Dissertations / Theses on the topic 'Soils Zinc content'

Metal cation adsorption is the predominant chemical mechanism governing the attenuation of toxic metal movement in soils. Clay minerals are the primary adsorbent surfaces in soils due to their ubiquitous nature and large reactive surface area. This study examined the relative affinity of the metals cadmium, nickel and zinc for the clay minerals kaolinite and montmorillonite. The influence which different mineral adsorbents and different complexing ligands in solution have on the adsorption of metal ions was assessed using the Hard-Soft Acid-Base Principle as a theoretical framework for predicting the maximum extent of adsorption and rate of adsorption. The HSAB principle is that hard bases prefer to complex hard acids and soft bases prefer to complex soft acids. The hypothesis that initiated these investigations was that the hard-soft character of mineral surfaces is due to their surface functional groups and can be measured using metal cation adsorption selectivity experiments where pH and complex ion formation are controlled. When complex ion formation in aqueous solution was minimized (i.e. in Ca(ClO₄)₂), adsorption decreased in the order of decreasing softness, CD > Zn > Ni for both clay minerals. Montmorillonite behaved as a slightly harder Lewis base than kaolinite, sorbing the harder Ni and Zn ions to a greater extent than Cd, although both minerals behaved as soft Lewis bases. In the presence of chloride and sulfate ligands, adsorption sequences changed and reflected results from typical soil solution studies. In some cases the adsorption sequences can be explained using the HSAB principle together with computer speciation data and this approach merits further consideration and research. Adsorption over time and calculated adsorption rate constants were generally consistent with equilibrium selectivity data. Adsorption rates decreased in the order Cd > Zn > Ni in Ca(ClO₄)₂ for both clay minerals. The adsorption curves reflect a two-step adsorption process involving a rapid exchange-type reaction followed by a much slower adsorption involving diffusion into the crystal or alteration of the surface through the formation of a new solid phase involving the adsorbed ions.

High levels of Cu and Zn application to agricultural soils are considered to pose a potential hazard to plants and animals. The levels of Cu and Zn which can be safely added to cropland have yet to be established. This study was conducted on a Davidson silty clay (Rhodic Paleudult) to determine the response of corn (Zea mays L.) to cumulative application of up to 469 kg Cu and 1032 kg Zn ha⁻¹ as sulfates over the 22-year period from 1967 through 1988. Neither corn grain nor silage yield was affected by the metal additions even though the cumulative amount of Cu and Zn added exceeded the maximum allowable Cu and Zn loading rates based on the U.S. Environmental Protection Agency guidelines (i.e., 250 kg Cu and 560 kg Zn ha⁻¹) for this soil. The twenty-first annual application of Cu as CuSO₄, increased Cu concentrations in ear leaves. However, Cu concentrations in ear leaves were unaffected by the twenty-second year of Cu application. Concentrations of Zn in ear leaves were increased by the high level of Zn application during the two years of the study. Twenty-first year Cu and Zn concentrations in com grain were not increased by the high levels of Cu and Zn sulfates. All grain and ear leaf Cu and Zn concentrations were within the normal ranges from the high amount of metal application. The DTPA extractable Cu and Zn in the soil increased with an increase in level of applied Cu and Zn. More Cu and Zn were extracted from the soil by the Mehlich-3 method than by the DTPA method. This higher rate of extraction was attributed to the ethylenediaminetetraacetic acid (EDTA) in the Mehlich-3 solution.
Master of Science

Thesis (PhD (Botany and Zoology))—University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Metal pollution is a problem of increasing global concern. It could arise from industrial activities, as well as pesticide use in agriculture, among other sources. For adequate protection of the soil ecosystem from metal toxicity, the bioavailability of metals must be properly evaluated. A plethora of soil factors affect the bioavailability of metals to soil organisms. These include pH, clay and organic matter contents, salinity among others. While much is known about the influence of some of these parameters, little is known on how clay content and salinity modify the bioavailability of metals to soil organisms. This study investigated the influence of clay content and salinity on partitioning, uptake and toxicity of two essential metals (Cu and Zn) to the earthworm Eisenia fetida in separate laboratory trials. Partitioning of the metals was evaluated with 0.01 M CaCl2, DTPA (di-ethylene-triamine-penta acetic acid), and nitric acid extractions. The metal content of worms was determined by acid digestion, while growth, cocoon production, and mortality were used as endpoints showing toxicity to metals and/or salinity. To test the validity of some of the laboratory results, a field study was undertaken, using the earthworm Aporrectodea caliginosa. Further, the study assessed the effect of salinity, using a battery of laboratory tests (acute, chronic and avoidance tests) with natural and/or artificial soils on four species of organisms (a collembolan Folsomia candida, a potworm Enchytraeus doerjesi and two earthworm species E. fetida and A. caliginosa), representing different feeding patterns and ecological roles in soil. Results showed that with increased clay content, there was increased availability of Cu in the substrate, and increased toxicity to E. fetida as shown by data for mortality and growth. The situation with Zn was less significant at sub-lethal concentrations but much so at lethal concentrations. DTPA and CaCl2 extracted metals revealed changes in partitioning of Cu and Zn with changes in clay content, but this trend was not always consistent. Both DTPA and CaCl2 revealed increased availability of Zn in substrates with increased salinity. Salinity had an additive to synergistic effect with Zn in toxicity to E. fetida. When combined with Cu, salinity also increased the availability of Cu as shown by CaCl2 extracted fraction, and had additive effect on toxicity of Cu to the earthworm. The field study did not succeed in in iv confirming the results of the laboratory study due to confounding role of flooding after heavy rainfall and subsequent leaching of salts and Cu. The results of the experiment on acute and chronic toxicity tests for NaCl on E. fetida showed LC50 of 5436 mg/kg NaCl and EC50 for growth and cocoon production of 4985 and 2020 mg/kg NaCl. These values showed that earthworms might be negatively affected in many soils containing fairly moderate concentrations of salts. Similarly, A. caliginosa could not survive in natural soil containing relatively low salt concentrations (EC = 1.62 dS/m) while reproduction was severely affected at lower EC value of 0.52 dS/m. F. candida and E. doerjesi could survive in the highest salinity soil (EC = 1.62 dS/m) used in this study but their reproduction was severely affected from 1.03 dS/m. Overall, it appears that of all the taxa used, earthworm species were the most sensitive to saline stress and could proof useful in determining ‘safe levels’ of salt in contaminated soils. The results of the avoidance test showed that A. caliginosa avoided both natural and artificial saline soil containing concentrations lower than those avoided by E. fetida. The conclusion is that the influence of clay content and salinity on the bioavailability of Cu and Zn depends largely on the metal in question, but generally speaking, bioavailability and toxicity of the metals were reduced with increased clay content while the opposite was true for salinity. If the species used in this study can be seen as fairly representative of a wide range of soil organisms, the conclusion is that salinisation of soil will be detrimental to most soil organisms at relatively low saline concentrations. Given the role of beneficial soil organisms in several soil processes which in turn contribute to soil fertility and sustainable use of land, it is recommended that any farming practices that may lead to an increase in salt content of agricultural soils should be discouraged.
AFRIKAANSE OPSOMMING: Metaalbesoedeling is ‘n probleem wat toenemende globale kommer veroorsaak. Dit kan ontstaan as gevolg van industriële aktiwiteite sowel as van plaagmiddelgebruik in die landbou en ander bronne.Ten einde die grondekostelsel genoegsaam te beskerm, moet die biobeskikbaarheid van metale ge-evalueer word. ‘n Verskeidenheid van grondfaktore be-invloed die biobeskikbaarheid van metale vir grondorganismes Hulle sluit onder andere in pH, klei, organiese inhoud en soutgehalte. Hoewel heelwat bekend is oor die rol van sommige van hierdie parameters, is min bekend oor hoe klei en soutgehalte die biobeskikbaarheid van metale vir grondorganismes kan modifieer. Hierdie studie het die invloed van kleiinhoud and soutgehalte op die verdeling/partisie, opname en toksisiteit van twee essensiële metale (Cu en Zn) vir die erdwurm Eisenia fetida in afsonderlike laboratoriumproewe ondersoek. Kompartementele verdeling van die metale is geevalueer deur middel van ekstraksie-metodes met 0.01 M CaCl2, DTPA (di-etileentriamien- penta asysnsuur), en salpertersuur ekstraksies. Die metaalinhoud van wurms is bepaal deur suurverterings en spektrofotometriese analises te doen terwyl groei, kokonproduksie en mortaliteit van organismes gebruik is as gevoeligheidseindpunte om toksisiteit van metale en soutgehalte aan te toon. Om die geldigheid van somige van die laboratoriumresultate te toets, is ‘n veldstudie ook onderneem met die erdwurm Aporrectodea caliginosa. Die effek van soutgehalte is verder ondersoek deur ‘n battery van laboratoriumtoetse met vier spesies (‘n kollembool Folsomia candida,’n potwurm Enchytraeus doerjesi en twee erdwurmspesies E. fetida en A. caliginosa), wat verskillende voedingspatrone verteenwoordig. Die resultate het getoon dat met toenmende klei-inhoud was daar ‘n toename in die beskikbaarheid van Cu vir opname vanuit die substraat, asook ‘n toename in toksisiteit vir E. fetida soos deur die gegewens vir mortaliteit en groei uitgewys. Die situasie met Zn was minder betekenisvol by subletale konsentrasies en selfs baie minder so by letale konsentrasies. DTPA en CaCl2 ge-ekstraheerde metale het veranderinge in die partisie/verdeling van Cu en Zn uitgewys met verandering in klei-inhoud, maar die tendens was nie altyd konstant nie. Beide DTPA en CaCl2 ekstraksie het toenemende beskikbaarheid van Zn in substrate uitgewys met toenemende soutinhoud. Soutinhoud het ‘n additiewe/toegevoegde tot sinergistiese vi toksisiteitseffek saam met Zn vir E. fetida. In kombinasie met Cu het soutgehalte ook die geskatte biobeskikbaarheid van Cu verhoog soos uitgewys deur die CaCl2, geekstraheerde fraksie, en het ‘n additiewe effek gehad op die toksisitiet van Cu vir die erdwurm. Die veldstudie kon nie die resultate van die laboratoriumstudie bevestig nie weens die belemmerende rol van vloede na swaar reënneerslae en daaropvolgende uitloging van soute en Cu. Die resultate van die eksperimentele ondersoek na die akute en chroniese effekte van NaCl op E. fetida het ‘n LC50 van 5436 mg/kg NaCl en EC50 vir groei en kokonproduksie van 4985 en 2020 mg/kg NaCl opgelewer. Hierdie waardes het aangetoon dat erdwurms moontlik negatief beinvloed kan word in baie gronde wat ‘n redelike gemiddelde konsentrasie van soute bevat. Soortgelyk kon A. caliginosa nie oorleef in natuurllike grond wat relatief lae soutkonsentrasies bevat het (EC=1.62 dS/m) nie terwyl voortplanting sterk ge-affekteer is by ‘n lae EC waarde van 0.52 dS/m. F. candida en E. doerjesi kon oorleef in die grond met die hoogste soutgehalte (EC= 1.62 dS/m) maar hulle voortplanting is ernstig geknou vanaf 1.03 dS/m. In geheel blyk dit dat van allle taksa wat gebruik is, erdwurms die sensitiefste was vir die stres wat deur soutgehalte veroorsaak is. Die kennis kan nuttig wees in die bepaling van “veilige vlakke” van sout in gekontamineerde gronde. Die resultate van die vermydingstoetse het getoon dat A. caliginosa beide natuurlike en kunsmatig versoute gronde vermy het by konsentrasies wat heelwat laer was as dié wat deur E. fetida vermy is Die gevolgtrekking is dat die invloed van klei en soutgehalte op die biobeskikbaarheid van Cu en Zn grootliks afhanklik is van die metale wat betrokke is en dat biobeskikbaarheid en toksisiteit normaalweg verminder het met verhoogde klei-inhoud, met die teenoorgestelde wat waar was in die geval van soutgehalte. Indien die spesies wat in die studie gebruik is beskou kan word as redelik verteenwoordigend van ‘n wye reeks van grondorganismes, is die gevolgtrekking dat versouting van gronde nadelig sal wees vir meeste grondorganismes, selfs by relatief lae soutkonsentrasies. In die lig van die rol wat nuttige grondorganismes speel in verskeie grondprosesse wat bydraend is tot grondvrugbaarheid en volhoubare gebruik van gronde, word dit aanbeveel dat enige boerderypraktyk wat mag lei tot verhoging van die soutinhoud van landbougronde ontmoedig moet word.

Copies of author's previously published articles inserted. Bibliography: leaves 195-230. In this study the soil aqueous phase chemistry of Zn and Cu in alkaline sodic soils are investigated. The chemistry of trace metal ions at indigenous concentrations in alkaline sodic soils are reported. Metal ions at low concentrations are measured by the graphite furnace atomic absorption spectrometry (GFAAS) technique.

Bibliography: leaves 174-204. "This work provides a starting point for understanding the molecular mechanisms of zinc uptake and the regulation of zinc transport in cereals. Zinc efficient cereals would yield more on soild with low zinc and could potentially result in increased zinc content grain."

Thesis (MTech (Agriculture))--Cape Peninsula University of Technology, 2018.
Zinc deficiency on various soil types have been reported in arable soils of sub Saharan Africa (SSA) including South Africa. A pot trial was conducted at the Cape Peninsula University of Technology, Wellington campus to investigate the interaction of different application rates of Zn at various soil pH on the grain yield and quality of spring wheat in a completely randomized factorial design replicated three times. The four soil pH tested were: pHA: 5.1, pHB: 5.6, pHC: 6.1, pHD: 6.6 which correspond to lime application at 0, 0.5, 1 and 1.5 t/ha. Five Zn rates (Zn1: 3.5; Zn2: 4.5; Zn3: 5.5 Zn4: 6.5, and Zn5: 7.5 mg /kg soil which correspond to Zn1: 7; Zn2: 9; Zn3: 11; Zn4: 13 and Zn5: 15 kg /ha) were applied at two (planting and flowering) growth stages. Yield and yield component data collected were analyzed using SAS version 9.2 and means were separated by Duncun’s Multiple Range Test (DMRT). The results showed that grain yield and yield components were significantly affected by lime application pHC (6.1): 1t/ha at planting. Zn application at planting had no significant effect on the grain yield and yield components. However, at flowering, the simultaneous increase of Zn along with increase in lime positively affected grain yield and yield components. Plant analysis showed that at both stages (planting and flowering), Zn application, especially at pH 6.6, significantly increased P, K, Ca, Na, Mg Fe, Cu and B concentrations in wheat grain, but the concentrations of N, Mn, Zn and protein remained unaffected. Zn application had no effect on most nutrients due to the presence of lime. While the absence of lime, Zn4: 6.5mg/kg (corresponding to 13kg/ha) significantly increased the nutrients. In addition, Zn3: 5.5mg/kg (corresponding to 11kg/ha) promoted Zn absorption by grain in all treatments.

A study was conducted to test for the presence of heavy metals (Cu, Mn, and Zn) in surface sediments of the Puerco River channel in the aftermath of a toxic spill in 1979 near Church Rock, New Mexico. Analysis of samples from five sites downstream from the spill showed that these substances were not present in unusually large amounts, though an increasing gradient of metal concentration with distance downstream was revealed. Statistical analysis revealed the Cu, Mn, and Zn were associated with clay and silt, soil organic matter, organic carbon, and carbonates, all of which existed as extraneous, uncontrolled variables. Adjusted metal concentrations, obtained with covariate analyses, confirmed the increasing gradient downstream. Clay and silt also increased downstream. Some toxic substances may have leached into the riverbed; possible mechanisms for this process are also discussed and further study to substantiate or disprove this hypothesis is recommended.

[Truncated abstract] Zinc deficiency in crops is the most widespread micronutrient deficiency, with about 50% of the cereal-growing areas worldwide containing low levels of plant-available Zn. Zinc plays multiple key roles in different metabolic and physiological processes; its deficiency in crops reduces not only grain yield, but also the nutritional quality of grains. Insufficient micronutrient intake, particularly Zn and Fe, afflicts over 3 billion people in the world, mainly in developing countries. Increasing the amount of Zn in food crops can contribute to improving the Zn status of people. Furthermore, Zn-dense seeds have agronomic benefits, resulting in greater seedling vigour, bigger root system and higher crop yield when sowed to soils with low plant-available Zn. Enhancing nutrient content and nutritional quality of crops for human nutrition is a global challenge currently, but it was mostly ignored during the breeding process in the past. There is a significant genotypic variation for seed Zn accumulation in several crops (including barley) which could be exploited in the breeding programs to produce genotypes with higher seed Zn concentration and content. However, the progress in Zn efficiency until now has mainly relied on conventional plant breeding approaches that have had limited success. Therefore, reliable alternative methods are required. Enhancing mineral nutrition through plant biotechnology may be a sustainable and beneficial approach in developing Zn-dense seeds in the staple crops. ... This DNA band was sequenced and converted into a simple sequence-specific PCR-based marker, which was designated as SZnR1 (seed Zn-regulator1). The developed marker is very easy to score, is inexpensive to run and amenable for a large number of plant samples. The successful development of SZnR1 molecular marker linked to chromosome region associated with seed Zn concentration and content using MFLP in this study illustrates the advantage of this technique over some other DNA fingerprinting methods used for identification of molecular markers for marker-assisted selection (MAS). In conclusion, the greater Zn efficiency of Sahara over Clipper under sufficient Zn supply may be attributed to its higher uptake of Zn. It appears that soil-based pot experiments under controlled condition may offer potential improvements over field experiments in screening for seed Zn accumulation. Shoot and seed Zn concentration and content can be used to diagnose the Zn statues of barley genotypes, and may be a useful selection criterion for Zn efficiency in large populations like doubled-haploid populations aimed at developing molecular markers for Zn efficiency. Identified QTLs influencing seed Zn concentration were repeatable in the field and glasshouse conditions, suggesting their robustness across environments as well as their value in marker-assisted selection. The developed PCR-based marker SZnR1 and other molecular markers associated with the QTLs on the short and long arms of chromosome 2H have the potential to be used for marker-assisted selection in breeding for Zn-dense seed in barley.

Thesis (MTech (Agriculture))--Cape Peninsula University of Technology, 2017.
Cowpea (Vigna unguiculata (L.) Walp) is an important grain and fodder legume grown around the world. It is a dual purpose grain legume crop, providing food for man and livestock. Cowpea is identified as a potential crop to diversify food production, minimize production input by improving soil fertility and improve micronutrients of seed, therefore, improving human nutrition. There is limited information available on cowpea production and suitable agronomic practices including planting date to best suit different environmental conditions in South Africa. The objective of this study was therefore to i) evaluate two soil types (sandy and clay soil) and its effect on cowpea, yield components and mineral composition, ii) the effect of different planting date and iii) assess the effect of zinc fertilizer application rate on vegetative, reproductive parameters and mineral content of cowpea seed. A field trial was conducted in Agricultural Research Council (ARC), in two locations Nietvoorbij (clay loam soil) and Bien Donne’ (sandy soil) during the 2015 summer planting season. The trial layout was conducted in a randomised complete block design (RCBD) with five replicates. The factors of the study include three cowpea lines: Cowpea Veg1, M217 and Qukawa with zinc application rate of (0, 15 and 30 kg/ha) through soil application and two planting date (2 October and 2 November 2015). The following agronomic variables were collected, in both locations: germination rate, number of leaves, number of branches, plant height, number of seed per pod, number of pods per plant, pod length, pods per treatment, pod weight, 100 seed weight, morphological traits, moisture content and seed mineral content. Vegetative data was collected on a fourth-night basis on six middle plants per treatment and reproductive parameters were taken after harvest. The variables were subjected to ANOVA using software SAS (2012). Treatments were tested at 5% level of significance and differences between treatments were separated using LSD and DMRT of the SAS 2012 test. The results indicated that vegetative and reproductive parameters measured varied significantly among cowpea lines in each location and across locations due to different cowpea lines and soil type. Line Cowpea Veg1 and Qukawa were the best performing line in both vegetative and yield parameters across the two planting dates in 2015. These lines significantly obtained higher plant height than line M217. Yield and yield parameters were significantly affected by cowpea line. Qukawa obtained the highest seed yield at Bien Donne’ with a mean of 1184.2 kg/ha and seed yield of 686.25 kg/ha for Cowpea Veg1 at Nietvoorbij. The second planting date (2 November 2015) improved germination of plants across the two locations, therefore improving vegetative growth. Zinc (Zn) fertilizer significantly improved plant height across all treatments. An inconsistent response to yield parameters due to Zn application rate was observed. However, though not significant, Zn application of 15 kg/ha increased most of the measured parameters. It was concluded that line Cowpea Veg1 and Qukawa were the best performing lines. The second planting date (2 November) increase germination rate for both locations. It is therefore, recommended that future research should evaluate Zn fertilizer time of application.

Copies of author's previously published articles inserted.
Bibliography: leaves 195-230.
xx, 320 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
In this study the soil aqueous phase chemistry of Zn and Cu in alkaline sodic soils are investigated. The chemistry of trace metal ions at indigenous concentrations in alkaline sodic soils are reported. Metal ions at low concentrations are measured by the graphite furnace atomic absorption spectrometry (GFAAS) technique.
Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1998

Bibliography: leaves 174-204.
xiii, 204 leaves : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
"This work provides a starting point for understanding the molecular mechanisms of zinc uptake and the regulation of zinc transport in cereals. Zinc efficient cereals would yield more on soild with low zinc and could potentially result in increased zinc content grain."
Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002?

Bibliography: leaves 174-204.
xiii, 204 leaves : ill. (some col.) ; 30 cm.
"This work provides a starting point for understanding the molecular mechanisms of zinc uptake and the regulation of zinc transport in cereals. Zinc efficient cereals would yield more on soild with low zinc and could potentially result in increased zinc content grain."
Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 2002?

Bibliography: leaves 290-324. This thesis investigates two avenues suggested by Graham and Ascher (1993) for approaching the problems of subsoil infertility, with particular reference to zinc. Field experiments with wheat and barley were established at Minnipa, on Eyre Peninsula in South Australia to investigate the effects of applying nutrients (principally zinc, nitrogen and phosphorus) to the subsoil to a depth of 0.4 m with a modified deep ripper. A deep pot experiment was designed to measure the zinc efficiencies (in terms of dry matter production) of a range of species grown in siliceous sand. The effects of added zinc on root growth were compared. A pot experiment was also designed to measure the effects of zinc placement in the soil on the zinc concentrations and uptake in Excalibur, particularly with respect to concentrations in grain.

Bibliography: leaves 290-324.
xxii, 324 leaves, [5] leaves of plates : col. ill. ; 30 cm.
This thesis investigates two avenues suggested by Graham and Ascher (1993) for approaching the problems of subsoil infertility, with particular reference to zinc. Field experiments with wheat and barley were established at Minnipa, on Eyre Peninsula in South Australia to investigate the effects of applying nutrients (principally zinc, nitrogen and phosphorus) to the subsoil to a depth of 0.4 m with a modified deep ripper. A deep pot experiment was designed to measure the zinc efficiencies (in terms of dry matter production) of a range of species grown in siliceous sand. The effects of added zinc on root growth were compared. A pot experiment was also designed to measure the effects of zinc placement in the soil on the zinc concentrations and uptake in Excalibur, particularly with respect to concentrations in grain.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 1997

Bibliography: leaves 153-156.
ix, 156 p. : ill. ; 30 cm.
This thesis describes the experiments conducted to determine the mechanisms that cause the decline in shoot Zn concentration and the responses of the wheat plant to Zn deficiency and chlorosulfuron stress. Root tip extension is used as a measure of wheat root growth during exposure to the sulfonylurea herbicide chlorsulfuron. Wheat plants differing in Zn efficiency are grown in HEDTA chelate-buffered nutrient solution in controlled conditions.
Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1997

碩士
大仁科技大學
環境管理研究所
95
The purpose of this study was to investigate the relationship between soil concentration of copper, zinc and selenium; and the tendency of onions (Allium cepa, L) to absorb these elements. copper, zinc and selenium solutions of 2.5ppm, 5ppm, 10ppm, 15ppm were tested. At the beginning of the experimental growing period, onions which had not been treated with fertilizer or pesticides were equated for size and transplanted to controlled soil. Samples were picked and analyzed 5, 7, 9 and 11 days after moving to the controlled soil. During the experimental growing period, only weeding and watering was performed. The experiment used ICP-AES to analyze the inorganic elements in the stalks, leaves and roots of the onions. The bulbs of onions grown in the soil under control were taken for the tests of three kinds of anti-oxidation activities: DPPH scavenging activity, metal chelating ability and ability of reduction. The results showed that the roots of onion, L had the highest copper uptake rate. By adding 15 ppm cooper solution to the soil, a phenomenon of decrease in copper content was observed in roots and bulbs of onion when the cooper content in the bulbs of onion reached 0.98 ppm. It is evaluated that bulbs may control the absorption of copper selectively, and that the Cu content in leaves tends to increase with the increase of Cu concentration and extension of growing period, which can be as high as 0.94 ppm. The zinc content in roots, bulbs and leaves of the onion was the highest when zinc solution of 15 ppm was added, and it showed a tendency to increase with the lengthened growing period. The best accumulative Zn absorption effect was found in the 11th day after transplantation of onion and reached 1.69 ppm in roots, 1.44 ppm in bulbs, and 1.3 ppm in leaves. It may be presumed that onion can accumulate Zn because the onion samples had the highest Se content when Se solution of 15 ppm was added to the soil; the Se content in the roots, bulbs and leaves of onion tended to increase with the increase of growing period and reached the highest in the 11th day after transplantation, which was 1.06 ppm in roots, 1.32 ppm in bulbs, and 1.39 ppm in leaves. Especially, the highest Se uptake rate was noted in leaves. Such a condition was the most obvious in the later stage, i.e., the 9-11th day after transplantation. The lowest Cu and Zn contents in the soil appeared in the 11th day after transplantation of the samples, and the downtrend was the most noticeable in 1-5 days after transplantation of onion. Se needed a longer period to convert into a substance which could be absorbed and utilized by soil and plants easily because it was insoluble in water. Therefore, the Se content in soil dropped significantly in the 7th day after transplantation. According to the results of the anti-oxidation activity tests, the DPPH scavenging activity is Zn > Cu > Se. The best effect is found in samples containing Zn (1.44 ppm) and Cu (1.32 ppm) if Zn and Cu solution of 15 ppm is added to the soil respectively, and in samples containing Se (0.98 ppm) if Se solution of 10 ppm is added to the soil. As to the metal chelating ability, the test results show Cu > Zn > Se. The effect is the best if Cu solution of 10 ppm (0.98 ppm), Zn solution of 5 ppm (1.31 ppm) and 10 ppm (1.39 ppm), and Se solution of 15 ppm (1.32 ppm) are added to the soil respectively. In the test of the ability of reduction, the results show Se > Cu > Zn. The effect is the best if all of the Cu, Zn and Se solutions of 15 ppm are added to the soil. The anti-oxidation tests conducted on the bulb extract of onion without adding any solution indicated the lowest activity. This means the addition of Cu, Zn and Se solutions to soil can facilitate the absorption of the three elements by onion during the process of their growth and further increase their antioxidation activity.

碩士
國立屏東科技大學
農園生產系所
96
Livestock manure usually includes a large amounts of copper and zinc, which causes increasing copper and zinc content in the soil, influences soil quality and plant growth, when long-term or large amount application in the soil. Phytoextraction is utilizing plants to accumulate the pollutant from contaminated soil into the tissue of plants, which were then harvested and incinerated, reduced the content of pollutant in the soil. This study is divided two parts, one part is sunflower growth experiment, and one part is Azolla pinnata growth experiment. In pot experiment of sunflower, sunflower (Helianthus annuus L.) is fast-growing and which with high ability to absorb the heavy metal. Soil pH is one of the important factors influencing the bioavailability of zinc in the soil. Two kinds of sunflower variety were used in the test, grown on the soil of organic farming vegetable garden, which added 0, 2, and 4 g/kg sulfur. The pH value is 6.83, the 0.1 N HCl extractable Zn content is 114 mg/kg. The results shown the soil pH value at flowering and maturity stage significantly reduced as increased with the amount of sulfur application. The extractable Zn and Mn content of soil in 4 g/kg treatment was lowest, 0 g/kg treatment was highest. The total Zn content of soil in 4 g/kg treatment in both stage had significantly lower than 0 g/kg treatment. It reduced 306 (green manure variety) and 281 (sunbright) mg/pot at florescence stage, and 884 (green manure variety) and 638 (sunbright) mg/pot at seed mature stage. Increased with the amount of sulfur application, the fresh matter, the dry matter and plant heights were significantly reduced. The N concentration of plant in 2 g/kg treatment was higher than others. The P, K, and Mg concentrations of plant in 4 g/kg treatment were higher than others. The Ca concentration of plant in 0 g/kg treatment was higher than others. The concentrations of Mn, Cu and Zn in plant organs significantly increased. N, K, Ca and Mg uptake of plant were reduced owing to the application of sulfur. Zn and Mn uptake of plant in 4 g/kg treatment were significantly higher than others. Cu uptake of plant in 0 g/kg treatment was higher than others. Fe uptake of plant in 2 g/kg treatment was higher than others. Zn uptake of plant in 4 g/kg treatment was significantly higher than 0 g/kg treatment, increased 3.31 (green manure variety) and 2.71 (sunbright) mg/pot at florescence stage, and 4.01 (green manure variety) and 7.54 (sunbright) mg/pot at seed mature stage. Zn uptake increased of plant in sulfur treatment was significantly lower than the total Zn content reduced of soil. Sulfur application significantly decreased the soil pH value, increased Zn solubility of soil. Under this status the Zn of soil must be leached outside when irrigated or rained during the experimental period, if applied same treatments in field, therefore, would be caused the Zn in the surface soil leached into the depth of soil. In pot experiment of Azolla pinnata, the plant of Azolla pinnata grown on the organic farming vegetable garden soil, which with or without plough. The pH value is 5.62, the 0.1N HCl extractable Zn content is 113 mg/kg. The results shown the temperature changes significantly influenced the grown period of Azolla pinnata. Fresh weight and dry weight of Azolla pinnata in the soil with/without plough were not significantly different. The P, K, Ca, and Mg concentrations of plant were not significantly different between both two treatments. The N, Fe and Mn concentrations of plant in the soil without plough were higher than the soil with plough, whereas the Cu and Zn concentrations of plant in the soil without plough were lower than the soil with plough. N, P, Ca, Mg, Fe, and Mn uptake of plant in the soil without plough were higher than the soil with plough, whereas Cu and Zn uptake of plant in the soil without plough were lower than the soil with plough. The accumulation of N and Mn uptake of plant in the soil without plough was significantly higher than the soil with plough. The first crop of Azolla pinnata included lots of the algae, caused dry weight, Zn concentration, and Zn uptake of Azolla pinnata enhanced at harvest, and that significantly higher than other crops, but the Zn concentration of Azolla pinnata was not high, and the dry weight of Azolla pinnata was not large, therefore the accumulation of Zn uptake of Azolla pinnata was not high. It were only 753 g/ha (without plough) and 820 g/ha (with plough) respectively. The soil under long-term flooded condition, soil pH value was significantly increased. The 0.1 N HCl extractable Zn content of soil was significantly reduced, but the total Zn content of soil was not significantly reduced. The soil with plough can not significantly increase the amount of Zn uptake of Azolla pinnata. Azolla pinnata in the experiment didn’t shown high zinc uptake ability. The soil with plough didn’t effective increase the zinc uptake of Azolla pinnata. The Zn must be still fixed in the soil, a few Zn content of soil dissolved, therefore, Azolla pinnata possibly grew in the water of low zinc content and so the amount of Zn uptake of Azolla pinnat was not high as expect.