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The relative costs and benefits of thermal acclimation for manipulating field performance of pest insects depend upon a number of factors including which traits are affected and how persistent any trait changes are in different environments. By assessing plastic trait responses of Ceratitis capitata (Mediterranean fruit fly) across three distinct operational environments (laboratory, semi-field, and field), we examined the influence of different thermal acclimation regimes (cool, intermediate [or handling control], and warm) on thermal tolerance traits (chill-coma recovery, heat-knockdown time, critical thermal minimum and critical thermal maximum) and flight performance (mark-release-recapture). Under laboratory conditions, thermal acclimation altered thermal limits in a relatively predictable manner and there was a generally positive effect across all traits assessed, although some traits responded more strongly. By contrast, dispersal-related performance yielded strongly contrasting results depending on the specific operational environment assessed. In semi-field conditions, warm- or cold-acclimated flies were recaptured more often than the control group at cooler ambient conditions suggesting an overall stimulatory influence of thermal variability on low-temperature dispersal. Under field conditions, a different pattern was identified: colder flies were recaptured more in warmer field conditions relative to other treatment groups. This study highlights the trait- and context-specific nature of how thermal acclimation influences traits of thermal performance and tolerance. Consequently, laboratory and semi-field assessments of dispersal may not provide results that extend into the field setting despite the apparent continuum of environmental complexity among them (laboratory < semi-field < field).

This paper introduces the application of technology solutions into the realm of bridge inspection methodologies in South Africa, aiming to enhance the current visual bridge inspection methodology. Unmanned Aerial Vehicles (UAVs) can be used as an alternative to collect bridge image data, and point cloud models can be created from captured images by using photogrammetry software. For this study, accredited bridge inspectors were approached to complete TMH 19 inspection sheets of bridge structures using only the point cloud models and captured images, as a proposed new inspection methodology. This paper compares historic inspection ratings and the point cloud inspection ratings to investigate the effectiveness and practicality of the new proposed inspection methodology. The study concluded that bridge inspectors could identify and rate critical defects of bridge structures using the new inspection methodology, but there are limitations and specific use cases that need to be identified.

Accurate, reliable and easy-to-use statistical methods in multifactorial age estimation from the skeleton remains a much-debated issue. In this paper, we explore the use of decision trees in adult age estimation. For this purpose, a dataset from 100 acetabula of South Africans, previously used for age estimation using transition analysis, were used to build a basic decision tree. A test sample of 25 individuals were then employed to assess the newly developed decision tree. Using the decision tree, 20 of the 25 individuals were classified into the correct age group (young, middle or older adults), with the remaining 5 falling within the adjacent age group. The decision tree provided a more accurate outcome as compared to the previous study using transition analysis. Although much research is still needed, this analysis suggests that decision trees may be usable in adult age estimation and may handle the non-linear relationship between chronological and biological age somewhat better than other traditional statistical methods.

Why this research Matters Plant–soil feedbacks (PSFs) give a mechanistic understanding on how soil properties established by previous plant species go on to influence the performance of the same or different species in monoculture, intercropping or crop rotation systems. We hypothesized that different dryland crops such as Zea mays L., Helianthus annuus L., Phaseolus vulgaris L., and Glycine max L. (Merr.) will have soil legacies that are related to the crop type. We used a two‐phase experiment to test plant performance in soils previously cultivated with the same or different plant species under greenhouse conditions. The positive plant growth for all species in their own soil microbiota suggests that mutualists had a greater impact on plant performance than pathogens. The consistent positive soil–feedback results of P. vulgaris were strongly associated with their own beneficial soil microbiota, meaning that the conditioning phase legacy of mutualists and decomposers were more significant than pathogens under monoculture. Despite successful nodulation in sterilized and inoculated soils, G. max unexpectedly showed neutral and insignificant positive plant feedbacks, respectively. Helianthus annuus was superior to other crop species in creating active carbon stocks and an enzymatically active soil for the next crop. Microbial biomass results suggest that raising fungal relative to bacterial biomass can be achieved by increasing the frequency of H. annuus in rotation sequences. However, more studies are necessary to evaluate whether these elevated ratios promote or depress plant performance under field conditions. This study showed that relative to other dryland crops, H. annuus seems to have the potential of increasing fungal to bacterial ratios, raising legacies in active carbon stocks and soil microbial activity that may be crucial to successional planting in dryland systems.

To observe and describe the development and underlying structure of the spinal manifestations of individuals osteologically diagnosed with DISH (Diffuse Idiopathic Skeletal Hyperostosis), using micro-XCT imaging.A total of 72 individuals with DISH were identified in two modern skeletal collections in South Africa.Vertebral columns affected by DISH were scanned at the micro-focus x-ray computed tomography facility at the Nuclear Energy Corporation of South Africa. Four features were macroscopically examined: (1) the origin of the new bone growth; (2) retention of the original vertebral cortex at the site of the new bone formation associated with DISH; (3) evidence of trabecular bone with or without sclerosis on the anterolateral surface of affected vertebrae; and (4) abnormal areas of osteosclerosis beyond features associated with DISH.Considerable variation across and between the four recorded features was found. Of note, 81% (n = 58) of individuals had both developed trabecular bone within the flowing new bone formation (feature 3), without retention of the original vertebral cortex (feature 2).Possible localised erosive/inflammatory processes destroyed the original cortex of the vertebral body and resulted in the expansion of trabeculae with new bone formation.Micro-XCT imaging shed new light on the development of DISH, adding to literature suggesting that it could be an inflammatory disease.Clinical histories of the individuals were not known.The role of chronic inflammatory disease in the development of DISH should be further explored including both the extra-spinal and spinal manifestations.

Upland rice (Oryza sativa L.) production systems in sub-Saharan Africa are faced with challenges of water stress and nitrogen (N) deficiency, which reduce grain yield, water use efficiency (WUE), and nitrogen use efficiency (NUE). The objective of the study was to determine the response of upland rice to N fertilizer rates under well-watered conditions and to clarify the relationships between WUE and NUE. Upland rice variety Nerica 10 was grown under well-watered conditions and varying N rates in 2014/2015 (Y1) and 2015/2016 (Y2) on the same field at the University of Pretoria&rsquo, s Hatfield Experimental Farm, South Africa. Yields at harvest increased with increasing N rates, linearly in Y1, and following a quadratic trend in Y2. Mean grain yield was highest (4.5 t ha&minus, 1) at 120 kg N ha&minus, 1 and lowest (2.4 t ha&minus, 1) at 0 kg N ha&minus, 1. Agronomic NUE was lowest for 160 kg N ha&minus, 1 (11.7 kg kg&minus, 1 N), while WUE was highest for the 120 kg N ha&minus, 1 (7.58 &plusmn, 1.7 kg mm&minus, 1) and lowest for 0 kg N ha&minus, 1 (4.1 &plusmn, 0.9 kg mm&minus, 1). Findings revealed that at high N levels, compensative N uptake during tillering can reduce harvest index, WUE, and to a lesser extent, grain N concentration.

In South Africa, the potato is produced in regions with different climates. Climate change is expected to result in higher temperatures, thus increasing the incidence of heat stress, but lowering t...

Several well-known correlations to determine the heat transfer coefficients of quasi-turbulent and turbulent flow in smooth tubes are available in literature. However, when these correlations are compared with each other, the results vary over a considerable range. The purpose of this study was therefore to conduct heat transfer and pressure drop experiments in the quasi-turbulent and turbulent flow regimes and to develop an accurate heat transfer correlation that can be combined with recently developed laminar and transitional flow correlations to obtain a single correlation that is valid for all flow regimes. A total of 1180 experimental data points were collected from careful experiments that were conducted ourselves using two different test section configurations. The first test section configuration consisted of a tube-in-tube test section on which the wall temperatures were obtained either indirectly using the Wilson plot method or by direct surface temperature measurements. The second test section configuration consisted of single tubes being electrically heated at a constant heat flux. Different test sections covering a range of tube diameters from 4 mm to 19 mm and a range of tube lengths from 1 m to 9.5 m, were used. Experiments were conducted from a Reynolds number of 2445, which corresponded to the start of the quasi-turbulent flow regime, up to 220,800, which was well into the turbulent flow regime. Water, as well as different concentrations of multi-walled carbon nanotubes, were used as the test fluid, which gave a Prandtl number range of 3–10. A new correlation was developed that could estimate 95% of all the experimental data points within 10% and an average deviation of

Integrated reporting requires a new form of disclosure to provide a holistic view of the organisation and aims to support integrated thinking, decision-making and actions that focus on the creation of value. The International Integrated Reporting Framework (IIRC 2013b) provides guidelines for the content elements required in an integrated report. One of the content elements is ‘risks and opportunities’. This study firstly assessed whether integrated reporting has enhanced integrated thinking between strategy and the risks and opportunities faced by the organisation. For this purpose, a web-based research questionnaire was sent to high-level implementers of integrated reporting at companies listed on the Johannesburg Stock Exchange (JSE) in South Africa, where integrated reporting is a listing requirement. The results of the study provide new insights for companies preparing integrated reports, as well as other stakeholders, which show that integrated reporting has driven change towards integrated thinking between strategy, risks and opportunities. Secondly, a content analysis was done on a sample derived from the top 100 companies listed on the JSE to determine whether integrated reporting has brought about a change in the disclosure of risks and opportunities. The results provide new research findings and indicate that most companies conform to the disclosure requirements noted in the International Framework (IIRC 2013b) regarding risks and opportunities except for disclosures relating to the assessment of specific risks. The content analysis further found that integrated reporting has driven limited change in the disclosure of risks and opportunities.Key words: integrated reporting, integrated thinking, disclosure, risk, opportunity and strategy

The worldwide decrease in available irrigation water is driving the need for the development of methods to minimize water losses in crop production. A field experiment was conducted at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa (25°45′0′’S, 28°16′0′’E and altitude of 1327 m.a.s.l.) in 2013. The objectives of the study were to determine crop-specific model parameters for dry beans and to successfully calibrate and validate the Soil Water Balance (SWB) model for predicting dry bean yield and water use from historical weather data. Model simulations of leaf area index, total dry mass, harvestable dry mass, and soil water deficits agreed reasonably well with measured values and statistical parameters for most variables were within acceptable limits. The SWB model simulated leaf area index, total dry mass, harvestable dry mass, and soil water deficits for drought stress treatments reasonably well. The calibrated model was then used to predict dry bean grain yield for three localities in Limpopo Province over a period of nine years. The scenario modelling results indicated that the model can be used as an irrigation scheduling tool and also be successfully used to estimate yields of dry beans under various conditions and at other localities.

The National Agricultural Research Organisation (NARO), Uganda, under the ATAAS Project and the University of Pretoria.

As the global desire for natural remedies derived from botanicals increases, the pressure on plant populations and biodiversity intensifies. Therefore, to conserve biodiversity as a valuable genetic and biochemical resource, sustainable utilisation and commercial production should be prioritised. Myrsine africana L. (MA), has recently been found to possess significant cosmeceutical properties, such as elastase inhibition (anti-wrinkle) and anti-tyrosinase (skin even tone) activity. However, this species is relatively slow growing, recalcitrant to adventitious root (AR) development, and has slightly insufficient bioactivity in raw extracts. These factors reduce the economic feasibility of producing this commercially valuable indigenous species. Consequently, this may enhance wild harvesting of this species, placing pressure on wild populations. Manipulation of light is a common practice in plant production to exploit plant growth and development, as light quantity and quality effectively influence the primary and secondary metabolism of plants. Therefore, the current study aimed to investigate the influence of selected photoselective shade net on vegetative growth and metabolites of MA shoot material. Results displayed significantly enhanced growth (p

Irish potato production in Zimbabwe can be traced back to the early 1900s. Large-scale commercial farmers dominated production until the early 2000s. Potato is the most important horticultural crop and has been declared a strategic national food security crop in 2012. In 2000, the Fast Track Land Reform Programme completely restructured commercial agriculture and potato farming. A product of the agrarian reforms, the A2 and A1 resettlement growers, started growing potato. The A1 resettlement model has individually owned cropping land and shared grazing, while A2 resettlement comprises of self-contained farm units. A survey was conducted to characterise potato growers, mainly to understand the current potato production systems and to assess the impact of the landmark reform programme on potato farming. Four production systems, large-scale commercial, communal area, A2 resettlement and A1 resettlement, were identified, and two main growing agro-ecological zones, the Highveld and Eastern Nyanga Highlands. In 1961–2013, significant positive trends for annual planted area, average yield and total production were observed. In terms of yield, Zimbabwe is fourth in southern Africa with an average yield of 17 t ha−1 in the 2009–2013 period. Large-scale commercial and A2 resettlement systems were well-mechanised, and growers owned large land holdings ranging from an average of 165–1600 and 31–390 ha across the different areas, respectively, with average potato areas of 11 and 8 ha, respectively. A1 resettlement and communal area growers owned an average of 4 and 3 ha cropping area, respectively, with average potato areas of 0.4 and 1.1 ha, respectively. Input use was significantly different among the production systems. High synthetic fertiliser and biocide use was observed.

Global food production relies on irrigation, especially in low rainfall areas such as South Africa. The study was conducted to determine the effect of drought stress on growth, yield, leaf gaseous exchange and chlorophyll fluorescence parameters of dry bean under field conditions and the after effects of drought stress upon lifting drought stress. A rain shelter field trial was conducted at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa. Dry bean cultivar DBS 360 was subjected to five levels of moisture stress arranged in a randomized complete block design with six replications. The plants were exposed to the following drought stress levels: the control: Irrigated to field capacity (S1), Withholding irrigation from 36 days after planting (DAP) for 24 days (S2), Withholding irrigation from 49 DAP for 24 days (S3), Withholding irrigation from 73 DAP to the end of the growing season (S4) and irrigated to field capacity on a fortnightly bases for the rest of the season from 36 DAP to the end of the growing season (S5).The results revealed that drought stress reduced dry matter production, leaf area index, number of pods per plant, number of seeds per plant, hundred seed weight and grain yield. Treatments S1, S4 and S5 produced statistically similar grain yield. Drought stress towards the end of the growing season may not cause serious harm in grain yield. Drought stress resulted in a reduction in photosynthetic rate, intercellular carbon dioxide concentration, stomatal conductance and transpiration. Chlorophyll fluorescence was also affected by drought stress. The highest WUE was found in the treatment which was irrigated on fortnightly bases from 36 DAP. This indicates that with appropriate irrigation it is possible to save water without a great yield loss in dry bean.

16 páginas, 6 figuras, 2 tablas, Land-use change from natural to managed agricultural ecosystems significantly impacts soil bacterial diversity and function. The Eastern Free State (EFS) is one of the most productive agricultural regions in South Africa. However, no studies aiming to understand the changes in bacterialdiversity,compositionandfunctionduetoland-usechangeinthisareahavebeenconducted. This study investigated, using high-throughput 16S rRNA gene amplicon sequencing, the effects of long-term agriculture on bacterial diversity, composition and putative function in the EFS by comparing microbiomes from lands that have been under agronomic activity for over 50 years to those from uncultivated land. Results indicate that agriculture increased bacterial diversity. Soil chemical analysis showed that land-use shifted soils from being oligotrophic to copiotrophic, whichchangedbacterialcommunitiesfrombeingActinobacteriadominatedtoProteobacteriadominated. Predictive functional analysis using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) suggested that agricultural soil was abundant in genes associated with plant fitness and plant growth promotion, while non-agricultural soil was abundant in genes related to organic matter degradation. Together, these results suggest that edaphic factors induced by long-term agriculture resulted in shifts in bacterial diversity and putative function in the EFS., This research was funded by Potatoes South Africa, grant specific unique reference number (UID) 105649

Lobostemon fruticosus is a semi-woody shrub used medicinally for treating wounds, blood poisoning, ringworms, skin diseases and syphilis. The material used is mostly wild harvested, leading to decline in natural populations. Propagation and cultivation methods to establish commercial production can assist in conservation of the species. The objective of this study was to determine the effect of delaying rooting hormone application on the success of vegetative propagation of L . fruticosus using basal stem cutting, cut at an angle of 30° at the base. It was done in a mist bed at the Agricultural Research Council-Vegetable and Ornamental Plant Institute (ARC-VOPI) (Pretoria, South Africa) in a factorial randomized complete block design with two growth media (cocopeat and cocopeat + potting soil1:1; v / v ), rooting hormone (Seradix No. 1 and control) and six application times, with five replications. The parameters assessed were callus development, rooting percentage, shoot and root length, survival rate and stem cutting anatomical analysis. Rooting percentage significantly increased with delaying the application of rooting hormone for one to two weeks from planting, as compared to the control (without hormone) and hormone application at the time of planting (week zero). Cocopeat medium gave the highest rooting percentage (67.1%) and lowest mortality rate (18%), whereas potting soil + cocopeat medium gave the lowest root development (31.5%). Anatomical observations in this study showed that with delayed auxin application up to two weeks after planting, the callus tissue started to develop from the vascular cambium close to the cut end of the cutting. Parenchyma gaps in the phloem fiber ring close to the cut end of the cuttings was also observed. This study concludes that delaying hormone application for two weeks after planting improved rooting of L. fruticosus cuttings.

Children leaving foster care are ill-prepared for life after foster care. They are left to face numerous challenges, such as unemployment, homelessness and lack of interpersonal relationships, which impact their young adult life. The transition into adulthood is a frightening process for any young person, but is most frightening for the child aging out of alternative care, such as foster care, especially if both of their parents are deceased. The South African legislation does make provision for independent living preparation for children aging out of foster care, however there are no guidelines or programmes in place to assist social workers to provide these services to foster children. This is a qualitative study aimed to explore the need for preparing children ageing out of foster care for independent living in South Africa. Semi-structured interviews were done with 12 participants. The findings indicated that the participants felt unprepared for life after foster care and that there is a need for programs to prepare youth for ageing out of foster care in South Africa.

High-value vegetable crops are typically grown under irrigation to reduce production risk. For water resource planning it is essential to be able to accurately estimate water use of irrigated crops under a wide range of climatic conditions. Crop water use models provide a means to make water use and yield estimates, but need crop- and even cultivar-specific parameters. There is generally a lack of crop-specific model parameters for some important commercially grown vegetable crops, especially parameters determined over both summer and winter seasons. The experimental site used in this study was on the Steenkoppies Aquifer, a catchment under stress and an important vegetable production area in South Africa. Crop-specific growth parameters and water use for 4 selected high-value vegetable crops (beetroot, cabbage, carrots and broccoli) were measured over multiple seasons (two summers and one winter). These were used to parameterise the Soil Water Balance (SWB) generic crop growth model for both summer and winter seasons. In seasons where the same cultivar was planted, a single set of model parameters could be used to successfully simulate crop growth and water use. Results show that the amount of irrigation water required is dependent on season and rainfall, with broccoli having the lowest (1.8–2.7 kg m −3 ) and beetroot the highest (12.2–23.4 kg m −3 ) water productivity (WPFM), defined as fresh mass of marketable product per unit water consumed. The root crops had a greater harvest index (HIDM) than cabbage and broccoli. The parameters obtained expand the current database of SWB crop growth parameters for vegetables and can be used in a wide range of mechanistic simulation models to improve water management at field and catchment levels. Keywords: SWB model, Steenkoppies Aquifer, carrot, broccoli, beetroot, cabbage

In 1994, LINTUL-POTATO was published, a comprehensive model of potato development and growth. The mechanistic model simulated early crop processes (emergence and leaf expansion) and light interception until extinction, through leaf layers. Photosynthesis and respiration in a previous crop growth model—SUCROS—were substituted by a temperature-dependent light use efficiency. Leaf senescence at initial crop stages was simulated by allowing a longevity per daily leaf class formed, and crop senescence started when all daily dry matter production was allocated to the tubers, leaving none for the foliage. The model performed well in, e.g., ideotyping studies. For other studies such as benchmarking production environments, agro-ecological zoning, climatic hazards, climate change, and yield gap analysis, the need was felt to develop from the original LINTUL-POTATO, a derivative LINTUL-POTATO-DSS with fewer equations—reducing the potential sources of error in calculations—and fewer parameters. This reduces the number of input parameters as well as the amount of data required that for many reasons are not available or not reliable. In LINTUL-POTATO-DSS calculating potential yields, initial crop development depends on a fixed temperature sum for ground cover development from 0% at emergence to 100%. Light use efficiency is temperature dependent. Dry matter distribution to the tubers starts at tuber initiation and linearly increases up to a fixed harvest index which is reached at crop end. Crop end is input of the model: it is assumed that the crop cycle determined by maturity matches the length of the available frost-free and or heat-free cropping season. LINTUL-POTATO-DSS includes novel calculations to explore tuber quality characteristics such as tuber size distribution and dry matter concentration depending on crop environment and management.

There is a significant increase in traffic loading on most roads in the developing African countries, and South Africa is one of them. Often this increased traffic loading results in the premature failure of pavement structures. Mechanistic-empirical (M-E) design methods based on fundamental principles are better able to accommodate changes in the design environment. The successful use of design methods depends on the accuracy of the input material parameters. Therefore, as design is moving towards M-E design methods, there is a need for the material parameters to reflect the actual pavement response to dynamic loads. The objective of this paper is to report on the investigation of the response of cement-stabilised sub-base layers to dynamic load by evaluating stiffness at a known strain level. This stiffness was compared with those derived from unconfined compressive strength (UCS) tests performed at static load. The strain and stiffness values were also evaluated against compacted density, cement content, moisture content and material type. It was found that stiffness of some of the cement-stabilised sub-base layers may possibly be overestimated through the use of static loads.

Deteriorating riding quality has a negative impact not only on infrastructure, but on the road user as well. Road users experience higher vehicle operating costs (VOCs), longer travel times, congestion and uncomfortable rides, to name a few. The purpose of this paper is to demonstrate the link between deteriorating riding quality and high vertical accelerations (awz) and VOCs for a bi-articulated bus on an identified bus route with different responsible road authorities in rural Mpumalanga, South Africa. The link, as identified, indicated that the speed the bus travelled played a big role in the generation of awz. Recommendations for future research are also proposed.

The authors would like to thank the Department of Science and Technology, South Africa 329 (DST-SA) for funding the study.

Irish potato is the third most important carbohydrate food crop in Zimbabwe after maize and wheat. In 2012, the Government of Zimbabwe declared it a strategic national food security crop. In this study, we examine the country's potential for increasing Irish potato yield and help ease the nation's food security challenges. The magnitude of food production increase on already existing croplands depends on the difference between the current actual yields and the potential yield of the crop in the given agro-ecological environment, also called the yield gap. We used three already well-understood types of yield gap: (1) the gap between actual farmer yields, Ya, and the maximum (potential) yield, Yp, achieved when a crop is grown under conditions of non-limiting water and nutrient supply with biotic stress effectively controlled; (2) the gap between Ya and the water-limited yield, Yw, which is the maximum yield attainable under rainfed systems; and (3) the gap between Ya, and the highest yield, Yh, achieved by the best farmers in an agro-ecological area. A grower survey was conducted on the different potato production systems in the country in order to establish the actual yields and input application rates used in potato production. The actual potato yields were used to calculate efficiencies of natural and synthetic resources use. Potential and water-limited yields, and planting times of potato were established for the different agro-ecological regions using the LINTUL-POTATO model, a model based on interception and utilisation of incoming solar radiation. The mean actual yield observed ranged from 8 to 35% of the potential yield, translating to a yield gap of 65 to 92%, hence there is a huge potential to increase production. Simulated potential water use efficiency based on evapotranspiration range was 19–27gpotato/l against the actual water use efficiency of 2–6gpotato/l based on irrigation and rainfall. The current high fertiliser application rates and low actual yields we report, suggest inefficient fertiliser use in potato production in Zimbabwe. The average actual fungicide and insecticide use efficiencies were 0.7 and 13kgpotato/g active ingredient, respectively, across all production systems. All sampled growers lacked knowledge on integrated pest management, a concept which could possibly improve the biocide use efficiency through lowering biocide application rates while maintaining or even improving yields. Our analysis suggests that there is opportunity to improve water, nutrients and biocides resource use efficiencies and increase potato actual yields in Zimbabwe.

Unbound granular material is used in the pavement structure and usually comprises the bulk of the structural and foundation layers of a typical South African pavement. The term unbound granular material refers to the classification of natural material, which has not been modified in any way. Unbound granular material is classified from a G1 to G10 quality according to its fundamental behaviour and strength characteristics. Young's modulus and Poisson's ratio are theoretical concepts of linear elasticity that can at best approximate experimental results of actual material elastic response. In their basic linear elastic form, Young's modulus and Poisson's ratio are rather poor approximations of actual unbound granular material behaviour. The non-linear, stress-dependent behaviour of unbound granular material can, however, be simulated using the linear elastic model as a basis, but with a proper constitutive material model that adheres to the observed material behaviour. The objective of this paper is to utilise a chord modulus model and calibrate it for a range of unbound granular material classifications. The model was calibrated for five bulk material samples, ranging from G2 to G8. The calibration process included linking variables of the model to mathematical functions that approximate the trends observed when variables were considered against degree of saturation. A parametric analysis indicated that the saturation-and stress-dependent chord modulus model realistically predict material behaviour. The trends depict the stress-dependent behaviour of unbound granular material, where an increase in initial modulus is observed for increasing confinement pressure, as well as initial stress softening with increasing stress ratio followed by stress stiffening. It can be concluded from the results presented in this paper that a saturation- and stress-dependent chord modulus model could be refined and calibrated for crushed and natural unbound granular material. This refinement did not negatively influence the accuracy or ability to realistically predict the material behaviour. The preliminary conclusions reported in this paper indicate that the chord model formulation yield satisfactory predictions, especially when the model is calibrated for each individual material type.

Emerging models for continuing professional development of teachers engage teachers in a collaborative learning through professional learning communities (PLC) as a way to spur their professional development and empowerment, and correspondingly, lead to positive changes in teaching practices and student learning. Learning communities are created in these collaborative models where teachers debate theoretical principles, share insights about their teaching and learning, design new instructional strategies, experiment new ideas in classrooms and reflect on results. Models such as Wenger’s “community of practice”, Hord’s Professional Learning Community, Katz and Earl’s collaboration model and Pedder and Opfer’s professional learning model will be described. Schools can support teacher learning by promoting collaboration, team learning and collegial dialogue among staff, creating continuous learning opportunities, instituting systems to learn and to share learning. This study explored how a South African primary school succeeded in implementing and developing a PLC culture to empower its teachers to improve their learning and that of their students. Key factors in the success of the school’s PLC were the leadership of the principal, who acknowledged the necessity for a collaborative learning culture, and the fact that the school had strong and experienced teaching staff who were committed to quality teaching and learning.

Higher education in general is regulated through government regulations and policies. This paper reports on part of an investigation done for a master's dissertation. The broad research aim of the study was to provide research-based documented evidence of the impact of the higher education regulatory context on the management of a private higher education institution in South Africa. This paper is limited to the findings of the study, though it focused on how the management team of a private higher education institution perceived the impact of regulatory legislation on private higher education. To study the phenomenon, a qualitative research methodology was used and data were collected through interviews with management team members. Official documents on higher education legislation also served as data sources. A case study using an accredited and registered private higher education institution was undertaken.

False codling moth (FCM), Thaumatotibia leucotreta, is a priority pest of citrus, stone fruit and table grapes, as it causes direct crop damage. Biological control of entomopathogenic nematodes (EPNs) has not been explored for use against FCM in stone fruit and table grapes. However, EPNs have been shown to provide exceptional control against the larvae and pupae of FCM in laboratory bioassays, compared to other biocontrol agents. EPNs are particularly attractive for the control of FCM, as they attack the soil stages. In this study, the mortality, quality and age of in vitro liquid-cultured Steinernema jeffreyense was assessed in the laboratory and tested in the field. Additionally, pre- and post-application pathogenicity tests with FCM larvae were conducted to assess the EPN virulence of in vitro-cultured nematodes. Field trials were conducted by means of applying infective juveniles (IJs) to the vineyard floor. Four different Steinernema jeffreyense concentrations (0, 10, 20, and 30 IJs/cm2) were applied to 40 1 m2 experimental plots that were artificially infested with FCM larvae. The insects were retrieved from the soil 48 hrs after application, to allow for the assessment of the immediate effect. The FCM-loaded cages were replaced over a period of four weeks, to determine the persistence of the original application. In a second trial, following the same procedure, S. jeffreyense and Steinernema yirgalemense were compared with regard to virulence and persistence over a four-week period. In the laboratory, the in vitro-cultured EPNs proved to be of similar quality to the in vivo-cultured S. jeffreyense, with a high percentage mortality of >80%. The semi-field study showed promising results, with the immediate effect yielding up to 77% mortality of FCM larvae, which remained >35% over the four-week period after application. The results compare favourably with those of previous field studies, using in vivo EPN, proving that EPNs would be a valuable addition to the current integrated pest management programme aimed at the control of FCM.

Potato response to environment, planting date and genotype was studied for different agro-ecological zones in Lesotho. Field experiments were conducted at four different sites with altitudes ranging from 1,655 to 2,250 m above sea level during the 2010/2011 and 2011/2012 summer growing seasons. Treatments consisted of three cultivars that varied in maturity type, two planting dates and four sites differing in altitude and weather patterns. Various plant parts were measured periodically. To understand and quantify the influence of abiotic factors that determine and limit yields, the LINTUL crop growth model was employed which simulated potential yields for the different agro-ecological zones using weather data collected per site during the study period. Observed actual crop yields were compared with model simulations to determine the yield gap. Model simulations helped to improve our understanding of yield limitations to further expand potato production in subtropical highlands, with emphasis on increasing production through increased yields rather than increased area. Substantial variation in yield between planting date, cultivar and site were observed. Average tuber dry matter (DM) yields for the highest yielding season were above 7.5 t DM ha−1 or over 37.5 t ha−1 fresh tuber yield. The lowest yield obtained was 2.39 t DM ha−1 or 12 t ha−1 fresh tuber yield for cultivar Vanderplank in the 2011/2012 growing season at the site with the lowest altitude. Modelled potential tuber yields were 9–14 t DM ha−1 or 45–70 t ha−1 fresh yield. Drought stress frequently resulted in lower radiation use efficiencies and to a lesser degree harvest indices, which reduced tuber yield. The site with the lowest altitude and highest temperatures had the lowest yields, while the site with the highest altitude had the highest yields. Later maturing cultivars yielded more than earlier maturing ones at all sites. It is concluded that the risk of low yields in rain-fed subtropical highlands can be minimised by planting late cultivars at the highest areas possible as early as the risks of late frosts permit.

This study aims to assess the risks and opportunities posed by climate change to potato growers in South Africa and to evaluate adaptation measures in the form of changes in planting time growers could adopt to optimise land and water use efficiencies in potato, using a climate model of past, present-day and future climate over southern Africa and the LINTUL crop growth model. This was done for distinct agro-ecosystems in South Africa: the southern Mediterranean area where potato still is grown year round with a doubling of the number of hot days between 1960 and 2050, the Eastern Free State with summer crops only and Limpopo with currently autumn, winter and spring crops where the number of hot days increases sevenfold and in future the crop will mainly be grown in winter. A benefit here will be a drastic reduction of frost days from 0.9 days per winter to 0. Potato crops in the agro-ecosystems will benefit considerably from increased CO2 levels such as increased tuber yield and reduced water use by the crop, if planting is shifted to appropriate times of the year. When the crop is grown in hot periods, however, these benefits are counteracted by an increased incidence of heat stress and increased evapotranspiration, leading in some instances to considerably lower yields and water use efficiencies. Therefore year-round total production at the Sandveld stabilizes at around 140 Mg¿ha-1 (yield reduction in summer and yield increase in winter), increases by about 30% in the Free State and stays at about 95 t¿ha-1 at Limpopo where yield increase due to CO2 is annulled by a shorter growing season. When the crop is grown in a cool period, there is an additional benefit of a reduced incidence of cold stress and a more rapid canopy development in the early stages of crop growth. In all three areas, potato growers are likely to respond to climate change by advancing planting. In Limpopo, a major benefit of climate change is a reduction in the risk of frost damage in winter. The relevance of these findings for potato grown in agro-ecosystems elsewhere in the world is discussed.

Taxonomic notes on Sericanthe andongensis and a new combination and status in Sericanthe from Limpopo, South Africa.

Enhanced dispersal ability may lead to accelerated range expansion and increased rates of population establishment, thereby affecting population genetic structure and evolutionary potential. Morphological, behavioural and physiological traits that characterize dispersive individuals from residents are poorly understood for many invertebrate systems, especially in non-polymorphic pterygote species. Here we examined phenotypic differences between dispersal-prone and philopatric individuals from repeated mark-release-recapture (MRR) experiments using an invasive agricultural pest,Ceratitis capitata. Comprehensive morphometric assessment and subsequent minimal adequate modelling using an information theoretic approach identified thorax mass : body mass ratio as a key predictor of disperser flies under semi-natural conditions. Performance differences in flight ability were then examined under controlled laboratory conditions to assess whether greater thorax mass : body mass ratio was associated with enhanced flight ability. The larger thorax : body mass ratio was associated with measurable differences in mean flight duration, most predominantly in males, and also by their willingness to disperse, scored as the number and duration of voluntary flights. No other measures of whole-animal flight performance (e.g. mean and peak vertical force, total or maximum flight duration) differed. Variation in voluntary behaviour may result in significant alterations of movement behaviour and realized dispersal in nature. This phenomenon may help explain intraspecific variation in the dispersal ability of insects.

Potato, the most important vegetable crop in South Africa, is produced in many distinct geographical regions differing in climate, soils, production seasons and management practices and access to markets. These differences affect the amount of input resources required to produce potatoes as well as yields and crop value, and therefore the use efficiencies of land, water, nutrients, seed and energy. Resource use efficiencies affect the ecological and financial sustainability of potato production in this region, which has in general less favourable potato growing conditions than north-western Europe and the U.S.A., where high resource use efficiencies are usually recorded. This study aimed to assess and benchmark South African potato production regions, representing a wide range of growing conditions, regarding their use of input resources and to identify resource-intensive practices, which may suggest inefficient use of inputs. Surveys were conducted in 2013 and 2014 by interviewing growers in all production regions, to provide data on resource use efficiencies. Quantitative modelling approaches were applied to calculate carbon footprints as a proxy of energy use efficiency, potential crop yields and irrigation needs for each region. Variability in the gap between potential and actual yield was used to identify yield limiting factors. Actual yields achieved were on average 60% of the potential yield, suggesting fairly efficient use of available production factors. Water, seed and nutrient use efficiencies differed widely between and within regions and were not directly proportional to water requirements and yields achieved. Fertilizers (34%) and irrigation (30%) were the greatest contributors to energy use in potato crop production. Energy required to pump water was strongly related to the amount of irrigation applied, pumping depth and distance. Long distance travel of produce to retail points contributed substantially to energy use. Significant improvements in efficiencies are possible by improving management practices. Analysis of the variability in resource use efficiencies between farms and regions provided production sustainability indicators that can assist growers in identifying inefficient practices and yield limiting factors. These can be addressed through the use of decision support systems, such as irrigation scheduling tools, to improve resource use efficiencies and the sustainability of production, not only for the production efficiency of the specific study area, but also for the economic efficiency of potato production anywhere else.

The LINTUL-Potato-DSS model uses the linear relationship between radiation intercepted by the crop and radiation-use efficiency (RUE), to calculate dry matter production. The model was developed into a yield forecasting system for processing potatoes based on long-term and actual weather and crop data. The model outcome (Attainable yield, Yatt) was compared to actual yields (Yact) of a summer crop in South Africa and the ratio Yact to Yatt was used for forecasting yield in winter crops. Results showed that accurate forecasts (

The effect of irrigation frequency on leaf physiomorphological processes of rose-scented geranium ( Pelargonium capitatum × P. radens cv. Rose) was investigated in a glasshouse study at the Hatfield Experimental Farm of the University of Pretoria, Pretoria, South Africa, from November 2005 to October 2006. Daily, and every 2nd, 3rd, 4th , and 5th day irrigation were applied as treatments. Leaf samples for electron-microscopic observations were taken one week prior to harvesting, whereafter all plants were re-watered. For each of the irrigation frequency treatments, 50% of the plants were then exposed to a one-week irrigation withholding period (brief stress treatment) prior to harvesting. During this period, physiological properties were recorded on a daily basis to identify or monitor change. Higher irrigation frequency and a brief water stress period increased essential oil yield. Lower irrigation frequency tended to increase the citronellol to geraniol (C:G) ratio to unacceptably high levels (C:G > 3). Upon re-watering, stomatal conductance (G s ) and transpiration rate (R t ) were significantly lower for the lower irrigation frequency treatments, compared to the higher irrigation frequency treatments, while no noticeable differences were observed in water potential (ψ w ) and relative water content (RWC). At the end of the one-week stress period, G s , R t , ψ w and RWC were lower for the plants that were more frequently irrigated compared to the less frequently irrigated treatments. Water stress reduced leaf size, and apparently increased trichome density, whereas the total number of trichomes per leaf remained more or less the same, indicating that total essential oil yield is mainly affected by leaf number (and not by leaf size or trichome number). Stomatal closure was the main water stress avoiding/adaptation mechanism. These results demonstrate that rose-scented geranium plants can make physiomorphological adaptations to save water. However, such a water saving strategy was counter-productive, since it resulted in lower essential oil yield and lower water-use efficiency.