Environmental and nutritional imperatives make it necessary to carry out regular and reliable / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2007.

The current research was done to evaluate the nutritive values and the ruminal degradation of dry matter (DM) and crude protein (CP) from three non-conventional oil cakes, viz: amarula (Sclerocarya birrea) (AOC), macadamia (Integrifolia) (MOC) and baobab (Adansonia digitate L.) (BOC). The oil cakes were collected from biodiesel producers in Limpopo Province, transported to the ARC-Animal Production campus, where proximate and ruminal nutrient degradation analysis were conducted. Triplicates samples from each oil cake were analyzed for the nutritive values, mineral and amino acids contents. Three rumen cannulated mid-lactating (days in milk; DIM: 180±5) Holstein cows weighing 667±43 kg body weight were allocated to determine the in situ ruminal dry matter (DM) and crude protein (CP) degradation. The cows were offered a totally mixed ration (TMR) (60 concentrate: 40 forage ratio) that was compounded according to their daily nutrient requirements, and were milking was done twice per day at 12 hrs intervals. The three oil cake samples were ground using a 2-mm screen after which sub-samples (6.5 g) were put in 10 x 20 cm; 50 μm pore size polyester bags to achieve 15 mg/cm² (ratio of the sample size to surface area). The bags were then fistulated in each cow’s rumen in triplicate for a period of 2, 4, 8, 16, 24, or 48 hrs. After being incubated, the bags were removed from the rumen and washed with cold (4°C) water in 20-L buckets. Following immersing in cold water, the bags were machine washed until clean water was obtained. The bags were then dried at 60 °C in an oven for 48 hrs. The dried bags were individually weighed, and the content of each bag were removed and stored into glass vial until analysis. The remaining two duplicate sets of each sample were rinsed using cold water in order to determine solubility at 0 hrs. The AOC had higher (P<0.05) ether extract (EE) and CP content than both BOC and MOC. Macadamia oilcake (MOC) and BOC had higher (P<0.05) fractions of fibre (NDF, ADF and ADL) compared to the AOC. The AOC had greater (P<0.05) content of essential amino acids than in the BOC and MOC. Additionally, AOC had a high (P<0.05) phosphorus, but low calcium and potassium concentration. While AOC had high effective degradability of DM, it also had high water soluble as well as DM and CP rapidly degradable fractions. Effective degradation of CP was higher in AOC and BOC than in MOC. However, BOC had a high insoluble but degradable fraction of CP. Further work to determine the toxicology of these non-conventional oil cakes and animal feeding experiments is needed / Agriculture and  Animal Health / MSc. Agriculture

PhD (Zoology) / Department of Zoology / Ecosystem services and disservices are important features in agro-ecosystems and both can have relevant economic impacts on farmers. While there has been much research on the value of ecosystem services, especially that of pest control by bats and birds, ecosystem disservices are often overlooked or estimated separately. Both, services and disservices, however, change with landscape and may be supported by natural vegetation. It is hence inevitable to assess them together to uncover their relative value and importance. Habitat loss and fragmentation are major threats to biodiversity and ecosystem services. Agricultural intensification can cause habitat loss and can negatively affect natural ecosystems and their services. However, the removal of natural vegetation can also reduce ecosystem disservices that origin from natural areas. This study focused on the economic trade-off between biocontrol by bats and birds and crop raiding by vervet monkeys in South African macadamia orchards, using vertebrate exclusion experiments. Crop quality and yield were assessed and extrapolated to income values. The study furthermore focused in more detail on the impact of orchard edge habitat and farm management on bats as ecosystem service providers as well as the arthropod community, which can provide both services (pollination, biocontrol) as well as disservices (crop damage). The macadamia industry is highly profitable and plantings are expanding worldwide. South Africa is currently the largest macadamia producer in the world and the study area, Levubu, holds some of the oldest macadamia plantings in the country. The subtropical climate and high annual rainfall make this area an intensively farmed landscape. Levubu lies at the foothills of the Soutpansberg, a centre of biodiversity and patches of natural vegetation wind through orchards of macadamia, avocado, banana and timber. Insect pest pressure is high in the macadamia industry, with several stink bug species (Hemiptera) and two moth species (Lepidoptera) accounting for most of the damage to the crop. Chapter One provides a detailed overlook over the South African macadamia industry, describes the major pest insect species and their impact on the crop and highlights the role of ecosystem services and disservices and the potential importance of remaining natural areas. Over three consecutive seasons, between September 2015 and May 2018, bats, birds and monkeys were excluded, using cages with nets, from a total of 96 macadamia trees. Four treatments were applied (Full, Day, Night, Control) to distinguish between effects of the different functional groups. Exclusions took place at orchard edges with natural or human-modified edge habitat to assess the impact of vicinity to natural vegetation on pest control and crop raiding. Results presented in Chapter Two showed that biocontrol by bats and birds was stronger near natural vegetation and significantly impacted crop quality as well as yield. Effects of bats and birds were still significant at human-modified edges, whereas crop raiding by monkeys is limited to the natural orchard edges. The economic impact analysis shows that the benefits of biocontrol through bats and birds outweighed the income losses due to crop-raiding monkeys. The value of bats and birds was as high as USD 5000 per hectare per year through prevented insect damage and a 60% crop increase. Crop-raiding affected the yield, which dropped by about 26% and resulted in losses of about USD 1500 per hectare. These results highlight the importance of integrating natural areas into agricultural landscapes, even if they incur the risk of being disadvantageous. Farmers need to be made aware of the enormous economic benefits. Effective crop raiding mitigation strategies still need to be researched to avoid negative association with natural areas. These can, however, possibly also limit access for biocntrol agents, like bats and birds and thereby reduce their economic impact. Especially the removal of natural areas or establishment of buffer zones of unpalatable crops between agricultural land and forests is not advisable. Integrative research in agro-ecosystems on trade-offs between a variety of ecosystem services and disservices is necessary in future, rather than assessing them separately. The bat community on macadamia farms was monitored monthly and compared between orchard edges. Stationary bat detectors were placed at each set of exclosures for two consecutive nights a month, automatically recording from sunset to sunrise. Recorded bat calls were identified manually to species level and activity converted to Miller’s activity index, which counts the number of active minutes per species per night. We analysed the activity per feeding guild over season and landscape setting, estimated species richness and diversity (Hill’s numbers) and species turnover between farms, season and landscape setting, using diversity partitioning. The bat community was mostly influenced by seasonality with season turn-over accounting for 21% of total bat diversity (21.25 species). Edge habitat on the other hand only accounted for 5%. We found higher species richness and activity in the high season compared to the low. While there was no difference in diversity in the high season between the two orchard edge types, species diversity at the human-modified edge was lower than in the natural during the low season. Natural habitat might therefore be more important in the low season, while its effect is overwritten by high food availability during the high season. Clutter-edge species furthermore were more active at the natural orchard edges than open-air feeders, which were in turn more active at human-modified edges. Both activities dropped significantly during the low season. Chapter Three concludes that the macadamia landscape is able to support a high bat species diversity, which is affected by seasonal differences, probably due to food availability. Natural areas are important to be maintained to support sensitive species, relying on clutter habitat and natural roosts. Habitat features as well as farm management can also influence arthropod communities. Visual observations took place each month for 20 minutes per tree. Observations were counted and identified to at least order level. Chapter Four concentrates on the impact of orchard edge habitat and insecticide treatment on honey bees (83% of Hymenoptera observations) abundance. Honey bees were the only taxon significantly responding to both variables, with higher abundance close to natural areas and increasing abundance with increasing time since pesticide application. Honey bees furthermore seemed to recover slightly quicker from population crashes after insecticide treatments at natural edges than they did at human-modified edges. Hymenoptera can be highly beneficial to macadamia farmers, as farmers are heavily relying on pollination by honey bees and parasitoids are known to feed on major macadamia pest insect species. These ecosystem service providers were mostly affected by habitat and management practices, which may compromise their ecosystem service provision. Although commercial bee hives are exposed throughout macadamia orchards, they do not appear to fully replace the pollination and biocontrol services provided by feral species, which can be enhanced through resource supplementation by patches of nearby natural vegetation. Chapter Five concludes with emphasizing the general importance of natural vegetation in landscape planning of agricultural areas. This study proved confidently that benefits through ecosystem services largely outweigh negative impacts of ecosystem disservices, both stemming from these natural areas. Through the inclusion, maintenance and restoration of such patches of natural vegetation, farmers can potentially increase the value and effectiveness of biocontrol by bats and birds or other services. Seasonality largely determined bat species diversity, and a general high species diversity was observed in the macadamia landscape, possibly due to a certain degree of landscape heterogeneity and high food availability. Activity patterns of clutter-edge and open-air feeding bats varied with edge habitat, while clutter-dependent bat species / NRF

Department of Ecology and Resource Management / PhDENV / The main aim of the research was to contribute means for converting conventional, high-input production systems to more sustainable ecological systems, thereby improving the sustainability of macadamia production and ultimately contributing to food security. This was achieved by a) investigating the potential use of cover crops and compost to enhance soil quality in macadamia orchards and b) investigating the potential use of use of cover crops and orchard heterogeneity to control stinkbug pests that target macadamia crops. Field experiments were conducted in three phases: phase one tested the potential of six cover crops for crop protection (as trap crops) and simultaneously for soil restoration or fertility enhancement purposes in macadamia orchards. Phase two repeated the trials of phase one (both soil restoration and trap crops) but with modifications to both categories. Soil restoration treatments were conducted with trees which were growing in what appeared to be healthy soils, and then repeated with trees in the same orchard where the topsoil had been degraded (totally removed) by agricultural operations. The third phase repeated the trap crop trials only, but this time on three different study areas (all commercial farms) with the single cover crop which performed the best as a trap crop during phase two. Trials were modified from the first to the last phase to overcome practical implementation problems encountered along the way and to adapt to local conditions experienced in the commercial macadamia farming systems which served as research sites. Diversity of natural orchard vegetation was enhanced in phase three to improve conditions for natural predators as part of the trap crop treatments in the last phase and cover crops were finally first composted and then returned to the root zones of the macadamia trees as part of the soil quality enhancement treatments in the second phase. The results from the trap crop trials shows a significant effect of trap crops combined with increased orchard diversity in reducing unsound kernel percentages caused by stinkbug pests and demonstrate that trap crops combined with an increase in orchard diversity could be utilized in macadamia orchards as a more sustainable alternative to inorganic pesticides against the stinkbug complex. The most notable changes in the soil that took place with soil quality enhancement treatments were the significant increases in soil phosphorous content and pH which resulted not in an improvement in soil quality in terms of these two indicators but revealed an important issue about the use of compost containing animal manure originating from dairies or feedlots. In summary however, it was clear that although not all the soil quality indicators that were employed to assess changes in the soil with compost treatments improved significantly, a holistic consideration of all indicators portrays an overall improvement which was particularly significant in the degraded soil plots where the topsoil had been removed by prior agricultural activities. / NRF

MSCAGR (Plant Production) / Department of Plant Production / Poor soil fertility caused by inadequate supply of nutrients on soil is one of the major constraints limiting crop production especially in the Vhembe District Municipality, Limpopo, South Africa. Therefore, management practices such as application of organic manure to minimize soil infertility is considered as good practice for smallholder farmers. This study aimed at evaluating the effect of macadamia husk compost on selected soil properties as well as the growth and yield of Chinese cabbage on sandy loam soil. A field experiment was carried out during 2018 and 2019 winter season at the Agricultural Research Council (ARC) research farm in Levubu. The experiment was laid out in a randomized complete block design (RCBD) with 4 treatments (control (zero)), inorganic fertilizer (100:60:60 NPK Kg ha-1) and compost at 15t ha-1 & 30t ha-1 replicated 3 times. Soil was analyzed before planting and after harvesting to determine the influence of applied compost on selected physical properties (soil bulk density and water holding capacity) and chemical properties (soil pH, soil organic matter, soil organic C, EC, total N, P, K, Ca, Mg, Na, Al, Zn and Mn). Number of leaves, fresh mass, dry mass and leaf area was collected at three harvests interval (28, 46 and 74 days after transplanting). After each harvest period, leaves were analysed for nutrient content (N, P, K, Ca, Mg, Zn, Cu, Mn and B). During the final harvest crops were uprooted and root biomass (fresh mass, dry mass and root length) were recorded. Analysis of variance (ANOVA) were conducted on all data using Genstat package 18th addition. Differences between treatment means were separated using the least significant differences (LSD) procedure and correlations analysis was determined using Pearson’s simple correlation coefficient. Macadamia husk compost application had a significant effect on soil bulk density and water holding capacity. Addition of macadamia husk compost significantly increased soil pH, OC, N, C: N K, P, Mg, Ca, Na, Al, Zn, Ca and Mn. In contrast, addition of macadamia husk compost had no effect on soil EC. Yield components (number of leaves, fresh mass, dry mass), root biomass, root length and leaf area increased with application of macadamia husk compost. Yield components, root biomass, root length and leaf area were significantly affected (p<0.01) by harvesting time. Yield components in the second cropping season was greater than yield components in the first season. Macadamia husk compost application showed no significant effect on leaf nutrient content of Chinese cabbage. However, leaf nutrient content was affected by harvesting time. It is evident from the results of this study that macadamia husk compost affects soil fertility and plant production. The results suggest that macadamia husk compost has a potential to be used as a reliable fertilizer by famers especially smallholder farmers who struggle to buy inorganic fertilizer because they are expensive. Since this study was conducted over two seasons and compost effect tend to be long term, further research is needed on application of macadamia husk compost on soil properties and yield of other crops over wide range of soils. / NRF