Thesis (MTech (Agriculture))--Cape Peninsula University of Technology, 2014. / In this study, laboratory and greenhouse experiments were conducted to evaluate the effects of utilization of land fill leachate for irrigation purposes on potted soil and Swiss chard, to provide more insight into effects of landfill leachates on the environment. Swiss chard was grown and irrigated with different concentrations of leachates in pot experiments. For several weeks, the experimental soil and Swiss chard leaves was analyzed to assess extent of change in different chemical compositions, post-irrigation. The leachate samples had a high electrical conductivity (mean = 383 mS cm-1) and high soluble salts content (mean values, Na = 714.5 mg/L, K= 56.8 mg/L, Ca = 133.7 mg/L, Mg = 68.8 mg/L, Cl = 983 mg/L); while the composition of heavy metals in these wastewater leachates were of low concentrations. The application of leachates in irrigation resulted in increased soil cation concentrations, particularly those of Na ions (increased sodicity). Similarly, an increase in electrical conductivity and pH were recorded in the soils after irrigation with leachates. The soil metal concentrations were low and there was no significant difference in soil heavy metal concentrations between the soils irrigated with leachate and those of the controls. The results also show significant (p <0.05) reduction (up to 50%) in Swiss chard growth with application of (100%, 50% and 25%) of leachate as source of irrigation water compared to the growth observed in leachate-free (control) irrigation systems. This reduction in growth was best attributed to the high cation content in plant tissue picked up from the soil which was high in cations as a result of leachate irrigation.

Non-point source pollution of surface waters with phosphorous (P) transported from agricultural soils has emerged as a major environmental issue in the last decade. Regulations limiting P accumulation in surface soils have been established to protect surface water quality. Yet, little information is available on the quantities of P that may leach through soils and the factors influencing P leaching in agricultural soils. One important factor may be the type of fertilizer P applied, since it is known that P solubility varies among fertilizer sources. The purpose of this thesis was to quantify P leaching in soils amended with inorganic and organic fertilizers. / In a field study, we found that the fertilizer P source (triple superphosphate, composted cattle manure, or a mixture of the two) did not affect soil test P concentration, the degree of soil P saturation, or P leaching in a sandy-loam soil. The soil test P level in the 0--15-cm depth (146 mg P kg -1) exceeded the critical limit of 66-mg kg-1 established in Quebec, and ortho-P and DOP concentrations in leachates collected from piezometers were generally higher than the provincial water quality standard of 0.03 mg P L-1. If transported from our study site, P leached through this coarse-textured soil could pose a threat to groundwater and surface water quality. / These findings were verified in the laboratory with two coarse-textured soils. We found that more NO3-N and DON were leached from soils receiving inorganic N and P fertilizers than composted cattle manure, but the amounts of ortho-P and DOP leached were not affected by fertilizer sources. In coarse-textured soils, the quantities of P leached can be substantial, but depends more on soil characteristics than the fertilizer P source.

CNPQ / A atrazina (2-cloro-4-etilamino-6-isopropilamino-striazina) é um herbicida mundialmente utilizado no controle de plantas daninhas, com potencial para contaminar águas subterrâneas e prejudicar culturas sensíveis em sucessão. O uso de formulações de liberação lenta de atrazina poderia se constituir estratégia mitigadora do impacto ambiental e contribuir para a melhoria da eficiência de controle de plantas daninhas. Com o objetivo de determinar o comportamento ambiental e a eficiência agronômica de formulação de atrazina com liberação lenta (xerogel), comparando-a com formulação comercial, foram realizados um experimento a campo e três bioensaios em casa de vegetação. O experimento a campo foi implantado com a cultura do milho, utilizando-se o delineamento de blocos ao acaso, em parcelas subdivididas, em um esquema (2 x 6) + 4. Nas parcelas principais foram locadas as formulações (atrazina WG e atrazina xerogel), e nas subparcelas as concentrações de atrazina (0, 3200, 3600, 4200, 5400 e 8000 g ha-1), com acréscimo de quatro parcelas testemunha capinadas. Amostras de solo foram coletadas nas parcelas com 8000 g ha-1 para realização de bioensaios em casa de vegetação para avaliação da persistência e lixiviação das formulações. Nos bioensaios, o delineamento experimental foi inteiramente casualizado. No experimento a campo, avaliou-se a densidade e o controle visual de plantas daninhas e o rendimento de grãos de milho. Nos bioensaios, as principais variáveis avaliadas foram estatura, fitotoxicidade, massas de planta verde e seca. No primeiro bioensaio, selecionou-se a espécie cultivada mais adequada para utilização em testes para determinação da lixiviação e persistência das formulações de atrazina. No experimento a campo, a formulação WG exerceu maior controle de B. plantaginea que xerogel nas avaliações de mais precoces, mas nas avaliações mais tardias a atrazina xerogel foi mais eficiente. Não ocorreram diferenças de rendimento de grãos de milho entre as formulações e doses testadas. O grau de sensibilidade à atrazina variou de acordo com a espécie: quiabo e ervilha apresentaram pequena sensibilidade; aveia e trigo apresentaram nível intermediário e tomate e rabanete o mais alto nível de sensibilidade à presença de atrazina no solo. A biodisponibilização de atrazina ao solo variou em função do tempo e da formulação: até 5 dias após a aplicação, a disponibilização com a formulação xerogel foi maior; no período entre 14 e 28 dias, a biodisponibilização por atrazina WG foi superior à por xerogel; aos 35 dias após a aplicação, xerogel proporcionou maior atrazina ao solo do que WG. A meia vida foi de 30 e 38 dias, para atrazina WG e atrazina xerogel, respectivamente. Maior concentração de atrazina foi encontrada na superfície do solo (0 a 4 cm), nas duas formulações. Porém, a quantificação de atrazina por bioensaio indicou maior concentração da formulação WG entre 2 e 4 cm, em contraste com o resultado da análise cromatográfica, que indicou maior concentração da formulação xerogel. / Atrazine (2-chloro-4-ethylamine-6-isopropylamine-striazina) is an herbicide used worldwide to control weeds with potential to contaminate groundwater and harm sensitive crops in succession. The use of controlled release formulations of atrazine could be a strategy to mitigate environmental impact and contribute to improving the efficiency of weed control with atrazine. Aiming to determine the environmental performance and agronomic efficiency of atrazine formulation of controlled release (xerogel), compared with the commercial formulation were conducted one experiment in the field and three bioassays in greenhouse. The field experiment was implemented with the corn, using randomized blocks design, with split plots in a scheme (2 x 6) + 4. In the main plots were located formulations (atrazine xerogel and WG), and in sub-plots the atrazine concentrations (0, 3200, 3600, 4200, 5400 and 8000 g ha-1), with four additional control plots weeded. Soil samples were collected from each plot with 8000 g ha-1 for bioassays in the greenhouse to evaluate the persistence and leaching of the formulations. The experimental designs of bioassays were completely randomized. In the field experiment, we evaluated the density and visual control of weeds and yield of maize. In bioassays, the main variables were height, phytotoxicity, green and dry plant mass. In the first bioassay was selected cultivated species most suitable for use in tests to determine the persistence and leaching of atrazine formulations. In the field experiment, the formulation WG produced greater control of B. plantaginea than xerogel in earlier assessments, but in later assessments atrazine xerogel was more effective. There were no differences in grain yield of maize between the formulations and doses tested. The degree of sensitivity to atrazine varied according to species: okra and peas showed little sensitivity; oats and wheat had an intermediate; radish and tomato had the highest level of sensitivity to the presence of atrazine in soil. The bioavailability of atrazine to soil varied depending on the time and formulation: until 5 days after application, atrazine disponibility by xerogel formulation was higher and in period between 14 and 28 days, the bioavailability of atrazine by WG was higher than by xerogel; 35 days after application, atrazine xerogel showed higher disponibility than the WG. The half-life was 30 and 38 days for atrazine WG and xerogel, respectively. Higher concentrations of atrazine were found in surface soil (0-4 cm) in two formulations. However, the quantification of atrazine by bioassay indicated a greater concentration of WG formulation between 2 and 4 cm, in contrast with the results of chromatographic analysis, which indicated a greater concentration of the xerogel formulation.

Fertilized croplands unintentionally export large amounts of reactive nitrogen (N), which degrades water and air quality and contributes to climate change. In this dissertation, I focus on how these reactive N losses are likely to change in the near future as agriculture intensifies in the tropics, and ecological intensification strategies to mitigate N losses are more widely adopted. I use a combination of empirical field measurements in Mato Grosso, Brazil and Skåne, Sweden, literature review, and statistical models to quantify trends. In chapter one, I quantified emissions of nitric oxide (N₂O) and nitrous oxide (N₂O) in forest, single cropped soybean, and N-fertilized double-cropped soybean-maize at three nitrogen fertilizer levels within the largest area of recent cropland expansion on earth, in the Amazon and Cerrado biomes in Mato Grosso, Brazil. I found that NO emissions do not increase when forests are converted to croplands under current fertilization levels, and that NO will respond more strongly than N₂O fluxes to increases in fertilizer applications. In chapter two, I investigated anion exchange capacity and soil nitrate (NO₃¯) pools in deep soils in Mato Grosso, Brazil in the southern Amazon. I found that soil NO₃¯ pools in the top 8 m increased from 143 kg N ha¯¹ in forest to 1,052 and 1,161 kg N ha¯¹ in soybean and soybean-maize croplands. This NO₃¯ accumulation in croplands compared with forest soils matched the estimated amount of surplus N from the croplands, and could be explained by the soil’s positive charge through its anion exchange capacity. In chapter three, I conducted a meta-analysis of the effects of fertilization amount on of NO₃¯ leaching, N₂O emissions, NO emissions, and ammonia (NH₃) volatilization, totaling over 1,000 observations. I found that the relationship between N inputs and losses differed little between temperate and tropical croplands, although total NO losses were higher in the tropics. Among the potential drivers I studied, the N input rate controlled all N losses, but soil texture and water inputs also controlled NO₃¯ leaching losses. In chapter four, I explored the differences in NO₃¯ leaching, fertilizer N use efficiency, and soil N cycling in perennial wheat, which is being domesticated as a more sustainable alternative to annual crops, and annual wheat at a long-term experimental site in Skåne, Sweden. I found that NO₃ leaching was more than two orders of magnitude lower in perennial wheat, overall ecosystem recovery of fertilizer was quite high and not significantly different between perennial and annual wheat after the first growing season, and that measures of soil N cycling were largely the same between both crops. Together, these chapters highlight that reactive N losses will remain a critical global challenge in the coming decades, but that there are also key opportunities to reduce N losses by increasing the use of perennial crops and focusing tropical agricultural intensification on Oxisol soils which buffer against NO₃¯ leaching.

No description available.

A two year field study was carried out in western Quebec to investigate methods of predicting and reducing NO3--N leaching. Corn (Zea mays L.) was planted on the expel site and them were four treatments: water table controlled at 600 mm and 120 kg/ha of N fertilizer (WT120), water table controlled at 600 mm and 200 kg/ha of N fertilizer (WT200), free drainage and 120 kg/ha of N fertilizer (FD120), and free drainage and 200 kg/ha of N fertilizer (FD200). Drain flow was monitored and water samples were taken and analyzed for NO3- -N. Soil NO3- levels were measured along with led chlorophyll and denitrification throughout the two growing seasons. / Drain flow was dependent on both rainfall and the soil moisture content. In 1996, water table control decreased drain flow. However, in 1997 (a drier year), the drain flows for all treatments were similar. NO3 --N was reduced significantly in the controlled water table plots. In 1996, there was 59.2% less NO3--N in the controlled water table plots than in the free drainage plots and in 1997 this increased to 75.9% less NO3--N in the controlled water table compared to the fire drainage plots. In 1996, denitrification was enhanced by the controlled water table plots, with 72.2% more denitrification occurring in the controlled water table plots than in the free drainage plots. In 1997, there was a 93.2% increase in denitrification occurring in the water table plots than in the free drainage plots. / The controlled water table plots had no effect on plant chlorophyll levels. Chlorophyll contents of the corn plants were higher where fertilizer was applied at 200 kg/ha. Overall, it was shown that water table management can significantly decrease NO3--N pollution in drainage water. (Abstract shortened by UMI.)

No description available.

by Leung Chi Kam Joseph. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985 / Bibliography: leaves 178-198

The temporal fate of selected parameters, including redox potential; pH; phenol; nitrates; sulphates; copper and zinc, of a young synthetic acetogenic phase landfill leachate was assessed by perfusing a series of sequential soil (Hutton) microcosms (arrays) at two hydraulic loading rates (HLR). We chose HLRs that were representative of areas in South Africa with typically elevated rainfall (Pietermaritzburg – HLRh) and one with relatively low rainfall (Kimberley – HLRl). Preliminary phenol, copper, and zinc adsorption investigations on gamma radiation sterilized soil and unsterilized soil revealed superior adsorption rates for each compound in the unsterilized soil. This revealed the importance of the biological component of soil in phenol, copper, and zinc attenuation in soil. The results presented in this thesis suggest that the HLR of leachate into soil arrays contributes to significant differences in the fate of the landfill leachate parameters mentioned earlier. In addition, we assessed the temporal and spatial succession of bacterial community diversity in each of the soil arrays by polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). Prior to this, we compared two soil DNA isolation techniques, the modified method of Duarte et al. (1998) (Bead Beat) and the commercial Mo-Bio UltraClean™ Soil DNA isolation kit (Kit). The DNA isolated by the Kit method was significantly superior regarding purity and absence of DNA fragmentation. However, the Bead Beat method produced a significantly higher yield per reaction before further purification with Wizard™ Clean-Up columns produced DNA extracts of similar purity at the cost of a significant reduction in DNA yield. The Kit method was chosen for future DNA isolation and PCR-DGGE based on the quality of the PCR amplicons generated from the Kit isolated DNA. PCR-DGGE was further optimized by comparing the efficiency and sensitivity of a silver stain against ethidium bromide. Silver stain generated DGGE gels with greater number of bands (species richness – S) and stronger band signal intensities. Captured DGGE fingerprints generated data that were subjected to the Shannon-Weaver Index (H’) and the associated Shannon-Weaver Evenness Index (EH) to measure the change in spatial and temporal bacterial diversity. There was a significant shift in S and H’ for both HLRs but a significant change in EH was only observed for HLRh. Furthermore, a temporal comparison of S and H’ between both HLRs revealed significant differences throughout the investigation. Canonical Correspondence Analysis (CCA) revealed spatial distribution of bacterial community diversity with depth. Effects of phenol concentration, redox potential, and pH of the effluent leachate on bacterial community diversity was tentatively assessed by three-dimensional graphical representation on PlotIT 3.2 software. Bacterial community diversity showed a decrease with elevated pH and phenol concentration along with decreasing redox potentials for both HLRs. While this study reveals the spatial and temporal dynamics of bacterial community diversity in situ, it provides important evidence with respect to: (i) the effects of rainfall / leaching rates (HLR) on spatial and temporal bacterial community succession; (ii) the importance of the biological component in natural attenuation; (iii) the ability of soil, previously unexposed to landfill leachate, to initiate natural attenuation of phenol and other leachate constituents; (iv) the capacity of PCRDGGE to fingerprint successional changes in bacterial community diversity, (v) and the potential to clone and sequence selected members of bacterial associations for future reference in environmental remediation strategies. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

CAPES / O uso de coberturas vegetais é uma estratégia fundamental para o manejo de plantas daninhas na região Sul do Brasil. Em áreas com elevadas infestações de plantas daninhas, é crescente a utilização de herbicidas, que aumentam os custos de produção das lavouras e a contaminação ambiental. A aveia preta e a mucuna possuem características contrastantes quanto à velocidade de decomposição dos resíduos e capacidade de mobilização do nitrogênio do solo, proporcionando resultados distintos de supressão de plantas daninhas ao longo do tempo e, portanto, demandando estratégias distintas de manejo antes, durante e após a implantação da cultura do milho. O objetivo geral do experimento foi avaliar a dinâmica ambiental do herbicida atrazina, os resultados sobre o rendimento de grãos do milho e eficiência de controle de plantas daninhas, considerando áreas com distintos históricos de utilização de cobertura morta, distintos níveis de palha e do herbicida. Para isso foram realizadas duas etapas de experimentos: na primeira etapa, foram implantados dois experimentos com a cultura do milho, um com utilização de aveia preta e outro com mucuna preta como espécies de cobertura de solo. O delineamento utilizado em ambos os experimentos a campo foi o de blocos ao acaso, com quatro repetições. O fator A foi constituído de quatro níveis de palha (0, 0,75x, 1,5x e 3x) e o fator B foi constituído por quatro doses do herbicida atrazina (0, 2100, 4200 e 8400 g i.a. ha-1). Amostras de solo foram coletadas para realização de bioensaios em casa de vegetação para avaliação da persistência. A avaliação de lixiviação de atrazina foi efetuada por cromatografia, por meio de amostras coletadas ao longo do perfil do solo.No experimento a campo, avaliou-se a densidade de plantas daninhas, massa da parte aérea verde, massa da parte aérea seca e o rendimento de grãos de milho. Nos bioensaios, as principais variáveis avaliadas foram estatura efitotoxicidade. Na segunda etapa, foram coletados solos com diferentes históricos de cultivo de cultura de cobertura e os estudos de mineralização e sorção, ambos com com 14C-atrazina, foram conduzidos em laboratório. O delineamento utilizado foi inteiramente casualizado, com quatro repetições. Os resultados obtidos a partir do experimento a campo, indicam que o uso de elevados níveis de palha sobre o solo, de forma isolada, não são eficientes para controlar as espécies daninhas e queelevados níveis de palha de mucuna preta sobre o solo reduzem o potencial produtivo do milho. Os bioensaios demonstraram que quantidades elevadas de palha de aveia preta impedem a passagem da atrazina até o solo, sendoa influência do nível de palha sobre a disponibilidade do herbicida detectada até 12 dias após a aplicação. A meia-vida da atrazina aplicada sobre a palha de aveia variou de 7 a 14 dias após a aplicação, enquanto que a meia-vida da atrazina aplicada sobre a palha de mucuna varia de 5 a 14 dias após a aplicação. Níveis crescentes de palha de aveia preta sobre o solo apresentam capacidade de redução da lixiviação de atrazina no perfil, porém esse efeito não foi comprovado com a utilização de palha de mucuna preta, porque o herbicida não foi detectado no perfil do solo, aos 21 dias após a aplicação.As análises cromatográficas indicam que a atrazina se concentra mais próximo à superfície do solo independentemente do volume de palha, não sendo detectada em profundidade superior a 8 cm. A mineralização acumulada da 14C-atrazina aplicada a solos com V. sativa é superior se comparada a solos com S. cereale ou solos com ausência de cultura de cobertura. O coeficiente de sorção da atrazina é superior quando o herbicida é aplicado à palha do que ao solo. / The use of cover crops is a fundamental strategy to the weed management in Southern Brazil. In highly infested areas, the herbicides use is increasing, which increases the costs of the crops production as well as the environmental contamination. Oat and velvet bean plants havecontrasting characteristics regarding to residues decomposition speed and the capacity to immobilize Nitrogen in the soil, providing distinct results of weeds suppression throughout the time, and therefore, requiring distinct management strategies before, during, and after the corn crop establishment. The general objective of the experiment was to evaluate the environmental dynamics of the herbicide atrazine, the corn grain yield, and the efficiency of the weed control, considering areas with distinct history regarding the use of mulching, levels of straw and rates of atrazine. For this, the experiment was carried out in two parts: in the first part, two trials with the corn crop were established, one using oat and the other using velvet bean as cover crops. The experimental design used for both field trials was randomized complete blocks arrangement with four replications. The factor A was constituted by four levels of straw (0; 0.75x; 1.5x; 3x) and the factor B was constituted by four rates of the herbicide atrazine (0; 2100; 4200; 8400 g a i. ha-1). Soil samples were collected for greenhouse trialsto determine the persistence. Atrazine leaching evaluation was performed by chromatography using samples collected over the soil profile.In the field, the weed density, the fresh and dry weight and the yield of the corn were evaluated. In the greenhouse trials, the main variables evaluated were plant height and injury caused by the herbicide toxicity. In the second part, soils with distinct covering history were sampled, and the mineralization and sorption studies, both with 14C-atrazine, were conducted in the laboratory. The experimental design was randomized complete blocks arrangement with four replications. The results from the field experiment show that the high levels of straw above ground, isolated, were not efficient to control completely the weeds, and that high levels of velvet bean`s straw decreased the corn potential yield. The greenhouse trials showed that high levels of oat straw prevent the scape of atrazine to soil, this effect of oat straw upon the herbicide availability on soil was detected up to 12 days after spraying. The half-life of atrazine sprayed over oat straw varied from 7 to 14 days after spraying, while the half-life of atrazine sprayed over velvet bean varied from 5 to 14 days after spraying. Increasing oat straw levels presents the capacity to reduce the lixiviation of atrazine in the soil profile, however, this effect was not verified when using velvet bean straw, because the herbicide was not detected in the soil profile, at 21 days after spraying. The chromatographic analysis indicate thatthe atrazine concentrates closer to the soil surface regardless of amount of straw, not being detected deeper than 8 cm in the soil. The accumulated mineralization of 14C-arazine sprayed over V. sativa is superior if compared to soils with S. cereale or non-covered soils. The sorption coefficient of atrazine is superior when sprayed over straw than over the soil.