Sequential injection has, over the past eight years, developed into a viable alternative to flow-injection, but its full potential has not yet been fully realized. It developed out of existing flow-injection methods when a need for mechanically simple and robust flow-injection methodology arose. In this study the development of this method is discussed with its numerous advantages and disadvantages over existing flow-injection methods. The theoretical basis on which this technique is based is outlined as well as parameters that influence the design of the manifold. With the manifold design principles established, the manifold is evaluated using real sample analysis, with liquid fertilizer as the source of selected elements. Adjustments made to existing flow-injection methods, for the determination of nitrite with sequential injection analysis, are discussed, while a new method is proposed for nitrate determination. The viability of solid-phase reductors and in situ preparation of reagents, combined with sequential injection analysis, is also studied. / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

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The citrus industry is one of South Africa's largest agricultural sectors in terms of export earnings with lemon fruits and juice as a trendsetter due to their high grade quality. According to growers, the Eastern Cape Province of South Africa alone produces an excess of about 10-14,000 tons of lemon juice which is presently of no economic value due to the sour taste and “bitterness”. As a result of this excess and in order to make use of the polyprotic acids naturally occurring in the lemon juice, four fertilizer nutrient mixtures are formulated, using lemon juice as base. From a conceptual scientific approach, characterization (physico-chemical and functional properties determinations) of Eureka Lemon fruit juices were undertaken, followed by smaller scale batch formulation experiments. On the basis that these lemon juice-based fertilizer mixtures are prepared following standard liquid fertilizer formulation guidelines, a field test was conducted to evaluate their potential effectiveness to influence plant growth. A growth chamber testing on tomato plants revealed high growth response (> 99.9 % certainty) potential in two of the semi-organic mixtures formulated while the organic mixture showed a relatively good growth rate as compared to the control (pure tap water). According to statistical analysis (ANOVA) comparison, two of the semi-organic mixtures performed considerably better than the two commercial samples evaluated. Potential benefits profoundly associated with these nutrient mixtures as compared to similar liquid fertilizer products on the market is that most nutrients are chelated and dissolved in solution. Also, the mixtures contain all necessary nutrients including plant growth substances required for healthier plant growth. The most important socioeconomic impact is the value addition to the technology chain in the citrus industry. The use of fluid fertilizers in significant quantities is less than twenty years old. Nevertheless, growth has been so rapid that in South Africa demand for mixed liquid fertilizer has greatly increased from 90 000 tons NPK & blended micronutrients in 1955 to more than 600 000 per annum tons today (Report 41/2003, Department of Minerals and Energy). The liquid fertilizers market is sparsely specialized with major competitors like Omnia, Kynoch and Foskor supplying more than 50 % of the market demand. Amongst the nutrient mixtures formulated, mixture one is an NPK (1-1-2) based nutrient mixture containing both secondary nutrients (0.5 % Mg & 1.0 % Ca) and seven micronutrients (0.1 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co). The composition of this mixture offers the formula a potential to be used as a general purpose (all stages of plant growth) fertilization mixture in view of its balanced composition (containing all essential plant nutrients). Mixture two contains essentially the micronutrients and in higher concentrations (0.3 % Fe, 0.3 % Cu, 0.1 % Zn, 0.2 % Mn, 0.02 % B, 0.0005 % Mo and 0.0005 % Co) as compared to mixture one except for boron, molybdenum and cobalt. The concentration of the micronutrients contained in this mixture is adequately high which offers a potential for it to be used in supplementing nutrition in plants with critical micronutrient-deficient symptoms. Mixture three is very similar to mixture two (1.0 % Fe, 0.05 % Cu, 0.05 % Zn, 0.05 Mn, 0.05 % B, 0.0005 % Mo and 0.0005 % Co) except that the concentrations of all seven micronutrients are considerably less than those of contained in mixture two. However, the concentration of iron in this mixture is as high as 1.0 %. The mixture has a potential to be used in high iron-deficient situations. Mixture four is an organic formula with relatively low nutrient concentrations (NPK-0.02-0.02-1, 0.27 % Mg, 0.02 % Ca, 0.008 % Fe, 0.26 % Cu, 0.012 % Zn, 0.009 % Mn). Nevertheless, this mixture is appealing for organically grown crops where the use of chemicals is prohibited by standards. These lemon juice-based nutrient mixtures were further characterized and tested for stability and storability over a period of eight weeks. This study revealed no major change in the physical quality (colour, pH and “salt out” effect). The basic formulation methodology is a two-step procedure that involves filtration of the lemon juice to remove membranous materials, mixing at ambient temperature and stabilization of the nutrient mixtures. However, for the organic nutrient formula mix, filtration follows after extraction of nutrients from plant materials using the lemon juice.

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The association between a monoculture crop, an established pest and a means of chemical pest control is an important consideration in modern agriculture. Collembola, in particular the Onychluridae Tullbergia krausbaueri and Onychlurus armatus, have been associated with the cultivation of sugar beet (Beta vulgaris) since 1958 (Jones and Dunning, 1972). Since the 1960's, pests of sugar beet have been controlled with gamma-benzene hexachloride (BHC). Although the association between sugar beet, Collembola and BHC has been established for some time, the specific interactions have not been evaluated by laboratory methods. The aims of this study were to clarify the plant, pest and pesticide interactions and to develop mathematical models to assist in control of the pest.

The effects of poultry manure versus inorganic fertilizer use on copper, zinc and manganese concentrations and the sustainability of metal contents under raspberry cultivation was investigated on two aeolian soils in the Lower Fraser Valley, British Columbia. Total elemental analysis by a teflon bomb procedure using reverse aqua regia and hydrofluoric acid was done on soils sampled at three depths (0-15 cm, 15-30 cm and +40 cm) and results were compared to metal contents extracted by the Mehlich III method. High variability of some of the soil data was attributed to mixing of the loess capping with the underlying glacio-fluvial outwash material, differences in site conditions of the test fields, variations in sampling depth, and inadequate analytical reproducibility at the low concentrations found in some of the soils. For the variables tested, differences between sites most often occurred in the first 30 cm and never at the +40 cm depth. Higher contents in the 0-30 cm depth than in the lower depths indicated an enrichment of the surface layers either by anthropogenic inputs or by bioaccumulation. Poultry manure applications had a significant effect on organic matter content, total and available manganese, and total and available zinc in both soils studied. The comparison of the manured versus the inorganically fertilized site indicated that zinc was the metal most effected by the manure application. The other metals were not significantly increased by poultry manure amendments. The comparison of the site that had been under long-term raspberry cultivation against the site that had been only recently converted to raspberries from long-term pasture cover, showed that long-term raspberry cultivation reduced metal and organic matter contents in the 0-15 cm depth and increased these variables in the 15-30 cm depth. It was hypothesised that this was in direct response to differing biocycling patterns under different land uses. Total and available manganese and zinc were strongly interconnected and their correlation to the organic matter content appeared most interesting in terms of fluxes between the various soil components. inorganically fertilized site indicated that zinc was the metal most effected by the manure application. The other metals were not significantly increased by poultry manure amendments. The comparison of the site that had been under long-term raspberry cultivation against the site that had been only recently converted to raspberries from long-term pasture cover, showed that long-term raspberry cultivation reduced metal and organic matter contents in the 0-15 cm depth and increased these variables in the 15-30 cm depth. It was hypothesised that this was in direct response to differing biocycling patterns under different land uses. Total and available manganese and zinc were strongly interconnected and their correlation to the organic matter content appeared most interesting in terms of fluxes between the various soil components. / Land and Food Systems, Faculty of / Graduate

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