• July 12th, 2020

Rainfall alone cannot guarantee optimal rangeland recovery

Erastus Ngaruka

A rangeland refers to a land area inhabited by native plants (grass, forbs, shrubs & trees) utilized by domestic and wild animals. Rangelands have direct or indirect support to all forms of life and is the cheapest source of food for livestock.  Humans also derive food, medicine, and construction materials amongst others from the rangeland. This is an indication that there is huge demand and competition for rangelands’ 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, seeds availability, and utilization amongst others. The productive potential of Namibian rangelands has been compromised, especially in communal areas due to degradation, and the main forms of rangeland degradation are bush encroachment and soil erosion. These two forms of degradation are resulting from improper rangeland utilization practices such as overgrazing, land clearing, and soil mining practices amongst others. 

Forage plants live in competition for space, sunlight, water and soil nutrients to establish and re-generate themselves. When a plant is overused, its competitive ability is reduced. For example, overgrazing reduces the density and the competitive ability of grasses, thus, promoting the undesired opportunistic plants such the woody encroachers and other weeds to inhabit the grazing areas. The competition is not only between the grass and the woody plants, but also between the grass plants themselves. Selective grazing (target specific grass species) has also led to the disappearance of the most valuable grass species, leaving the undesired grasses (e.g. Aristida stipitata) dominate the rangelands.  

Grasses can be differentiated as annual or perennial, where an annual grass only grow and live during the rainy season and dies but only regrow from the seed in the next season, whereas the perennial grass 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 their grounds or dominance to annual grasses especially in grassland areas (southern and eastern parts of the country). 

The current rainfall activities seem to be favourable as many farmers are observing an abundance of grasses in the grazing areas, and areas that had bare patches in the previous seasons. This is not optimal rangeland recovery yet.  Rangelands recovery occurs in three basic succession stages (pioneer, sub-climax and climax) distinguished by the type and species of grasses observed. The pioneer is the lower ranked stage with grasses having little grazing value compared to the climax stage that recruits the most valuable grass species. The grazing value entails; palatability (acceptance or taste), nutritional composition, and quantity (amount of leave and stem produced). 

Currently, Namibian rangelands are in their pioneer stage of recovery. 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 amongst others. These annual grasses have taken over large parts of grazing areas in central, eastern and northern regions, and they will disappear in July/August leaving most of these grazing areas bare or empty.

Given the recurrent erratic rainfall activities and the continued pressure on the rangelands, the shifts in the plant/grass succession stages will take longer than wished for, 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). The practice can be done at various scales, in backyard gardens, planting fields, in 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 stabilize and shield the soil from adverse impact of rainfall, wind and temperatures.  Optimal rangeland/grazing recovery assessment should be based on species composition, grass density and soil organic matter and stability. Any rangeland rehabilitation intervention should be supported with sustainable utilization/grazing regime. 
Erastus Ngaruka, a Livestock Technical Advisor for Agribank’s Advisory Services Division.

Staff Reporter
2020-03-24 08:51:04 | 3 months ago

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