agricultural production guidelines
m
Veld in KwaZulu-Natal
Co-ordinated Extension KwaZulu-Natal Veld 4.7 1999
BIORESOURCE GROUPS 13, 14 & 16:DRY TALL GRASSVELD, SOUR SANDVELD AND DRY LOWLAND TALL GRASSVELD
C R Hurt
ARC - Range and Forage Institute, Cedara
K G T Camp
KwaZulu-Natal Department of Agriculture
Vegetation
Structure and Compositions
Veld Benchmark
Animal Production
INTRODUCTION
The Dry Tall Grassveld, Sour Sandveld and Dry Lowland Tall Grassveld are characteristically a sparse tall grassveld that has, in certain areas, become encroached by woody plants to varying degrees due to bad veld management in the past. Grass basal cover is generally low, giving the grassveld its sparse nature. The area is, however, widely used for livestock production, and, indeed, is well suited to this type of land use.
The Dry Tall Grassveld (BRG 13) occurs mainly as a transitional zone between the dry valley vegetation and the moist BRGs. Its southern-most limit is north-east of Mooi River and sub-groups are distributed throughout the western and north-western areas of KwaZulu-Natal. The most extensive sub-group extends from Estcourt to an area north-west of Ladysmith.
The Sour Sandveld (BRG 14) occurs as an extensive area roughly in the triangle between Newcastle, Vryheid and Dundee, with a second sub-group in the Wasbank district and a third sub-group on the Cedarville flats. It has much the same climate as the Dry Tall Grassveld but is characterised by the sandy soils which have a marked effect on the vegetation and the potential of the BRG. Many pockets of Sour Sandveld are found within the Dry Tall Grassveld while similarly pockets of Dry Tall Grassveld are found within the Sour Sandveld. By recognising the characteristics of the respective BRG’s, correct norms can be applied. While the Cedarville Flats may not be regarded as typical Sour Sandveld, it has been housed in this BRG as it more closely resembles its criteria than that of other BRG’s.
The Dry Lowland Tall Grassveld (BRG 16) is situated in the north of KwaZulu-Natal, at elevations between 450 m and 900 m. In the Pongola River valley sub-groups are situated on the escarpments of both the north and south side of the valley. Other areas lie in the Mkuzi River valley while an extensive area lies east and south of Nongoma, and to the west of the Hluhluwe Game Reserve. In the Black Mfolozi River valley a sub-group is situated in the Swart Umfolosi district and a large area lies between the Black and White Mfolozi rivers.
VEGETATION STRUCTURE AND COMPOSITION
Dry Tall Grassveld (BRG 13)
A large proportion of the veld within this vegetation type comprises old lands which are now dominated by Hyparrhenia hirta (common thatchgrass). Undisturbed veld is usually sour, and is dominated by Tristachya leucothrix (tridentgrass) and Themeda triandra (redgrass), often with many forbs. Scrub forest patches may be found in sheltered situations (rocky, fire-protected slopes or moist, southern aspects). Bushveld dominated by Acacia karroo (sweet thorn), but including many other species, is found in areas adjacent to river valleys.Species which dominate in veld in reasonable to good condition are Themeda triandra, Tristachya leucothrix, Hyparrhenia hirta, Eragrostis racemosa, E. capensis and Heteropogon contortus, while species which are less frequent are Diheteropogon amplectens, Andropogon appendiculatus, Brachiaria serrata, Digitaria tricholaenoides, Panicum natalense and Setaria nigrirostris. On disturbed areas, and this includes overgrazed areas, Hyparrhenia hirta increases in abundance. With increased disturbance or overgrazing, there is an increase in the abundance of species such as Digitaria monodactyla, Eragrostis chloromelas, E. curvula, Sporobolus pyramidalis and Sporobolus africanus. In the driest areas Aristida barbicollis, A. congesta and Cynodon dactylon become dominant with severe overgrazing.
Soil plays an important role in determining species composition and veld condition. The red or black top soils derived from dolerite are particularly resistant to erosion and to disturbance due to grazing. Yellow-brown soils over a plinthic subsoil are moderately resistant while grey soils over a plinthic horizon produce veld that has a low resistance to grazing pressure. The shallow duplex soils that are common in this BRG have a particularly low resistance to grazing pressure and generally the veld based on these soils is in a poor condition and erosion is a common occurrence on these soils.
Sour Sandveld (BRG 14)
This vegetation type occurs on shallow, sandy, poorly-drained soils, and is essentially a sourveld dominated by Tristachya leucothrix (tridentgrass). Other grass species, typical of sourveld vegetation, are common and include Alloteropsis semialata, Monocymbium ceresiiforme, Digitaria tricholaenoides, Harpochloa falx and Setaria nigrirostris. Soils vary considerable from deep sands to shallow poorly drained sands and this is reflected by the species composition of these areas. On deep sandy soils Tristachya leucothrix and Digitaria tricholaenoides are dominant while on shallow soils Aristida congesta, Cynodon dactylon and Microchloa caffra are common. In the seasonally wet areas, grasses such as Andropogon appendiculatus, A. eucomus and Imperata cylindrica occur. Sedges such as Pycreus spp. and Fimbristylis complanata are also common. Other grass species frequently encountered are Themeda triandra, Andropogon schirensis, Aristida barbicollis, A. junciformis, Cymbopogon excavatus, C. plurinodis, Digitaria monodactyla, Diheteropogon amplectens, Eragrostis racemosa, E. chloromelas, E. capensis, E. curvula, E. gummiflua, Elionurus muticus, Hyparrhenia hirta, Loudetia simplex, Panicum natalense, Trachypogon spicatus and Urelytrum squarrosum.Heavy grazing pressure results in an increase in abundance of Aristida spp., Cynodon dactylon, Eragrostis spp., and Sporobolus spp. Elionurus muticus shows an increase in abundance in veld that has been selectively overgrazed by sheep.
Dry Lowland Tall Grassveld (BRG 16)
For the most part BRG 16 is a grassland vegetation dominated by Hyparrhenia hirta. Sporobolus pyramidalis is an important species which indicates overgrazed areas. A secondary pattern of bushed grassland occurs due to the invading Acacia species. These included Acacia karroo, A. nilotica, A. tortilis and A. sieberana. Dichrostachys cinerea has become a major problem species in the bush encroachment process and has formed thickets in some areas together with the Acacia species.
Grassveld in good condition in these Bioresource Groups can be expected to have a species composition similar to that presented in Table 1. It is important to remember that species abundances in this area will vary somewhat according to topographical position. In addition, Table 1 presents other grass species which occur in these Bioresource Groups, but are not necessarily found in the benchmark. The species groupings (i.e. Increaser and Decreaser species), and concepts related to this classification, are explained in detail in Production Guidelines 6.1 to 6.3 in this series.
As with other grassveld types in Natal, the predominance of redgrass is indicative of veld in good condition. Abundances of other key grass species may be used in conjunction with redgrass to determine veld condition using the Weighted Key Species method (refer to Production Guideline 6.2 in this series for a description of this method). Key species and their weightings proposed for use in this veld type are presented in Table 2.
Dry Tall Grassveld (BRG 13)
The animal production potential of the Dry Tall Grassveld is low relative to other grassveld areas, due to the low and erratic rainfall, the poor soils and the often degenerate nature of the grass sward. Generally, the vegetation provides fair grazing in spring before the sward grows out. This is particularly true of the old lands that have become dominated by common thatchgrass. Cattle production potential is only moderate (steers, for example, are able to gain in the region of 120 to 130 kg during the summer at a stocking rate of about 3 ha/AU). Nitrogen-containing licks are needed to prevent excessive mass loss in animals during the winter, unless farmers are able to provide sufficient winter fodder. Sheep production has a higher potential, provided that management is good, as badly-managed sheep enterprises tend to induce veld deterioration.Sour Sandveld (BRG 14)
In the Sour Sandveld the livestock production potential of the natural grassveld is somewhat lower than in the Dry Tall Grassveld. Here, growing steers are able to gain no more than about 100 kg during the summer season at a stocking rate of about 4.5 ha/AU. Winter mass losses are likely to be greater than in the Dry Tall Grassveld and greater provision, in the form of supplementary feeding, has to be made for the winter season.Dry Lowland Tall Grassveld (BRG 16)
The Dry Lowland Tall Grassveld has a livestock production potential similar to that of the Dry Tall Grassveld (BRG 13).
VELD MANAGEMENT NORMS AND GENERAL INFORMATION FOR BRG’s 13, 14 & 16: DRY TALL GRASSVELD, SOUR SANDVELD AND DRY LOWLAND TALL GRASSVELD
BRG 13
BRG 14
BRG 16
Total area (1 000 ha)
Area of veld (1 000 ha)
Potential grazing capacity (ha/AU)
Current grazing capacity (ha/AU)
Grazing season (days)
Grazing cycle (days)
Period of stay (days)
Period of absence (days)
AU grazing days per hectare
Expected intake (kg/AU/annum)
Livestock production potential (kg livemass per ha/annum)
Excellent condition veld (90%)
Moderate condition veld (60%)
Poor condition veld (30%)
449
371
2.1
3.5
300
63
21
42
115
3 000
48
32
16
504
406
2.7
4.5
275
63
21
42
83
2 750
51
34
17
208
171
2.1
3.5
300
63
21
42
115
3 000
52
34
17
Rested area
Each camp should be rested once every four years
Winter grazing
Licks are required when grazing rested veld in winter; supplementary feeding (hay and silage) is also necessary during winter
Animal types
Cattle and Sheep (moderate potential); Goats (low potential)
Burning
Burn to remove moribund and excess herbage
1 In areas where stocking rates are higher than those given for potential grazing capacity, the livestock production potential will not be achieved. This is particularly so where continuous grazing is practiced.
2 Current grazing capacity is based on the average condition of veld in the BRG as estimated in 1997.
3 Animal Unit (AU) grazing days per hectare are based on the estimated average CGC of the BRG.
4 Livestock production potential refers to the expected amount of live mass (kg) gain per hectare using a beef weaner production system (see the example of such a system in Production Guideline 2.6).
Table 2. Proposed key grass species and species weightings for grassland in the Dry Tall Grassveld (BRG 13), Sour Sandveld (BRG 14) and Dry Low Lowland Tall Grassveld (BRG 16).
Scientific name
Common name
Species weighting
Cynodon dactylon
Hyparrhenia hirta
Eragrostis chloromelas
Eragrostis plana
Heteropogon contortus
Themeda triandra
Tristachya leucothrix
Couch grass
Common thatchgrass
Fan lovegrass
Speargrass
Redgrass, rooigras
Tridentgrass
1
2
3
4
6
9
10
Table 1. Benchmark species abundances and species not occurring in the benchmark for grassland in the Dry Tall Grassveld (BRG 13), Sour Sandveld (BRG 14) and Dry Lowland Tall Grassveld (BRG 16).
Scientific name
Common name
Relative abundance (%)
BRG 13
BRG 14
BRG 16
Increaser Ia
Alloteropsis semialata
Andropogon eucomis
Cymbopogon excavatus
Digitaria tricholaenoides
Eulalia villosa
Setaria nigrirostris
Trachypogon spicatus
Tristachya leucothrix
Blackseed grass
Snowflake grass
Common turpentine grass
Purple finger grass
Golden velvetgrass
Large seed setaria
Giant speargrass
Tridentgrass
11
1
12
6
1
25
1
2
2
3
24
Decreaser
Andropogon schirensis
Bracharia serrata
Diheteropogon amplectens
Melinis nerviglumis
Monocymbium ceresiiforme
Panicum natalense
Themeda triandra
Velvet signalgrass
Broadleaved bluestem
Bristleleaved redtop
Wild oatgrass
Natal panic
Redgrass, rooigras
1
67
1
2
25
1
2
3
3
30
Increaser IIa
Eragrostis capensis
Harpochloa falx
Heteropogon contortus
Heartseed lovegrass
Catterpillar grass
Speargrass
2
2
4
1
2
3
3
Increaser IIb
Bothriochloa insculpta
Digitaria monodactyla
Eragrostis chloromelas
Eragrostis curvula
Eragrostis gummiflua
Eragrostis plana
Eragrostis racemosa
Eragrostis superba
Hyparrhenia hirta
Loudetia simplex
Setaria sphacelata var. torta
Sporobolus africanus
Pinhole grass
One finger grass
Weeping lovegrass
Gum grass
Fan lovegrass
Narrow-heart lovegrass
Sawtooth lovegrass
Common thatchgrass
Common russet grass
Creeping setaria
Ratstail dropseed
1
1
2
2
1
2
2
1
1
1
4
1
2
1
1
4
4
Increaser IIc
Aristida congesta subsp. barbicollis
Cynodon dactylon
Microchloa caffra
Paspalum scrobiculatum
Forbs
Sedges
Spreading bristlegrass
Couch grass
Pincushion grass
Veld paspalum
2
4
1
1
2
2
2
4
2
Increaser III
Diheteropogon filifolius
Elionurus muticus
Rendlia altera
Wire bluestem
Wire lemongrass
Toothbrush grass
1
3
1
4