| Soil colour variation between topsoil and subsoil horizons in a plinthic catena on the Mpumalanga Highveld, South Africa | van der Waals, JH | 2013 |
KeywordsE horizon, Munsell value, orthic A horizon, red apedal B horizon, yellow-brown apedal B horizon AbstractThe South African plinthic catena is characterised by a grading of soils from red through yellow to grey (bleached) soils down a slope. The colour sequence is ascribed to different Fe-minerals stable at increasing degrees of wetness. Soil survey data (422 points) was obtained from three soil surveys on the Mpumalanga Highveld. For each survey point, the topsoil and subsoil horizon Munsell® colour was determined. The data was compared for topsoil horizons overlying different subsoil horizons. A distinct trend was observed in that orthic A horizons overlying yellow-brown apedal B horizons exhibited a marked lighter colour (similar to E horizons) compared to the underlying B-horizon as well as orthic A horizons overlying red apedal B horizons. This implied that topsoil colour is not indicative of subsoil horizon colour – especially in soils of the Avalon, Clovelly, Glencoe and Pinedene forms. The lighter-coloured A horizons also exhibited a marked lower clay content compared to the underlying B horizon. The lighter-coloured A horizons on high chroma B horizons have major implications for the conceptual classification of the soils as well as description of hillslope hydrology and mapping of soils from aerial photographs and satellite images. Authorsvan der Waals, JH Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.777132 This article contributed by:
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| Growth, phenological and yield responses of a bambara groundnut (Vigna subterranea (L.) Verdc.) landrace to imposed water stress under field conditions | Mabhaudhi, Tafadzwanashe | 2013 |
Keywordsbambara groundnut landraces, chlorophyll, drought, leaf area index, stomatal conductance, yield AbstractBambara groundnut (Vigna subterranea (L.) Verdc.) is an underutilised species with potential to contribute nutritional and food security in marginal areas. Growth, phenology and yield of a local bambara groundnut landrace from Jozini, KwaZulu-Natal, characterised into three selections according to seed coat colour, namely Brown, Red and Light Brown, were evaluated under irrigated and rain-fed field conditions at Roodeplaat, Pretoria, over two seasons (2010/11 and 2011/12). Trials with three replicates were planted under rain-fed and irrigated conditions with seed colour as a subfactor. Emergence (up to 35 d after planting), plant height, leaf number, leaf area index, chlorophyll content index and stomatal conductance were measured in situ. Yield and components of yield were determined at harvest. The Red, Brown and Light Brown landrace selections emerged well (84%, 81% and 51%, respectively). Plant physiological and growth parameters of stomatal conductance, chlorophyll content index, plant height, leaf number, leaf area index and biomass accumulation were lower under rain-fed relative to irrigated conditions. Adaptations were landrace selection-specific, with the Brown and Red landrace selections showing better adaptation to rain-fed conditions. Under rain-fed conditions, bambara groundnut landrace selections flowered, senesced and matured earlier relative to irrigated conditions. Consequently, there were lower yields under rain-fed compared with irrigated conditions. The Red and Brown landrace selections may have drought-avoidance mechanisms. Seed colour may be used as a selection criterion for drought tolerance in bambara groundnut landraces. AuthorsMabhaudhi, Tafadzwanashe and Modi, Albert T Year Published2013 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2013.790492 This article contributed by:
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