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Manganese (Mn) mining produces a large amount of Mn-rich solid waste contributing to soil and groundwater pollution. Adding Mn-rich waste to soils could reduce mining pollution by allowing specialised plants to take up this mineral for growth, that is, phytoremediation. However, Mn interacts with other soil major and trace minerals. The interaction with phosphorus (P), a key element for plant nutrition and growth, has received less attention. In this study, we aimed to evaluate the effects of P sources (i.e. rock phosphate and monopotassium [KH2PO4]) and application rates on the P and Mn relationships in clay and sandy soils mixed with Mn-rich waste. Soils differing in texture were incubated for 60 days at room temperature (±20 °C), and changes in available P, Mn and soil pH were determined at 0, 30 and 60 days. The addition of Mn-rich solid waste significantly decreased available soil P in both soils with the greatest reduction of 62% and 52% from the sandy soil subjected to KH2PO4 and rock phosphate, respectively. In the clayey soil, the reduction was higher for the rock phosphate source implying more P was released from the rock phosphate in Mn-rich soils. This explanation was supported by the significant positive correlation between P and Mn for both soils when P is added in the form of rock phosphate. Our results suggest that Mn-rich waste is better in clay soils subjected to rock phosphate addition. Further research is needed to control Mn solid waste pollution levels in soils using specific crops with known phytoremediation properties. [ABSTRACT FROM AUTHOR]

Background: One of the main causes of land degradation in South Africa is bush thickening (BT) of mainly Senegalia or Vachellia species. Restoration methods are required to control BT, and to improve grass biomass production and soil conditions in South Africa. Objectives: The objectives of this study were to determine the effect of brush packing (BP) as a restoration method to increase grass biomass production, assess soil moisture after BP on different soil types, and document the perceptions of the local communities towards BP. Method: Methods included cutting the stems of woodies with a diameter of at least 10 cm at knee height by chainsaw and manual clipping after which an arborocide was applied to the stumps. A neutron probe was used to measure volumetric moisture content at two different soil depths. The grass biomass was analysed using ANOVA at a confidence level of 95%. Quantitative and qualitative approaches were used to gather information about the perceptions of local communities towards restoration in group discussions. Results: The short-term data showed that the implementation of BP as restoration method increased grass biomass production. The soil texture influenced the volumetric soil moisture. Higher soil moisture content was found in the deeper clayey soils. The local participants' interpretation towards the restoration project was positive. Conclusion: The project increased the grazing potential and contributed to job creation to improve the well-being of the people in the community. [ABSTRACT FROM AUTHOR]

Background: One of the main causes of land degradation in South Africa is bush thickening (BT) of mainly Senegalia or Vachellia species. Restoration methods are required to control BT, and to improve grass biomass production and soil conditions in South Africa. Objectives: The objectives of this study were to determine the effect of brush packing (BP) as a restoration method to increase grass biomass production, assess soil moisture after BP on different soil types, and document the perceptions of the local communities towards BP. Method: Methods included cutting the stems of woodies with a diameter of at least 10 cm at knee height by chainsaw and manual clipping after which an arborocide was applied to the stumps. A neutron probe was used to measure volumetric moisture content at two different soil depths. The grass biomass was analysed using ANOVA at a confidence level of 95%. Quantitative and qualitative approaches were used to gather information about the perceptions of local communities towards restoration in group discussions. Results: The short-term data showed that the implementation of BP as restoration method increased grass biomass production. The soil texture influenced the volumetric soil moisture. Higher soil moisture content was found in the deeper clayey soils. The local participants' interpretation towards the restoration project was positive. Conclusion: The project increased the grazing potential and contributed to job creation to improve the well-being of the people in the community. [ABSTRACT FROM AUTHOR]

In savannas, partitioning of below‐ground resources by depth could facilitate tree–grass coexistence and shape vegetation responses to changing rainfall patterns. However, most studies assessing tree versus grass root‐niche partitioning have focused on one or two sites, limiting generalization about how rainfall and soil conditions influence the degree of rooting overlap across environmental gradients.We used two complementary stable isotope techniques to quantify variation (a) in water uptake depths and (b) in fine‐root biomass distributions among dominant trees and grasses at eight semi‐arid savanna sites in Kruger National Park, South Africa. Sites were located on contrasting soil textures (clayey basaltic soils vs. sandy granitic soils) and paired along a gradient of mean annual rainfall.Soil texture predicted variation in mean water uptake depths and fine‐root allocation. While grasses maintained roots close to the surface and consistently used shallow water, trees on sandy soils distributed roots more evenly across soil depths and used deeper soil water, resulting in greater divergence between tree and grass rooting on sandy soils. Mean annual rainfall predicted some variation among sites in tree water uptake depth, but had a weaker influence on fine‐root allocation.Synthesis. Savanna trees overlapped more with shallow‐rooted grasses on clayey soils and were more distinct in their use of deeper soil layers on sandy soils, consistent with expected differences in infiltration and percolation. These differences, which could allow trees to escape grass competition more effectively on sandy soils, may explain observed differences in tree densities and rates of woody encroachment with soil texture. Differences in the degree of root‐niche separation could also drive heterogeneous responses of savanna vegetation to predicted shifts in the frequency and intensity of rainfall. [ABSTRACT FROM AUTHOR]

Soils in the semi-arid regions such as north-eastern South Africa, where chickpea was recently introduced, are commonly characterized by poor fertility and low pH. Preliminary studies show that the crop has a huge potential in the region, but lack of nodulation has consistently been a problem. We assessed the response of soil pH and nodulation of three chickpea genotypes (ACC #4, ACC #5, and ACC #6) to biochar application (0, 10, and 20 t ha−1) and rhizobium inoculation (inoculated and uninoculated) in Thohoyandou (clay soil) and Nelspruit (loamy sand soil), South Africa in 2015 and 2016. Nodulation was assessed at flowering by determining the number of nodules per plant and nodule dry weight, and soil pH was analyzed after harvest in both seasons. Biochar increased pH by 0.7 (clay soils) and 0.7–0.8 (the more acidic loamy sand soils) pH units. Similarly, biochar increased nodulation in inoculated treatments in both locations and seasons, and this was mainly associated with the effect of biochar on soil pH. The increase in nodulation with inoculation varied amongst the genotypes. Clearly biochar and rhizobium inoculation may be crucial for improving soil pH and nodulation in chickpea cropping systems characterized by poor soils. [ABSTRACT FROM AUTHOR]

Moringa oleifera Lam , often grows well under cultivation in the tropics and sub-tropics. It does well in sandy to clayey soils and tolerates low rainfall. The plant is well-known for its nutritional and medicinal properties, hence it is fast gaining popularity in South Africa and the rest of the world. The objective of this study was to predict the suitable areas for cultivating M. oleifera in South Africa using climate and edaphic variables that significantly affect its growth and development. We used an Analytical Hierarchical Process (AHP) and Geographic Information System (GIS) weight function to assign suitability weights to criteria and sub-criteria that affect the plant's growth and a predictive cultivation suitability map. Area under the curve (AUC) was used to evaluate the model's performance. The Analytical Hierarchical Process indicated that the most influential variable determining M. oleifera cultivation were, minimum temperature, soil texture, annual rainfall, mean temperature and soil pH, respectively. Further, the results showed that approximately 16.5% (200,837 km2) of South Africa land area has optimal growth conditions, 17.8% (216,758 km2) suitable conditions, 46% (560,794 km2) less suitable conditions and 19% (240,699 km2) not suitable conditions for cultivating M. oleifera. The area under the curve (AUC) metric of our suitability model suggested that the map is 81% accurate for predicting the spatial suitability of cultivating M. oleifera in South Africa. The results also confirm that the use of AHP model with GIS weight function is useful for explicit identification of sites for M. oleifera cultivation for maximum production output. The results of this study can be useful information for the land-use policy makers and farmers for informed decision regarding the cultivation of M. oleifera in South Africa. • Moringa oleifera is fast gaining popularity in South Africa. • We predicted the spatial suitability of cultivating Moringa. • Minimum temperature mostly influences Moringa growth. • Soil pH has the least influence on Moringa growth. • 16.5% of South Africa area has optimal conditions for cultivating Moringa. [ABSTRACT FROM AUTHOR]

Aim: High‐resolution spatial soil data are crucial to species distribution modelling for fundamental research and conservation planning. Recent globally modelled soil layers (e.g. SoilGrids) have transformed distribution modelling, but may fail to represent regional soil characteristics accurately. We hypothesize that in the Cape biodiversity hotspot of South Africa, the use of global soil layers has led to underestimation of the importance of edaphic factors as determinants of species' and vegetation distributions. We present a series of new, regionally modelled layers to address this deficiency. Location: Greater Cape Floristic Region (GCFR, South Africa). Methods: We georeferenced edaphic characteristics from literature and other sources and used boosted regression trees (BRT) to associate edaphic characteristics with spatially explicit topographic, climatic, soil texture and biotic variables. Multinomial BRTs were used to predict mapped vegetation types from the collated edaphic and other data. Results: BRTs reliably predicted pH (92% of variance), Na (87%), K (85%), electrical conductivity (81%) and P (73%), but were less accurate for total N (55%) and total C (61%), for which data were sparser. Soil clay and pH values differed markedly in range and in spatial variation from those in SoilGrids. Using our new edaphic layers, we were able to accurately predict spatial distributions of vegetation types within the GCFR (multi‐class AUC = 0.96). The multinomial BRT predicted vegetation less well when based on SoilGrids data alone (AUC = 0.84). Main conclusions: The more faithful representation of soil properties in our model is attributable both to its use of ca. 10‐fold more samples, and to its regional focus. Our model of edaphic characteristics captures important edaphic variability that is vital for understanding plant and consequently faunal distributions, with wide‐ranging conservation implications. Ongoing development of global syntheses of soil data requires more samples, especially in areas with high spatial heterogeneity and extreme edaphic conditions. [ABSTRACT FROM AUTHOR]

Grapevine leafroll is the most damaging grapevine virus disease in South Africa, and the primary vector of Grapevine leafroll-associated virus 3 (GLRaV-3) is vine mealybug, Planococcus ficus (Signoret). Preventing re-infection of newly planted, virus-free grapevines is critical to control and prevent the spread of leafroll disease. Results from a previous survey raised concern that mealybugs surviving on leafroll-infected root remnants in the soil could transmit the virus to newly planted grapevines. This study aimed to determine if P. ficus commonly occurs on grapevine roots in the Western Cape Province of South Africa, if and for how long it can survive on remnant roots in soil, and if it can transmit GLRaV-3 to healthy grapevines after surviving on remnant roots. Surveys to determine the occurrence of mealybugs on grapevine roots were conducted at different times of the growing season in vineyards near Robertson, McGregor, Montagu, Somerset West and Malmesbury over three seasons. A field trial was conducted on a sand-clay-loam soil with 23% clay and a sandy-loam soil with 10% clay over 12 months to determine survival of different life stages of vine mealybug confined on root sections from leafroll-infected Pinotage/R110 grapevines. Results indicate that P. ficus does not readily occur on grapevine roots in the Western Cape, and that it does not survive well on root remnants of grapevines for any length of time. Implications for planting virus-free grapevines in soil where leafroll-infected vines were removed, are discussed. [ABSTRACT FROM AUTHOR]

Abstract Precise and accurate measurement of soil water for monitoring crop water uptake, irrigation scheduling and management can be provided through continuous soil water monitoring, which is made possible with the aid of automated capacitance probes such as HydraScout. This study was carried out to develop HydraScout capacitance probe calibration equations for selected soil types and to evaluate the accuracy levels of the calibration equations for continuous measurement of soil water. The selected soil textural classes were sand, loamy fine sand, sandy loam, sandy clay loam, clay loam, sandy clay and clay. The volumetric water contents were plotted against the sensors readings to develop calibration equations. The best fit of the regression function was used on the basis of highest adjusted coefficient of determination (R2). Results indicated that calibration functions developed for the soils were linear (clay, clay loam and sandy soils) and polynomial (loamy fine sand, sandy loam, sandy clay loam, sandy clay soils). Volumetric water content was well predicted with the text-specific equation for clay loam (RMSE of 0.001 m3 m−3 and D-index of 0.99) and sandy loam (RMSE of 0.001 m3 m−3 and D-index of 0.99) soil textural classes. Prediction of volumetric water content for sandy clay produced the highest RMSE (0.009 m3 m−3) and lowest D-index (0.68) for all the soil textural classes. It was recommended that the text-specific laboratory calibration equations developed during this study should be used especially, for sandy loam soil type, in a situation where high numbers of the probes are in use. In the case where few of the probes are in use, each sensor must be calibrated. Highlights • The HydraScout capacitance probes can measure soil water continuously. • Calibrations equations developed were both linear and polynomials. • Each soil textural class has calibration equation peculiar for that specific soil. • Calibration equations were able to predict soil water with high accuracy. • The capacitance probe can be used on most of the soil textural classes in South Africa. [ABSTRACT FROM AUTHOR]

Abstract: The grassland biome of South Africa is a major resource for livestock farming; yet the soils of these rangelands are stressed differently by various management systems. The aim of this study was to investigate how basic soil properties respond to different management systems. For this purpose we sampled rangeland management systems under communal (continuous grazing), commercial (rotational grazing) and land reform (mixture of grazing systems) farming. Within each of these systems a grazing gradient was identified with decreasing grazing pressure with increasing distance to the water points. Results showed that communal farms with continuous grazing were generally depleted in the respective nutrient stocks. The depletion increased with rising grazing pressure. Along that line there was a breakdown of macroaggregates with losses of the C and N stored therein. However, the commercial farms also exhibited a decline of macroaggregates and their associated C content nearby the water points. Aggregate fractionation is a sensitive indicator for detecting the beginning of soil degradation in this biome; yet, degradation was less pronounced under the rotational grazing of the commercial farms than under communal property right conditions. Hence, soil analyses confirm that fences and appropriate grazing periods are needed to manage these rangelands sustainably. [Copyright &y& Elsevier]

This study extended the association between hookworm transmission in KwaZulu-Natal and the sandy coastal plain by investigating the parasite's occurrence in isolated areas of sandy soils further inland. A school-based prevalence survey was carried out in selected inland sandy areas and in surrounding areas dominated by clay soils within a narrow altitudinal range of between 500 and 700 m to reduce the effect of altitude on climate-related factors (rainfall and temperature). Sandy areas situated on the coastal plain were included in the analysis for comparative purposes. Soil samples (0–50 mm depth) were collected from each locality to assess their nematode loadings and to analyse selected physical and chemical properties. Significant differences were found between the moderate prevalence of hookworm infection among children living in inland areas with sandy soils (17.3%) and the low prevalence in surrounding non-sandy areas (5.3%, P < 0.001), and between infection among children living in all inland areas (9.3%) and the high prevalence on the coastal plain (62.5%, P < 0.001). Amounts of fine and medium sand were highest in both the coastal plain soils and in inland sandy areas and these fractions showed a significant positive correlation with hookworm prevalence and nematode loadings. Clay, coarse sand and organic matter contents were highest in surrounding non-sandy soils and showed a significant negative correlation with the nematode variables. No statistically significant correlations were found with soil pH at study localities. We conclude that properties of inland sandy soils, particularly particle size distribution, correlate well with hookworm prevalence and nematode loadings and therefore provide a more suitable habitat for nematodes than surrounding non-sandy areas. These results suggest that particle size distribution of sand fractions, organic matter and clay content in the soil influence the survival of hookworm larvae and hence the parasite's transmission. [ABSTRACT FROM AUTHOR]

(a-c) SEM-EDX images of sepiolite textures in calcareous nodules from coastal soil (sample 6869/iii). (d) TEM images of coastal soil clay fraction (sample 6869/iv) showing sepiolite, kaolinite, and accessory palygorskite. • High-Mg, sepiolite-bearing soils at coast. • High-Mg, palygorskite-bearing soils 130 km inland. • Low-Mg, palygorskite-bearing soils 600 km from the coast. • Geographic mirror of chemical variation in sepiolite-palygorskite continuum. • Evaporation of pore water in coastal region increases Mg and Ca, decreases pH. Some coastal soils in Namaqualand have significant amounts of sepiolite. Palygorskite is relatively low in coastal soils but it is abundant at some inland sites up to 600 km from the coast. This distribution is explained by examining relationships of major ionic species in saturated paste extracts. Our study found two categories of geographically and chemically distinct palygorskite-containing soils: 1) high Mg, palygorskite soils 130 km inland with similar Mg levels to coastal sepiolitic soils, and 2) low Mg, palygorskite soils 600 km inland. The geographic progression from high-Mg sepiolite-containing soils at the coast, through high-Mg palygorskite soils to low-Mg palygorskite soils farthest from the coast parallels the chemical variation in the sepiolite-palygorskite continuum from sepiolite, the most magnesic endmember at the coast, to palygorskite the least magnesic endmember farthest inland. MgSO 4 0 and MgCl+ ion complexes do not appear to depress Mg2+ activity to an extent that is able to distinguish sepiolite-containing from palygorskite-containing soils. Calcite in the profile is strongly associated with occurrence of fibrous clay minerals, and dolomite is absent. Compositions of soil saturated paste extracts conform to their respective mineral stability fields, contrasting with previous work in the area. The previous interpretation, therefore, that fibrous minerals may currently be in a state of alteration requires revision. Evaporation of soil pore waters in the marine-influenced region results in increased Mg and Ca and decreased pH, even with precipitation of sepiolite and calcite. These chemical changes with evaporation are important for understanding the evolution of soil solutions and precipitating minerals in arid coastal environments and the chemistry of waterbodies associated with them. [ABSTRACT FROM AUTHOR]

• APSIM tested against six and eight-year crop rotation trials in southern Africa. • Effect of diversification on average productivity, yield trends, soil carbon and nitrogen properties investigated. • Low input systems benefited from crop diversification that included legumes through increased Nmin content. • Commercial systems faced a productivity-environment trade-off in the short term, but intercropping seemed promising. Diversification of cropping is perceived as a strategy to simultaneously achieve high productivity and maintain environmental sustainability. In southern Africa, however, due to a lack of medium to long-term field trials, there is missing quantitative information. Utilising the capability of agro-ecosystem models to quantify the interactions of crop productivity with management and environmental variables, the APSIM model was evaluated against six and an eight-year field trial datasets comprised of different crop rotations and fertiliser rates under two contrasting agro-ecological conditions in South Africa (clay soil with a mean rainfall of 871 mm versus a sandy soil with a 570 mm rainfall). Model output was compared to observed grain yield, aboveground dry matter, soil organic carbon (SOC), and mineral nitrogen (N min) dynamics. APSIM was able to reproduce the observed grain yield dynamics fairly well as indicated by a Wilmott index of agreement of 0.90. Prediction accuracy, as indicated by the absolute model error across all crops, however, only reached 39%. Simulated N min and SOC dynamics showed similar patterns to the observations. Subsequently, the model was applied in a ten-year simulation experiment with rotation treatments (14 rotations, respectively intercropping systems, including a maize monoculture control), fertiliser levels (zero and 70 kg N ha−1), and residue management (retained and removed) for the two sites. For low input systems, such as smallholder farms, residue management and legume integration are of the utmost importance to maintain SOC and more pronounced Nmin levels, which, for the sandy soil, resulted in an average maize yield increase of up to 1000 kg ha−1. Maize monoculture treatments with residues removed reduced SOC moderately by 0.04–0.08 %, while yields declined strongly (>1000 kg ha−1) over the simulated period of ten years. In commercial, fertilised cropping systems, allocating land to cultivate crops other than maize reduced the simulated total yield performance. This diversification disadvantage has to be considered against the benefits of increased SOC and yields in the medium-term, i.e. a period of ten years. For the commercial systems, maize intercropped with delayed sown oats or cowpea appeared promising. [ABSTRACT FROM AUTHOR]

The author comments on the study "Mineralogical and Geochemical Analyses of the Healing Elements in Clayey Soils From Isinuka Traditional Spa in Port St Johns, South Africa" published in a previous issue of the journal. According to the author, there is a need for clarification on springs' gas emissions. Particular focus is given to the inadequacy of the materials and methods section of the study, as well as questions raised by the geochemistry of analysed samples.