Erastus Ngaruka

Arangeland refers to land inhabited by native plants (grass, forbs, shrubs and trees) and utilised by domestic and wild animals. 

Rangelands offer direct or indirect support to all forms of life, and are the cheapest source of food for livestock. Humans also derive food, medicine and construction materials from the rangeland. 

This is an indication that there is huge demand and competition for rangeland resources, thus putting them under immense pressure to produce or continue to provide such services.

Rangeland productivity is influenced by a combination of factors. 

These include rainfall, soil condition, seed availability and utilisation. 

The productive potential of Namibian rangelands has been compromised, especially in communal areas due to degradation. 

The main forms of rangeland degradation are bush encroachment and soil erosion. 

These two forms of degradation are a consequence of improper rangeland utilisation practices such as overgrazing, land clearing and soil mining practices.

Forage plants live in competition for space, sunlight, water and soil nutrients to establish and regenerate themselves. 

When a plant is overused, its competitive ability is reduced. For example, overgrazing reduces the density and competitive ability of grasses, thus promoting the undesired opportunistic plants such the woody encroachers and other weeds to inhabit the grazing areas. 

Competition exists not only between the grass and woody plants, but also between the grass plants themselves. 

Selective grazing where only one grass species (e.g. Cenchrus ciliaris/blue buffalo grass) is targeted has also led to the disappearance of the most valuable grass species, leaving the undesired grasses (e.g. Aristida stipitata) to dominate the rangelands.

Grasses can be differentiated as annual or perennial. Annual grasses have short life cycles, and they grow and live during the rainy season, and die off. 

New horizon

Regrowth of annual grasses from the seed occurs in the next rainy season, whereas perennial grasses live for more than one season, stay dormant during winter, and re-grow from the same stump and seed in the next season. 

Therefore, grazing animals would depend on perennial grasses during the winter/dry season. Over the years, the most valuable perennial grasses have been disappearing from many grazing areas. 

Lately, the common drought- tolerant Stipagrostis uniplumis (Silky bushmen grass, Ongumba) and S. hochstetteriana (Gemsbok tail) that could save animals during the dry periods are slowly losing dominance to annual grasses, especially in grassland areas (southern and eastern parts of the country).

From the previous rainy season, there has been an abundance of grasses in some grazing areas that were carried over to the current season. 

This is not optimal rangeland recovery yet. Rangeland recovery occurs in three basic succession stages (pioneer, sub-climax and climax), distinguished by the type and species of grass observed.

 The pioneer is the lower-ranked stage with grasses having little grazing value, compared to the climax stage, which is characterised by the presence of the most valuable grass species. 

The grazing value entails palatability (acceptance or taste), nutritional composition, including the amount of vegetative matter and their digestibility.

Currently, most rangelands especially those that are overcrowded and are under continuous grazing will remain in the pioneer stage for a long period. 

The grasses in abundance are the annual type of grasses, with a short life cycle (only available during the rainy season). 

They include Urochloa brachyura, Enneapogon cencroides, Chloris virgata, Digitaria velutina and Eragrostis porosa. 

These annual grasses have taken over large parts of grazing areas in the central, eastern and northern regions, and will disappear in July/August, leaving most of these grazing areas bare or empty. 

However, some perennial sub-climax grasses, such as Eragrostis ridigior, Eragrostis pallens and Stipagrostis uniplumis maintain their presence in most grazing areas.

Erratic rainfall 

Given the recurrent erratic rainfall activities and the continued pressure on rangelands, the shifts in plant/grass succession stages will take longer than desired, unless there are human interventions to facilitate the natural processes of rangeland revegetation. 

One such practice is to re-introduce the valuable grasses by re-seeding (planting grass). 

This practice can be undertaken at various scales, in backyard gardens, planting fields, camps or grazing areas. 

The native valuable grasses that are commonly cultivated in the country include Cenchrus ciliaris (blue buffalo), Anthephora pubescens (wool grass) and Smitdia pappophoroides (Kalahari sand quick).

Apart from grazing value, perennial grasses also protect the soil. They stabilise and shield the soil from the adverse impact of rainfall, wind and extreme temperatures. 

Optimal rangeland/grazing recovery assessment should be based on species composition, grass density, soil organic matter and stability. 

Finally, any rangeland rehabilitation intervention should be supported with a sustainable utilisation/grazing regime.

 *Erastus Ngaruka is Agribank’s technical advisor on livestock and rangeland.