agricultural production guidelines
m
Veld in KwaZulu-Natal
Co-ordinated Extension KwaZulu-Natal Veld 4.1 1999
THE BIORESOURCE GROUPS OF KWAZULU-NATAL
K G T Camp
KwaZulu-Natal Department of Agriculture
The
Bioresource Unit (BRU)
The Bioresource Groups (BRG)
Vegetation and
Livestock Production Potential
INTRODUCTION
The stated aim of the Department of Agriculture of the Republic of South Africa is the optimum utilization of the natural resources through the promotion of farming enterprises which are i) adapted to the local environment, ii) strive for sound economic production and iii) aim to prevent a deterioration of the natural resources.
The importance of the correct use of the natural resources to the overall economy of the KwaZulu-Natal region cannot be over-emphasised. The degradation of the natural resources is also a matter of grave concern and both this and the economic pressures placed on agriculture indicate the urgent necessity for matching crop and animal requirements with the production potential of the natural resources.
The diversity of the natural resources in the province of KwaZulu-Natal is enormous. The topography ranges in elevation from sea level to over 3 000 m, resulting in a considerable range in temperature, while the topography varies from the undulating coastal plains of Maputoland to the rugged, broken terrain of the Valley of a Thousand Hills and the precipitous mountains of the Drakensberg. The rainfall also varies considerably, from approximately 580 mm to over 2 000 mm per annum. The geological formations of the Province run roughly north to south across an eastern-sloping terrain while the river systems run west to east, resulting in deeply incised valleys, cutting through the geological layers. With this great variation in topography, climate and geology, one could expect a wide variation in soil patterns and this is indeed so. Deep sands are found along the northern coastal belt, young weathering soils in the steep valleys, well-drained, deep soils are a feature of the midlands and the highland areas and poorly drained and duplex soils are common in the upland areas where the rainfall is below 750 mm per year.
In turn, the vegetation is affected by the changes in topography, rainfall and soils. Bushveld is found in the low-lying hot and dry areas of northern KwaZulu-Natal and in most of the river systems. In the high rainfall areas of the coastal belt, the midlands mistbelt, highland sourveld and the mountains of the Drakensberg, different forms of forest are found in areas which are protected from fire. In the northern plains of the province a tall grassveld is characteristic while in the cold highland areas the grassland is typically short.
This great variation in the natural resources in turn leads to variations in the type of farming and levels of production throughout the province. It can be seen that the challenge of providing for sound ecologically based development planning in agriculture and other fields, is a major problem when the complexity of the KwaZulu-Natal natural resources is considered. The Bioresource Unit project was developed to assist in ensuring informed planning of farming systems in the Province.
A Bioresource Unit is a demarcated area in which the environmental conditions such as soil, vegetation, climate and, to a lesser degree, terrain form, are sufficiently similar to permit uniform recommendations of land use and farm practices to be made, to assess the magnitude of crop yields that can be achieved, to provide a framework in which an adaptive research programme can be carried out, and to enable land users to make correct decisions. The uniformity of climate and soil type within each BRU should be such that the type of farming enterprise, and the productivity and management techniques required, can be clearly defined.
There are 590 BRU’s in KwaZulu-Natal. An inventory has been written for each BRU which describes it's climate, vegetation, soil patterns and in turn the crops, pastures and timber that can be grown there and the level of production that can be achieved. The BRU map and it's associated information is used at farm planning and advisory level.
The Bioresource Units have, in turn, been grouped into ecological units based primarily on climate and vegetation, and are referred to as Bioresource Groups (BRG’s). A BRG is an area with a reasonably uniform pattern of vegetation type, climate and soil pattern within its boundary. Broad veld management recom-mendations, such as potential grazing capacity, grazing systems, burning schedules, are made at the BRG scale. The BRG’s are listed below, together with a short description of their temperature and rainfall ranges. A map indicating the location of each BRG is given in Figure 1.
Rainfall is well distributed and the mean annual rainfall varies from 819 mm to 1 270 mm. The mean annual temperature varies from 18.3EC to 21.9EC. There are no ecologically dry months with rainfall less than 25mm, but dry spells lasting several weeks can cause a loss in production. Frost has been experienced on rare occasions in valleys. Lightning and hail are also rare. Strong winds are a common feature, and if combined with high temperatures, evapo-transpiration can be high.BRG 1: Moist Coast Forest, Thorn and Palm Veld (Moist Coast)
BRG 2: Dry Coast Forest, Thorn and Palm Veld (Dry Coast)
Similar to the Moist Coast, but much drier with the mean annual rainfall from 741 mm to 815 mm. The mean annual temperature varies from 19.0EC to 21.6EC.BRG 3: Moist Coast Hinterland Ngongoni Veld
(Moist Ngongoni Veld)
Annual rainfall varies from a minimum of 800 mm to an extreme of 1 160 mm. There are fewer than three ecologically dry months. Mean annual temperatures vary from 16.1EC to 19.6EC. Droughts are occasional, and frosts are light, mainly in the valleys.BRG 4: Dry Coast Hinterland Ngongoni Veld (Dry
Ngongoni Veld)
Usually situated at lower altitudes than the Moist Ngongoni Veld and has a mean annual rainfall varying from 712 mm to 836 mm. The mean annual temperature range is from 16.9EC to 19.6EC.BRG 5: Moist Midlands Mistbelt (Moist Mistbelt)
Mean annual rainfall varies from 800 mm to 1 276 mm. Mist is a common feature. The mean annual temperature varies from 15.4EC to 18.5EC. Crop production hazards include hail, occasional dry spells in summer and mist and cloud cover in early summer. Hot "Berg" winds in spring are frequently followed by cold spells. Frosts are usually moderate, but severe frosts occur occasionally.BRG 6: Dry Midlands Mistbelt (Dry Mistbelt)
This BRG experiences less mist than the Moist Midlands Mistbelt and dry summer spells are more frequent. The mean annual rainfall varies from 738 mm to 825 mm. The mean temperature varies from 16.2EC to 17.6EC.BRG 7: Northern Mistbelt
Similar, in most respects regarding climate, to the Moist Midlands Mistbelt with a mean annual temperature varying from 16.0EC to 17.4EC, and mean annual rainfall of between 980 mm and 1 123 mm.BRG 8: Moist Highland Sourveld
The mean annual rainfall varies from 800 mm to 1 265 mm and the temperature is between 11.5EC and 16.6EC. The rainfall is reasonably reliable. Summers are cool and winters cold, with severe to very severe frost. Snow is experienced occasionally, more frequently on the high-lying areas. The growing season is short, hail is a hazard and hot "Berg" winds increase the risk of serious fires.BRG 9: Dry Highland Sourveld
Droughts are quite frequent occurrences and the mean annual rainfall varies from 620 mm to 816 mm, with the lower extremes in the East Griqualand and Newcastle areas. Snow is infrequent. The mean annual temperature varies from 12.9EC to 15.6EC.BRG 10: Montane Veld
Mean annual rainfall varies from 900 mm to 1 390 mm and 6 to 7 months are wet, exceeding 100 mm. Torrential downpours are common. The mean annual temperature varies from 7.5EC to 13.2EC, frosts are very severe and snow is a regular feature. This area is South Africa's most important water source.BRG 11: Moist Transitional Tall Grassveld (Transitional Tall Grassveld)
The mean annual rainfall is from 800 mm to 1 116 mm. Mists are a frequent occurrence. The mean annual temperature varies from 15.0EC to 18.7EC. Frosts are generally moderate, but occasional severe frosts do occur.BRG 12: Moist Tall Grassveld
The mean annual rainfall varies from 712 mm to 805 mm. There are 3 to 4 ecologically dry months. The mean annual temperature varies from 15.3EC to 18.9EC. Occasional drought periods occur during the summer, frosts are moderate to severe, and hail storms are experienced.BRG 13: Dry Tall Grassveld
The mean annual rainfall varies from 666 mm to 745 mm and there are 4 to 5 ecologically dry months. The rainfall is not reliable and is poorly distributed. The mean annual temperature varies from 15.6EC to 19.0EC and frost is moderate to severe.BRG 14: Sour Sandveld
The Sour Sandveld has sandier soils than the Dry Tall Grassveld but the climate can be regarded as being similar to the climate of that BRG. The mean annual rainfall varies from 645 mm to 737 mm, and the mean annual temperature is between 14.7EC and 17.3EC.BRG 15: Moist Lowland Tall Grassveld
The rainfall range of this BRG is from 800 mm to 1 000 mm. The mean annual temperature varies from 18.5EC to 20.5EC. Frosts are moderate, and severe frosts rare.BRG 16: Dry Lowland Tall Grassveld
This BRG has a mean annual rainfall varying from 706 mm to 795 mm, and the mean annual temperature varies from 17.9EC to 20.8EC.BRG 17: Coast Hinterland Thornveld
The mean annual rainfall varies from 644 to 838 mm with frequent summer dry spells. The mean annual temperature varies from 17.2EC to 19.5EC with rare, moderate frosts.BRG 18: Mixed Thornveld
The mean annual rainfall varies from 650 mm to 786mm, and there are 4 to 5 dry months. Rainfall is poorly distributed and droughts occur frequently. The mean annual temperature varies from 16.0EC to 18.1EC. Frosts are generally moderate, but severe frosts are experienced in some valleys.BRG 19: Moist Zululand Thornveld
The mean annual rainfall varies from 760mm to 846mm and there are 4 ecologically dry months. The rainfall is poorly distributed. The mean annual temperature is between 20.7EC and 21.5EC. Frost is rare.BRG 20: Dry Zululand Thornveld
The mean annual rainfall varies from 678mm to 788mm and the mean annual temperature ranges from 19.2EC to 21.6EC. Droughts are more frequent than in the Moist Zululand Thornveld.BRG 21: Valley Bushveld
The mean annual rainfall varies from 595mm to 830mm and drought is a serious hazard. The mean annual temperature range is from 17.1EC to 20.8EC. The range in extreme temperatures can be wide. Weenen, for example, experiences the widest range in temperature in the Tugela Basin, ranging from a low of - 6.7EC to a high of 42.8EC. The low temperatures are the result of cold air flowing into the valleys from the surrounding high-lying country. Climate hazards include frequent periods of drought, occasional severe frosts, considerable heat, lightning and hail.BRG 22: Lowveld
The mean annual temperature of this warm area ranges from 17.5EC to 22.2EC. Evaporation exceeds 1 524 mm per annum. The mean annual rainfall varies from 587 mm to 750 mm. Rainfall is erratic and droughts often severe.BRG 23: Sandy Bushveld
The mean annual rainfall varies from 635 mm to 775 mm. Rainfall is unreliable. The mean annual temperature is from 21.7EC to 22.0EC.
VEGETATION AND LIVESTOCK PRODUCTION POTENTIAL
A more detailed description of the Bioresource Groups follows in Production Guidelines 4.2 to 4.10. For practical veld management purposes, Bioresource Groups with similar veld management requirements have been combined. Combinations of BRG’s has been based on local knowledge and the veld management recommend-ations given for the previously defined Bioclimatic Groups of KwaZulu-Natal.