Nitrogen management strategies on perennial ryegrass-white clover pastures in the Western Cape Province

Thesis (PhD(Agric) (Agronomy))--University of Stellenbosch, 2005.The response of perennial ryegrass and white clover, grown under controlled conditions, to fertiliser N rates applied under variable soil temperature (6, 12 and 18 °C), soil water potential (-10, -20, -25 and -35 kPa) and seasonal growing (June/July and October/November) conditions as well as field conditions, were evaluated. Primary- (PDM), residual- (RDM) and total dry matter (TDM) production (g pot-1) were recorded over the first- and second regrowth cycles as well as the accumulative DM production over the two regrowth cycles, respectively. Leaf N content (%) was recorded at the end of first and second regrowth cycles. Tiller/stolon numbers and root dry mass (g pot-1) were recorded at the end of the second regrowth cycle. Soil ammonium-N and nitrate-N (mg kg-1) content was monitored after fertiliser N application. Decreasing soil temperatures resulted in decreased TDM production in both crops. Only perennial ryegrass was influenced by fertiliser N rate, with a general increase in dry matter production as fertiliser N rate was increased. Ryegrass TDM production did not differ between the 100 and 150 kg N ha-1 rates but were both higher (P=0.05) if compared to the 0 and 50 kg N ha-1 treatments. Soil nitrate levels 31 days after application of 150 kg N ha–1 were still sufficient to stimulate ryegrass RDM production. The 173.8% increase in ryegrass TDM production measured at 6 °C where 150 kg N ha-1 was applied compared to the 0 kg N ha-1 treatment illustrated the ability of ryegrass to respond to fertiliser N at low soil temperatures. Soil water potential of -20 kPa resulted in higher ryegrass PDM and TDM production compared to the -25 and -35 kPa levels. White clover PDM and TDM production were however not influenced by soil water potential or fertiliser N rate. Ryegrass TDM production increased (P=0.05) as fertiliser N rates were increased. The most favourable soil water level for both ryegrass and clover root development was found to be -35 kPa. Perennial ryegrass and white clover PDM, RDM and TDM production were higher during the October/November season compared to the June/July season. Increased fertiliser N rates resulted in increased (P=0.05) ryegrass PDM and TDM production. White clover dry matter production was not influenced by fertiliser N rates. In the field study the effect of 0, 50, 100 and 150 kg N ha-1 applied as a single application either in autumn, early winter, late winter, early spring or late spring on pasture dry matter production, clover content and selected quality parameters of a perennial ryegrass-white clover pasture were investigated. Soil nitrogen dynamics in the 0-100, 200-300 and 400-500 mm soil layers were studied for 49 days following fertiliser N application. The effect of 50 kg N ha-1 on soil N dynamics was generally the same as found at the 0 kg N ha-1 applications and may therefore be regarded as a low risk treatment. The application of 150 kg N ha-1 especially in autumn and early winter showed a tendency to exceed the absorption capacity of the pasture and thereby expose fertiliser N to possible leaching and contamination of natural resources. Increased fertiliser N rate resulted in a general increase in pasture dry matter production with the highest yields recorded where N was applied in early and late spring and the lowest in early winter. The application of 150 kg N ha-1 in early and late spring resulted in the highest TDM production, however, the 50 kg N ha-1 resulted in a more efficient conversion of N applied to additional DM produced. In contrast to DM production, the clover percentage generally decreased as fertiliser N rate was increased. The effect of season of application was inconsistent. Annual trends show that the clover percentage eventually recovered to the same levels as the 0 kg N ha-1 treatments. Due to the above minimum levels recorded for most mineral and quality parameters tested it is envisaged that treatment combinations as used in this study will not be at any disadvantage to pasture and animal productivity. The study has shown that the use of fertiliser N to boost perennial ryegrass-white clover productivity and thereby minimising the negative effect of the winter gap on fodder flow management during the cool season in the Western Cape Province, may be an important management tool. Except for late spring applications, all seasons of application reduced the negative impact of the winter gap on fodder availability. It is concluded that regression lines as summarised in Tables 7.2 and 8.2 show great potential to be instrumental in developing regression models, accurately predicting the effect of fertiliser N rate on pasture performance. Other factors to be considered includes the productivity of the pasture, initial clover content, expected clover content at the end of the first regrowth cycle after fertiliser N application and the quantity of additional fodder required. Additional requirements will be to maintain and 150 kg N ha-1) in winter, as the N uptake capacity of the pasture could be exceeded and thereby increasing the risk of N leaching, resulting in environmental pollution. The N response efficiency of the pasture is also the lowest at the 150 kg N ha-1 rates, thereby reducing the profitability of these treatments

A pedagogical approach to the formulation of fingering options for selected piano works of Debussy, Scriabin, Rachmaninoff, Ravel, Bartók, and Prokofiev : a practice-led study

This thesis is an investigation of piano fingering that can be applied to the practical study of problematic technical material and musical content in selected piano works of Debussy, Scriabin, Rachmaninoff, Ravel, Bartók, and Prokofiev. The appropriate and practical application of piano fingering forms the basis of a sustainable virtuoso piano technique. Most available literature relating to the domain of piano fingering only addresses the basic application thereof. This study aims to present and discuss effective approaches to the formulation of fingering options necessary to surmount musical and pianistic obstacles. Primary data was collected through the researcher’s practical study of the selected piano works, as suggested by the practice-led research design. The main objective was to devise fingering options that complement the composer’s indicated musical and pianistic intentions. Additionally, the influence of hand sizes on the appropriate choice of fingering was also investigated. When necessary, secondary movements produced by the wrist and forearms, which complement the suggested fingering options, were discussed. Taxing pianistic figurations and musical content can successfully be mastered by the employment of proper fingering. Various fingering possibilities should be investigated before deciding on the desired combinations. A thorough study of fingering at the onset of learning new repertoire is essential to achieve freedom in artistic interpretation and technical finesse.Thesis (DMus (Performing Art))--University of Pretoria, 2021.MusicDMus (Performing Art)Unrestricte

An explorative study of serial rape and victimisation risk in South Africa.

Serial rape attracts much media attention and has become a topic of increased interest and concern. However, both locally and internationally, there is a paucity of empirically based research. The limited research which exists often does not focus on the victim as a “subject” which could contribute to solving existing cases or in curtailing the serial rapist. In this article, socio-demographic characteristics of 75 victims of serial rape, and how they were selected by the rapist were used to construct a general profile of the people who are the targets of the serial rapist. Factors or contexts which put women at risk are also identified and investigated. Comparisons are made between the characteristics of the victims of serial rapists in other countries, while comparisons are also made between the victims of single-victim rapists and those of the serial rapist. Of great concern is, amongst others, that the results indicate that in South Africa a large number of victims of the serial rapist are girl children. Limitations of the research are indicated, while a suggestion for future research concludes the article

Tillage practices affect weeds differently in monoculture vs. crop rotation

Reduced tillage practices are widely considered to be more sustainable than conventional tillage practices, but many producers remain reluctant to reduce tillage due to difficulties controlling weeds. Crop rotation is often put forward as the best means to manage weeds in reduced tillage systems, but uncertainties remain around how different tillage practices and crop rotations interact. Here, we assess the effects of four different tillage practices on weed seedbank density and composition in wheat (Triticum aestivum) monoculture (WWWW), and two different rotations, wheat-medic-wheat-medic (annual medic, Medicago spp.; WMWM), and wheat-canola-wheat-lupin (Brassica napus, Lupinus spp.; WCWL). We use data across a whole four-year rotation period from a long-term experiment replicated at two sites in South Africa's winter rainfall region. The four tillage practices assessed follow a gradient of soil disturbance: conventional tillage (CT, soil inversion through ploughing), minimum tillage (MT, shallow soil loosening), no tillage (NT, direct drilling with tine openers) and zero tillage (ZT, direct drilling with disc openers)

An Investigation into the Use of Microchemistry Experiments in First-year University-level Practicals

In the case study reported on in this article the desirability to convert first-year university-level practicals in chemistry from conventional techniques to microscale methods was investigated. The results indicated that microscale experiments did not result in a noticeable saving in time and gave results that compare favourably with those of the conventional experiments. The most positive aspect of microscale experiments is a long-term financial one. A few negative aspects of microscale experiments were identified in the study. In hierdie bydrae word 'n gevallestudie gerapporteer oor die wenslikheid om eerstevlak universiteitschemie-prakties van konvensionele tegnieke na mikroskaaltegnieke om te skakel. Die resultate toon dat die mikroskaaleksperimente nie noemenswaardig tydsbesparend is nie en resultate lewer wat goed vergelyk met di? van konvensionele eksperimente. Die mees positiewe aspek van mikroskaaleksperimente is finansi?le besparing op die lang termyn. Enkele negatiewe aspekte van mikroskaaleksperimente is in die ondersoek ge?dentifiseer. Keywords: Microscale, Practicals, Chemicals, Microchemistry, First-level South African Journal of Chemistry Vol.57 2004: 19-2

Understanding the influence of manufacturing and material parameters on the mechanical properties of polymer-clay composites : an exploratory statistical analysis

Polymers are used in various industrial applications due to their ease of production, light weight and ductility. Adding fillers, such as clays, improves a range of thermo-mechanical properties, however manufacturing parameters may have an influence on the composite system. This paper provides a statistical analysis on a set of previously obtained experimental tensile data with various clay fillers added to high density polyethylene (HDPE). The composite material was compounded using an extrusion process and manufactured into tensile test samples by means of hot pressing. Various manufacturing parameters (number of extrusions, press time, sample cooling method), material (polymer grade, clay type, clay weight loading) and testing parameters (strain rate) were investigated to determine their influence on the mechanical properties, specifically strength (ultimate tensile strength) and ductility (percentage elongation at failure), of the composite system. The results showed wide variability, necessitating a statistical approach. The statistical analysis concluded that all parameters, except for press time, have a statistically significant influence on the mechanical properties of interest. The conclusions and insights gained from these analyses will be used to inform a statistical design of experiments to quantify the manufacturing variability and reliability in future work.https://aip.scitation.org/journal/apcpm2021Chemical EngineeringMechanical and Aeronautical Engineerin

Efficacy of alphacypermethrin-treated high density polyethylene mesh applied to jet stalls housing horses against Culicoides biting midges in South Africa

The efficacy of alphacypermethrin-treated high density polyethylene (HDPE) mesh appliedto jet stalls against Culicoides biting midges (Diptera: Ceratopogonidae) was determined bymechanical aspiration of midges from horses and using Onderstepoort 220 V downdraughtblack light traps in four blocks of a 3 × 2 randomised design under South African fieldconditions. The alphacypermethrin-treated HDPE mesh applied to the stall significantly(P = 0.008) reduced the number of Culicoides midges, predominantly Culicoides (Avaritia)imicola Kieffer, mechanically aspirated from horses housed in the stall. The mesh reducedthe Culicoides midge attack rate in the treated stall compared to the untreated stall and asentinel horse by 6 times and 14 times, respectively. The number of Culicoides midges andC. imicola collected in light traps from the untreated and alphacypermethrin HDPE mesh-treated stalls did not differ significantly (P = 0.82). Alphacypermethrin-treated HDPE meshcould be used to reduce exposure of horses in jet stalls to Culicoides midges, specifically C.imicola, and the risk of midge-borne Orbivirus transmission.The Equine Research Centre, MarySlack and Daughters Foundation, and the National ResearchFoundation (Grant 89686)http://www.elsevier.com/locate/vetpar2016-05-30hb201

Field and in vitro insecticidal efficacy of alphacypermethrin-treated high density polyethylene mesh against Culicoides biting midges in South Africa

The efficacy of untreated and alphacypermethrin-treated high density polyethylene (HDPE) mesh against Culicoides biting midges (Diptera: Ceratopogonidae) was determined using Onderstepoort downdraught black light traps and a contact bioassay. Three traps were operated overnight in four replicates of a 3 x 3 randomised Latin square design near horses under South African field conditions. Both the untreated and alphacypermethrin-treated HDPE mesh significantly (P < 0.05) reduced the numbers of Culicoides midges, predominantly Culicoides (Avaritia) imicola Kieffer, collected in the light traps by 4.2 and 7.2 times respectively. A repellent effect of the alphacypermethrin-treated mesh was not confirmed because the number of midges collected in the light traps with untreated and alphacypermethrin-treated HDPE mesh were not significantly different (P = 0.656). Bioassay of the insecticidal contact efficacy indicated median C. imicola mortality of 100% from 30 and 10 min following exposure to the alphacypermethrin-treated HDPE mesh for 1 or 3 min, respectively. In the bioassay, mortality was significantly higher (P = 0.016) at 5 min post exposure in the midges exposed to the alphacypermethrin-treated mesh for 3 min (74.8%) compared to the 1 min exposure group (59.5%). The HDPE mesh could be used to reduce exposure of housed animals to Culicoides midges, specifically C. imicola, and viruses transmitted by these midges. Mesh treated with alphacypermethrin had the additional benefit of a rapid insecticidal effect on C. imicola.The Faculty of Veterinary ScienceResearch Fund, Department of Companion Animal ClinicalStudies, Equine Research Centre and the Mary Slack and Daughters Foundation.http://www.elsevier.com/locate/vetparhb201

Extent of soil acidity in no-tillage systems in the Western Cape Province of South Africa

CITATION: Liebenberg, A., et al. 2020. Extent of soil acidity in no-tillage systems in the Western Cape Province of South Africa. Land, 9(10):361, doi:10.3390/land9100361.The original publication is available at https://www.mdpi.comPublication of this article was funded by the Stellenbosch University Open Access FundRoughly 90% of farmers in the Western Cape Province of South Africa have converted to no-tillage systems to improve the efficiency of crop production. Implementation of no-tillage restricts the mixing of soil amendments, such as limestone, into soil. Stratification of nutrients and pH is expected. A soil survey was conducted to determine the extent and geographical spread of acid soils and pH stratification throughout the Western Cape. Soil samples (n = 653) were taken at three depths (0–5, 5–15, 15–30 cm) from no-tillage fields. Differential responses (p ≤ 0.05) between the two regions (Swartland and southern Cape), as well as soil depth, and annual rainfall influenced (p ≤ 0.05) exchangeable acidity, Ca and Mg, pH(KCl), and acid saturation. A large portion (19.3%) of soils (specifically in the Swartland region) had at least one depth increment with pH(KCl) ≤ 5.0, which is suboptimal for wheat (Triticum aestivum), barley (Hordeum vulgare), and canola (Brassica napus). Acid saturation in the 5–15 cm depth increment in the Swartland was above the 8% threshold for production of most crops. Acid soils are a significant threat to crop production in the region and needs tactical agronomic intervention (e.g. strategic tillage) to ensure sustainability.https://www.mdpi.com/2073-445X/9/10/361Publisher's versio

Long-term evidence for ecological intensification as a pathway to sustainable agriculture

Ecological intensification (EI) could help return agriculture into a 'safe operating space' for humanity. Using a novel application of meta-analysis to data from 30 long-term experiments from Europe and Africa (comprising 25,565 yield records), we investigated how field-scale EI practices interact with each other, and with N fertilizer and tillage, in their effects on long-term crop yields. Here we confirmed that EI practices (specifically, increasing crop diversity and adding fertility crops and organic matter) have generally positive effects on the yield of staple crops. However, we show that EI practices have a largely substitutive interaction with N fertilizer, so that EI practices substantially increase yield at low N fertilizer doses but have minimal or no effect on yield at high N fertilizer doses. EI practices had comparable effects across different tillage intensities, and reducing tillage did not strongly affect yields.Intensifying food production sustainably is critical given growing demand and agriculture's environmental footprint. This meta-analysis finds that practices such as adding organic matter and increasing crop diversity can partly substitute for nitrogen fertilizer to sustain or increase yields