Influence of stocking rate and grazing system on plant basal cover and botanical composition of veld in the northern cape 1

Abstract

Changes in basal cover and botanical composition were recorded at four stocking rates, both under continuous and rotational grazing in the Northern Cape. The experiment was conducted with cattle. Results suggested that heavier stocking rates could be applied under rotational grazing than under continuous grazing without veld deterioration occuring. After four seasons, botanical composition deteriorated only under continuous grazing. Plant basal cover decreased significantly at the heavy stocking rates, both under rotational and continuous grazing. This result illustrates the danger of grazing strategies based on an injudicious increase in stock numbers.

Basal cover was found to be a better indicator of trends in veld condition than botanical composition, despite annual fluctuations resulting from rainfall variability. Changes in the botanical composition apparently occur only where veld deterioration is more advanced.     

Effect of continuous grazing in the dohne sourveld on species composition and basal cover

Abstract

In a grazing trial conducted at the Dohne Agricultural Research Station, natural grassland was grazed continuously for 36 years with cattle. In a second investigation conducted on similar grassland, paddocks were grazed or rested, in all combinations of the four seasons of the year, over a ten year period. Changes in botanical composition and cover of the sward were monitored at regular intervals. The results of these investigations indicate that under a regime of non‐selective grazing the composition of Dohne Sourveld is remarkably stable. After 36 years of continuous grazing the species composition of the sward was largely maintained. Floristically Dohne Sourveld is dominated by a small number of grass species of which Andropogon appendiculatus, Elionurus muticus, Heteropogon contortus, Sporobolus africanus, Themeda triandra and Tristachya leucothrix are the most important. These species react differently to under‐utilization or increasingly severe defoliation, enabling them to be classified into decreaser or increaser categories. Severe defoliation resulted in a marked decrease in basal cover but only small changes in relative species composition. As the intensity of defoliation increases, decrease in grass cover is associated with an increase of forbs, such as Senecio retrorsus.     

Forage production of some grass species in the false Thornveld of the Eastern Cape

Abstract

The most commonly occurring grass species in the False Thornveld (Acocks, 1953; veld type no. 21) were clipped before and after grazing on veld in good and poor condition at different times of the year. Herbage yield per species was expressed per unit basal tuft area, and the difference in yield before and after grazing was considered to reflect the production of available forage. Themeda triandra produced more forage than any other species at all times of the year. Sporobolus fimbriatus generally produced the second highest amount of available forage. Cymbopogon plurinodis, despite having the second highest herbage yield before grazing, was not grazed to a significant extent. On the basis of the results, Themeda triandra and Sporobolus fimbriatus were identified as key grass species in the False Thornveld of the Eastern Cape.     

Korttermyn invloed van strawwe droogte op veldtoestand en waterverbruiksdoeltreffendheid van grasveld in die sentrale Oranje‐Vrystaat

Short‐term effect of severe drought on veld condition and water use efficiency of grassveld in the central Orange Free State. The impact of an intensive drought (1982/1983 and 1983/84‐growing seasons) on botanical composition, basal cover, mortality of grazing plants and water use efficiency (WUE) of veld in good, moderate and poor condition was identified. Increaser II species were apparently more capable of surviving drought than the Decreaser species. Under optimal soil moisture conditions the Decreaser species increased and the Increaser II species decreased. During the drought extensive grass mortality took place. Veld condition plays an important role in determining mortality during drought. Decreaser species have a high water requirement for optimal WUE, while Increaser II species can reach maximum WUE with less water. Under water stress conditions Increaser II species significantly (P≤0.01) do not use the water as efficiently as do Decreaser species. The WUE under water stress conditions for veld in good, moderate and poor condition was on average, during the study period, 0.90; 0.90 and 0.40 kg ha^?1 mm^?1, respectively, and towards under optimal water conditions, 2.47; 1.67 and 0.23 kg ha^?1 mm^?1, respectively.     

The effect of stocking rate and lick supplementation on the performance of lactating beef cows and its impact on Highland Sourveld

Abstract

The Highland Sourveld of Natal is an important beef producing area. Although it covers only 13% of the total area of the province, it supports 18% of the beef cattle population.

The performance of cows and their calves stocked at four stocking rates on Highland Sourveld was studied. Two stocking rates were duplicated to test the benefit of an energy lick against a mineral lick. The effect of stocking rate on the veld was monitored in terms of compositional change.

Stocking rate significantly affected cow performance and consequently calf performance. An energy lick supplement, as opposed to a mineral lick supplement, was beneficial at the 1,0 LSU/ha stocking rate, but not at the 1,67 LSU/ha stocking rate.

The composition of the veld in the low to moderately stocked treatments changed relatively little, over the recording period, whilst the very high stocking rate treatments showed a rapid delcine in veld composition score.     

Exploratory trials on reinforcement of veld with legumes in the south‐eastern transvaal highveld

Abstract

The feasibility and potential of reinforcing veld with legumes in the south‐eastern Transvaal highveld was assessed in a number of trials during the period 1974–84. Experience was gained with regard to methods of establishment, adaptation of legumes to the local environment, responses to fertilization, especially with lime and superphosphate, and the reaction of legumes to fire and grazing. In all, 17 legumes were involved, including the genera Coronilla, Desmodium, Glycine, Lespedeza, Lotus, Macroptilium, Medicago, Neoto‐nonia, Trifolium and Vigna. Only Coronilla varia (crownvetch) showed a satisfactory degree of persistence. However, crownvetch is slow to establish, is intolerant of waterlogging and has a relatively high requirement for lime and phosphate. Considering these features, and the probability of undesirable changes in grass species composition in reinforced veld, it is recommended that intensification be achieved through development of improved pastures for use in conjunction with veld, rather than by means of veld reinforcement.     

Interrelationships between veld condition,herbage mass,stocking rate and animal performance in the Tall Grassland of Natal

Grazing trials were established at three sites in the Tall Grassveld of Natal. The objectives were to determine (a) patterns in herbage mass in relation to veld condition, stocking rate and commencement of spring grazing, and (b) animal performance in relation to herbage availability and stocking rate for the period November 1986 to September 1987. Rainfall exceeded the mean annual rainfall and, for moderate condition veld in particular, was very favourably distributed. Distinct patterns in herbage availability were seen during the season. A multiple linear regression model was developed for determining peak herbage mass (HM) in April from veld condition (VCI), stocking rate (SR) and time that grazing commenced in spring (T) (r=0,71; P<0,01). HM was positively related to VCI and delayed T and negatively related to SR. Seasonal growth phases in cattle were similar for different sites despite their spatial separation and differences in veld condition. It was essentially only the magnitude of mass loss or gain that varied. No linear relationships existed between SR and average daily gain (ADG). A multiple linear regression model was developed for determining ADG from SR, HM and the initial mass of the animals (IM) (r=0,93; P<0,01). ADG was positively related to IM and negatively related to SR and HM.     

The effect of severe drought and management after drought on the mortality and recovery of semi‐arid grassveld

Abstract

The False Thornveld of the Eastern Cape experienced a particularly intense drought during the 1982/83 growing season. Extensive grass mortality took place during the drought. After the drought, recovery was particularly sensitive to the post‐drought management treatment applied. Veld that was grazed immediately after the drought recovered far more slowly than veld that was rested. This effect was still evident three years later, illustrating the considerable importance of resting semi‐arid grassveld after a drought.

Increaser I grass species present were apparently more capable of surviving drought than the Decreaser species, which in turn were more stable than the Increaser II species. Their ability to recover after the drought followed an opposite trend. On this basis, the desirability of Decreaser dominated veld, in situations that are likely to be poorly managed, is questioned.     

An evaluation of the economic viability of commercial pastoralism in the smaldeel area of the Eastern Cape

Abstract

Carrying capacity models and financial data from study group farmers were used to derive attainable net revenue per ha on veld in good, moderate and poor condition. From these data, minimum farm sizes required for a reasonable standard of living (R20 000 net personal income per annum) were estimated for each veld condition class. These minimum sizes were compared with actual farming unit sizes determined from a farm survey.

Most farming units are large enough to provide a reasonable standard of living, on condition that the farmer has little debt and does not have to incur costs of land development. However, most farmers cannot afford to implement the development required for currently recommended conservation practices. If conservation is required by society, subsidization of conservation practices should be considered.     

Composition,pattern and diversity of some Transkeian grasslands

Abstract

Species composition, pattern and diversity of selected grassland communities were determined by using point samples, transects and quadrats. The continuously grazed grasslands of Dohne Sourveld generally had the richer species composition, the highest diversity and the most variable intra‐community pattern. Forb species were mainly responsible for the higher diversity in these grasslands compared with more severely disturbed sites (e.g. old fields). The intra‐community pattern was, however, determined by the relative proportions and distribution of the grass species.     

Measuring the impact of indigenous herbivores: reply to Kerley andLandman

Pteronia paniculata is an indigenous, unpalatable shrub that invades mismanaged Karooveld, resulting in degraded rangelands with low species diversity and grazing potential. We conducted a series of trials in the Succulent Karoo Randteveld near Barrydale to determine if the uniform defoliation of P. paniculata dominated vegetation at two heights (0.05 m and 0.20 m above ground level) using a brush-cutter and, in one trial, application of a second cut will improve the plant species composition, productivity and grazing capacity of the veld. Brush-cutting treatments and the uncut control all resulted in a change in species composition towards greater species diversity and more palatable species and an average increase of 540 kg ha^?1 (28%) in above-ground biomass over four years. It appears that there was a pervasive improvement in species composition associated with a general decline in the cover and abundance of P. paniculata over the time-scale of the present study that was not influenced by the defoliation treatments, except for the 1996-cut treatment where the cover of P. paniculata increased. The absence of propagules of palatable species in the soil seed bank and competition from P. paniculata (a long-lived, perennial shrub) are assumed to be among the main reasons for the lack of response of the vegetation community to the defoliation treatments. Brush-cutting (in the absence of reseeding), aimed at reducing the dominance of unpalatable karoo shrubs, was more costly but not significantly better than long-term resting in improving veld composition or forage production.     

Identification and selection of benchmark sites on litholitic soils of the western grassland biome of South Africa

Abstract

An approach to identify benchmarks for different ecological situations in the grassland biome is described. The approach is illustrated by using information on vegetation change, role of habitat factors and the relative palatability differences between the species of the vegetation on shallow soils of the litholitic complexes in the western parts of the grassland biome. The information was obtained from the ordination and interpretation of vegetation and habitat data gathered at different distances from watering points and in vegetation under different grazing pressures.     

A comparison of five methods for assessing veld condition in the natal midlands

Abstract

Site rankings obtained from five methods of scoring veld condition in the highland sourveld and the moist tall grassveld of the Natal Midlands were correlated with rankings from methods of multivariate analysis. With few exceptions, all methods gave rankings which were strongly correlated with rankings from detrended correspondence analysis, thus indicating that they all provide a practical means of indexing the relative veld condition of sites with reasonable precision. The weighted quantitative climax and key species methods were superior to the other three methods in this respect. The key species method has the advantage of simplicity and speed, and should stimulate farmers to undertake routine monitoring of their veld in these two regions.     

The effect of supplementation on productive performance of Boer goat bucks fed winter veld hay

Fifteen Boer goat bucks, (6–8 months old), were allocated into two groups and fed ad libitum for a period of 29 days. The WH group (winter hay; n = 8) received a chopped diet consisting of grass hay, predominantly Themeda trianda grass (cut during the winter) from a natural pasture (veld). The WH+S group (winter hay plus supplement; n = 7) received a chopped diet consisting of Themeda trianda veld hay, supplemented with maize meal, molasses meal and urea. Body weights and feed consumption were recorded. Animals were slaughtered and carcass characteristics (weight and percentages of selected carcass cuts) and the carcass chemical composition were determined. The WH+S animals showed a higher live weight and cumulated feed intake. Carcass cuts from WH animals represented a higher percentage of the total carcass, especially cuts where muscle depots are higher (legs, best end chops and prime cuts). There is an attempt by non-supplemented animals to preserve the body's nitrogen reserves under prolonged nutritional stress conditions, and there is consequently a necessity to supplement feeding of small ruminants fed winter veld hay, especially if the animals are to be used in subsequent breeding seasons.     

Conservative stocking or maximum profit: A grazing management dilemma?

Abstract

Swards in the False Thornveld of the Eastern Cape are generally stocked considerably in excess of the rate currently recommended for maximised production on a sustained basis. Economic analysis of the relationship between stocking rate and production per ha reveals that there is no financial justification for such heavy stocking. Moreover, conservative stocking rates increase the farmer's ability to withstand drought without adversely affecting profit. Veld condition also plays a considerable role in determining financial return per ha. Despite these observations, farmers continue to stock heavily and this is accompanied by veld deterioration. A possible explanation is that the productive value of land is relatively insignificant when compared with its investment value.     

The quality of herbage ingested by cattle in rotationally grazed semi‐arid grassveld of the eastern Cape

Oesophageal fistulated steers were used to sample herbage daily during periods of occupation on veld in good and moderate condition. Forage quality was assessed in terms of in vitro dry matter digestibility and digestible crude protein. The quality of herbage ingested remained fairly constant as forage availability declined during periods of occupation, even when swards were grazed very severely. Digestibility declined somewhat from spring through to winter, but digestible crude protein content in the diet was unaffected by time of year. The quality of forage ingested during winter was nevertheless still high, even after a full growing season's rest. It was sufficient for growing steers to gain 0,75 kg livemass per day. Trends were similar on both veld condition types. It was concluded that, in semi‐arid grassveld of the eastern Cape, forage availability is likely to have a greater influence on animal performance than forage quality.     

A comparative study of three veld types of the Northern Cape: Species evaluation and yield 1

A comparative study was undertaken of the grass component of the three main veld types of the Vryburg district; namely Sand veld, Dolomite veld and Lime veld. Results indicate that different species within the same veld type and the same species in different veld types differ in their dry matter production, digestibility and digestible organic matter production. Botanical composition and basal cover also varied between veld types. Veld types also differ in DM yields, digestibility and DOM yield.

The average digestibility of all species at three growth stages (leafy, flowering and mature) was 48,7% in sand veld, 54,8% in dolomite veld and 54,7% in lime veld. The average dry matter production and digestible organic matter production per m² at three growth stages were 2 083,9 g and 844,5 g in Sand veld, 2 108,6 g and 952,5 g Dolomite veld, and 1 776,0 g and 808,8 g in Lime veld, respectively. The possibility of deficiencies of Zn, Cu and P is indicated in all three veld types.

The percentage basal covers of sand veld, Dolomite veld and Lime veld were 4,3%, 2,1% and 5,0% respectively. The average DM yield and DOM yield of the veld types were 786,4 and 301,1 kg/ha in Sand veld, 403,9 and 189,2 kg/ha in Dolomite veld, and and 365,7 kg/ha in Lime veld respectively. The average digestibility of the veld types were 44,0%in Sand veld, 56,3% in Dolomite veld and 52,3% in Lime veld.     

The effect of veld condition on the quality of diet selected by cattle grazing the Natal Sour Sandveld

The quality of diet selected by steers fistulated at the oesophagous was related to veld condition in a simulated rotational grazing system on the Natal Sour Sandveld. Six camps, ranging in veld condition score from 8,5 to 53%, were grazed simultaneously for a two‐week period in spring, summer, autumn and winter. Fistula samples were collected on the first, middle and last day of a period of occupation in a camp. Samples were analysed in terms of crude protein (CP), in vitro digestibility (IVD) and plant‐part (% leaf, % stem and % dead material) composition. Dietary quality in terms of CP, IVD and plant‐part composition was not related to veld condition but was dependent largely (P≤0,01) upon season and to a lesser extent upon period of occupation in a camp. It was concluded that in sourveld areas, where dietary quality may be limiting, the veld condition score may be a poor index of potential animal production.     

Research note: Grazing‐index method procedures of vegetation surveys

Abstract

In the past, veld condition in the Karoo was assessed using the ecological index method. This recently changed to the grazing‐index method on account of the differently estimated grazing‐index values being used. The principles governing the method of survey remain the same. The method employs canopy‐spread‐cover strikes to record the species composition of different sites. By appropriate management of these line‐point data, different sites can be compared with one another by employing the Z‐index of agreement (similarity).     

Influence of sowing depth on the germination of Karoo shrubs and grasses

Abstract

Knowledge of the germination behaviour of desirable plants to be sown in the veld for veld improvement is still inadequate. To gain this knowledge, seed of different species of Karoo bushes and grasses were planted on two soil types at different planting depths.

Germination percentage of all species tested were significantly lower when planted on the surface in sand as compared with depths of 10 and 20 mm. Germination percentages were also lower at the 0 to 2 mm planting depth than the 10 mm and 20 mm planting depths when planted in a sandy loam soil.