Research Articles (Soil Science)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/565

Browse

Browsing Research Articles (Soil Science) by Author "De Clercq, Willem P."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Quantifying the catchment salt balance : an important component of salinity assessments
    (Academy of Science of South Africa, 2015) Bugan, Richard D. H.; Jovanovic, Nebo Z.; De Clercq, Willem P.
    Soil and stream salinisation is a major environmental problem because it reduces the productivity of landscapes and degrades water quality. The Berg River (South Africa) has been exhibiting a trend of increasing salinity levels, which has primarily been attributed to the manifestation of dryland salinity. Dryland salinity occurs as a result of changes in land use (indigenous vegetation to agriculture and/or pasture), which cause a change in the water and salt balance of the landscape, consequently mobilising stored salts. The quantification of salinity fluxes at the catchment scale is an initial step and integral part of developing dryland salinity mitigation measures. The objective of this study was to quantify the salinity fluxes in the Sandspruit catchment, a tributary catchment of the Berg River. This included the quantification of salt storage, salt input (rainfall) and salt output (in run‑off). The results of the catchment salt balance computations indicate that the Sandspruit catchment is exporting salts, i.e. salt output exceeds salt input, which may have serious implications for downstream water users. Interpolated regolith salt storage generally exhibited increasing storage with decreasing ground elevation. A salinity hotspot was identified in the lower reaches of the catchment. It is envisaged that the data presented in this study may be used to classify the land according to the levels of salinity present; inform land management decisions; and provide a guide and framework for the prioritisation of areas for intervention and the choice and implementation of salinity management options. The data which were generated may also be used to calibrate hydrosalinity models.
  • Thumbnail Image
    Item
    Trace element composition of two wild vegetables in response to soil-applied micronutrients
    (Academy of Science of South Africa, 2014) Mavengahama, Sydney; De Clercq, Willem P.; McLachlan, Milla
    Wild vegetables are an important commodity in the subsistence farming sector. They are considered to be rich in micronutrients and can therefore be used to overcome inadequate nutrition. However, research on micronutrients in wild vegetables remains limited and sporadic. In this study, we evaluated the responses of two wild vegetables – Corchorus olitorius and Amaranthus cruentus var. Arusha – to micronutrients added to the soil in comparison with a reference crop, Swiss chard (Beta vulgaris var. cicla). Swiss chard concentrated significantly (p<0.01) higher amounts of Cu, Zn and Mn in the leaves than did the wild vegetables. Variations in micronutrients among the vegetables were greater for Zn (72–363 mg/kg) and Mn (97.9–285.9 mg/kg) than for Cu (8.8–14 mg/kg). C. olitorius had the least capacity to concentrate Mn and Zn in the leaves. However, C. olitorius concentrated significantly more Fe (327 mg/kg) in the leaves than did A. cruentus (223 mg/kg) or B. vulgaris (295 mg/kg). The mean per cent S concentration in the leaves ranged from 0.26% in C. olitorius to 0.34% in A. cruentus and B. vulgaris. We conclude that the different vegetables had different abilities to concentrate Cu and Zn in the order B. vulgaris > A. cruentus > C. olitorius. These results seem to contradict the belief that wild vegetables have an inherent ability to concentrate mineral micronutrients in their tissues.