Presidential Address:Ethics, legislation and profit as determinanats of conservation farming.

Keywords: conservation; conservation farming; economics; ethics; farming; grassland society of southern africa; legislation; presidential address; research; south afric

A consideration of veld condition assessment techniques for commercial livestock production in South Africa.

A number of procedures have been developed for the evaluation of veld condition in a variety of vegetation types in South Africa. These include both agronomic and ecologically based methods, about which there still remain a great deal of controversy. However, the urgent need for methods which can be applied in practice has recently prompted the recommendation of specific methods for the vegetation types representative of the major livestock producing areas of South Africa.Language: EnglishKeywords: botany; decreaser species; evaluation; Grazing; grazing capacity; increaser species; Livestock; Livestock production; procedure; south africa; vegetation type; vegetation types; veld condition; veld condition assessment; Veld condition

Presidential Address:The management of sown pastures in southern Africa.

Keywords: grassland society of southern africa; grazing management; grazing systems; management; pastures; presidential address; southern afric

Stability, resilience and animal production in continuously grazed sour grassveld.

The Jones-Sandland model, popularly used in southern Africa, may be criticised because it ignores firstly the long-term effects of grazing intensity on the acceptability and productivity of pasture or veld, and secondly possible discontinuities in the animal performance - stocking rate relationship. A mathematical model is developed to investigate these issues in sour grassveld. From the model and independent grazing trials, it is concluded that there is a critical stocking rate above which grazing intensity induces veld deterioration and change in the animal performance - stocking rate relationship. In veld in excellent condition this critical stocking rate coincides with that maximising animal production per ha. However, on poor veld the critical stocking rate is less than the rate yielding maximal animal production per ha. Degraded sour grassveld which is being used for animal production is therefore resilient - grazing intensity is likely often to exceed the threshold below which veld recovery is possible. Regarding discontinuities, these do not occur. However, there is a small range of stocking rate over which the rate of change in animal performance is extreme in relation to the rate of change in stocking rate. Adopting the Jones-Sandland model would thus yield highly variable results between replicates and seasons.Keywords: animal performance; animal production; grassveld; grazing; grazing intensity; mathematical model; model; performance; productivity; southern africa; stocking rate; yiel

A proposed method for determining long term optimum utilization intensities of pastures and veld.

Application of utilization intensity as an experimental variable by the use of the pasture disc meter and the put- and take technique is recommended as an alternative to stocking rate experiments. Utilization intensity allows stocking rate to be used as a measure of pasture productivity and consequently the relationship between animal gain and stocking rate and the relationship between veld condition score and utilization intensity could be used to determine a long term optimum utilization intensity for veld in good condition and a range of acceptable utilization intensities which will allow veld in poor condition to recover.Keywords: condition; disc meter; method; optimum utilization; pasture; pasture disc meter; productivity; range; stocking rate; technique; utilization; veld; veld condition; veld condition scor

Short Communication:The function of the hygroscopic awn of Themeda triandra.

The hygroscopic awn of species such as Themeda triandra is widely believed to be a device ensuring the early burial of its seed. This belief has been extensively tested and no tendency for such self-burial has been found. It has been demonstrated that the propelling action of the awn does cause the seed to move along the surface and its possible function as a dispersal mechanism is tentatively suggested.Keywords: botany; burial; caryopses; dispersal; function; germination; hygroscopic awn; seed; themeda triandr

The disc pasture meter: Possible applications in grazing management.

The disc meter is a simple inexpensive instrument which may be used to make rapid yield estimates of standing forage. Linear regression relationships between meter reading and pasture dry matter yield are usually fairly good, but these may be affected by a number of different factors. The meter should therefore be calibrated for each specific set of conditions in which it is to be used. Estimation of pasture yield with this instrument provides an objective basis on which to adjust animal numbers in grazing trials and enables pasture intake by grazing animals to be estimated in rotational grazing systems. It may also be useful for quantitatively describing pasture-animal relationships and for construction pasture growth curves.Keywords: botany; disc meter; dry matter yield; equipment; forage; grazing; grazing management; grazing systems; growth curves; intake; pasture; rotational grazing; sampling; yiel

A comparison of four different standards of reference for the animal unit for determining stocking rate.

No single standard of reference for the animal unit (AU) for determining stocking rates has materialized. Often, therefore, it is not clear which standard of reference for the AU or which method of determining stocking rate has been used in the presentation of research results. A comparison is made of four different standards of reference for the AU, namely; 1. the individual animal, 2. animal biomass, 3. metabolic mass, and 4. the Large Stock Unit (LSU). In comparing these methods, as the standard of reference is able to characterize animals more accurately, their simplicity decreases but generality of application increases. The generality of application should be the primary factor influencing the choice of a standard of reference for the AU. However, to avoid prescription on which standard of reference and method should be used for determining stocking rate, a simple descriptive notation is proposed.Keywords: animal biomass; animal units; large stock unit; mass; metabolic mass; method; south africa; standards; stocking rate

The effect of different winter and early spring removal treatments on Themeda triandra in the tall grassveld of Natal.

Themeda triandra dominated tall grassveld was mown to different heights, mown and trampled with sheep or burned, from mid-April through to mid-November, and the effect of treatments on the parent tiller, the subsequent production of lateral tillers and plant vigour monitored during the post-treatment period. Regrowth of parent tillers was appreciable only where clipping was lenient (to 10 cm). Burning destroyed all parent tillers. Lateral tillers developed poorly on all plots mown in early and mid-winter and on those burned in late winter and early spring. Lateral tillers yielded best all over treatment times when cutting was intense (to 5 cm). Herbage yields from lateral growth were higher when treatments were applied in April and August, than when applied in June or October. Regrowth vigour, measured in December and January was greater the more lenient the treatment, and was poor when defoliation was delayed to October. Even in control plots, flowering of T. triandra occurred in only 52% of the parent tiller population. The apices of the non-flowering tillers were damaged by a wasp, Oscinella truncata, whose effect increased in severity as defoliation intensity increased.Keywords: burning; clipping; cutting; defoliation; herbage; herbage yield; lateral tillers; natal; oscinella truncata; plant vigour; regrowth; south africa; tall grassveld; themeda triandra; tillers; ukulinga research station; yiel