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Calobota sericea is a native legume of South Africa, confined to the water-limited rangelands, and it has recently been prioritised for additional characterisation regarding its pasture potential. ...

Access to good-quality forages is one of the major limitations to livestock production in semi-arid pastoral systems. This study aimed to determine whether there are differences in the nutritional quality of diets selected by herded and free-ranging goat and sheep flocks utilising Namaqualand Granite Renosterveld vegetation during the wet and dry seasons. Plant samples collected along the grazing routes of livestock were dried and analysed for their fibre, condensed tannin, total phenolic and mineral nutrient contents. The study showed that a large variety of forages were on offer and livestock groups selected different diets of which some were different to the total diet on offer. In general, significant deficiencies in phosphate, protein and energy in the diets selected by herded and free-ranging goats and sheep were observed in both wet and dry season. The quality of the diets selected by herded and free-ranging livestock was also found to be different from each other, with herded livestock generally selecting more nutrient-dense diets. Herding, therefore, allows livestock to access better-quality forage in the Namaqualand Granite Renosterveld rangeland, where it is generally poor.Keywords: herding, Namaqualand Granite Renosterveld, pastoral livestock, protein deficiencies, small stock nutrition

Calobota sericea is a perennial legume species from South Africa that has the potential to be implemented as a fodder crop in water-limited agro-ecosystems. Apart from dormancy breaking requirements, no information regarding the germination and seedling establishment requirements of C. sericea is currently available. Therefore, the aim of this study was to determine the germination and establishment abilities of C. sericea at different temperatures, water potentials and seed burial depths. In the first trial seeds were incubated at constant temperatures of 5–30 °C at 5 °C increments and in the second trial, seeds were incubated at 20 °C, at water potentials ranging from 0 to − 1.0 MPa. The seedling emergence trial consisted of a complete randomised block greenhouse trial where seeds were sown at five burial depths (1–5 cm). Seeds were found to germinate best at temperatures ranging between 10 and 20 °C, but still had a germination percentage greater than 80% at 5 °C. The C. sericea seeds were also found to require a water potential of at least – 0.3 MPa to reach a germination potential of 60%, below which germination was severely impacted. Seedling emergence was found to be highest at burial depths of 2–4 cm. After establishment, seedlings generally displayed a decrease in above ground plant part height with increasing burial depth, but an increase in seedling mass. More resources, in terms of mass, were allocated to early root development as opposed to leaves and stems. Results from the current study therefore suggests that C. sericea seeds can be planted between 2 and 3 cm deep, during winter season, when temperatures are lower, and rainfall more prevalent and less erratic.

The importance of evaluating the tolerance of forages to deeper seed burial is often overlooked. Therefore, this study evaluated the effects of increased seed burial depth on the emergence, vigour ...

Acid mine drainage (AMD) severely impacts the water chemistry of a receiving resource, changing the occurrence, speciation and toxicity of metals such as Aluminium (Al). The toxicity of Al is determined by its speciation represented by the labile monomer Al fraction or Al(3+). The purpose of the study was to combine fractionation and Visual MINTEQ speciation to calculate the effect of AMD altered water chemistry on Al speciation and Al(3+) concentration. Water in rivers impacted by AMD presented with monomeric Al (Almon) concentrations between 0.35 and 15.37mgL(-)(1) which existed almost exclusively in the toxic labile form (98%). For the reference site, Almon was less than 2% (10μgL(-1)), suggesting significantly lower Al toxicity. Principal component analysis plots illustrated that labile Al was directly related to the total Al and iron concentrations and strongly influenced by parameters such as pH, electrical conductivity, sulphate and dissolved organic carbon. Visual MINTEQ modelling was used to determine the primary Al species distribution. The dominant form of Al in AMD impacted water was AlSO4(+), which increased proportionally with the sulphate and Al(3+) concentration. Heavily impacted areas, presented with an average of 1mgmL(-)(1) Al(3+), which poses a potential human health risk. A novel centrifugal ultrafiltration method was investigated as an alternative to determining Almon to simplify the speciation of Al. Monomeric and centrifugal ultrafiltrated (

An increase in bioavailable tin in the environment could result in bioaccumulation thereof in agricultural crops, and therefore, have adverse health consequences on humans that eat these crops. The aims of the current study were thus to assess the uptake of Sn by spinach plants, and the subsequent effects this will have on the uptake of Na, Zn, K, Ca, and Mg as well as the growth of spinach plants. Spinach plants were grown in sand culture and received tin at concentrations of 0.02, 0.2, 2 and 20 mg/L along with a nutrient solution. The uptake of tin at detectible concentrations only occurred at the highest concentrations (2 and 20 mg/L), and it was mostly retained in the roots of the plants. Tin additions also resulted in no visual toxicity symptoms, and might be beneficial to biomass production. Further field trials are needed to ensure that these experimental results remain true under field conditions.

This study evaluated Co, Cr, Mn, Ni, Se, Sn and V status in the soils of the PHA, as well as the vegetables produced on these soils. We also determined the agronomic sources of these elements to the soils in the PHA. Farmyard manures applied as fertilizer amendments to the soils in the PHA were found to be the major agronomic sources of the metal and metalloid elements. These elements were however, retained in significantly higher concentrations in the soils compared to the concentrations found in the edible portions of the vegetable crops collected. This, in turn, resulted in these vegetables being poor sources of several of the essential mineral nutrients. It is therefore suggested that: (1) a wider variety of crops are assessed for their mineral nutrient status, (2) to find ways to increase the availability of these mineral nutrients and (3), that the possibilities of micronutrient and trace element deficiencies be assessed in the communities surrounding the PHA.

Heavy metal toxicity in agro-ecosystems is a global problem. Recently, it has been indicated that the soils used for agriculture and the fresh produce grown on these soils in the Philippi Horticultural Area (PHA) contains heavy metals exceeding the maximum permissible concentrations thereof in South Africa. This study was therefore aimed at evaluating the concentrations of heavy metals in the soils and vegetables produced in the PHA, as well as to determine the major agronomic sources of these metals in this area. Cu, Pb, and Zn concentrations in the soils exceeded the maximum permissible concentrations of 6.6, 6.6, and 46 mg/kg, respectively. Cd, Pb, and Zn concentrations in the vegetables also exceeded the maximum permissible concentrations of 0.1, 0.5, and 40 mg/kg, respectively. The biggest agronomic contributors of these heavy metals to the soils in the PHA were found to be the farmyard manures. Knowing what the major sources of these heavy metals are, it is important to determine ways to mitigate the inputs thereof, as well as to remove existing concentrations from the soils without contaminating the groundwater resources in the area.

The effect of saline spray and saline irrigation on the growth and chemical composition of two varieties of Didelta carnosa (an indigenous West coast daisy) was studied. Variety tomentosa is largely littoral, and variety carnosa mainly distributed inland. Plants were grown under greenhouse conditions and subjected to nine treatments that resulted from the combination of three levels of saline spray, and three of saline irrigation: 0, 10 and 90% seawater were used. Growth was reduced at high salinity, but stimulated at 10% sea water concentrations. There were variations in element concentrations with treatments. However, for these plants, aerial or root applied salinity made very little difference overall, and are not sufficient on their own to explain distribution patterns.