Die benutting en bewaring van die weidingsekosisteem in die R.S.A.

nullKeywords: afrikaans; conservation; grassland biome; grazing; grazing ecosystems; south africa; utilizatio

The phenological development of Themeda triandra, Elyonurus argenteus and Heteropogon contortus under field conditions in the central Orange Free State.

Range managers must take into consideration the phenological development of plants, especially shoot apex development, when planning pasture management systems. The damaging of the shoot apex by grazing, cutting, fire or drought may have a detrimental effect on leaf, shoot and seed production. The shoot apices of Themeda triandra, Elyonurus argenteus and Heteropogon contortus showed the same tendency with respect to elevation before and during flowering. The shoot apices were not elevated more than 1 cm to 1, 5 cm above the soil level for a period of 11 to 14 months. After the shoot apices become reproductive they are raised slowly 2 to 3 cm above soil level. If soil moisture conditions become favourable flowering occurs in due time. Elyonurus argenteus tends to flower 21 to 28 days earlier than T. triandra and H. contortus. Flowering of T. triandra and H. contortus may occur as late as March if soil moisture conditions are not favourable earlier. The carbohydrate (reserve) content of the stubble of all three grasses decreased rapidly under fluctuation soil conditions that resulted in successive regrowth and dying off of the aerial parts of the plants. The moisture content of the leaves dropped quickly under moisture stress conditions. Elyonurus argenteus compares favourably with T. triandra and H. contortus with respect to their in vitro digestibility and crude protein content.Keywords: afrikaans; botany; carbohydrate; crude protein content; cutting; digestibility; drought; elyonurus argenteus; fire; flowering; grasses; grazing; heteropogon contortus; in vitro digestibility; moisture content; moisture stress; orange free state; pasture management; production; protein; regrowth; seed production; shoot apex; shoot apices; soil moisture; south africa; themeda triandr

The effect of defoliation and moisture stress on the productivity of Themeda triandra Forsk. under controlled conditions.

Range managers in semi-arid and arid regions in the Republic of South Africa must take into consideration the incidence of droughts and the detrimental effect of incorrect grazing practices during drought periods. Trials were conducted with Themeda triandra, during three phenological phases, in pots to determine the effect of severe, moderate and no defoliation, before and during periods of moisture stress, on the productivity of the plants. Themeda triandra plants in the vegetative and reproductive stage were affected the most severely as reflected by dry matter production, root mass and total available carbohydrate (TAC) content. When Themeda triandra in any phenological phase was subjected to relative short periods (up to three weeks) of moisture stress there was a significant increase in root mass. The TAC content of the roots and stubble increased during periods of moisture stress but decreased significantly after the plants had been re-watered. Themeda triandra plants in three phenological phases showed marked differences in respect to water use efficiency and dry matter production under the different treatments. Lenient defoliation before and during periods of moisture stress seems to be more beneficial than severe or no defoliation.Keywords: afrikaans; carbohydrate; defoliation; drought; dry matter production; grazing; moisture stress; productivity; root mass; south africa; stress; themeda triandra; water use; water use efficienc

Production of natural grassland in the central Orange Free State in relation to climate.

In order to plan a livestock enterprise it is imperative to know the production potential of the natural grassland. Grassland production is determined mainly by climate and soil, provided reasonably sound management practices are employed. It is thus evident that effective planning must necessarily depend heavily on a reliable knowledge of the climate/plant/soil interaction. Photosynthesis is the source of primary production in grassland. A simulation model Putu 2 computes the potential total production, environmental limiting factors as well as the daily water balance, taking rainfall into account. Environmental limitation and total dry matter production for Bloemfontein was computed over three growing seasons. The results show that fairly accurate estimates of total production are possible with the Putu 2 simulation model especially during years of normal and above normal rainfall. The soil water status computed for Themeda triandra dominated veld agrees well with the results obtained in field trials. The limiting environmental factors for three growing seasons were computed with moisture representing by far the greatest limitation on production.Keywords: bloemfontein; climate; dry matter production; environmental factors; field trial; grassland; limiting factor; management; model; photosynthesis; primary production; production potential; rainfall; simulation model; soil; soil water; south africa; themeda triandra; water balanc

Hydrological cycle and water use efficiency of veld in different successional stages.

Hydraulic non-floating lysimeters were used to determine the evapotranspiration (Et) and water use efficiency (W.U.E.) of veld in different successional stages for the period September 1978 to June 1979. In addition runoff of the various successional stages was recorded on runoff plots.Averages of 1,018 litres, 1,258 litres and 1,771 litres of water were lost by evapotranspiration from climax, subclimax and pioneerveld respectively for each gram D.M. produced during the second half of the growing season. The highest Et-losses were recorded during the last week of November, when the grasses were in the reproduction phase.The runoff from the pioneer-runoff plots was 171 percent higher than that of the climax runoff plot. A computer programme was used to fit harmonic curves to the weekly Et/Eo relationship of each successional stage for the 1978/79 growing season.Keywords: afrikaans; botany; evapotranspiration; grass; grasses; hydraulic non-floating lysimeters; lysimeter; orange free state; runoff; season; south africa; sydenham; university of the free state; veld; water use efficienc

Ranking of grass species according to visible wilting order and rate of recovery in the central Orange Free State.

A number of grasses were ranked according to the order in which they wilted with diminishing moisture availability, and according to their ability to recover after water replenishment. Digitaria eriantha and Digitaria argyrograpta were the most sensitive to moisture stress, whereas Sporobolus fimbriatus and Panicum stapfianum were last to show signs of wilting. The latter two grass species were the first to recover from wilting during optimum soil water conditions. The leaf water potential and soil water content at which each grass species wilted were recorded.Keywords: availability; digitaria argyrograpta; digitaria eriantha; grasses; leaf water potential; moisture stress; neutron probe; orange free state; panicum stapfianum; soil water; soil water content; soil water potential; south africa; sporobolus fimbriatus; stress; water use efficiency; wiltin

The utilisation of grassveld in the central Orange Free State by sheep.

A study of the utilization of climax grassveld by sheep in the central Orange Free State revealed a preference for certain species. The selection pattern differed very little from summer to winter unless material of preferred species became scarce and the animals were forced to graze proportionately more of the less palatable species. In calculating the corrected species importance the customary correction for presence (percentage frequency) was made, as well as corrections for dry matter production per cm 2 basal cover and for quality (crude protein and digestible organic matter content). These correction factors facilitated a more reliable value of the relative importance of the different species being obtained.Keywords: afrikaans; basal cover; crude protein; dry matter production; grassveld; orange free state; organic matter; palatability; preference; production; protein; sheep; south africa; utilizatio

The production of Smuts finger grass in the western Transvaal.

The production of Smuts finger grass (Digitaria eriantha) was evaluated in various trials in the Highveld region, at Potchefstroom. These trials were carried out over a long period on several soil types and with different fertilizer levels. All results were pooled and a multiple regression analysis was done to estimate the production potential under different rainfall, nitrogen and phosphate regimes.Keywords: afrikaans; digitaria eriantha; fertilizer; grasses; highveld; multiple regression analysis; nitrogen levels; phosphate; potchefstroom; production; production potential; rainfall regimes; regression analysis; smuts fingergrass; soil types; south afric