By: Erastus Ngaruka
In Namibia, livestock production is heavily dependent on the rangeland, which grows a variety of forage resources including trees, shrubs, grasses and forbs. These plants differ in growth forms, structure, life cycles, habitat preferences and their uses.
Cattle, sheep and goats characterize livestock farming in the country and these animals have different forage preferences and foraging habits.
Cattle and sheep are predominant grazers (grass eating) whereas goats are browsers (eating leaves and twigs).
However, these animals can still utilize any forage resource available to meet their daily feed intake and nutritional needs.
For example, goats do eat grass and cattle also browse. When one describes a grazing area, several attributes should be key to determining the grazing value of that area. These are grass species composition, frequency, abundance, richness and density.
Fundamentally, the quality of the grass plant can be attributed to its species, growth structure and life cycle. Farmers commonly use the term palatability as an assertion of the quality of the grass, however, different grass species 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, selective grazing becomes dangerous especially when species diversity or composition is narrow, thus leading to the local extinction of very sensitive valuable grass species.
One of the important attributes that farmers should understand is the grass life cycle or life span.
There are two different life spans under which grasses can be classified, these are annual and perennial. Annual grasses refer to grasses that have a shorter life span 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, usually by August. 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 (stop growing) during the dry season to conserve nutrients for regrowth from the same stump in the next rainy season.
There are many different species of perennial grasses, however, not all are palatable or well utilized by grazing animals. The most valuable perennial grasses are more sensitive to continuous grazing; thus, their dominance decreases with overgrazing of 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 competition amongst others.
The reaction of the rangeland to these perturbations can be observed through its plant population establishment and distribution.
The dominant annual grasses in almost all grazing areas in Namibia currently include Schmidtia kalahariensis, Chloris virgata, Eragrostis porosa, Eneapogon cencroides, and Urochloa brachyura amongst others. The dominating perennial grasses are Stipagrostis uniplumis, Stipagrostis obtusa, Stipagrostis hochstetteriana, Eragrostis pallens, Eragrostis rigidior, and Aristida stipitata amongst others.
The most valuable perennial grasses such as Cenchrus ciliaris, Brachiaria nigropedata, Anthephora pubescens, and Schmidtia pappophoroides are only observed in well managed or least disturbed areas in some parts of the country.
Farmers can obtain more knowledge of these grasses from descriptive literature books (e.g. Grasses of Namibia) and can find common names as well.
These literature materials and information can be found on the internet, book shops, Namibia Botanical Research Institute, and university libraries amongst others.
It is advisable that farmers engage in restorative practices on their rangelands.
These include improving soil conditions, controlling bush densities, reintroducing valuable perennial grasses by reseeding their grazing areas, and cultivating them in gardens or crop fields.
These efforts should all be aimed at reducing pressure and adding value on the rangelands, and to ensure sustainable fodder availability for livestock. Lastly, “Farm with nature and farm with grass for profit.”
Erastus Ngaruka is the AASD Technical Advisor on Rangeland and Livestock at the Agricultural Bank of Namibia. The views expressed herein are his own.
