Browsing by Author "Botha, A."

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    Effects of alien plant management, fire and soil chemistry on selected soil microbial populations in the Table Mountain National Park, South Africa
    (NISC Pty Ltd., 2005-06) Cilliers, C. D.; Botha, A.; Esler, K. J.; Boucher, C.
    This pilot study examined changes in soil chemistry and microbial population sizes following the extensive wildfires in 2000 on the Cape Peninsula. The effects of standing alien plants and stacks of mechanically-cleared alien plant material on selected post-fire microbial populations and their recovery were investigated. These were compared to burnt fynbos and the burnt cleared areas surrounding wildfire burnt stacks. Microbial population sizes and chemical changes were also monitored in unburnt fynbos and dense unburnt stands of invasive alien plants. Differences in soil chemistry and microbial population sizes occurred in the samples taken from the various post-fire environments while marked seasonal changes were also apparent. Microbial population sizes were linked to pre-fire vegetation characteristics, fire intensity, the management of alien plants, soil chemical changes and seasonal influences. High volumes of woody alien plant biomass impacted on post wildfire microbial population sizes during summer. During winter, however, microbial population sizes were primarily influenced by soil texture and nutrient composition. Copyright © NISC Pty Ltd.
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    Fertility in dairy cows and ways to improve it
    (South African Society for Animal Science, 2018-11-17) Muller, C. J. C.; Cloete, S. W. P. (Schalk Willem Petrus van der Merwe); Botha, A.
    The fertility of dairy cows affects the genetic improvement and financial sustainability of dairy herds. Fertility is a complex trait that is affected by several factors. Genetically, fertility is difficult to improve because of low heritability. Cows that do not become pregnant are usually culled from the herd. This paper reviews results from studies conducted in South Africa that are aimed at improving the reproductive performance of dairy cows. Records from 9 046 cows in 14 Holstein herds showed that, while lactation number, calving year and calving season affected fertility traits significantly, herd management had the largest effect. Mean ± sd for calving to first service (CFS) and from calving to conception (DO) intervals were 77 ± 30 and 134 ± 74 days, respectively. The number of services per conception (SPC) was 2.55 ± 1.79. The proportion of first services within 80 days post partum and cows confirmed pregnant within 100 and 200 days post partum were 0.64 ± 0.48, 0.36 ± 0.48, and 0.71 ± 0.45, respectively. Heritability (h²) estimates were 0.06, 0.08 and 0.07 for CFS, DO, and SPC, respectively. Albeit low h² estimates were consistent with literature results, the genetic correlation between CFS and DO was positive (0.56), and negative (-0.29) between CFS and pregnancy success. Crossbreeding, using a dual-purpose breed, improved fertility, similar to studies conducted overseas. Increasing the energy content of the total diet of Holstein cows on kikuyu-ryegrass pasture by feeding 7 kg versus 12 kg concentrates/cow/day, improved fertility as a higher proportion of cows were pregnant by 150 days in milk, being 0.52 versus 0.84 and 0.56 versus 0.76 for primi- and multiparous cows, respectively. Estimating breeding values for fertility traits for breeding sires would assist in improving fertility in dairy cows
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    The occurrence and infectivity of arbuscular mycorrhizal fungi in inoculated and uninoculated rhizosphere soils of two-year-old commercial grapevines
    (South African Society for Enology and Viticulture, 2005) Meyer, A. H.; Botha, A.; Valentine, A. J.; Archer, E.; Louw, P. J. E.
    Arbuscular mycorrhizal (AM) fungal populations present in the rhizosphere of vine roots in the vineyards of a commercial farm in the Stellenbosch Region were investigated using microscopic analyses. AM root colonisation levels of between 70% and 90% were found in both grapevine roots that were previously artificially inoculated with commercial AM inocula, and in uninoculated (control) grapevine roots. The AM fungal isolates in the rhizosphere soil, identified using morphological criteria, belonged to the genera Acaulospora, Gigaspora, Glomus, Sclerocystis and Scutellospora. The majority of species found was not present in the commercial inocula and was either indigenous to the vineyard or originated from the nursery where the vines were obtained. Isolates of Glomus and Acaulospora appeared to be the most abundant. The AM fungal species occurred at a soil phosphorus (P) concentration of up to 80 mg/kg P and a soil pH (KCl) that ranged between 5.63 and 6.10. Total spore counts ranged between 1 000 and 3 779 spores/100 g dry soil. In accordance with literature, lower spore concentrations were recorded for the heavier soil types with no cover crop system, compared with the sandy soil type on which cover crops were sown annually.
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    Young grapevine response and root colonisation following inoculation with arbuscular mycorrhizal fungi
    (South African Society for Enology and Viticulture, 2004) Meyer, A. H.; Valentine, A. J.; Botha, A.; Archer, E.; Louw, P. J. E.
    The host plant response following inoculation with commercially available arbuscular mycorrhizal (AM) fungi was determined in young grapevines under field conditions which would prevail on a typical farm. Measurements regarding growth improvement, nutrition and water relations were made in a field trial carried out on a commercial farm in the Stellenbosch region. Merlot noir grafted onto 101-14 Mgt and 110 Richter (110 R) in a Westleigh soil form and 99 Richter (99 R) in a Fernwood soil form was planted in December 1998. Vine roots were inoculated during planting with Biocult, Vaminoc and Glomus sp. 1054. Inoculation generally had little effect on xylem sap and leaf nutrient concentrations, water relations or growth responses. This was mainly ascribed to indigenous AM fungi, which seemed to have masked the effects of inoculation. A high soil P concentration was also implicated as a possible contributing factor to the general lack of grapevine response to AM inoculation.