter-specific species competitions, amongst others. The reaction of the rangeland to these perturbations can be observed through its plant population establishment and distribution.”
He added that it is advisable that farmers engage in restorative practices on their rangelands. These include improving soil conditions, controlling bush densities, reintroducing the valuable perennial grasses by reseeding on their grazing areas, and cultivating them in gardens or crop fields.