Production potential of lucerne (Medicago sativa) over-sown into kikuyu (Pennisetum clandestinum) based pasture
- Authors: Fourie, Ilze , Du Preez, Derek
- Date: 2019
- Subjects: Alfalfa -- South Africa , Field crops , Agriculture -- South Africa , Botany -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39918 , vital:35510
- Description: Dairy farming in the southern Cape region of South Africa is based on irrigated kikuyu (Pennisetum clandestinum) over-sown with different ryegrass species (Lolium spp.). Although this system can be highly productive, sustainable production of kikuyu is dependent on expensive nitrogen (N) fertiliser inputs and irrigation due to a high water requirement to maintain production. The introduction of lucerne (Medicago sativa) into pasture systems can lower the risk of high input cost and droughts. Lucerne has a high nutritive value, is able to fix atmospheric N, has high water-use efficiency and is adapted to local climatic conditions. The aim of this study was to determine the DM production potential of lucerne cultivars from various dormancy groups when over-sown into an existing kikuyu pasture base on soils that are suitable for lucerne cultivation, without any N fertiliser application. The study was carried out on the Outeniqua Research Farm near George, Western Cape. Two cultivars were selected from each of the four lucerne dormancy groups and sown into an existing kikuyu pasture based on soils suited for lucerne cultivation. Three establishment methods namely glyphosate/planter (Gly/Plant), glyphosate/rotavator (Gly/Rot) and rotavator (Rot) were used. The statistical design was a randomised block design with three replicates. The botanical composition (lucerne-, kikuyu-, clover-, grass- and weed content), growth rate (kg DM ha-1 day-1), total DM production (kg DM ha-1) and DM content of the treatments were determined before every grazing. The nutritional value (CP-, ME-, NDF-, Ca-, and P content) of the treatments was determined seasonally. Establishing lucerne into kikuyu with the glyphosate/rotavator (Gly/Rot) and rotavator (Rot) method yielded an overall higher percentage of established seedlings compared to the glyphosate/planter (Gly/Plant) establishment method. The establishment method used affected the botanical composition. Lucerne established with the Gly/Plant or Gly/Rot establishment method into kikuyu had a higher lucerne content than the Rot establishment method. The seasonal growth rates of the kikuyu-lucerne pasture varied between 14.8 kg DM ha-1 day-1 during winter to 84.1 kg DM ha-1 day-1 during summer. The establishment method and cultivar influenced the seasonal growth rate and total seasonal production. The cultivar WL 711 established with Gly/Plant establishment method had the highest or did not differ significantly from the highest lucerne content, seasonal growth rate and total seasonal production within seasons. The total annual production ranged between 13805 to 19975 kg DM ha-1 year-1 with the Gly/Plant establishment method yielding the highest or did not differ significantly from the highest annual production when compared with the other establishment methods. The botanical composition affects the nutritive value of the kikuyu-lucerne pasture. The ME content of kikuyu and kikuyu-lucerne pasture did not meet the daily ME requirements for a lactating dairy cow to maintain milk production throughout both years. The CP and Ca content decreased as the lucerne content decreased and the kikuyu content increased. The P content of kikuyu-lucerne and kikuyu pasture met the daily P requirement of a lactating dairy cow. The dormancy groups D2 and D5 were the only dormancy groups that could meet the recommended Ca:P ratio for dairy cows over all the seasons. Lucerne can be successfully established into kikuyu with the use of herbicide as part of the establishment method. Kikuyu-lucerne pasture has a higher DM production with an improved quality compared to kikuyu pasture. By establishing lucerne into kikuyu the cost of N fertiliser application could be lowered as no N needs to be applied.
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- Date Issued: 2019
Terrestrial alien ferns (Polypodiophyta): a global assessment of traits associated with invasiveness and their distribution and status in South Africa
- Authors: Jones, Emily Joy
- Date: 2019
- Subjects: Biodiversity -- South Africa , Alien plants -- South Africa , Botany -- South Africa , Plant ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39995 , vital:35643
- Description: Globally, invasive alien plants (IAPs) are one of the greatest threats to biodiversity, ecosystems and ecosystem services. The threats posed by IAPs have prompted inventory compilations and screening exercises which aim to understand why some taxa become invasive and others do not. Ferns are a diverse taxon that appear to have a high invasive potential, however ferns have been vastly understudied in the field of invasion biology. This study aimed to establish a basic understanding of terrestrial alien true ferns (Polypodiophyta, hereafter ‘alien ferns’) at both global and national (South African) scales. We developed a global inventory of alien ferns comprising 157 species using published literature and online inventories. Our global inventory indicated that there are significantly more alien fern species than previously estimated (60 species). We used generalised linear models with binomial response variables to determine which traits influenced the probability that an alien fern would become naturalised or invasive. Our models explained 30-40 % of the variance associated with invasiveness and showed that ground-dwelling life forms, reproductive plasticity, tolerance to disturbances and varied light conditions, and a broad introduced range (interpreted as high environmental tolerance and popularity in horticulture) were important determinants of invasiveness in alien ferns. Ultimately, we found that the probability of alien ferns becoming naturalised or invasive is more than 50 %. We further established which geographic regions and fern families had the highest incidences of alien ferns and identified species that were invasive over extensive introduced ranges. For the national scale study, we aimed to assess the distribution, abundance, invasion status, and habitat associations of terrestrial alien fern species present outside of cultivation in South Africa. Field surveys were conducted across the country in habitats suitable for ferns, guided by pre-existing records of alien fern occurrences. Thirteen species occurred outside of cultivation, all of which were classified as invasive, and among these, approximately 5000 plants were recorded across 300 localities. Species richness and abundance peaked along the Indian Ocean Coastal Belt and the Afro-montane phytogeographical regions. A multiple correspondence analysis revealed that alien ferns in South Africa were most strongly associated with indigenous forest habitats and the majority of species selected for shaded conditions, close to water. Only two species were closely associated with open habitats under high light conditions, with plantations also infrequently selected by alien ferns. Habitat generalists were closely associated with disturbance, but avoided open habitats, far from water. Compared to the most prominent angiosperm invaders in South Africa, alien ferns have a lower potential for widespread ii invasion and range expansion, probably due to their habitat specificity. We identified four species as potential targets for eradication and which should be listed as Category 1a under the Alien and Invasive Species regulations of the National Environmental Management: Biodiversity Act of South Africa. The remaining species should be listed as Category 1b since they occupied an extensive geographic range. The most prominent ferns included Adiantum raddianum, Sphaeropteris cooperi, Deparia japonica and Cyrtomium falcatum. Our study informed appropriate regulation for several species of alien ferns that were deemed to be data deficient and in need of assessment by a recent report on the status of biological invasions in South Africa. A risk analysis completed for S. cooperi confirmed that the species has a high invasion risk in South Africa and should be listed as Category 1b. Given that the outcomes of the risk analysis completed for S. cooperi matched the findings from our field surveys, this study supported risk analysis as a reliable (literature-based) method to evaluate IAPs. The findings of our assessments at the global and national scale corresponded in that various traits that promoted invasiveness in alien ferns globally were also facilitating invasion in South Africa. Additionally, of the eleven species found to be invasive over extensive introduced ranges at global scale, only two (Lygodium microphyllum and Angiopteris evecta) were not yet recorded in South Africa. Since horticulture was established as the primary pathway for the introduction of alien ferns, the management of alien ferns (globally and in South Africa) should focus on regulating trade. The sources of cultivation and the pathways of dissemination across the globe also need consideration. Basic environmental and biological associations of alien ferns were evident in this study, but to fully understand their invasive potential further research should focus on niche-based modelling to predict potential invasion ranges, the effects of biological traits on invasiveness, and the potential ecological impacts of these species.
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- Date Issued: 2019
Reading the signs : inaugural address delivered at Rhodes University
- Authors: Seagrief, S C
- Date: 1976
- Subjects: Botany -- South Africa , Marine algae -- South Africa
- Language: English
- Type: Text
- Identifier: vital:667 , http://hdl.handle.net/10962/d1020736 , ISBN 0949980749
- Description: Inaugural address delivered at Rhodes University , Rhodes University Libraries (Digitisation)
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- Date Issued: 1976