Estudos sobre a dinâmica da água no solo não-saturado passam pela medição, estimativa e/ou previsão do potencial matricial ou do teor de água. Diante disso, o objetivo da presente proposta foi realizar testes e avaliações de três instrumentos com características distintas, capazes de medir o potencial matricial da água no solo seco, sendo eles: um medidor baseado no ponto de orvalho (WP4), um instrumento baseado na pressão (tensiômetro de polímero-PoT) e um instrumento baseado na capacitância elétrica (FDR EC-5). A análise foi realizada em três partes: 1. Avaliação do WP4 com amostras com potencial equilibrado na câmara de Richards ou secas ao ar; 2. Avaliação dos PoT e 3. Experimento comparativo entre instrumentos em colunas de solo. Nesses experimentos foram utilizados materiais de solos com texturas diferentes (um de textura argilosa, um de textura média e um de textura arenosa). Os experimentos foram conduzidos no Laboratório de Física de Solo do CENA/USP em Piracicaba-SP. Os resultados mostram que o FDR EC-5 apresentou bons resultados em relação ao método que foi definido como padrão (método gravimétrico), por mais que possua erros associados à curva de retenção. O WP4, que possui uma ampla faixa de leitura de 0 a -30000 m, não se apresentou muito preciso para solos úmidos (h > -70 m) devido ao seu procedimento de leitura. Para solos muito secos, no entanto, ele se apresenta como uma boa opção. O tensiômetro de polímero mede a pressão diretamente na faixa entre 0 a -150 m. Esse instrumento requer cuidados com o coeficiente de calibração, a verificação do limite individual de funcionamento e o contato entre a cápsula porosa do tensiômetro e o solo / Studies about unsaturated soil water dynamics involve the measurement or prediction of matric potential and/or soil water content. In this study, the objective was to test and evaluate three measurement devices able to measure matric potential in dry soil: a dew point based instrument (WP4), a pressure based instrument (polymer tensiometer - PoT) and an electromagnetic capacitance based instrument (FDR EC-5). The analysis was performed in three steps: 1. Evaluation of WP4 using soil samples in equilibrium with a pressure chamber or with surrounding air; 2. Evaluation of PoT and 3. Experiments to compare devices in soil columns. In these experiments three soil textures were used (clay texture, silt texture and sand texture). The experiments were conducted in the soil physics lab at CENA/Universidade de São Paulo, Piracicaba, Brazil. Results show that the FDR EC-5 performed well when compared to the (standard) gravimetric method, even though it includes errors associated with the retention curve. The WP4 device has a wide reading range of 0 to -30000 m, but is not accurate for saturated or moist soils (h > -70 m) due to its working principle. For very dry soils, however, it is a good option. The polymer tensiometers measure pressure directly and perform in a range between 0 to -150 m. This equipment showed to require special care regarding its calibration coefficient, verification of individual reading limit and the porous cap-soil contact

Graduation date: 1991

Graduation date: 1994

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

In this work, a differential reactor was used to expose all the biofilter packing material (compost) to a uniform toluene concentration in air. The reactor was combined with water content control using the suction cell principle and traditional inlet concentration, temperature and humidity control. The matric potential was controlled using the suction cell principle between -5 to -300 cm H₂O which controlled the water content between 0.99 and 2.30 g g⁻¹ (dry weight). Two types of compost were used, with different water retention curves with no observed difference in elimination capacity. The elimination capacity varied between 2.7 g m⁻³r hr⁻¹ and 21 g m⁻³r hr⁻¹ with low potential causing low removal rates. The reduction in EC at low matric potentials was attributed to several factors: loss of water availability to the organisms, water redistribution in the medium, non-adaptable micro-organisms, and reduced mass transfer. Cultures isolated from compost were used to inoculate the reactor to create a biofilm. A maximal observed surface EC of is 0.17 g m⁻²r hr⁻¹ and a specific removal rate of 1250 g m⁻³b hr⁻¹ is measured. These values were used in modelling the biofilter performance. The EC was dependent on the residual toluene concentration. The EC increased with increasing toluene concentration until reaching a critical concentration. Above this concentration, 100 – 300 ppm (0.37- 1.11 g m⁻³) depending on biofilm thickness and area of coverage, the EC was constant. Three toluene dependency curves were fitted using a zero order and a composite model using a weighted average of a zero and first order component. From the data the critical concentration (Ccrit) and the ECcrit was found and used to determine the biofilm thickness. It was estimated to be between 68 and 134 µm. Using a qmax of 1250 g m⁻³b hr⁻¹ and optimising the model a Ks of 1.3•10⁻¹ g m⁻³g was found. This was comparable to values found in the literature. There was no significant difference in the fit between both models. The Ks was low compared to the majority of the data, which means that the zero order part of the composite model dominated. Nitrogen and other nutrients were added to investigate their influence on the elimination capacity (EC) of toluene. Also the effect of temperature on the EC was investigated between 14 and 60 °C. Maximal removal rates were found between 25 and 55 °C. The EC decreased by 90% going from 55 to 60 °C and took many weeks to recover. Without any extra nitrogen added to the media, the EC averaged around 6 ± 0.3 g m⁻³r h⁻¹. Although the average EC was lower than most reports for toluene removal, it was still in the general range reported. When NH4Cl (1 g l⁻¹) was added to the reactor, the EC increased to 41 ± 1.7 g m⁻³r hr⁻¹. Similar effects were observed with nitrate addition; the steady state EC doubled from 30.1 ± 0.9 g m⁻³r hr⁻¹ to 76.3 ± 2.5 g m⁻³r hr⁻¹. Other macronutrients tested like phosphate, sulphate, magnesium, calcium and iron did not increase the EC.

Aflatoxin contamination accounts for millions of dollars worth of losses for corn and cotton in Texas. Two atoxigenic strains of Aspergillus flavus, AF36 and Afla-Guard, are labeled for its management. The purpose of this study was to measure differences in the ability of these strains to sporulate and to track movement of their conidia in corn and cotton fields. Sporulation was evaluated by incubating the two strains on their commercial formulations (inoculated on cereal grains) at six constant humidity levels ranging from 0-100%, using closed chambers with saturated salt solutions. Conidial production by Afla-Guard was 3-fold greater than that of AF36 at 100% humidity. Sporulation of the two strains was also evaluated on one substrate by inoculating their conidia on sterile, hulled barley. After 3 days, there was a 234-fold increase in conidia recovered from the barley inoculated with Afla-Guard, compared with a 21-fold increase in conidia recovered from the AF36-inoculated barley. These data suggest that the Afla-Guard strain sporulates better than the AF36 strain, which may be a factor in effectiveness for biological control. An in vitro de-Wit competition experiment showed that sporulation by the Afla-Guard strain was not affected by co-inoculation with either AF36 or the wildtype NRRL3357 toxin producing strain. To measure conidial movement, an Afla-Guard nitrate non-utilizing mutant colonizing autoclaved corn seed, was placed at one point in a field of cotton and corn. For detection, aliquots washed from leaf samples were plated onto a medium containing potassium chlorate. The mutant was recovered at a maximum distance of 6.4 m in corn fields along the same row and as far as 10.2 m across rows from the point source. In cotton fields, the mutant was recovered at 9.1 meters along the same row and 6.1 m across rows from the point source. There was no recovery at 24.3 m from the point source - the maximum distance evaluated. The experiment was repeated in a second year with similar results. These data suggest that plots in field trials may not need wide separation in order to avoid cross contamination. To assess the viability of a toxigenic and atoxigenic strain of A. flavus over time, polycarbonate packets containing conidia and sclerotia of both strains were buried in Ships Clay soil with the matric potential held constant at -24 kPa or -154 kPa. After 10 months, viable conidia were recovered in all treatments. After 14 months, viability of the atoxigenic strain incubated at -154 kPa ψm was lost, while other treatments remained viable. Ears of corn were inoculated via silk channel at different stages of silk senescence. Sclerotia were enumerated from the same plants following harvest of the crop. Sclerotial production by A. flavus was greatest from ears with silks inoculated at senescence, compared with inoculation when silks were green. The isolation frequency of Penicillium sp. from surface-sterilized kernels at harvest was the highest from ears that were inoculated with A. flavus when silks were fresh, as compared with A. flavus inoculation of ears with senescent silks. A Fusarium and Penicillium species was isolated from harvested kernels, and their sterile Czapek-Dox broth culture filtrates were tested for their effect on development of three strains of A. flavus on agar. The Penicillium broth filtrate greatly reduced sclerotial numbers relative to the control and the Fusarium filtrate (P<0.05). When A. flavus was grown in the presence of autoclaved Penicillium culture filtrate, there was no effect on sclerotial production. The Penicillium filtrate increased the rate of radial hyphal growth of the A. flavus isolates on agar compared to the control and the Fusarium culture filtrate.

Thesis (M.Sc.(Agric))(Plant Production)--University of Pretoria, 2004. / Title from opening screen (viewed March 11th, 2005). Includes summary. Includes bibliographical references.

Estudos sobre a dinâmica da água no solo não-saturado passam pela medição, estimativa e/ou previsão do potencial matricial ou do teor de água. Diante disso, o objetivo da presente proposta foi realizar testes e avaliações de três instrumentos com características distintas, capazes de medir o potencial matricial da água no solo seco, sendo eles: um medidor baseado no ponto de orvalho (WP4), um instrumento baseado na pressão (tensiômetro de polímero-PoT) e um instrumento baseado na capacitância elétrica (FDR EC-5). A análise foi realizada em três partes: 1. Avaliação do WP4 com amostras com potencial equilibrado na câmara de Richards ou secas ao ar; 2. Avaliação dos PoT e 3. Experimento comparativo entre instrumentos em colunas de solo. Nesses experimentos foram utilizados materiais de solos com texturas diferentes (um de textura argilosa, um de textura média e um de textura arenosa). Os experimentos foram conduzidos no Laboratório de Física de Solo do CENA/USP em Piracicaba-SP. Os resultados mostram que o FDR EC-5 apresentou bons resultados em relação ao método que foi definido como padrão (método gravimétrico), por mais que possua erros associados à curva de retenção. O WP4, que possui uma ampla faixa de leitura de 0 a -30000 m, não se apresentou muito preciso para solos úmidos (h > -70 m) devido ao seu procedimento de leitura. Para solos muito secos, no entanto, ele se apresenta como uma boa opção. O tensiômetro de polímero mede a pressão diretamente na faixa entre 0 a -150 m. Esse instrumento requer cuidados com o coeficiente de calibração, a verificação do limite individual de funcionamento e o contato entre a cápsula porosa do tensiômetro e o solo / Studies about unsaturated soil water dynamics involve the measurement or prediction of matric potential and/or soil water content. In this study, the objective was to test and evaluate three measurement devices able to measure matric potential in dry soil: a dew point based instrument (WP4), a pressure based instrument (polymer tensiometer - PoT) and an electromagnetic capacitance based instrument (FDR EC-5). The analysis was performed in three steps: 1. Evaluation of WP4 using soil samples in equilibrium with a pressure chamber or with surrounding air; 2. Evaluation of PoT and 3. Experiments to compare devices in soil columns. In these experiments three soil textures were used (clay texture, silt texture and sand texture). The experiments were conducted in the soil physics lab at CENA/Universidade de São Paulo, Piracicaba, Brazil. Results show that the FDR EC-5 performed well when compared to the (standard) gravimetric method, even though it includes errors associated with the retention curve. The WP4 device has a wide reading range of 0 to -30000 m, but is not accurate for saturated or moist soils (h > -70 m) due to its working principle. For very dry soils, however, it is a good option. The polymer tensiometers measure pressure directly and perform in a range between 0 to -150 m. This equipment showed to require special care regarding its calibration coefficient, verification of individual reading limit and the porous cap-soil contact

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Anabilim Dalı, 2008. / Bibliyografya var.

Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished