Browsing by Author "Nel, Werner"

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    The abundance and diversity of meso- and macrofauna in vineyard soils under different management practices
    (Stellenbosch : Stellenbosch University, 2005-03) Nel, Werner; Reinecke, A. J.; Reinecke, S. A.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: The agricultural sector in South Africa relies heavily on the use of pesticides to protect crops against pest organisms. Pesticides can affect non-target organisms such as the meso- and macrofauna in the soil detrimentally. Since these organisms play an important role in the processes of mineralization and decomposition in the soil and contribute to soil fertility, it is important that they are protected. A large amount of published literature exists on the biological importance of soil meso- and macrofauna and the effects that various agricultural practices have on them. The main aim of this study was to investigate the influence of agricultural practices on the abundance and diversity of meso- and macrofauna in different vineyard soils. A comparative study was conducted of an organically managed, conventionally managed and an uncultivated control soil. A secondary aim was to determine the effect of these agricultural management practices on the biological activity of these animals. Soil samples were taken, from which mesofauna (Collembola and Acari) were extracted with a modified Tullgren extractor, identified and counted. Earthworms were extracted from the soil using hand sorting methods. Soil parameters such as pH, water holding capacity, organic matter content, soil texture and soil respiration were determined. Bait lamina and litter-bags were also used to help determine the biological activity within the soil. The mesofauna diversity was quantified using the Shannon Weiner diversity index, as well as a diversity index described by Cancela da Fonseca and Sarkar (1996). Differences in abundance of both the meso-and macrofauna were statistically measured using ANOVA's. Biological activity results were also interpreted using ANOV A's. Results indicate that the abundance of the meso fauna was the highest at the organically treated vineyard soil and lowest in the conventionally managed soil where pesticide application took place. The earthworms also showed the same trend as the mesofauna, but were much more influenced by seasonal changes. Biological activity, according to the bait lamina and the litter-bag results, was higher in both the conventionally and organically managed soils than in the control, but no statistical significant differences were found between the two experimental soils. The soil respiration (C02-flux), also indicating biological activity, was highest in the organically treated soil and lowest in the conventionally treated soil. The different sampling techniques used gave variable results and although the organically managed soil proved to have higher abundances of both meso- and macrofauna, the biological activity did not show the same trends. In conclusion the data did not give enough evidence as to whether organic management practices were more beneficial than conventional management practices for the maintenance of soil biodiversity.
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    Exploring South Africa’s southern frontier : a 20-year vision for polar research through the South African National Antarctic Programme
    (Academy of Science of South Africa, 2017) Ansorge, Isabelle J.; Skelton, Paul; Bekker, Annie; de Bruyn, P.J. Nico; Butterworth, Doug; Cilliers, Pierre; Cooper, John; Cowan, Don A.; Dorrington, Rosemary; Fawcett, Sarah; Fietz, Susanne; Findlay, Ken P.; Froneman, William P.; Grantham, Geoff H.; Greve, Michelle; Hedding, David; Hofmeyr, Greg G. J.; Kosch, Michael; Le Roux, Peter C.; Lucas, Mike; MacHutchon, Keith; Meiklejohn, Ian; Nel, Werner; Pistorius, Pierre; Ryan, Peter G.; Stander, Johan; Swart, Sebastiaan; Treasure, Anne; Vichi, Marcello; Van Vuuren, Bettine J.
    No abstract available