| Perspectives on the principles and structure of the soil classification system in South Africa: discussion and practical examples | Turner, David P | 2013 |
Keywordsdiagnostic horizons, horizon definitions, soil classification, soil classification structure, soil depth AbstractThe paper discusses revised principles, perspectives and structure for soil classification of natural soils in South Africa. An expanded ‘sphere of pedological interest’ is proposed through the formal recognition of a wider range of subsurface soil materials. The concept of soil groups has been recognised and is further developed as a formal classification category. In addition, a subgroup category is introduced with discussion using practical examples for the eluvial, yellow-brown apedal, and prismacutanic and pedocutanic horizons with the proposed orthic group of soils. Identification of soils within these examples is proposed to follow a formal key sequence that seeks to identify soils with subsurface gleying, and subsequently progressing from those subsurface horizons of generally more intense to less intense weathering. The key structure retains much of the existing soil-form structure. As such it should be readily suitable for implementation. A description for additional subsurface horizons is introduced, which in selected instances differs slightly from that which is currently understood from present definitions. It is advocated that the principle advantage for introducing an expanded sphere of pedological interest will be gained through improved soil recognition and interpretation that could be given to soil classification classes. The proposed structure is open-ended. This should facilitate a new freedom in the examination of soils that could lead to their improved description in both morphological and numerical soil properties. AuthorsTurner, David P Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.789130 This article contributed by:
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| Phytochemical content, antioxidant capacity and physicochemical properties of pomegranate grown in different microclimates in South Africa | Mditshwa, Asanda | 2013 |
Keywordsaltitude, antioxidant capacity, phytochemicals, principal component analysis, Punica granatum AbstractWe investigated the antioxidant and physicochemical properties of pomegranate (Punica granatum cv. Bhagwa) fruit grown in three microclimates in South Africa. The physicochemical properties of fruit peel and arils differed among the growing locations, including weight and redness color of both peel and arils. Contents of vitamin C, anthocyanin and total phenolics were 0.67–1.41 mg ml−1, 0.07–0.16 mg ml−1 and 8.54–13.91 mg ml−1, respectively. Fruit grown in locations with high light intensity had higher vitamin C content and lower phenolic content than those of fruit from low-altitude locations and high light intensity. The pH of juice did not significantly differ among locations, whereas significant variation was observed in total soluble solids (TSS), titratible acidity (TA) and TSS:TA ratio. Fruit from locations with low rainfall had high TSS and low TA. Principal component analysis was used successfully to classify fruit by growing location on the basis of antioxidant and phytochemical contents. AuthorsMditshwa, Asanda, Fawole, Olaniyi A, Al-Said, Fahad, Al-Yahyai, Rashid and Opara, Umezuruike L Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.802033 This article contributed by:
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| Estimation of thrips (Fulmekiola serrata Kobus) density in sugarcane using leaf-level hyperspectral data | Abdel-Rahman, Elfatih M | 2013 |
Keywordsdensity, Fulmekiola serrata, hyperspectral data, sugarcane, thrips AbstractThe aim of this study was to investigate the potential use of leaf-level hyperspectral data to predict the density of sugarcane thrips Fulmekiola serrata (Kobus). A hand-held spectroradiometer was used to make the spectral measurements on spindle leaves of 4- to 5-month-old plants of sugarcane cv. N19 growing in commercial fields near Umfolozi, South Africa. A random forest algorithm followed by partial least squares regression was used for the analysis. Developed models were adequate to predict nymph numbers in December and adult numbers in March, but different models were needed for the thrips life stage assessed and the season when the estimation took place. AuthorsAbdel-Rahman, Elfatih M, Way, Mike, Ahmed, Fethi, Ismail, Riyad and Adam, Elhadi Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.803616 This article contributed by:
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| A revised perspective on principles of soil classification in South Africa | Turner, David P | 2013 |
Keywordsdiagnostic horizons, horizon definitions, soil classification, soil depth AbstractLimited significance has been given to the formal recognition of certain subsoil materials in the South African Soil Classification System. Three principles in the current classification system are discussed using variants of soil profiles associated with the Avalon soil form. The retention of the arbitrary depth criterion is questioned in favour of the recognition of an enlarged ‘sphere of pedological interest’ extending formal classification to deeper soil materials. This implies that a greater number of soil classes will be required but these additional classes may be accommodated by recognising an additional soil group class in the classification system. It is proposed that the definitions of diagnostic horizons be rewritten to focus on the central concept of the horizon properties, dispensing with limitations on the nature of overlying or underlying horizons. An open class structure to the classification system is advocated. AuthorsTurner, David P Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.804602 This article contributed by:
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| Characterisation of alkaline tailings from a lead/zinc mine in South Africa and evaluation of their revegetation potential using five indigenous grass species | Titshall, Louis W | 2013 |
Keywordscarbonate-rich, dolomitic tailings, indigenous, low cost, phytorestoration AbstractTailings from a lead/zinc (Pb/Zn) mine were characterised and their revegetation potential investigated under glasshouse conditions using five grass species with three rates of inorganic fertiliser. The tailings were alkaline with low nutrient concentrations but high total and extractable Zn. The yield of all grass species increased with an increase in fertiliser rate. The yield of Cenchrus ciliaris at the full fertiliser application rate was significantly higher than the other species tested, followed by Digitaria eriantha. Cymbopogon plurinodis was the third-highest-yielding species, whereas yields of Eragrostis superba and Fingeruthia africana were similar. Concentrations of Zn in the foliage tended to be over the reported grass foliage ranges, whereas Pb concentrations were within typical norms. It is recommended that C. ciliaris, D. eriantha and E. superba be used for initial revegetation, with other species used to improve biodiversity after initial cover has been established. AuthorsTitshall, Louis W, Hughes, Jeffrey C and Bester, H Christopher Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.807361 This article contributed by:
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| Effect of pH on growth, mineral content and essential oil quality of buchu (Agathosma betulina) grown under controlled conditions | Ntwana, Babalwa | 2013 |
KeywordsAgathosma betulina, biomass yield, essential oil, pH variation AbstractBuchu (Agathosma betulina) is a traditional medicinal plant in the Western Cape province of South Africa and the essential oil derived from the leaves is exported in large volumes. The essential oil is not only used for medicinal purposes, but also as a flavour enhancer in the food industry. Agathosma betulina seedlings were transplanted into 9.5 l pots filled with a 1:1 mixture of graded, washed sand and coco peat. Five pH treatments (3–3.99, 4–4.99, 5–5.99, 6–6.99 and 7–7.99), replicated eight times, were applied using a hydroponic system to determine the optimum pH (H2O) range for the production of high-yielding buchu with acceptable essential oil quality. Plant height displayed an exponential increase over time, but plants in the pH 7–7.99 treatment grew less vigorously compared to other treatments. Biomass production was higher in the pH 4–4.99 treatment. High levels of diosphenol and absence of any measurable amounts of cis- and trans-acetylthio-p-menthan-3-one isomers were obtained in the oil analyses from all pH treatments, which indicated that the oil originated from pure A. betulina. AuthorsNtwana, Babalwa, Agenbag, G André and Langenhoven, Petrus Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.811299 This article contributed by:
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| Morphological characters and ascorbic acid content of an elite genotype of Corchorus olitorius: the influence of moisture stress | Ashafa, Anofi OT | 2013 |
Keywordsascorbic acid, Corchorus olitorius, elite genotype, harvest age, moisture stress, morphological characters AbstractMoisture stress can be deleterious to physicochemical properties of crop species to a varying degree. The influence of moisture stress on the ascorbic acid content in the leaf and morphological characters of an elite genotype of Corchorus olitorius were tested in a glasshouse experiment. The experiment was arranged in a completely randomized design replicated four times. The results of the study showed that a distinct moisture-stress threshold, described as heavy moisture stress, existed for the genotype and ascorbic acid accumulation in the leaves decreased by up to 88.7% because of moisture stress. A comparison of the control with heavy moisture stress showed a decline of 57.1% and 68.4% for plant height and number of leaves, respectively. A degree of resilience of C. olitorius to moisture stress was observed with increasing plant age, but with a significant trade-off in the nutritional quality of the genotype at harvest. AuthorsAshafa, Anofi OT, Abass, Abidemi A, Osinaike, Titilola and Lewu, Francis B Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.811300 This article contributed by:
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| Effect of species, cutting position and exogenous rooting substances on rooting of honeybush (Cyclopia spp.) cuttings | Mbangcolo, MM | 2013 |
KeywordsCyclopia genistoides, Cyclopia intermedia, honeybush, subterminal cutting, terminal cutting AbstractEffect of the cutting position, terminal and subterminal, and rooting substance on the rooting of cuttings of two Cyclopia species (Cyclopia genistoides and C. intermedia) taken in winter, spring or summer was studied under controlled glasshouse conditions. Cuttings taken in summer, irrespective of the species, rooted better than cuttings taken either in winter or spring. This poor rooting performance of cuttings in winter and spring resulted in no significant treatment effects and for this reason only results of cuttings taken in summer are discussed. Cyclopia genistoides rooted significantly better than C. intermedia as measured by rooting percentage, number of roots per cutting, length of longest root and mean root length. Terminal cuttings from C. genistoides also increased rooting percentage and number of roots compared to subterminal cuttings, but not so in C. intermedia. Longest roots were produced by terminal cuttings irrespective of species. Treatment with different exogenous rooting substances as a main factor did not have any significant effect on rooting in this study. AuthorsMbangcolo, MM, Reinten, EY and Agenbag, GA Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.765045 This article contributed by:
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| Selected soil properties as indicators of soil water regime in the Cathedral Peak VI catchment of KwaZulu-Natal, South Africa | Kuenene, BT | 2013 |
Keywordscation exchange capacity, clay, iron, manganese AbstractThe morphological features and physicochemical properties of 14 soil profiles, representing the major soil types, were studied in the Cathedral Peak VI catchment of KwaZulu-Natal, South Africa. The soils are characterised by a high organic carbon content in the topsoil, red and yellow freely drained subsoils, and some signs of water saturation in the deep subsoil and saprolite. The lack of variability in the morphology of the soils is probably a result of deep weathering of the chemically homogeneous basaltic parent material. Shelving controls the development of return flow on the slopes, feeding into the two prominent wetlands. The freely drained nature of the subsoil horizons are reflected in the red colour and low pH values of these horizons. The iron and manganese redoximorphic features, occurring in the lower horizons, are indicative of periodic short periods of water saturation. AuthorsKuenene, BT, van Huyssteen, CW and Le Roux, PAL Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.767387 This article contributed by:
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| Host-specificity testing of Puccinia xanthii var. parthenii-hysterophorae, a potential biocontrol agent for Parthenium hysterophorus in South Africa | Retief, Estianne | 2013 |
Keywordsbiological control, host specificity, Parthenium hysterophorus, parthenium weed, Puccinia xanthii var. parthenii-hysterophorae AbstractFollowing its introduction into Australia, the rust fungus Puccinia xanthii var. parthenii-hysterophorae has played an important role in the integrated approach to manage Parthenium hysterophorus. The rust was imported from Australia and established within quarantine facilities in South Africa. Supplementary host-specificity testing of the rust on indigenous members from the tribe Heliantheae and 13 commercial sunflower cultivars was conducted. The rust was shown to be highly specific to parthenium, with only a single incident of symptom development on leaves of the native Spilanthes mauritiana. The symptoms on S. mauritiana were considered to be a laboratory artifact as no further symptoms were observed on this species during subsequent inoculations. Microscopic evaluations revealed that although basidiospores germinate on the surface of S. mauritiana leaves, they do not penetrate the epidermis. Spilanthes mauritiana is host to Puccinia africana, but cross-inoculation greenhouse studies showed that although P. africana is assumed to belong to the P. xanthii complex, it can be separated as a morphospecies from P. xanthii var. parthenii-hysterophorae as it is highly specific to its host. Based on these results it was concluded that P. xanthii var. parthenii-hysterophorae was suitable for release as a biological control agent on Pa. hysterophorus in South Africa. AuthorsRetief, Estianne, Ntushelo, Khayalethu and Wood, Alan R Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.767388 This article contributed by:
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