Siga este link para ver outros tipos de publicações sobre o tema: Soils Agricultural chemical content.
Teses / dissertações sobre o tema "Soils Agricultural chemical content"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 44 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Soils Agricultural chemical content".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
1
Edvantoro, Bagus Bina. "Bioavailability, toxicity and microbial volatilisation of arsenic in soils from cattle dip sites". Title page, Contents and Abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09A/09ae24.pdf.
Texto completo da fonte
2
Taillon, Kate. "Modeling surface complexation relationships in forest and agricultural soil". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82435.
Texto completo da fonteResumo:
The adsorption behaviour of trace metals in soil may provide us with a way to more accurately predict and assess the toxicity of metals in the environment. This thesis reports efforts to apply surface complexation modeling to agricultural and forest soil and to relate model parameters to common soil properties. This study considered Ca, Cd, Cu, Pb and Zn but the methods here could be applied to other metals. In Chapter 2, the surface charge and adsorption behaviour of a set of Ap horizons was characterised using back-titration and batch adsorption techniques. With the objective of simplifying the application of the NICCA model to surface charge and cation adsorption in whole soils the parameters of the NICCA model were related to soil properties (Chapter 3). Four of the six surface charge parameters could be predicted from soil properties and this enabled me to reasonably predict the surface charge of a second group of soils from soil properties. These results suggest that it is possible to make reasonable predictions about the surface charge and adsorption behaviour of a given type of soil using some easily measurable soil properties and a set of generic NICCA adsorption parameters for that soil type. In Chapter 4 this idea is applied to the determination of lime requirement for the agricultural soils.
3
Ahmad, Riaz. "Sorption and release of pesticides in soils : the role of chemical nature of soil organic matter /". Title page, table of contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09pha2853.pdf.
Texto completo da fonte
4
Drlíková, Barbora. "Posouzení kvality půdy zpracované klasickým způsobem ve vybrané lokalitě v Olomouckém kraji". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265451.
Texto completo da fonteResumo:
Diploma thesis documents the problems of soil quality, which is assessed on the basis of physical, chemical or biological indicators of soil quality. The paper describes the various indicators, its methodology and evaluation. In the practical part evaluates the quality of soil cultivated with the traditional way - using plowing. The experimental area, where the samples were taken from the soil, lies in the Olomouc region in the municipality Šumvald. Evaluated were selected physical, chemical and physico-chemical properties of soil, e.g. particle size distribution, bulk density, porosity, air capacity, hydrolimits, pH, carbonates, humus content and salinity of the soil.
5
Mallory, Ellen B. "Crop/Livestock Integration Effects on Soil Quality, Crop Production, and Soil Nitrogen Dynamics". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/MalloryEB2007.pdf.
Texto completo da fonte
6
Zhang, Tiequan. "Chemical behavior of phosphorus over time in fertilized soils". Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=34486.
Texto completo da fonteResumo:
Fertilizer P accumulates in soils, with potential for movement to waterways, causing eutrophication. Fertilizer P reactions in monoculture corn (Zea mays L.) production over time will determine environmentally sound soil management practices. Soil P changes over time were determined on a Chicot sandy clay loam (Grey Brown Luvisol) and a Ste. Rosalie clay (Humic Gleysol). Fertilizer P was added at 44 and 132 kg P ha$ sp{-1}$ and to the Chicot soil only, manure containing 60 kg P for the first five years. Mehlich-3 (M3) extraction, soil P fractionation, $ sp{31}$P NMR analysis, P in leaching water, and path analysis were measured. Added P increased M3 P more when manure was also added, and in clay soils. To increase M3 P by 1 kg ha$ sp{-1}$ required from 3.6 to 8.1 kg ha$ sp{-1}$ fertilizer P, and when "net" fertilizer additions were used, fertilizer required was from 1.8 to 5.3 kg P ha$ sp{-1}.$ Moderately labile organic P (Po) decreased at 0 added P. With P at the rate of plant removal, inorganic (Pi) and Po fractions were unchanged. Excess P increased labile P and resistant P through moderately labile Pi. More P remained in labile Pi fractions when manure P was added, or in the soil with the higher clay content. Soil organic P levels increased upon fertilization only in the sandy loam soil. Labile and moderately labile Po could be estimated using monoester phosphate values determined by $ sp{31}$P NMR. Inorganic P values in gravitational water increased above 0.05 mg P L$ sp{-1}$ when soil labile Pi increased above 108 mg kg$ sp{-1}$ in the sandy loam soil and 69 mg L$ sp{-1}$ in the clay soil. Thus soil P movement was related to inorganic P additions. Increased fertilizer P did not increase organic P leaching losses. Fertilizer P in corn production may result in groundwater eutrophication.
7
Batchily, Abdul Karim 1952. "Use of Chroma Meter color measurements to evaluate the organic carbon, iron, and water content of soils". Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277947.
Texto completo da fonteResumo:
The soil color components of 127 samples from five Arizona Agricultural Research Centers and 52 WEPP samples occurring in various parts of the U.S.A. were evaluated using a Minolta Chroma Meter. This instrument is designed to minimize the variability in color determination utilizing a built-in light source to generate a primary source of radiation. Simple and multiple linear regression equations relating Hue, Value, and Chroma color components were obtained to predict the organic carbon and iron content of these soils. The results show that using global data is less reliable than specific groupings of soils. Moist value and moist chroma moist are the two most important color components in estimating the organic carbon content of soils. Chroma and Hue were highly correlated to iron at all moisture levels. Chroma was least affected by soil moisture, but Value and Hue consistently decreased for all soils.
8
Jiang, Zhiyong. "Modeling agricultural chemical transport and fate in soils under controlled water table /". The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487867541733368.
Texto completo da fonte
9
Reeves, Alastair Ian. "Contaminant tracking through dendro-chemical analysis of tree-radii". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69688.
Texto completo da fonteResumo:
The research used dendro-chemical analysis of ash tree rings and current year leaf litter to track Cd, Pb, Zn, Cu, Mn, Cr, and Sn spread and cycling from a closed garbage dump-toxic waste site. This technique allowed for determination of areal extent, contaminant levels and time period of initial contaminant contact. Only Zn, Sn, and Cu were found in elevated quantities in the xylem wood and Pb in the leaf litter. Elemental concentrations of Pb, Sn and Cd in xylem wood and leaves of ash were positively correlated. Tin was the only element to demonstrate a clear initial contact period and elemental accumulation with age. Significant levels of Cu accumulated in the heartwood while Zn revealed significant but inconsistent accumulated patterns. Expected attenuation zones associated with municipal solid waste landfill leachate dispersion were not found; thus the pathway for contaminant dispersion was likely through groundwater flow.An elemental index was developed to facilitate the use of dendro-chemical analysis in periods of suppressed tree growth resulting from environmental pollution.
10
Adrover, Fiol Maria. "Efectes del reg amb aigües residuals tractades en els sols i els cultius". Doctoral thesis, Universitat de les Illes Balears, 2010. http://hdl.handle.net/10803/9377.
Texto completo da fonteResumo:
El reg amb aigües residuals tractades s'ha convertit avui en dia en una necessitat, ja que permet preservar els recursos hídrics de més qualitat i constitueix una alternativa necessària per al manteniment de regadius tradicionals. En aquesta tesi s'avaluen els efectes del reg amb aigües residuals tractades d'origen domèstic sobre les característiques químiques i biològiques de diferents tipologies de sòls a l'illa de Mallorca, així com sobre el creixement dels cultius i la seva composició mineral mitjançant diferents estudis de camp i en cultius en contenidors. En general no s'han apreciat efectes negatius importants causats pel reg amb aquestes aigües excepte alguns valors puntualment més elevats de crom i plom que es relacionen amb aportacions d'aigües poc depurades realitzades en el passat. Segons els resultats obtinguts amb el reg amb aigües residuals tractades d'origen domèstic es contribueix a millorar la qualitat del sòl i s'aporten part dels nutrients que requereixen els cultius per al seu creixement.El riego con aguas residuales tratadas se ha convertido hoy en día en una necesidad, ya que permite preservar los recursos hídricos de más calidad y constituye una alternativa necesaria para el mantenimiento de regadíos tradicionales. En esta tesis se evalúan los efectos del riego con aguas residuales tratadas de origen doméstico sobre las características químicas i biológicas de diferentes tipologías de suelos en la isla de Mallorca, así como sobre el crecimiento de los cultivos y su composición mineral mediante diferentes estudios de campo i en cultivos en contenedores. En general no se han apreciado efectos negativos importantes causados por el riego con estas aguas, excepto algunos valores puntualmente más elevados de cromo y plomo que se relaciona con aportaciones de aguas poco depuradas realizadas en el pasado. Según los resultados obtenidos con el riego con aguas residuales tratadas de origen doméstico se contribuye a mejorar la calidad del suelo y se aportan parte de los nutrientes que requieren los cultivos para su crecimiento.
Nowadays the irrigation with treated waste water has become a necessity, not only, because it allows preserving fresh water but it also constitutes an important alternative to the maintenance of traditional irrigating lands. Considering different chemical and biological characteristics of soil samples of Mallorca island (Spain), this thesis investigates the effect of irrigation with treated domestic waste water on soil properties. In addition, several studies were conducted in a series of pot experiments and land conditions to monitor the crops growth and evaluate their mineral compositions. In general, no negative effects caused by this type of irrigation have been observed, except of some high values of chromium and lead which were related to past irrigation realized with untreated effluents. According to our results, the irrigation with treated domestic wastewater contributes to improve soil quality and supplies part of the nutrient requirements of the crops.
11
Dockeray, Craig. "Drainage and nitrogen dynamics in an agricultural field". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0007/MQ44159.pdf.
Texto completo da fonte
12
Kenimer, Ann Lee. "A computer simulation model for predicting pesticide losses from agricultural lands". Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45817.
Texto completo da fonteResumo:
A field scale model for predicting the surface losses of pesticides (Pesticide Losses In Erosion and Runoff Simulator, PLIERS) was developed. PLIERS accounts for pesticide losses by degradation and volatilization, the washoff of pesticides from plant canopy and surface residue, the adsorption and desorption of pesticides to and from soil particles, and the movement of pesticides in the dissolved and adsorbed phases. Hydrologic data are generated by the comprehensive watershed model, FESHM; which contains an extended sediment detachment and transport algorithrn. PLIERS uses first order rate equations to describe degradation and volatilization, and pesticide washoff. The adsorption of pesticides to individual particle size classes is estimated using the Freundlich equation.
Movement of atrazine and 2,4-D in runoff and sediment was measured on twelve field plots under simulated rainfall. The plots were treated with conventional or no-tillage in combination with one of three residue levels (0, 750, and 1500 kg/ha). Runoff and sediment losses were found to increase with decreasing residue cover for both tillage systems. No·till reduced sediment loss and total runoff volume by 98 and 92 percent, respectively, compared to conventional tillage. Concentrations of atrazine and 2,4-D ir1 runoff and sediment were greater from the no-till plots than from the conventional plots but the total losses were less. Both pesticides were carried predominately in the dissolved phase. Averaged over all plots, the atrazine losses were 2.9 percent of applied amount for conventional tillage and 0.3 percent for no-tillage. The corresponding values for 2,4-D were 0.3 percent and 0.02 percent.
PLIERS was validated using data from the rainfall simulator field plot studies. Agreement between predicted and observed data was very good for dissolved pesticide losses and satisfactory for adsorbed pesticide losses. In addition, the effects of tillage type and residue level were reflected in PLIERS predictions. PLIERS shows great potential as a flexible planning tool since it could be used with any comprehensive hydrologic model and is able to predict the losses of pesticides under various field conditions.
Master of Science
13
Stakland, Steven Keyes. "Effect of Mica Content on Surface Infiltration of Soils in Northwestern Kern County, California". DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/840.
Texto completo da fonteResumo:
A soils infiltration rate (IR) is the measured rate that soil is able to absorb water, either from precipitation or irrigation. A low IR can cause damage to crops if the necessary amount of water cannot penetrate to the plant roots in the time needed. The damage can be common in permanent plantings such as almond and pistachio orchards where regular tillage is avoided. This indicates a physical aspect to the problem because tillage increases IR. However, there is also an electrochemical side to infiltration problems because certain calcium surfactant treatments can increase IR. Various other methods have been used to increase IR such as using cover crops and increasing organic matter. Despite these different approaches to the problem, the specific cause of low IR is often unknown. This study was conducted to determine what physical properties of soils from a site in California cause low IR. This research shows the relationship of these properties to low IR.
It was assumed that high amounts of mica in the very fine sand and coarse silt fraction of soils in Northwestern Kern County, California may interact with other physical and chemical properties to reduce IR. Fourteen sites were sampled in the area near the towns of Wasco and Shafter. The soils sampled represented the typical agricultural soils of the area and exhibited three levels of infiltration, Good (no amendments), Moderate (requires gypsum), and Poor (gypsum application is insufficient). Mica percentages in the very fine sand and coarse silt were calculated using a petrographic microscope and compared to the overall IR of the fields. Mica was shown to be significant factor at all three levels of IR.
14
Luo, Yongming. "The fate and chemical speciation of heavy metals applied to soils in a sewage sludge-derived organic fertiliser". Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388065.
Texto completo da fonte
15
Scherr, Frank. "Sorption, degradation and transport of estrogens and estrogen sulphates in agricultural soils". Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1017.
Texto completo da fonteResumo:
The fate and behaviour of estrogens in the environment are of concern due to the compounds’ endocrine disruption potential. Estrogens, namely 17β-estradiol (E2), estrone (E1), and estrogen sulphates, i.e. 17β-estradiol-3-sulphate (E2-3S) and estrone-3-sulphate (E1-3S) excreted by livestock constitute a potential source for estrogen contamination in the environment. A method was developed to separate and quantify the hormones by high-performance-liquid-chromatography (HPLC) and ultraviolet detection (UV). A combination of dichloromethane (DCM) and dicyclohexylamine hydrochloride (DCH·HCl) gave recoveries from 97.3 to 107% for E1-3S extraction from aqueous solutions. The recoveries from soil samples ranged from 80.9 to 95.2% (E2-3S), and from 86.3 to 91.7% (E1-3S), respectively. Results of batch sorption studies showed that Freundlich isotherms were nonlinear (N ≠ 1) with Kf values ranging from 34.2 to 57.2, and from 3.42 to 4.18 mg¹-N LN kg⁻¹ for E1, and E1-3S, respectively, indicating the sorption affinity of E1-3S was about an order of magnitude lower than that of E1. The hydrophilic sulphate group of E1-3S possibly shielded the compound from hydrophobic interactions with the soil organic matter and allophanic clay minerals that were proposed as sorbents for E1. Contraction of clay minerals, “salting out” and competitive sorption of artificial urine constituents were likely to have been responsible for observed changes in Freundlich parameters when artificial urine was used as mediator matrix. Plotting the effective distribution coefficient as a function of hypothetical exposure concentrations facilitated the comparison of the sorption behaviour of both compounds as influenced by the mediator solution. The results emphasized that using the CaCl₂ matrix might result in false inferences for the sorption behaviour of these compounds in a dairying environment. The four hormones rapidly degraded in the agricultural soils under aerobic conditions, and the majority of the compounds degraded > 50% within the first 24 hrs. Soil arylsulphatase activities were directly correlated with degradation rate constants of the estrogen sulphates. Estrone was identified as a metabolite of E2 and E1-3S, and these three compounds were observed as metabolites of E2-3S. Single-first order (SFO) and double first-order in parallel (DFOP) kinetics were used to model the degradation and metabolite formation data. The results showed that the DFOP model was in most cases better able to predict the parent compound degradation than the SFO model, and also enabled to estimate accurate degradation endpoints. ER-CALUX® analysis revealed the formation of estrogenicity during E2-3S degradation, which could partly be explained by the formation of the metabolites E2 and E1. Transport studies with E1-3S and E1 showed that the transport and retention of both compounds were significantly influenced by the mediator matrix. While no breakthrough curves (BTCs) were recorded during hormone application in CaCl₂ (10 mM) both hormones were detected in the leachate when applied in artificial urine. Rate-limited sorption processes were proposed for the delayed arrival of the hormone BTCs compared with a conservative bromide tracer. Intense colouration of the leachate during the artificial urine experiments suggested the hormones were likely to be moved by colloid-facilitated transport. Furthermore, the detection of residue hormone and metabolite concentrations implied that degradation of E1-3S and E1 was hampered by urine constituents such as glycine and urea.
16
Croat, Samantha Jo. "Phosphorus Dynamics and Crop Productivity in Bakken Crude-Oil Remediated Soils". Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/29169.
Texto completo da fonteResumo:
Thermal desorption (TD), a remediation method used to remove hydrocarbons from contaminated soils, may cause changes in soil properties that threaten soil function and plant productivity. The goal of this research is to better understand the effect that TD treatment has on soils intended for agricultural use. A series of soil phosphorus (P) sorption and desorption experiments were conducted on soils before and after TD treatment to determine P availability for plant uptake and risk for run-off. TD-treated soils retained more P, likely due to mineral transformations of Fe- and Al-oxides. In addition, a three-year field study using mixtures of topsoil (A), crude-contaminated soil (SP), and TD-treated soils (TDU) was conducted. Yields were significantly greater in plots that included A in the mixture compared to SP and TDU soils alone. TD-treated soils can be a replacement for topsoil, but the addition of topsoil will reduce the time to successful reclamation.
17
Eibisch, Nina [Verfasser]. "Physico-chemical properties and effects of biochars from hydrothermal carbonization and pyrolysis of organic residues in agricultural soils / Nina Eibisch". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1073605744/34.
Texto completo da fonte
18
Weigel, Gerolf. "The soils of the Maybar/Wello and Gununo/Sidamo area : their potential and constraints for agricultural development : a case study in the Ethiopian Highlands /". [S.l.] : [s.n.], 1986. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
Texto completo da fonte
19
Suliman, Ahmed S., e Donald F. Post. "Relationship Between Soil Spectral Properties and Sand, Silt, and Clay Content of the Soils on the University of Arizona Maricopa Agricultural Center". Arizona-Nevada Academy of Science, 1988. http://hdl.handle.net/10150/296411.
Texto completo da fonteResumo:
From the Proceedings of the 1988 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 16, 1988, University of Arizona, Tucson, Arizona
20
Nkqenkqa, Vuyiseka. "Metal and microbial contamination of agricultural soil and the Veldwachters River, Stellenbosch, South Africa". Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2423.
Texto completo da fonteResumo:
Thesis (MTech (Environmental Health))--Cape Peninsula University of Technology, 2017.Surface water is used as a source of water supply in many countries, including South Africa. One of the sources of surface water pollution is leachate and surface runoff from landfills. In agricultural soils, the landfill runoff and leachate deteriorate the quality and affect the fertility of soil. The entry of metals and microorganisms from landfill leachate to adjacent environments is through surface runoff due to rainfall. Adverse effects on human- and environmental health triggers a need to monitor and control contaminants in the environment. The aims of the study are to determine the effect of landfill runoff and leachate on agricultural soil and river water (Veldwachters River) running adjacent to the Devon Valley landfill site and to identify potential metal-tolerant organisms in environmental samples collected in Stellenbosch, Western Cape, South Africa. Samples (agricultural soil, river water and sediments) were collected once a month for a period of six months from the study area for analysis. Physicochemical parameters that are known to have major effects on environmental samples were assessed and the concentrations of various metals (Al, Pb, Cr, Mn, Mo, Co, Ni, Cu, Zn, Fe, Cd and V) were also determined by means of inductively coupled plasma mass spectrometry (ICP-MS). Soil texture analysis was tested in order to monitor the metal distribution in soils under the influence of environmental factors.
21
Hoyle, Frances Carmen. "The effect of soluble organic carbon substrates, and environmental modulators on soil microbial function and diversity". University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0050.
Texto completo da fonteResumo:
[Truncated abstract] The principal aim of this thesis was to examine the response of the microbial community to the addition of small amounts (<50 μg C g-1 soil) of organic C substrates (‘trigger molecules’) to soil. This addition is comparative to indigenous soluble C concentrations for a range of soil types in Western Australia (typically measured between 20 and 55 μg C g-1 soil). Previously it has been reported that the application of trigger molecules to European soils has caused more CO2-C to be evolved (up to six fold) than was applied . . . Findings from this study indicated that there was an additional CO2 release (i.e. greater than the C added) on application of organic C substrates to some soil treatments. However, findings from this study indicate that the response of the microbial community to small additions of soluble C substrate is not consistent for all soil types and may vary due to greater availability of C, and supports the premise that microbial responses vary in a yet to be predicted manner between soil type and ecosystems. Differences in microbial response to the addition of soluble organic C are likely attributable to differences in soil attributes and environmental factors influencing both the diversity of microbes present and the frequency of food events. Theoretically, trigger molecules could also provide a possible control mechanism for microorganisms in arable farming systems. These mechanisms include stimulating either targeted pathogenic microorganisms that starve after depletion of a suitable substrate; or stimulating beneficial microorganisms to manipulate nutrient cycling, by targeting specific functional groups and altering mineralisation and immobilisation turnover rates.
22
Ekanayake, Jagath C. "Soil water movement through swelling soils". Lincoln University, 1990. http://hdl.handle.net/10182/1761.
Texto completo da fonteResumo:
The present work is a contribution to description and understanding of the distribution and movement of water in swelling soils. In order to investigate the moisture distribution in swelling soils a detailed knowledge of volume change properties, flow characteristics and total potential of water in the soil is essential. Therefore, a possible volume change mechanism is first described by dividing the swelling soils into four categories and volume change of a swelling soil is measured under different overburden pressures. The measured and calculated (from volume change data) overburden potential components are used to check the validity of the derivation of a load factor, ∝. Moisture diffusivity in swelling soil under different overburden pressures is measured using Gardner's (1956) outflow method. Behaviour of equilibrium moisture profiles in swelling soils is theoretically explained, solving the differential equation by considering the physical variation of individual soil properties with moisture content and overburden pressure. Using the measured volume change data and moisture potentials under various overburden pressures, the behaviour of possible moisture profiles are described at equilibrium and under steady vertical flows in swelling soils. It is shown that high overburden pressures lead to soil water behaviour quite different from any previously reported.
23
Sheldon, Bonita Joy. "Heavy metal uptake and accumulation in agricultural crops in urban areas of the Western Cape". Thesis, Cape Peninsula University of Technology, 2005. http://hdl.handle.net/20.500.11838/2006.
Texto completo da fonteResumo:
Thesis (MTech (Physical Sciences))--Cape Peninsula University of Technology, 2005.A research study into heavy metals in the Cape Town area, found significant amounts of potentially toxic metals such as lead, cadmium, chromium and iron leaching into the underground aquifer. A further additional study conducted on a community garden in Khayelitsha, showed that vegetable crops have the tendency to accumulate certain heavy metals if they are present in soil and water resources. This study was centered around the Philippi Horticultural Area, which is a large significant farming area within the Cape Metropolitan Region. The significance of the study lies in the fact that at least 50% of the local farmers' produce is sold directly to street traders, residents, local supermarket-chains and restaurants. The remainder of the produce is sold at the Epping Market. The purpose of this study was to investigate heavy metal accumulation in various vegetable crop species taken from some of the local farms in the Phillipi Farming area with the objective to: • investigate heavy metal accumulation in various vegetable crop species taken from some local farms in the Phillipi Farming area. • determine the concentrations of heavy metals present in water and soil resource since these will be the primary source of heavy metals to the vegetables. • determine the soil pH and soil organic matter as these two factors would determine the bie-availability ofthe heavy metals. • identify those crops that pose a definite health risk by means of comparing the determined results to the allowed limits.
24
Delin, Sofia. "Site-specific nitrogen fertilization demand in relation to plant available soil nitrogen and water : potential for prediction based on soil characteristics /". Skara : Department of Soil Sciences, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200506.pdf.
Texto completo da fonte
25
Moloto, K. P. "The potential of sustainable agricultural practices to enhance soil carbon sequestration and improve soil quality". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4257.
Texto completo da fonteResumo:
Thesis (MPhil (Sustainable Development, Planning and Management))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Sustainable agricultural management practices have a profound impact on soil carbon sequestration. The amount of carbon that can be stored in a given soil is influenced by climate, soil type, and the quality and quantity of organic inputs. Together, the interactive effect of these factors determines the Soil Organic Content (SOC). Sustainable agricultural management practices influencing Soil Organic Matter (SOM) include application of organic amendments, conservation tillage, and use of cover crops, crop rotations, crop residue management, and nutrient management. Increasing SOC enhances soil quality, reduces soil erosion, and increases agricultural productivity with considerable on-farm and off-farm benefits. To assess how management practices affect SOC, two case studies were conducted in Yavatmal district of Maharashtra in India and Lynedoch near Stellenbosch. The first case study examined the differences in SOC content on four farms each managed with 13 different sustainable agricultural techniques and one farm managed under conventional management practices. The second case study investigated the SOC differences between an organic and a conventional vegetable farm. The results of both studies show that farms that are managed under sustainable agricultural practices generally contain higher SOC content than farms that are managed under conventional agricultural practices.
AFRIKAANSE OPSOMMING: Om te bepaal hoe bestuurspraktyke Grondlikke Organise Koolstoff raak, is twee gevallestudies in die distrikte Yavatmal in Maharashtra, Indië, en Lynedoch buite Stellenbosch uitgevoer. Die eerste gevallestudie het die verskille in Grondlikke Organise Koolstoff -inhoud bekyk op vier plase waar 13 verskillende Volhoubare landboubestuurspraktyke het ‟n diepgaande impak op grondkoolstof-beslaglegging. Die hoeveelheid koolstof wat binne gegewe grond gestoor kan word, word deur klimaat, grondsoort en die gehalte en hoeveelheid organiese toevoer beïnvloed. Saam bepaal die interaktiewe effek van vermelde faktore die Grondlikke Organise Koolstoff -inhoud. Volhoubare landboubestuurspraktyke wat Grondlikke Organise Materiaal beïnvloed, sluit in die toediening van organiese verbeterings, bewaringsgrondbewerking, die gebruik van dekkingsoeste, oesrotasies, die hantering van oesresidu en voedingstofbestuur. Vermeerdering van Grondlikke Organise Koolstoff verhoog grondgehalte, verminder gronderosie en vermeerder landbouproduktiwiteit met aansienlike voordele op en verwyderd van die plaas. volhoubare landboutegnieke in die bestuurproses toegepas word, en een plaas wat volgens konvensionele bestuurspraktyke bedryf word. Met die tweede gevallestudie is ondersoek gedoen na die Grondlikke Organise Koolstoff -verskille tussen ‟n organiese en ‟n konvensionele groenteplaas. Die uitslae van albei studies dui daarop dat plase wat volgens volhoubare landboupraktyke bestuur word oor die algemeen hoër Grondlikke Organise Koolstoff-inhoud aantoon in vergelyking met plase wat volgens konvensionele landboupraktyke bedryf word.
26
Kraft, Edward Alton. "Summarizing Regional Research Data Contributing to the U.S. Rapid Carbon Assessment in the Northern Great Plains". Master's thesis, North Dakota State University, 2016. http://hdl.handle.net/10365/25549.
Texto completo da fonteResumo:
Research on soil organic carbon (SOC) within the northern Great Plains has not been clearly documented. Objectives of this study were (i) to inventory literature reporting SOC responses to agroecosystem management, (ii) extract data for the Northern Great Plains Rapid Carbon Assessment, and (iii) summarize data to identify relationships between SOC and land use management. Soil organic carbon at 0 ? 15 cm depth was 1.57 ? 6.87 kg C m-2, 1.56 ? 5.34 kg C m-2, and 1.48 ? 5.48 kg C m-2 under grasslands, conservation tillage (CST), and conventional tillage (CT), respectively. Soils with a Productivity Index (PI) of 80 ? 100 had greater mean SOC (4.14 kg C m-2) across all managements. Correlation between SOC and PI for CT was significant (r=0.240) (P=0.05) and highly significant (r=0.418) (P=0.01) for CST. Management practices for cropland soils combined with productivity potential appear to relate to the C accrual potential of northern Great Plains soils.
27
Henderson, Kelsey. "Reverse Osmosis as a Chemical-Free Technology for the Removal of Nutrients from Cure Meat Processing Wastewater". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563470474960378.
Texto completo da fonte
28
Steiner, Laure D. "A Study of the fate and transport of estrogenic hormones in dairy effluent applied to pasture soils". Diss., Lincoln University, 2009. http://hdl.handle.net/10182/1306.
Texto completo da fonteResumo:
The disposal of waste from agricultural activities has been recognised as a source of environmental contamination by endocrine disrupting chemicals (EDCs). The New Zealand dairy industry produces a large volume of dairy farm effluent, which contains EDCs in the form of estrogens. Most of this dairy farm effluent is applied onto the land for disposal. Groundwater and soil contamination by estrogens following waste application on the land have been reported overseas, but our understanding of the processes and factors governing the fate of estrogens in the soil is poor. Therefore the main goal of the present study was to better understand the fate and transport of estrogens, in particular 17β-estradiol (E2) and estrone (E1) in soil. In order to quantify E1 and E2 in drainage water and soil samples, chemical analysis by gas-chromatography mass-spectrometry (GC-MS) was carried out. This included sample extraction, sample clean-up through silica gel and gel permeation chromatography, and sample extract derivatisation prior to analysis. In order to develop a reliable method to extract estrogens from soil, research was conducted to optimise E1 and E2 extraction conditions by adjusting the number of sonication and shaking events, as well as the volume and type of solvent. Among five solvents and solvent mixtures tested, the best recovery on spiked and aged soil was obtained using an isopropanol/water (1:1) mix. A microcosm experiment was carried out to determine the dissipation rates of E2 and E1, at 8°C and at field capacity, in the Templeton soil sampled at two different depths (5-10 cm and 30-35 cm). The dissipation rates decreased with time and half-life values of 0.6-0.8 d for E1 and 0.3-0.4 d for E2 were found for the two depths studied. A field transport experiment was also carried out in winter, over three months, by applying dairy farm effluent spiked with estrogens onto undisturbed Templeton soil lysimeters (50 cm in diameter and 70 cm deep). The hormones were applied in dairy farm effluent at 120 mg m⁻² for E2 and 137 mg m⁻² for E1. The results of the transport experiment showed that in the presence of preferential/macropore flow pathways 0.3-0.7% of E2 and 8-13% of E1 was recovered in the leachate at the bottom of the lysimeters after 3 months, and 1-7% of the recovered E2 and 3-54% of the recovered E1 was leached within 2 days of application. These results suggest that leaching of estrogens via preferential/macropore flow pathways is the greatest concern for groundwater contamination. In the absence of preferential/macropore flow pathways, a significant amount (> 99.94%) of both hormones dissipated in the top 70 cm of soil, due to sorption and rapid biodegradation. Surprisingly, in all cases, estrogen breakthrough occurred before that of an inert tracer (bromide). This could not be explained by the advection-dispersion transport of estrogens, nor by their presence as antecedent concentrations in the soil. It was therefore suggested that colloidal enhanced transport of estrogens was responsible for the earlier breakthrough of estrogens and caused the leaching of a fraction of the applied estrogens to a soil depth of 70 cm. A two-phase model, adapted from a state-space mixing cell model, was built to describe the observed estrogen transport processes under transient flow. The model takes into account 3 transport processes namely, advection-dispersion, preferential/macropore flow and colloidal enhanced transport. This model was able to successfully describe the estrogen transport observed from the lysimeters.
29
Brandi-Dohrn, Florian M. "Field evaluation of passive capillary samplers in monitoring the leaching of agrochemicals". Thesis, 1993. http://hdl.handle.net/1957/37559.
Texto completo da fonteResumo:
Soil solution samplers have certain inadequacies that limit their range of
possible applications. Passive Capillary Samplers (PCAPS), which apply suction to the
soil pore-water via a fiber glass wick, have shown promising results in preliminary
experiments in regard to collection efficiency of water and of bromide tracers. The
objectives of this study were to evaluate PCAPS under non-steady state field conditions
with respect to (1) effect of installation procedure and operational characteristics, (2)
ability to estimate the soil-water flux, and (3) ability to estimate the mean concentration
of agrochemicals. At the same time, samplers were used to (4) evaluate the effect of a
cereal rye (Secale cereale (L.)) cover crop on NO₃⁻ leaching.
Thirty-two PCAPS and 32 suction cup samplers were installed below the root
zone at a depth of 120 cm in a Willamette Variant loam wet soil (fine loamy mixed
mesic Pachic Ultic Argixeroll). Samplers were installed in an ongoing cover crop/crop
rotation study. Regarding overall performance, flux measurements were within 20 %
of the native values as determined by a water balance. The air release from the sample
bottles was a point of concern and might have slowed down the sampling rate. The
installation procedure introduced bias into volume and concentration measurements of
the part of the PCAPS closest to the refilled trench. The leachate concentration as
calculated using the arithmetic mean of suction cup sampler measurements holds a
significant bias, deviating by up to 97 % for bromide concentrations. Phosphate was
not detected by the suction cup samplers indicating that ceramic cups should not be
used for phosphate sampling. Matrix and preferential flow could clearly be
distinguished using the PCAPS, showing that PCAPS are a valuable tool to assess the
hydrology and solute transport mechanisms of a field site.
The cover crop reduced NO₃⁻-N leaching significantly at the recommended
N rate as evaluated by PCAPS. The cover crop reduced the seasonal mean NO₃⁻-N
concentration at the recommended N rate from 13.5 mg LI to 8.1 mg L⁻¹, which is
under the E.P.A. drinking water quality standard of 10 mg L⁻¹. The total NO₃⁻-N mass
lost under the fallow treatment at the recommended N rate was 48 kg N ha⁻' which
compares to 32 kg N ha⁻' under the cover crop treatment. Given the increasing
problems with nitrate contamination of ground water, programs to support the
cultivation of catch crops in conjunction with nitrogen soil testing should be considered
as a relatively easy, effective, and biologically sound means to reduce nitrate
concentrations in the recharge to the ground water in agricultural settings.Graduation date: 1994
30
Edvantoro, Bagus Bina. "Bioavailability, toxicity and microbial volatilisation of arsenic in soils from cattle dip sites". Thesis, 2000. http://hdl.handle.net/2440/110365.
Texto completo da fonte
31
Al-ismaily, Said S. "Genesis of silica-enriched agricultural pans in soils managed under wheat-fallow cropping systems". Thesis, 1997. http://hdl.handle.net/1957/33736.
Texto completo da fonte
32
Reilly, Richard John. "Nitrate reduction in agricultural acid sulfate soil". Phd thesis, 2011. http://hdl.handle.net/1885/149927.
Texto completo da fonteResumo:
A significant proportion of Australia's sugarcane crop is grown on east-coast estuarine floodplains underlain by pyritic gel-clay subsoils. At the current study site these agricultural acid sulfate soils are typically characterised by a topsoil horizon of river alluvium, a subsoil of oxidised actual acid sulfate soil (AASS), a zone of partially oxidised AASS and a deep sulfidic horizon of pyritic potential acid sulfate soil (PASS). Addition of nitrogenous fertiliser at key points in the sugarcane cropping cycle can create soil nitrogen levels in excess of immediate soil flora/fauna and crop requirements. In high rainfall tropical and sub-tropical regions conditions are thus suitable for nitrate, a strong oxidising agent, to leach down to the sulfidic soil layers with the consequent risk of pyrite oxidation. Little information is available on the fate of nitrogenous fertilisers in these pyritic subsoils. The purpose of this field and laboratory study was to evaluate the potential for nitrate reduction to occur in the presence of pyrite in sugarcane soils in the Tweed River valley, northern NSW, Australia. The study focus was on examining the soil profile hydrology including leaching mechanisms and nitrate concentrations down the profile to the AASS/PASS interface, as well as evaluating the potential for nitrate to increase the rate of pyrite oxidation in this generally anoxic soil zone.
Following an investigative nitrogen field trial to gather initial data, a second replicated urea fertiliser treatment trial with a nil-treatment control plot and three nitrogen (N) treatments was set up on a plant-cane-block in collaboration with a Tweed region cane grower, Robert Quirk. Installed loggers recorded rainfall, air and soil temperature, soil moisture and watertable data. Separate surveys and analytical work characterised selected soil physical, morphological and geochemical aspects. Soil profile sampling on four occasions over the twelve month crop cycle was analysed for N-species, NH{u2084}{u207A} and N0{u2083}{u207B}.
Hydraulic data analysis showed the watertable generally varying between 0.2 and 1.4 m below ground level with observed strong and rapid responses to rainfall events greater than approximately 15 mm per day. This and associated data supports the postulate that soil nitrate could move down the profile under even moderate precipitation events in these soils. Temperature, pH, redox potential and biological substrate soil data demonstrated the biogeochemical suitability of these subsoil zones to support nitrate reduction. Soil-N analysis revealed significant differences between N-trial treatments using urea fertiliser and also significant nitrogen transformation and movement within the soil profile.
Over a period of weeks, the urea fertiliser was rapidly transformed and appeared in the upper profile as elevated levels of ammonium and nitrate ions. The initial high ammonium levels quickly declined to be replaced almost completely by nitrate in the upper layers of the cane soil. Subsequently, increasing soil nitrate concentrations were evident deeper in the soil profile on higher nitrogen treatment plots during the middle phase of the crop cycle. In no instances were significant levels of nitrate detected below the soil redoxcline (the oxic-anoxic boundary) at around 1.0 m depth, nor was nitrate pooling evident anywhere in the AASS transition zone. Laboratory experimental work was undertaken to evaluate nitrate reduction coupled with pyrite oxidation under the biogeochemical conditions existing in the AASS transition zone. Results indicated that nitrate reduction associated with pyrite oxidation does take place in pyritic gel clay from the field site.
33
Clough, Angela. "Nitrogen and carbon mineralisation in agricultural soils of South Australia / by Angela Clough". 2001. http://hdl.handle.net/2440/22426.
Texto completo da fonteResumo:
"September 2001"Bibliography: leaves 144-159.
xix, 159 leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The two main aims of this study were: 1) to determine if the presence of Calcium carbonate in soil was the reason behind soils from Yorke Peninsula having relatively high OC (organic carbon) contents, given local farming practices, and 2) to determine the effect that the composition of the soils' OC has on the mineralisation rates.
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002
34
Valzano, Frank Phillip. "The effects of chemical ameliorants, tillage and stubble practices on sodic soils in Australia". Phd thesis, 2000. http://hdl.handle.net/1885/147924.
Texto completo da fonte
35
Withana, Herath Aruna. "Chemical Fractions And Predictions For Long-term Releases of Phosphorus In Typical Canadian Agricultural Soils". Thesis, 2013. http://hdl.handle.net/10214/6647.
Texto completo da fonteResumo:
Phosphorus (P) pollution has been identified as the most significant agriculture-related threat to water quality impairment in Canada. One approach to reduce P pollution is to identify soils with high P loss potential and develop management strategies to minimize that risk. This thesis contributes towards greater understanding of short- and long- term P dynamics in soils to which different P sources had been applied (Chapters 3 and 4) and improvement in the P measurements for determining long-term P loss potential (Chapter 5). Chapter 3 evaluated immediate and residual effects of swine manure and fertilizer on soil P. Soils were sampled from Brookston clay loam in south-western Ontario, Canada which were treated with liquid (LM), solid (SM), composted (MC) manure and fertilizer, only in the corn phase. Soils were analyzed using a modified Hedley’s fractionation. All P sources influenced soil labile and moderately labile P in the year of application, while MC and SM showed significant residual impacts in the following year. Residual effects of MC and SM are beneficial for crops; however, there may be a P loss potential through leaching and runoff.
Chapter 4 considered long-term effects of dairy manure slurry (DMS) and ammonium nitrate (AN) on soil P. Soils were sampled from south coastal region of BC, Canada, which were treated with DMS or AN at 50 or 100 kg NH4-N ha-1, and analyzed using a modified Hedley’s fractionation. DMS significantly increased labile and moderately stable P in surface soil, indicating short- and long-term impacts on P availability and loss potential.
Chapter 5 analyzed a new test to predict long-term soil P loss potential. Soils were collected from four agro-ecological areas across Canada, and analyzed using Mehlich-3, Olsen, Resin strips (RMS), FeO-strips, and new procedures: various combinations of NaOH with and without EDTA, with four shaking periods. Statistically significant linear and quadratic relationships between the RMS and NaOH with EDTA-P indicated that the latter provide an efficient basis for predicting long-term soil P loss potential. A highly significant relationship between RMS-P and 0.025M NaOH with EDTA-P indicates this extractant was effective for measuring Total Releasable P.Agriculture and Agri-Food Canada
36
Rami, Reddy P. Mohan. "Role Of Physico-Chemical Factors In The Heave And Collapse Behaviour Of Laboratory Desiccated Soils". Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1684.
Texto completo da fonte
37
Blanche, Claire. "The use of riparian buffer zones for the attenuation of nitrate in agricultural landscapes". 2002. http://hdl.handle.net/10413/4504.
Texto completo da fonteResumo:
The focus of this mini-dissertation is the use of riparian buffer zones to manage nitrate pollution
of water resources. Riparian buffer zones are vegetated areas adjacent to streams, lakes and
rivers, that are managed to enhance and protect aquatic resources from the adverse impacts
of agricultural practices. These zones are recognised globally for their function in water quality
amelioration. Despite the growing literature, there is little consensus on how to design, assess
and manage these riparian buffer zones specifically for nitrate attenuation.
For the purpose of this mini-dissertation, a literature review of world-wide research into the
nitrate attenuation efficiencies of riparian buffer zones was undertaken. A database was
created using the key information from this literature. Two key processes responsible for
immobilising and/or removing nitrate from surface and subsurface flows are generally
recognised in the available literature, namely: vegetative uptake and the process of
denitrification. A comparison of the available riparian studies indicated that there are similar
characteristics in riparian buffer zones that may be responsible for enhancing these key
mechanisms. Studies where there was shallow lateral subsurface or uniform surface water
delivery pathways, vegetation of close structure and composition, high organic matter in the
soils and fluctuating soil surface saturation rates showed the most significant nitrate attenuation
efficiencies.
The mini-dissertation proposes that these similarities can be used to both assess a riparian
landscape for its potential to attenuate nitrate, and to size a riparian buffer zone specifically to
meet this function. A set of proposed guidelines based on the findings of the dissertation
attempt to illustrate how riparian pollution control recommendations can be achieved. These
guidelines are an example of how to assist a farmer or similar landowner in achieving good
nitrate removal efficiencies from a riparian buffer zone. The guidelines work through three
steps, which help to establish and prioritise management zones, assess each zone's potential
for nitrate attenuation, and determine adequate riparian buffer widths for each management
zone. A case study was used to illustrate the practical application of the guidelines. Full testing
of these guidelines was not within the scope of this mini-dissertation, however the guidelines
are an indication of how information regarding riparian function can be applied to a system to determine effective management of water resources.Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 2002
38
Majaule, Ugele. "Phosphorous dynamics in soils under contrasting long-term agricultural management practices in the KwaZulu-Natal midlands". Thesis, 2006. http://hdl.handle.net/10413/3457.
Texto completo da fonteResumo:
Little is known regarding the effects of land use on soil organic matter and P
status of South African soils. For that reason, the effects of the main
agricultural land uses in the midlands region of KwaZulu-Natal [maize (Zea
mays), sugarcane (Saccharum spp), annual ryegrass pasture (Lolium
multiflorum), permanent kikuyu pasture (Pennisetum clandestnum), gum
(Eucalyptus grandis) and pine (Pinus patula)] on soil organic matter content,
microbial biomass C and P and inorganic and organic P pools derived from a
modified Hedley P fractionation was investigated on two sites where the longterm
history of land management was known.
In comparison with undisturbed native grassland, permanent kikuyu pasture
resulted in an increase in organic C, organic P and microbial biomass C and
P. Maize and sugarcane production resulted in a decrease in organic C,
organic P and microbial C and P. Under annual pasture, gum and pine
forests, organic matter and microbial biomass concentrations remained similar
to those under native grassland. Under native grassland, extractable organic
P accounted for 50% or more of the total P content of soils but under
agricultural management with regular applications of fertilizer P, there was an
increase in the percentage of total P present as inorganic P.
Agricultural management greatly affected the distribution of P among the
various inorganic and organic P fractions. Resin-Pi and NaHC03-Pi (the
potentially-available forms of Pi) showed similar trends with land use being
greatly elevated under kikuyu pasture at both sites and sugarcane and maize
at one site. This accumulated Pi was thought to have originated from recent
fertilizer applications and possibly recently mineralized organic P. Trends for
NaOH-Pi with land use differed greatly from those of the Resin- and NaHC03Pi
fractions. Concentrations were notably high under maize and sugarcane
production. Of the pools of soil organic P, the NaHC03-Po fraction was most
greatly affected by land use, being elevated under kikuyu and decreased
under maize and sugarcane. This supports the assertion that it is the
NaHC03-Po fraction that is the most labile soil organic P pool. It was concluded that land use greatly affects soil organic C and P status, soil
microbial biomass C and P contents, soil inorganic P concentrations and the
distribution of P among the various P fractions.
A short-term (8 weeks) laboratory incubation experiment was carried out to
compare the effects of inorganic (KH2P04) and organic (cattle manure, poultry
manure and maize crop residues) sources of P, applied at a rate equivalent to
30 kg P ha-1
, on soil inorganic and organic P fractions and the potential
availability of soil P. Additional treatments consisted of lime [Ca(OHhl at 5 ton
ha-1 and lime plus inorganic P. Applications of lime raised soil pH to a similar
extent after 1, 4 and 8 weeks incubation. After 8 weeks, a small increase in
soil pH was also noted for the cattle and poultry manure and maize residue
treatments. For the inorganic P fractions, substantial treatment effects were
observed only for the Resin-Pi fraction. The inorganic P source was more
effective than the organic ones at increasing Resin-Pi after 1 and 4 weeks
incubation and of the organic sources, cattle and poultry manure were more
effective than maize residues. Resin-Pi concentrations generally increased
between 1 and 4 weeks incubation but then declined rapidly between 4 and 8
weeks incubation. After 8 weeks incubation, treatment effects on Resin-Pi
were small. Concentrations of NaHC03-Pi, dilute HCI-Pi and concentrated
HCI-Pi all declined over the incubation period. There was no clear trend with
incubation for NaOH-Pi although for the poultry manure and maize
treatments, concentrations declined between 4 and 8 weeks incubation. In
general, concentrations of NaHC03-Po were greater for organic than
inorganic P sources after 8 weeks incubation suggesting microbial
immobilization of P in these treatments. There were increases in NaHC03-Po
and concentrated HCI-Po over the incubation period suggesting progressive
immobilization of P from the Pi fractions that declined in concentration during
the incubation. Concentrations of NaOH-Po were not greatly affected by
incubation period. The lime treatments, however, had lower NaOH-Po
concentrations than the others suggesting that liming may have stimulated
microbial mineralization of Po. Residual-P concentrations increased over the
incubation period. This was attributed to conversion of extractable Pi fractions
into recalcitrant, non-extractable Pi forms and/or immobilization of Pinto
intransigent organic forms.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
39
Adcock, Damien Paul. "Soil water and nitrogen dynamics of farming systems on the upper Eyre Peninsula, South Australia". Thesis, 2005. http://hdl.handle.net/2440/37810.
Texto completo da fonteResumo:
In the semi - arid Mediterranean - type environments of southern Australia, soil
and water resources largely determine crop productivity and ultimately the sustainability of farming systems within the region. The development of sustainable farming systems is a constantly evolving process, of which cropping
sequences ( rotations ) are an essential component. This thesis focused on two important soil resources, soil water and nitrogen, and studied the effects of different crop sequences on the dynamic of these resources within current farming systems practiced on the upper Eyre Peninsula of South Australia.
The hypothesis tested was that : continuous cropping may alter N dynamics but will not necessarily alter water use efficiency in semi - arid Mediterranean - type environments. Continuous cropping altered N - dynamics ; increases in inorganic N were dependent on the inclusion of a legume in the cropping sequence.
Associated with the increase in inorganic N supply was a decrease in WUE by the subsequent wheat crop. Overall, estimates of water use efficiency, a common index of the sustainability of farming systems, in this study concur with reported values for the semi - arid Murray - Mallee region of southern Australia and other
semi - arid environments worldwide.
Soil water balance and determination of WUE for a series of crop sequences in this thesis suggests that the adoption of continuous cropping may increase WUE and confer a yield benefit compared to crop sequences including a legume component in this environment. No differences in total water use ( ET ) at anthesis or maturity were measured for wheat regardless of the previous crop. Soil evaporation ( E [subscript s] ) was significantly affected by crop canopy development, measured as LAI from tillering until anthesis in 2002, however total seasonal E [subscript s] did not differ between crop sequences. Indeed in environments with infrequent
rainfall, such as the upper Eyre Peninsula, soil evaporation may be water - limited rather than energy limited and the potential benefits from greater LAI and reduced E [subscript s] are less.
Greater shoot dry matter production and LAI due to an enhanced inorganic N supply for wheat after legumes, and to a lesser degree wheat after canola, relative to continuous cereal crop sequences resulted in increases in WUE calculated at anthesis, as reported by others. Nonetheless the increase in WUE was not sustained due to limitations on available soil water capacity caused by soil physical and chemical constraints. Access to more soil water at depth ( > 0.8m ) through additional root growth was unavailable due to soil chemical limitations. More importantly, the amount of plant available water within the ' effective rooting depth ' ( 0 - 0.8m ) was significantly reduced when soil physical factors were accounted for using the integral water capacity ( IWC ) concept. The difference between the magnitude of the plant available water capacity and the integral water capacity was approximately 90mm within the ' effective rooting depth ' when measured at field capacity, suggesting that the ability of the soil to store water and buffer against periodic water deficit was severely limited. The IWC concept offers a method of evaluating the physical quality of soils and the limitations that these physical properties, viz. aeration, soil strength and hydraulic conductivity, impose on the water supply capacity of the soil.
The inability of the soil to maintain a constant supply of water to satisfy maximal transpiration efficiency combined with large amounts of N resulted in ' haying off ', and reduced grain yields. A strong negative linear relationship was established between WUE of grain production by wheat and increasing soil NO₃ - N at sowing in 2000 and 2002, which conflicts with results from experiments in
semi - arid Mediterranean climates in other regions of the world where applications of N increased water use efficiency of grain.
Estimates of proportional dependence on N₂ fixation ( % N [subscript dfa] ) for annual medics and vetch from this study ( 43 - 80 % ) are comparable to others for environments in southern Australia ( < 450mm average annual rainfall ). Such
estimates of fixation are considered low ( < 65 % ) to adequate ( 65 - 80 % ). Nevertheless, the amount of plant available N present at sowing for subsequent
wheat crops, and the occurrence of ' haying off ', suggests that WUE is not N - limited
per se, as implied by some reports, but constrained by the capacity of a soil to balance the co - limiting factors of water and nitrogen.Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2005.
40
Musarurwa, Herbert. "Method development for the determination of residual pesticides and heavy metals in complex samples using modern preconcentration techniques". Diss., 2019. http://hdl.handle.net/11602/1503.
Texto completo da fonteResumo:
MSc (Chemistry)Department of Chemistry
In this work, modern pre-concentration techniques, namely dispersive liquid-liquid micro-extraction (DLLME) and QuEChERS, were used to analyse pesticides and heavy metals in complex matrices. The work is divided into six papers. In Papers 1, the recent developments and applications of DLLME during analysis of pesticides in food matrices were reviewed. The DLLME technique has captured the interests of many researchers in recent years. The major advantage, among others, of DLLME is miniaturisation in which the acceptor-to-donor ratio is reduced tremendously leading to high enrichment compared to other sample preparation techniques. In the present work, the different complex matrices where the DLLME technique has been employed for the analysis of pesticides are reviewed as well as the challenges associated with this technique. Papers II reviewed the recent applications and developments of the QuEChERS technique during the analysis of pesticides in food matrices. QuEChERS is a versatile pre-concentration method whose application spans the whole breath of organic compounds. There are three common standard methods used during QuEChERS and these are the original QuEChERS, AOAC and the EN methods. In this paper, recent developments and applications of QuEChERS techniques in the analysis of pesticides in food samples were reviewed. In Paper III, green pre-concentration techniques employed during analysis of pesticides were reviewed. Recently, the parameter of “greenness” during sample pre-concentration of pesticides in food matrices is as important as selectivity in order to avoid using large amounts of harmful organic solvents during sample preparation. Developing new green pre-concentration techniques is one of the key subjects in green chemistry in order to minimize the release of large volume of toxic organic solvents into the environment. Thus, to reduce the impact on the environment during trace analysis of pesticides in food matrices, new developments in pesticide pre-concentration have gone in three separate directions (which are reviewed in this paper): one is the search for more environmentally friendly solvents, the second one is miniaturization and the third one is the development of solvent-free pre-concentration techniques. Eco-friendly solvents such as supercritical fluids, ionic liquids and natural deep eutectic solvents have been developed for use as extraction solvents during pre-concentration of pesticides in food matrices. Also miniaturized pre-concentration techniques such as QuEChERS, dispersive liquid-liquid micro-extraction and hollow-fibre liquid phase micro-extraction have been used during trace analysis of pesticides in food samples as well as solvent-free techniques such as solid phase micro-extraction and stir bar sorptive extraction. All these developments are geared to ensure that pesticide pre-concentration in food matrices is green and were reviewed in this paper. The effect of vehicular emissions on the concentrations of selected heavy metals was investigated in Paper IV. The samples were pre-concentrated using DLLME prior to analysis with flame atomic absorption spectroscopy. Dithizone, chloroform and methanol were used as chelating agent, extraction solvent and dispersion solvent respectively during the DLLME technique. The pH of the sample was adjusted to around 8 using sulphuric acid or sodium hydroxide solution. The influential DLLME parameters, such as pH volume and type of extraction solvent, and voume of disperser solvent, were optimized prior to the application of the developed method to real samples (roadside dust, fruits and vegetables). In Paper V, chromium speciation in fruits and vegetables was studied. The chromium in fruit and vegetable sample juices was pre-concentrated using DLLME prior to analysis with flame atomic absorption spectroscopy. Diphenylcarbazide (DPC) was used as a chelating agent in this study, and salting out of the complex from the aqueous medium into the organic phase was effected using sodium acetate. Chloroform and methanol were used as extraction and dispersion solvents respectively in the DLLME method for the determination of chromium (VI). For total chromium, the trivalent chromium was oxidised using acidified KMnO4 to hexavalent chromium before performing the DLLME technique. The concentration of chromium (III) was determined by finding the difference between total chromium and concentration of chromium (VI). The important parameters that influence the efficiency of the DLLME technique were also optimized using the univariate approach. After optimization, the developed method was applied to real samples. In Paper VI, the concentration of malathion pesticide in fruits was determined using QuECHERS for pre-concentration and UV-Vis spectrophotometry for instrumental analysis. Acetonitrile was used as the extraction solvent and Z-sep+/PSA sorbent combination was used for sample clean-up. The acetonitrile extract from QuEChERS was then hydrolysed using KOH followed by reaction with acidified potassium bromate for colour development. The coloured product formed was then analysed using UV-Vis spectrophotometry. Among the fruits analysed, Oranges had no malathion residue in them. However, trace amounts of malathion, below WHO maximum allowable limits, were found in pears and apples.
NRF
41
Adcock, Damien Paul. "Soil water and nitrogen dynamics of farming systems on the upper Eyre Peninsula, South Australia". 2005. http://hdl.handle.net/2440/37810.
Texto completo da fonteResumo:
In the semi - arid Mediterranean - type environments of southern Australia, soil and water resources largely determine crop productivity and ultimately the sustainability of farming systems within the region. The development of sustainable farming systems is a constantly evolving process, of which cropping sequences ( rotations ) are an essential component. This thesis focused on two important soil resources, soil water and nitrogen, and studied the effects of different crop sequences on the dynamic of these resources within current farming systems practiced on the upper Eyre Peninsula of South Australia. The hypothesis tested was that : continuous cropping may alter N dynamics but will not necessarily alter water use efficiency in semi - arid Mediterranean - type environments. Continuous cropping altered N - dynamics ; increases in inorganic N were dependent on the inclusion of a legume in the cropping sequence. Associated with the increase in inorganic N supply was a decrease in WUE by the subsequent wheat crop. Overall, estimates of water use efficiency, a common index of the sustainability of farming systems, in this study concur with reported values for the semi - arid Murray - Mallee region of southern Australia and other semi - arid environments worldwide. Soil water balance and determination of WUE for a series of crop sequences in this thesis suggests that the adoption of continuous cropping may increase WUE and confer a yield benefit compared to crop sequences including a legume component in this environment. No differences in total water use ( ET ) at anthesis or maturity were measured for wheat regardless of the previous crop. Soil evaporation ( E [subscript s] ) was significantly affected by crop canopy development, measured as LAI from tillering until anthesis in 2002, however total seasonal E [subscript s] did not differ between crop sequences. Indeed in environments with infrequent rainfall, such as the upper Eyre Peninsula, soil evaporation may be water - limited rather than energy limited and the potential benefits from greater LAI and reduced E [subscript s] are less. Greater shoot dry matter production and LAI due to an enhanced inorganic N supply for wheat after legumes, and to a lesser degree wheat after canola, relative to continuous cereal crop sequences resulted in increases in WUE calculated at anthesis, as reported by others. Nonetheless the increase in WUE was not sustained due to limitations on available soil water capacity caused by soil physical and chemical constraints. Access to more soil water at depth ( > 0.8m ) through additional root growth was unavailable due to soil chemical limitations. More importantly, the amount of plant available water within the ' effective rooting depth ' ( 0 - 0.8m ) was significantly reduced when soil physical factors were accounted for using the integral water capacity ( IWC ) concept. The difference between the magnitude of the plant available water capacity and the integral water capacity was approximately 90mm within the ' effective rooting depth ' when measured at field capacity, suggesting that the ability of the soil to store water and buffer against periodic water deficit was severely limited. The IWC concept offers a method of evaluating the physical quality of soils and the limitations that these physical properties, viz. aeration, soil strength and hydraulic conductivity, impose on the water supply capacity of the soil. The inability of the soil to maintain a constant supply of water to satisfy maximal transpiration efficiency combined with large amounts of N resulted in ' haying off ', and reduced grain yields. A strong negative linear relationship was established between WUE of grain production by wheat and increasing soil NO [subscript 3] - N at sowing in 2000 and 2002, which conflicts with results from experiments in semi - arid Mediterranean climates in other regions of the world where applications of N increased water use efficiency of grain. Estimates of proportional dependence on N [subscript 2] fixation ( % N [subscript dfa] ) for annual medics and vetch from this study ( 43 - 80 % ) are comparable to others for environments in southern Australia ( < 450mm average annual rainfall ). Such estimates of fixation are considered low ( < 65 % ) to adequate ( 65 - 80 % ). Nevertheless, the amount of plant available N present at sowing for subsequent wheat crops, and the occurrence of ' haying off ', suggests that WUE is not N - limited per se, as implied by some reports, but constrained by the capacity of a soil to balance the co - limiting factors of water and nitrogen.Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.
42
Liu, Qianhe. "Rhizosphere processes influencing soil and fertilizer phosphorus availability to Pinus radiata : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand". 2005. http://hdl.handle.net/10179/1669.
Texto completo da fonteResumo:
Production of Pinus radiata is a major contributor to New Zealand's economy and new plantings are a valuable carbon sink. Phosphorus (P) deficiency and high P fixing capacity of some volcanic ash soils (e.g. Allophanic Soil) may constrain radiata productivity. This thesis investigates the role of ectomycorrhizal (ECM) root processes in the acquisition of P by P. radiata fiom native soil and soil fertilised with two reactive phosphate rock (RPR) fertilisers. The application of finely-divided RPRs to a P deficient Allophanic Soil significantly increased P. radiata seedling growth and P uptake in 10 month pot trials. RPR dissolution was high in this soil, and it was further enhanced by the radiata rhizosphere processes. The development and formation of ECM in radiata seedlings was stimulated by low rates of RPR application but was hindered in unfertilised soils and high rates of RPR application. The P. radiata ECM roots induced acidification and increased oxalate concentration and phosphatase activities in the rhizosphere soil. These changes in rhizosphere biochemical properties were associated with enhanced solubilisation of fertiliser and soil inorganic P and increased mineralisation of organic P, leading to increased P bioavailability in the rhizosphere. ECM inoculation of P. radiata roots with Rhizopogen rubescens and Suillus luteus stimulated production of phosphatase enzymes and oxalate and induced acidification in the rhizosphere. The extent of root-induced changes in the rhizosphere soils was associated with ECM hyphae length density. A technique using pulse labelling of radiata shoots with 14CO2 showed promise in estimating the active ECM hyphae density. The 14C activity was highly correlated with ECM hyphae density measured by an agar film technique. Overall, observations made in this thesis indicate that sparingly soluble forms of organic and inorganic P in soils low in plant-available P are readily solubilised and utilised for P. radiata growth through ECM rhizosphere processes.
43
Cichota, Rogerio. "Modelling sulphate dynamics in soils : the effect of ion-pair adsorption : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University". 2007. http://hdl.handle.net/10179/1443.
Texto completo da fonteResumo:
Sulphur is an important nutrient to plants, and reports of its deficiency have been increasing worldwide. Sulphur starvation causes losses in both yield and quality, and it reduces nitrogen use efficiency of plants. As the timing for fertilisation can be decisive for avoiding deleterious effects, improvements in the description of the sulphur balance in fields are a valuable contribution for assisting fertiliser management. Sulphate is the most important inorganic form of sulphur in soils. Being the mobile form, sulphate is readily available for plants, and also prone to be leached. Therefore the description of the movement of sulphate is the key component of the sulphur balance. Leaching of sulphate from the soil can be significantly delayed by its adsorption onto the soil particles. Soil type and pH are the main factors defining the sulphate adsorption capacity; although the presence of other ions in the soil solution can have a considerable effect. It has been reported that in some soils, typically volcanic and tropical soils with variable-charge characteristics, the co-presence of sulphate and calcium can substantially enhance their retention via ion-pair adsorption (IPA). To determine the influence of cations on the movement of sulphate, series of batch and miscible displacement experiments were conducted using two New Zealand soils, of contrasting ion adsorption capacities: the Taupo sandy and Egmont loam soils. These experiments demonstrated the occurrence of cooperative adsorption of sulphate and calcium in the Egmont soil, but not in the Taupo soil. Batch experiments were conducted to examine the IPA adsorption process in the Egmont soil in more detail. Based on the analyses of the results from these two series of experiments, plus the review of published data, three different mathematical approaches for evaluating the amount of solute adsorbed as ion-pairs are proposed. A computer program was built for solving an adsorption model using these three approaches, and was used to compare the model's predictions and the observed adsorption data. An extension of this program, coupling the adsorption model with a solute transport description, was used to simulate the movement of sulphate and calcium. Comparisons between the data from the miscible displacements and the results from this model are used to demonstrate the applicability of the proposed IPA description for modelling the transport of these ions in the soil. Finally, results from a pot trial with Egmont soil are used to examine the relevance of IPA for the movement of sulphate under non-equilibrium conditions, and with active plant growth. Although the results from this experiment regarding IPA were statistically non-significant, some insights could be obtained and are discussed. More studies involving IPA under non-equilibrium experiments are needed for a better understanding of the relevance of IPA in field conditions.
44
(8300103), Shams R. Rahmani. "Digital Soil Mapping of the Purdue Agronomy Center for Research and Education". Thesis, 2020.
Encontre o texto completo da fonteResumo:
This research work concentrate on developing digital soil maps to support field based plant phenotyping research. We have developed soil organic matter content (OM), cation exchange capacity (CEC), natural soil drainage class, and tile drainage line maps using topographic indices and aerial imagery. Various prediction models (universal kriging, cubist, random forest, C5.0, artificial neural network, and multinomial logistic regression) were used to estimate the soil properties of interest.