In the extreme climatic conditions of the Karoo, the choice between three- and six-month breaks between grazing periods can make the difference between healthy veld and a man-made desert. Roelof Bezuidenhout reports.
Long rest periods can soften the effect of drought in the Karoo and make veld production and animal output more sustainable in the long term. So says Paul Malan of the Department of Animal, Wildlife and Grassland Sciences at the University of the Free State.
Paul is studying the impact of the intensity and frequency of grazing, as well as the effect of rainfall on the quality and production of two “bread-and-butter” Karoo shrubs, Anchor Karoo (Pentzia incana) and Daggapit Karoo (Nenax microphylla). These species occur from the eastern Karoo right up to the Free State and Northern Cape, and are both well-utilised by sheep and goats.
Paul says far too little is known about the dynamics of the arid Nama Karoo ecosystem, particularly about the moisture use and adaptability of Karoo bushes. “We have to find the ideal grazing intensity for Karoo veld before we can recommend a scientifically based grazing system for the region,” he explains. “With global warming threatening this risky farming area, it’s essential for landowners to understand the production capabilities of this very sensitive veld.”
The research is still in progress, but Paul has already observed that plants defoliated every three months have root systems only half the size of shrubs that rest for six months. These, in turn, produce 25% fewer roots than those rested for 12 months before grazing.
Regular grazing might have an even greater influence on root development than droughts. A combination of low rainfall and regular grazing aggravates the situation.
The poor root systems, says Paul, don’t only reduce the plant’s production but also its ability to survive drought, which is the rule rather than the exception in the Karoo.
“Here, the plant must take up every millimetre of rain as effectively as possible,” he explains. “Plants grazed too often or too regularly simply won’t be able to use the rainfall properly. If you don’t give camps enough rest, you increase your risk as edible Karoo bushes keep losing vigour as their root systems get weaker. This kind of bad management causes man-made drought, even in normal rainfall seasons.”
Paul points out that although all farmers know how important rain is, not all of them fully appreciate the detrimental impact of regular or continuous grazing on grazing ecosystems.
Contact Paul Malan on (051) 401 2385 or fax (051) 401 2608. |fw
The shrubs in the study
Pentzia incana – Anchor Karoo Found right across the Karoo where it’s an important part of the animals’ diet, this shrub has an average grazing index of 5,7. It can grow to a height of 25cm and cover an area up to 40cm wide. The leaves are greyish green with a strong odour when bruised. Shoots form after rain, and bend to the ground to form roots and a new plant. Flowers are round and yellow. Anchor Karoo can endure intensive grazing, but not continuously.
Nenax microphylla – Daggapit Karoo
This very palatable, high-producing dwarf shrub is widely distributed especially in the Northern Cape, Eastern Cape, and Free State. It grows 15cm to 20cm high, with a diameter of up to 50cm. The small leaves bend towards the stem, have a greenish-red colour and are shiny on top. After good rain the plant produces small red to red-brownish fruits. It’s found mostly in stony soils and on hills and is resistant to droughts and heavy grazing.