Last update: April 5, 2012 10:26:46 AM E-mail Print

 

GRAZING EXPERIMENT SUCCEEDS

Ordonnantie's carrying capacity trebled

J. L. VAN DER WALT 

 

IN 1950 a grazing trial was laid out on broken Karoo veld on the farm Ordonnantie, in the district of Graaff-Reinet, when the deterioration of the veld in one camp was beginning to cause grave concern to the owner.

Very favourable results were obtained after the prescribed systems of grazing had been meticulously applied for a period of nine years. The most important results were the following:

 

The accompanying graphs clearly illustrate how rapidly and uniformly the increase in carrying capacity and palatable plants took place. On the other hand, the amount of unpalatable plants and "vygies" remained practically the same throughout.

The camp concerned was divided into three smaller camps, which were then subjected to a suitable grazing system from September, 1950, to August, 1959. For the first five years a special reclamation system was followed and thereafter the so-called Karoo three-camp system.

Plant surveys were carried out regularly every three years in order to record any changes in the vegetation. Rainfall, grazing periods and grazing intensity were also recorded regularly, and the condition of the veld was carefully watched by the owner, extension officer and soil-conservation committee. Stock numbers were adapted accordingly.

When the demonstration experiment was nine years old, the progress made was closely examined and analysed. The stock numbers were reduced to Merino units and the numbers in respect of each of the years recorded and given in Fig. 2.

 

 

The vegetation was divided into three main groups, namely, palatable plants, unpalatable plants and a third group, "vygies", found in these parts and eaten by stock during certain parts of the year. The representative number of each of these three groups during every survey is given in Fig. 1 (foliage cover calculated according to the wheel-point survey technique of Tidmarsh and Havenga).

The extremely rapid increase in the number of palatable plants is striking, and so is the correspondence of this curve, to the curve of the stock numbers. These palatable plants consist mainly of perennial grasses, such as the love grasses (Eragrostis sp.), and palatable shrubs, such as the Karoo shrub (Pentzia incana). On the other hand, the pioneer and unpalatable plants underwent no significant changes during the period of nine years.

It is moreover of particular importance that the prescribed system of grazing was maintained without interruption. This is regarded as no mean achievement since the entire district was subject to severe drought conditions during more than one of these nine years. The average rainfall for the nine years in question was 305.87 mm. (12.04 inches), which is very similar to the expected average for the region.

The experiment will be continued with a view to determining the changes in the vegetation over a number of years. Thus far it has served as proof that judicious veld management favours the growth of palatable plants in particular, and can result in considerable improvement of the veld on this type of broken veld.

 

Published

Farming in South Africa 37 (5)