9 research outputs found
Assessing the liming effect of ground eggshells relative to aglime on two texture contrasting acidic soils
No full textMSc (Crop Science), North-West University, Mahikeng CampusSoil acidity is one of the major land degradation problems that affects almost 50% of the
world’s arable land. It is usually associated with toxicities of elements such as aluminum and
manganese, deficiencies of calcium and magnesium, and reduced microbial activity and
diversity. Consequently, all these factors can result in reduced crop yield and economic losses
for the farmers. The current effective method of mitigating soil acidity is the application of
lime. However, the costs associated with the acquisition of lime make it challenging for
small-scale farmers to lime their soils since large quantities of lime are required for
substantial effects. Alternative cost-effective liming materials have been sought and these
include industrial by-products such as fly ash and stainless steel slag. However, there are
environmental and health concerns about using these liming materials since they contain
potentially toxic elements. Eggshells were discovered to be composed of almost 97% CaCO3
and 40% pure calcium, which is similar to traditional aglime. Moreover, eggshells contain
very small amounts of potentially toxic elements and thus would not pose the risk of food
chain contamination. However, due to limited research of eggshells on soil application, the
question remains on the effectiveness of eggshells as a liming material.
The aim of this study was to evaluate the liming potential of ground eggshells relative to
aglime in two texture contrasting acidic soils, and their subsequent effect on the growth of
Swiss chard (Beta vulgaris L). The soils used in the study were, sandy clay loam, which had
an initial pH of 4.52 and sandy loam with an initial pH of 5.23. The set objectives of the
study were then achieved through an incubation and greenhouse study for 120 days. Both
studies showed that the application of both eggshells and aglime significantly increased the
soil pH in comparison to the control for all application rates in both soils, moreover, there was
no significant difference between the two applied lime sources. The results also showed a
quick response within 7 days from the application of the two lime sources. The subsequent
effects of the applied liming sources in the incubation period of the study were analyzed
through the exchangeable acidity and plant-available phosphorus, whereas the subsequent
effect of the liming materials in the greenhouse study were analyzed through plant-available
phosphorus and plant dry weight of Swiss chard. The applied lime sources completely
neutralized the acidity in the soil, and the exchangeable acidity under the application of the
two lime sources was significantly lower than the controls at all application rates. The
plant-available phosphorus was not significantly different between the applied lime sources
at all application rates and the controls, however, the two lime sources increased the
plant-available phosphorus above 25 ppm, which is the minimum health level of
plant-available phosphorus. There was no significant difference between the two applied lime
sources compared to the controls at all application rates on the plant dry weight. However, it
was observed that Swiss chard growing at the 0 t/ha (control) in the sandy clay loam showed
poor and stunted growth throughout the study while Swiss chard growing at the 0 t/ha
(control) in the sandy loam did not exhibit poorand stunted growth. According to the study’s
results, eggshells have a similar liming effect asaglime and their dissolution rate is similar,
therefore, eggshells can be used together with aglime or as a substitute of aglime in
increasing soil pH.Master
Potassium reserves and fixation capacity in soils of the South African sugar industry and potential for their inclusion in soil testing and fertilizer recommendations.
No full textDoctor of Philosophy in Soil Science. University of KwaZulu-Natal, Pietermaritzburg, 2018.Abstract available in PDF file
A comparative study of the BCR sequential and batch extractions for wastes and waste-amended soil.
No full textThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.The use of standard soil tests to assess waste materials has become a common practice in waste management. However, the suitability of using standard soil tests on waste materials is questionable. Therefore, this investigation was undertaken to compare commonly used chemical extraction methods for their ability to extract elements from soil, waste, and soil-waste mixtures. This was carried out by:
· Assessing the effects of extraction time on the extractability of Al,Ca, Co, Cu, Fe, Mg, Mn, Ni, Pb, S, Si, and Zn;
· Assessing the comparability between single and sequential extraction.
Two manganese rich wastes namely electro-winning waste (EW) and silicate-rich smelter slag (SS) and an acid soil (Inanda, Ia) were used for this study. Waste amended soils were obtained by incubating the EW and SS with Ia soil at field capacity at a rate of 20 g kg-1 and 120 g kg-1 soil respectively, and were sampled at day 0, 7, 28, 56, and 140.
The effect of extraction time was assessed on the EW, SS, and Ia soil with carbonated water used in the acid rain test conducted at 16, 20, 30, and 50 hours. The equilibration time was different for different materials and elements. The concentration of Al and Zn did not change appreciably with increasing extraction time in the EW. Similar results were found for Mg, S, and Si in the SS and S in the Ia soil. This was attributed to ‘equilibrium’ being reached before 16 hours. The equilibration time of 20 hours which would release the exchangeable and specifically adsorbed elements was obtained for Co, Mg, Si, S, and Mn in the EW. The concentration of Ca decreased with extraction time in the EW and was attributed to readsorption. The concentration of Ca and Mn in the SS and Al, Fe, and Si in the Ia soil increased with extraction time and the ‘equilibrium’ was not reached even after 50 hours. This was attributed to the release of elements due to dissolution of minerals.
In the comparison between Community Bureau of Reference (BCR) sequential and batch extraction, the concentrations of Ca, Co, Mg, Mn, and S were higher in batch extraction than in sequential extraction, particularly for the EW and the EW treated soils. This was possibly caused by the readsorption of released elements during water extraction. On the contrary, sequential extraction had higher concentration of Al and Fe compared to batch extraction for the EW, Ia soil, SS treated soils, and EW treated soils. These were attributed to a continued desorption of elements and dissolution of minerals due to exposed surfaces which occurs in sequential extraction.
The comparison between single and sequential extraction for the BCR sequential extraction showed that hydroxylammonium chloride (HAC) applied in sequential extraction had higher concentration of Al, Co, Fe, Pb, and Zn than the single HAC extraction. This was probably due to incomplete dissolution of minerals, precipitation of amorphous minerals, and readsorption of released elements occurring for a single HAC extraction. These were minimised for hydrogen peroxide (H2O2) extraction and hence comparability between single and sequential H2O2 extraction was observed. This was probably due to the presence of complexing agent in the extracting reagent which would minimise the formation of secondary precipitates and hence, improved dissolution of minerals was obtained. Similarly, the concentrations of elements were comparable between single and sequential aqua regia extraction. These results indicated that comparability is improved between single and sequential extraction when aggressive conditions are used.
The results from this investigation indicated that when chemical extraction methods are applied to wastes, the effects of the waste properties on the results of extraction need to be well understood. Consequently, when the chemical extraction methods are used in waste management scenarios certain modifications might have to be made. These modifications include the use of a high solution:solid ratio and an extracting solution which has high complexing abilit
Effect of Potassium Application Rates on Sugarcane Yield in Soils with Different Non-Exchangeable Potassium Reserves and Fixation Capacity
No full textReliable fertilizer recommendations should account for factors influencing nutrient supply, including non-exchangeable potassium (K) reserves and fixation capacity, to ensure optimum crop yields. The combined effects of non-exchangeable K reserves and fixation capacity of soils on crop response to K application has not been evaluated. This study evaluated the response of sugarcane yields to K application on two soils with contrasting combinations of non-exchangeable K reserves and fixation capacity. Potassium was applied at 0, 120, and 240 kg K ha−1 at the commencement of the field trials and after each harvest on an umbric Acrisol, which had low non-exchangeable K reserves and medium K fixation capacity, and a cutanic Acrisol, which had ‘very high’ non-exchangeable K reserves and fixation capacity. Sugarcane stalk and sucrose yield, leaf, and exchangeable K were measured for each season. In the umbric Acrisol, a lower sucrose yield was measured in the 240 kg K ha−1 treatment compared to the control for the plant crop, but this application rate had higher yields for the second ratoon. In contrast, there was no yield response to K application in cutanic Acrisol. This study indicated the importance of non-exchangeable K reserves and fixation capacity when calculating K requirements and conducting field calibration studies
Eggshells Improve Soil pH and P Availability in Sandy Loam and Sandy Clay Loamy Soil
No full textThe current effective method of mitigating soil acidity is the application of lime. However, the costs associated with acquiring lime make it challenging for small-scale farmers in South Africa. Therefore, the aim of this study was to evaluate the liming potential of ground eggshells relative to aglime and its effect on P availability in two acidic soils differing in textural classes, and its subsequent effect on the growth of Swiss chard (Beta vulgaris L.). Two soils used in the study were sandy clay loam, which had an initial pH of 4.52, and sandy loam with an initial pH of 5.23. Both lime sources were applied at a rate of 0, 1, 2.5, and 5 t/ha through incubation for 120 days. Our results indicated that applying eggshells and aglime significantly increased soil pH within 7 days (p < 0.05) compared to the 0-rate application across all application rates in both soil types. There were no differences (p > 0.05) in pH between the two applied lime sources. Plant-available P was not significantly different between the applied lime sources at all application rates and the 0-rate application; however, the two lime sources increased plant-available phosphorus above 25 ppm, which is the minimum health level of plant-available phosphorus. The results of plant yield showed no differences (p > 0.05) between the plant dry weights. However, Swiss chard growing at the 0-rate application in the sandy clay loam showed poor and stunted growth while Swiss chard growing at the 0-rate application in the sandy loam did not exhibit poor and stunted growth. According to the study’s results, eggshells have a similar liming effect as aglime and their dissolution rate is similar; therefore, eggshells can be used as a substitute of aglime to increase soil pH. Using eggshells as a substitute for aglime could offer substantial benefits to small-scale farmers by reducing input costs and providing a locally sourced, sustainable alternative. This approach can also enhance economic sustainability in rural communities by promoting the recycling of agricultural by-products and making essential soil amendments more affordable and accessible
Unlocking soil phosphorus resources in semi-arid regions using arbuscular mycorrhizal fungi and phosphorus solubilising bacteria: a systematic review
No full textAbstract Semi-arid regions are generally alkaline and deficient in nutrients, specifically phosphorus (P), due to extremely dry climates. In such soils, integrating phosphate-solubilising bacteria (PSB) and arbuscular mycorrhizal fungi (AMF) can provide a synergistic effect that will unlock fixed P resources, thus promoting nutrient uptake, plant growth, and crop yields. Therefore, this study aimed to review and discuss the role of PSB and AMF on soil fertility, crop growth, and factors affecting their performance in semi-arid regions, consolidate findings from various studies to allow for comparisons across different soils, crops, and microorganisms. Twenty-nine primary studies were selected from various databases based on the inclusion and exclusion criteria of the Preferred Reporting Items for Systematic Reviews and Meta-analyses method. The inoculation of PSB and AMF individually increased available P, plant growth, yield, and P-uptake. However, dual inoculation of PSB and AMF outperformed the application of PSB or AMF alone, suggesting a synergism between these microorganisms in improving plant growth and available P. The lack of response of available P and P uptake to PSB and AMF inoculation in some studies was likely caused by high P-fixation, which was not reported in all the studies. Our study highlights the potential benefits of PSB and AMF inoculation for sustainable agriculture. Initial soil properties, type of plant and microbial strain population were identified as regulatory factors influencing the efficiency of PSB and AMF inoculation. However, future studies should account for P-fixation and fractions when investigating the inoculation effects of PSB and/or AMF to clarify and locate where P is being released
Black (Acacia mearnsii) and silver wattle (Acacia dealbata) invasive tree species impact on soil physicochemical properties in South Africa: A systematic literature review
No full textInvasive alien plant species are a problem to global biodiversity, ecosystem dynamics, and human livelihood. The risks and potential effects of invasive alien species on local vegetation are growing, particularly the potential loss of ecological services. Thus, this study aimed to synthesise the impacts of acacia 'species' on soil physicochemical properties in South Africa. A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework for conducting a systematic review was followed. A total of 16 studies that met the study selection criteria were used. Data were extracted and evaluated by checking if any soil physicochemical parameters increased (+) or decreased (−) the impacts on invaded and cleared soils. The results showed increased quantities of soil organic carbon, total nitrogen, and gravimetric water content in invaded soil than in cleared soil. Acacia species generally positively improved the soil's physical and chemical properties during their invasion, and some minor changes may occur after their clearance, such as a decrease in cations. The results of this study only explain how acacias affect soil physical and chemical properties in three provinces; therefore, there need to be more studies from other provinces which could have further given insights into a particular region
Climate change effects on water footprint of crop production: A meta-analysis
No full textThe impact of climate change on both natural and human systems is becoming increasingly severe. One of the areas that is most affected is agriculture, which is responsible for utilising around 70 % of the planet's freshwater and is also under significant pressure to feed the ever-growing global population. This meta-analysis examined the complex relationships between water footprint and climate change, focusing on the effects of rainfall and temperature changes in different geographical areas. The study used a combination of the following search words: climate change, climate variability, global warming, drought, water footprint, blue water footprint, green water footprint, grey water footprint, crop production, crop yield, crop water footprint, crop water use, water usage, precipitation, rainfall, and temperature. The selection of articles followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram procedure, ultimately including 33 articles that met the study criteria out of the 938 articles initially retrieved. The study's findings indicated that the most influential factors of the water footprint varied globally due to natural and human interference conditions. The findings also indicated that all crops were susceptible to changes in temperatures and rainfall distribution, resulting in a decrease in WFblue, WFgrey, and WFtotal, while WFgreen increased with increasing rainfall and temperatures. Temperature had a notable effect on the WFblue of crops grown in areas that receive limited rainfall. Future research should conduct a meta-analysis on the uncertainty associated with climate change projections and its implications for estimating the water footprint of crop production
The short-term effects of surface-applied dolomitic lime and gypsum on soil chemical properties and yields of sugarcane ratoon crops in KwaZulu-Natal, South Africa
No full textThis study investigated the effects of surface-application of lime and gypsum on soil properties and yields of ratoon sugarcane crops. Treatments involved once-off surface application of dolomitic lime (L), gypsum (G) and dolomitic lime plus gypsum (LG) in factorial combination, with four replications. Soil chemical properties were measured on samples collected at intervals of 20 between depths of 0 and 80 cm in the first and fifth years after treatment application. Yield parameters were measured annually. In the first year, treatment effects were mainly restricted to a depth of 0–20 cm. The LG increased pH(CaCl2) from 3.9 to 4.5, and calcium from 123 to 350 mg L−1. Little treatment effect was observed on yield parameters in the first year. In the fifth year, L and LG generally showed similar impacts on soil properties. The L treatment led to markedly increased pH(CaCl2) and calcium and somewhat decreased magnesium levels in the topsoil. The sucrose and cane yields in LG were significantly higher than in other treatments, which all had similar results. It was, therefore, concluded that LG may be a viable option for the correction of soil acidity through surface application in the sugarcane ratoon crops grown in the sandy soils of KwaZulu-Natal.</p
