Last update: April 5, 2012 07:36:42 AM E-mail Print

 

Save the Bushman Grass

TE Skinner

 

THE general impression seems to be that grass-veld occurs only in the higher rainfall areas of South Africa and that bushes are almost the only vegetation in the arid Western Karoo regions.

Many people are surprised to learn that extensive areas of grass-veld occur in regions where the average annual rainfall is not higher than 100 to 150 mm!

These grass-veld areas consist in most cases mainly of one or both of the bushman grasses: Stipagrostis ciliata (large bushman grass, or gemsbokgrass) and S. obtusa (bushman grass, or small bushman grass).

These two grasses occur not only in the Republic but also in most of the desert regions of Africa and the Middle East: in South-West Africa, Arabia, Sudan, Abyssinia, Egypt, Palestine, Tunisia, Algeria, the Hoggar Mountains in the central Sahara, Morocco, the Canary Islands and Kuwait.

 

SEEDS WITHSTAND DROUGHTS

As will be seen from Fig. 1, which shows the geographical distribution of grasses in South Africa, the bushman grasses occur naturally in an area where droughts are fairly general. This is true particularly of the primary distribution area, where droughts occur during 24.7 per cent of the time.

 

 

Within the area of distribution as a whole, bushman grass occurs mainly on deep, well-drained sandy apron veld. In fact, the physical characteristics of the soil and the germination behaviour of the seeds mainly determine the places where the grass occurs. The germination behaviour is such that the bushman grasses are particularly well adapted to grow and propagate themselves in drought stricken areas.

Wind spreads the seeds of the bushman grasses, which are produced in great numbers during favourable seasons. It has been calculated that a single tuft of bushman grass can produce up to 30,000 seeds during the first season, and even more during subsequent seasons.

These seeds retain their viability for years, even after they have been exposed to extreme temperatures. They are particularly resistant, therefore, to protracted droughts. Although the established bushman grasses are highly resistant to droughts, it is probably mainly the seeds, which bridge serious and even calamitous droughts. The small bushman grass produces the most seed and its seed is hardier than that of the large bushman grass.

 

PLANT THEMSELVES

The bushman grass seeds plant themselves about one centimetre deep in the soil with the aid of wind movements, and then lie dormant to germinate when conditions become favourable. Seeds sow themselves more easily in the softer sandy apron soils than in the heavier soils of the more low-lying plains and hollows.

Young bushman grass seed contains a water-soluble inhibitor, which retards germination unless it is leached out. Even the older seeds require very favourable moisture conditions for germination. Sandy soils are usually very well drained. The downward movement of the water leaches the inhibitors out of the embedded seeds and ensures at the same time that the maximum amount of moisture is collected for the young seedling to use later on.

Good germination under veld conditions can, therefore, occur only when enough rain has fallen and the seedlings will have a reasonable chance of becoming permanently established. Such rains occur mainly during the late summer and autumn months.

 

USE EVERY SHOWER

Once the bushman grasses have become established, they are very highly resistant to drought and even at a comparatively young stage they can withstand seasonal droughts from four to six months in an apparently dormant condition. Plants, which have been established for a longer period usually, survive droughts from 12 to 18 months, but ramp droughts can cause heavy losses. Established bushman grasses can make good use of all casual rain showers, and their growth and seed production periods are not limited to certain seasons.

After germination the bushman grasses develop very rapidly. Under favourable conditions the root systems may reach a depth of six feet within six to seven weeks and seed haulms are formed at eight to nine weeks. Established plants form seed haulms within two to three weeks after fall of rain. Under normal veld conditions, however, this development is considerably slower. Particularly when seasons are unfavourable the bushman grasses react very much like pioneer plants, using all their available energy to produce seed and producing comparatively few leaves.

 

RESTING PERIODS

In general, a good growing season of 90 days - that is a period in which both temperature and moisture conditions are favourable - is sufficient to enable young seedlings to become well established and to permit established plants to produce ripe seeds. Seed forming, however does not terminate the growing cycle of the grasses and longer resting periods are desirable.

During seasons in which large crops of seed are produced, such longer resting periods are often forced. The seeds, which have feathered angels giving the bushman grasses their characteristic silver-white gloss, sometimes cause losses of small stock. The feathered angels form “hair balls" in the rumen and if these balls enter the small intestine they cause stoppages. Under such conditions stock must be withdrawn until after the seed has been released.

This "additional resting" from the ripening of the seed until it has been shed", however, serves a very useful purpose. After the seed has ripened, the plant strengthens its root system and hence also its resistance to drought.

To derive the full benefit from casual rain showers and to ensure that young seedlings become properly established, it is advisable to rest bushman grass-veld uninterruptedly for at least 12 months. This long resting period will not involve any losses of grazing, since the bushman grasses can retain their palatability and nutritive value or several seasons. It will, however, increase the drought resistance and production capacity of the grasses during subsequent seasons.

Bushman grass-veld can hardly be rested for too long at a time, since the grasses become "bloudak" after a season or so. In this form the cluster assumes a greyish-blue colour and appears to be dead and worthless, but is nevertheless eaten avidly.

 

PROTECT VELD

Quite apart from their value as pasturage, these grasses are valuable because they help protect the highly vulnerable sandy soils of Bushmanland and the Kalahari. Indeed, it is even being said that a dense grass cover in these areas may have a beneficial effect on the climate of the more easterly Karoo areas.

As determined by plant surveys, these grasses may cover 10 to 45 per cent of the surface of the soil. The value of a dense grass cover, particularly as a measure against wind erosion, in these arid areas cannot be over-emphasized. We should spare no effort to maintain this cover as dense as possible. Without these grasses desert conditions will very quickly arise - and it might thereafter be virtually impossible to establish a plant cover on unstable, continually shifting loose sand.

Fortunately the Bushman grasses react very rapidly to favourably conditions. It is today still possible, therefore, to save these grasses, by means of judicious veld control, for the common benefit of soil and livestock.

 

Published

Farming in South Arica 41 (8)