MAKTARI, MOHAMMED SAEED. (The University of Arizona., 1983)
Two laboratory experiments were conducted to study the effects of salt and nitrogen-sulfur compounds on the transformations of nitrogen in three Arizona soils. In the first experiment the effect of NaCl in concentrations of 0 to 1 m (molal) at moisture levels of 1/3 and 15 bars was studied in the Gila and Laveen loam soils. At 1/3 moisture nitrification of urea-¹⁵N and native soil nitrogen was appreciably reduced only at 1 m salt level. At 15 bars moisture, nitrification was almost completely inhibited by the 1 m salt concentration. Mineralization of soil nitrogen was reduced more by decreasing moisture than by increasing salt concentrations. Ammonia volatilization was increased by both salt and moisture stress and was associated with inhibition of nitrification. Slight effects of salt were observed on ¹⁵N immobilization and ¹⁵N recovery (including volatilization). In the second experiment nitrogen-sulphur combinations (¹⁵N labelled) of KNO₃, KNO₃ + S, urea, urea + S, APS (ammonia polysulfide) and Thiosul (ammonium thiosulfate) were studied at field capacity (FC) and 1.5 FC moistures. In the calcareous Gila soil nitrification was suppressed by the presence of sulfur at 1.5 FC moisture. Volatilization losses were appreciable only from APS. Immobilization of ¹⁵N was greatest from treatments with the higher sulfur rate (elemental S). Denitrification was slightly increased by sulfur at FC, however, at 1.5 FC dramatic losses occurred by denitrification (autotrophic in the presence of sulfur, especially with elemental S. The nitrifying ability of the slightly acid and coarse textured Sonoita soil was low. Nitrification was suppressed more by the presence of sulfur at both moistures. Ammonia volatilization was appreciable from APS followed by urea. ¹⁵N immobilization was high from urea followed by APS. Appreciable losses by denitrification occurred only with APS. The Sonoita soil showed a lower sulfur oxidizing power than the Gila with the only appreciable rate of oxidation from Thiosul followed by APS.
Weinert, Tom L. (The University of Arizona., 2000)
A High N fertilizers citrus rates may contribute to a rise in the appearance of groundwater NO₃ around groves in central Arizona. Nitrogen fertilizer recommendations need to be reevaluated for citrus due to recent changes in fertilizers, irrigation technology, and increasing groundwater NO₃. Studies were initiated to optimize fertilizer N management for microsprinkler-irrigated citrus. Navel oranges were planted in Jan. 1997 with varying N rates and frequency of liquid urea NH₄-NO₃ or granular controlled-release fertilizers (CRFs) in order to determine tree response, N partitioning, N balance, and residual soil N. Trees grew slowly in 1997 with no more than 6% of the fertilizer N taken up by trees, while < 94% of fertilizer N remained in the top 0.9 m of soil. Leaf N was higher in fertilized plots than in controls as trees grew rapidly in 1998 with < 25% of the fertilizer N taken up by the trees. The soil contained low NO₃ concentrations, suggesting most of the fertilizer N was leached. Nitrogen is not needed during the first season after planting and rates of 68 to 136 g N tree⁻¹ applied in monthly intervals during the second season maintain adequate tree growth and N reserves. Application of CRFs resulted in little tree response during the two year study. Soil inorganic N was highest in the surface 0.6 m in 1997. In 1998, ammonium sulfate treatments resulted in higher NO₃ leaching than plots that received CRFs. Eight-year old 'Redblush' grapefruit trees were treated with two N rates and three fertigation frequencies in a factorial arrangement. There no differences in trunk diameter, or fruit quality on trees between 1996 and 1998. Leaf N content was > 18 mg kg⁻¹ in all plots in 1996. Leaf N declined in Aug. 1997 and control plots had lower leaf N than the other treatments. Yields tended to be the greatest at high N rates with monthly fertigation. Soil N levels were proportional to fertilizer N inputs. In 1998, the high N treatment at weekly and monthly frequencies increased leaf N compared to the other treatments. Results suggest that N rates of 272 to 408 g tree⁻¹ year⁻¹ at weekly or monthly frequencies may be optimal for desert-grown mature grapefruit.
Suliman, Ahmed Saeid Ahmed. (The University of Arizona., 1989)
Dry and wet fine earth spectral measurements were made on the Ap soil surface horizons on the Maricopa Agricultural Center by using a Barnes Modular Multiband Radiometer. Three subsets were used in the analyses 552, 101 and 11. There were three soil series, Casa Grande, Shontik and Trix, four soil mapping units, and three texture classes identified on the farm. The wet soil condition reduced the amplitude of the spectral curves over the entire spectrum range (0.45 to 2.35 μm). The spectral curves were statistically related to the soil mapping units to determine if the soil mapping units and texture classes could be separated. The wet soil condition and the smaller sample size increased the correct classification percentages for soil mapping units and texture classes. LSD tests showed there were significant differences between these groups. Simple- and Multiple-linear regression analysis were used to relate some soil physical (sand, silt and clay contents and color components) and chemical (iron oxide, organic carbon and calcium carbonate contents) to soil spectral responses in the seven bands under dry and wet conditions. There were high correlations levels among the spectral bands showing an overlap of spectral information. Generally, the red (MMR3) and near-infrared (MMR4) bands had the highest correlations with the studied soil properties under dry and wet conditions. Usually, the wet soil condition resulted in higher correlations than that for the dry soil condition over the total spectrum range. The predictive equations for sand, silt and clay and iron oxide contents were satisfactory. For organic carbon and color components, the greatest success was achieved when variation in spectral response within individual samples are smaller than that between soil mapping unit group averages. There was a poor relation between calcium carbonate and spectral response. A comparison of multi-level remotely sensed data collected by SPOT, aircraft, and ground instruments showed a strong agreement among the data sets, which correlated well to fine earth data, except for the SPOT data. Rough soil surfaces showed a reduction in reflectance altitude compared to laser level, and it appears to be directly proportional to the percent shadow in the viewing area measured by SPOT satellite and aircraft.
Barlas, Sajid Ali,1961- (The University of Arizona., 1995)
Changes in redox potential (Eh), major sulfur species and the solubility of selenium and boron in reduced flue gas desulfurization (FGD) sludge, when exposed to atmosphere were studied in laboratory experiments. Also the effect of organic carbon and temperature on reduction of FGD sludge and changes in concentration of major S species was studied. Stable isotopic ratios of sulfur and carbon compounds were used to investigate the possible pathways of S transformation in FGD sludge disposal site. Oxidation of reduced sludge appears to be a two step process, a fast step of chemical oxidation followed by a slow step of biological oxidation and is significantly affected by moisture content and mixing of the sludge. With the addition of organic carbon Eh of the FGD sludge dropped exponentially and reduction of sulfate initiated at Eh of about -75 mV and was maximum in the range of -265 to -320 mV. Temperatur8e of the profile and organic carbon appear to be the key factors affecting the rate and extent of reduction in flooded FGD sludge. Selenium solubility decreased four times as Eh dropped from 215 mV to -350 mV while boron solubility was unchanged in this range of Eh. Stable isotopic ratio of sulfate and sulfide are typical of bacterial reduction and suggest that only aqueous sulfate was being reduced. The low δ³⁴S values of CaSO₄ from the upper layers of profile indicate the production and upward movement of hydrogen sulfide gas in the FGD sludge.
Dawood, Faik Ahmad (The University of Arizona., 1980)
This study consisted of laboratory and greenhouse experiments designed to determine the effect of sulfur waste materials on acidulation and other properties of calcareous soils. The laboratory experiment was conducted in the Soils, Water and Engineering Department, University of Arizona, for a period of nine weeks. Laveen soil (containing 6% CaCO₃) was treated with two levels of Morocco rock phosphate (0, 500 ppm P), and two different waste materials of sulfur, Cake S and Foam S, each with three levels (0, 5000, 10000 ppm). Treated soils were incubated for two periods (three and nine weeks) at 27°C and 66% water holding capacity. The design of the experiment was a complete randomized block with 24 treatments and two replications. Data were evaluated by analysis of variance and multiple means comparison tests for soil pH, soluble phosphorus, and sulfate, and regression analysis for the isotherm. Results showed that Foam sulfur had a greater effect as compared with Cake sulfur on soil pH, soluble phosphorus and sulfate and significantly shifted the isotherm to the right. Rock phosphate had no effect on soil pH and sulfate, but tended to decrease soluble phosphorus and shifted the isotherm to the left as compared with the control. The second experiment was conducted in the greenhouse near the Agricultural Sciences Building, University of Arizona, for a period of 32 weeks starting on August 20, 1979. Two calcareous soils, Pima and Laveen, (2% and 6% CaCO₃, respectively) were investigated with three levels of rock phosphate (0, 250, 500 ppm P), and three sources of sulfur (Cake, Foam and pure sulfur) each at two levels (0, 8000 ppm S). Two levels of super phosphate were used as a standard treatment. The chemical treatments were mixed with the soil and transferred to plastic pots and moistened to 70% water holding capacity, then covered with plastic sheets and incubated for eight weeks. Following the incubation, tomatoes were planted and grown for a six week period. Dry weights were measured only in the Pima soil but were eliminated due to poor stand in the Laveen soil. Barley was planted after the tomato harvest. Tomato and barley plants were irrigated with distilled water until the first harvest, after which barley was irrigated with tap water and CaSO₄ saturated to eliminate sulfur deficiency detected prior to the first harvest. The experiment was a complete randomized block design with 36 treatments and three replications. Data for soils and plants were evaluated by analysis of variance, multiple means comparison test, and regression analysis. From the results of this study the conclusions were as follows: (1) Foam sulfur tended to increase soluble P and Zn, lowered soil pH, and shifted the P isotherm to the right in the soil. Plant P and dry weight were increased more by the Foam S than Cake S and pure sulfur. However, Foam S tended to increase soluble salts more than Cake S and pure S. (2) Cake S also caused an increase in soluble P in the soil, reduced soil pH, and increased plant P and dry weight as well, although the effects were less than with Foam S. (3) Rock phosphate plus sulfur resulted in an increase in soluble P after 32 weeks of application. (4) Soils with low CaCO₃ content, higher organic matter content, and higher cation exchange capacity favored increased oxidation of sulfur to sulfate resulting in increased soluble P and lower soil pH. (5) Linear regression analysis of the P sorption isotherm was carried out by plotting the P remaining in the solution (ppm) on the X-axis versis P sorbed by the soil (ppm); a linear power function resulted. By this relationship, any regression equation can be used to evaluate the P status of a soil and the statistical differences between treatments.
Alsharari, Musaed Amish (The University of Arizona., 1999)
The effects of various application rates of gypsum (Aqua-cal = finely ground gypsum), langbeinite (K₂SO₄.2MgSO₄), and CaCl₂ (anhydrous) on exchangeable Na removal and saturated hydraulic conductivity of a sodic soil were investigated under laboratory batch studies and laboratory column leaching studies. The research involved four phases of studies. Characterization of the soil and irrigation water indicated that the soil sample is sodic (ESP=35.3), ECₑ = 3.36 dS/m), and the irrigation water is moderately saline (EC = 2.2 dS/m). The laboratory batch studies showed that CaCl₂ and langbeinite treatments were more efficient in the displacement of Na than gypsum which increased with increasing application rate. In contrast, with gypsum, Na displacement increased to a maximum at an application rate of 7 tons/ha; then, no further increase in displacement was observed above that level. In the column leaching studies, applied amendments at equivalent rates of 7 tons/ha each and leaching with 5 pore volumes of irrigation water resulted in a total Na displacement of 60%, 80%, and 84% for gypsum, langbeinite, and CaCl₂, respectively. Moreover, the SAR of the soil was reduced significantly in the above treatments from 34.5 in the beginning of leaching to 6.80 for gypsum (G7), from 41.8 to 5.60 for langbeinite (L₇), and from 32.6 to 2.5 for CaCl₂(7). When amendments were applied at higher rates (G7 tons/ha gypsum and 13 tons/ha of each of CaCl₂ and langbeinite), the % total Na displaced was 60%, 100%, and 94% for gypsum, langbeinite, and CaCl₂, respectively. The corresponding SAR values at the end of reclamation were 6.80, 4.50, and 5.50 for gypsum, langbeinite, and CaCl₂, respectively. The combination treatments significantly improved the reclamation at 0.05 level as compared to the G7 treatment alone and saved more leaching water and displaced higher exchangeable Na as compared to the gypsum treatment (G7) alone. Saturated hydraulic conductivity (Ks) studies indicated that Ks was increased significantly when the amendments were applied at equivalent weights (7 tons/ha) and at higher application rates as compared to the control. The Ks of the gypsum treated soil (G7) was significantly higher than Ks of langbeinite and CaCl₂ treated soil at both equivalent rates and when applied at higher rates L13 and CaCl₂(13).
Roane, Timberly Michelle (The University of Arizona., 1999)
Current thinking is that co-contaminated sites (i.e., sites with both organic and metallic pollutants) are difficult to bioremediate because the metal toxicity is such that organic degradation is inhibited. The objective of this research was to evaluate the potential of bioaugmentation with metal-detoxifying microbial populations as a viable remediative approach for such sites. Divided into three sections, this research found that metal-detoxifying microorganisms could facilitate the remediation of co-contaminated systems. The objective of the first study was to compare the microbial community response to cadmium exposure between metal-contaminated and uncontaminated soils. This study found that while cadmium adversely affected the numbers of culturable microorganisms in all soils, cadmium-resistant isolates were found in each soil, regardless of prior metal exposure. However, the metal-contaminated soil microbial communities were more resistant than the uncontaminated soil community. In one metal-stressed soil, resistance increased with increasing cadmium stress. A cadmium-resistant Pseudomonas spp. was found to increase in numbers with increasing cadmium, suggesting a different mechanism of cadmium resistance at high cadmium concentrations. The second study evaluated the diversity of cadmium-resistance/detoxification mechanisms in six cadmium-resistant isolates found in the first study. Genetic and microscopic analyses found several different approaches to cadmium resistance. Two mechanisms known to confer resistance were observed, including exopolymer and biosurfactant production. Two other isolates demonstrated intracellular cadmium accumulation via as yet unknown mechanisms. The mechanism of resistance for one isolate could not be identified. Four out of the six isolates detoxified cadmium as part of their resistance. Since metal detoxification is necessary to allow for organic degradation, these four isolates were included in 2,4-D degradation studies under co-contaminated conditions. The last study examined the use of cadmium-detoxifying microorganisms to enhance organic degradation under co-contaminated conditions. In pure culture and laboratory soil microcosms with cadmium and 2,4-dichlorophenoxyacetic acid (2,4-D) as model contaminants, four cadmium-detoxifying isolates supported the degradation of 2,4-D by the cadmium-sensitive 2,4-D degrader Alcaligenes eutrophus JMP134 in the presence of toxic levels of cadmium. Ina pilot field study, a cadmium-detoxifying Pseudomonas isolate enhanced 2,4-D degradation by A. eutrophus JMP 13 4 in the presence of cadmium.
Alsanabani, Mohamed Moslih. (The University of Arizona., 1991)
This work investigates several aspects of time domain reflectometry (TDR) theory and application. One of these aspects is the study of the influence of TDR probe geometries on the travel time. No change in the travel time resulted from increasing either the diameter of wire or spacing. However, we found a linear relationship between the travel time and the length of the probe for measurements in water. Also we found the reflected voltage was inversely proportionally to the incident voltage in water. Another aspect is the volume of sensitivity for the TDR which depends on the electrical properties of the medium and the geometry of the probe. The sensitivity of TDR in soil is different than in water. The observations in soils indicate that soil with a high water content (θᵥ) has a smaller sample volume than the one with low θᵥ. A probe with a large wire diameter has a larger sample volume than a probe with a small wire diameter. Also, a simple model and a mixing model were investigated and compared to Topp's model, for relating θᵥ to the effective dielectric constant. The distance to wetting front over time was observed and calculated using an expression which relates the travel time in soil before and after water application. This was tested with probes of different geometries. The wetting front from a point source were monitored for two and three dimensions in a plexiglas tank using TDR. Contour maps for the calculated radius of wetting front vs. the depth over time were produced.
Chech, Andrea M. (The University of Arizona., 2003)
A greenhouse lysimeter experiment was performed to evaluate the use of in-situ bioremediation and phyto-remediation to reduce mineral oil concentrations in a weathered contaminated soil. The hypotheses for the study were (1) a combination of microbial- and phyto-remediation would yield a best remediation strategy, and (2) the addition of low levels (10 mg/L) of a biosurfactant would stimulate and increase the rate of remediation by increasing the bioavailability of the mineral oil in the soil. The results indicate, on average, a higher rate of mineral oil removal occurred in planted lysimeter tanks versus non-planted lysimeter tanks. Specifically, for unplanted treatments an average of 22% of the mineral oil was removed in 24 weeks in comparison to the planted treatments for which an average of 54% of the mineral oil was removed. The effect of application of fertilizer on mineral oil degradation was unclear, but a visual inspection showed that vegetated tanks receiving fertilizer had better growth. No conclusions can be made regarding the addition of biosurfactant. Though a couple of the lysimeter tanks receiving biosurfactant performed relatively well, overall, the results were inconclusive. Enumeration of mineral oil degraders showed that there was a statistical difference between planted tanks and unplanted tanks with planted tanks having higher numbers. These results help support the conclusion that plants enhanced mineral oil degradation. Enumeration of total heterotrophs showed that there was no statistical significant difference between the planted and unplanted treatments. In conclusion, this study demonstrated that a low-cost, low-maintenance approach to facilitate remediation of weathered mineral oil contaminated soil is a combination of microbial- and phyto-remediation.
Coelho, Mardonio Aguiar. (The University of Arizona., 1974)
A study of soil variability was performed on an 87 hectare area within a uniform mapping unit--Pima Clay loam-- at The University of Arizona Branch Experiment Station at Marana. The primary interest was with respect to soilwater parameters. From 36 sites selected by an unbalanced three-stage nested design, 180 core samples were collected at 30 cm depth intervals to 150 cm. In addition, 500 bulk samples were taken at the 60 cm depth on an equally spaced grid over a secondary sampling area of 96 by 76 meters. The measured parameters showed different patterns of spatial variation. For example, to estimate means within 10% for the 30 cm depth 5, 51, and 1,011 samples would be needed for bulk density, the porosity index, and the saturated hydraulic conductivity, respectively (using the 0.05 level of significance). Most of the other estimates for number of samples required were in a range of 50 to 100. Most coefficients of variation were between 10 and 50% with bulk density lower and saturated hydraulic conductivity higher. Variance components for the three stages obtained from the analysis of variance revealed that the variation among fields was smaller than within fields and sections for the majority of the measured parameters, their average relative contribution to the total variance being 25, 44, and 31%, respectively. Values of 15-bar moisture retention corresponding to the 500 bulk samples showed a frequency distribution close to the normal with a slight tendency toward skewness. Values of bulk density were normally distributed at each depth and on the combined 180 samples. The highly skewed distributed values of the saturated hydraulic conductivity proved to be normally distributed after a logarithmic transformation. The porosity index showed a nonconsistent distribution pattern at the different depths and a moderately skewed frequency distribution for the composite 180 samples. Close relationships were found between bulk density and per cent sand and silt. A highly significant correlation (significant at th 0.01 level) between 15-bar water retention and clay content existed. Values of the logarithm of the hydraulic conductivity showed a high degree of correlation with values of per cent pores drained at 50 millibars (correlation coefficients of high absolute values and significant at the 0.01 level). Particle size distribution exhibited a decrease of silt and clay and a corresponding increase of sand with depth. The average percentages of sand, silt, and clay at 30 cm depth were 23.3, 41.2, and 35.3, and at the 150 cm depth were 39.7, 35.6, and 24.7, respectively. A similar trend was revealed for bulk density which ranged from 1.42 at 30 cm depth to 1.57 g/cm³ at the 150 cm depth. Soil moisture release curves for each depth showed similar general shapes. The "porosity index" describing the moisture release curve in the low pressure range varied from 3.58 at 30 cm depth to 5.79 at the 150 cm depth. Mean values of the saturated hydraulic conductivity also tended to increase with depth--1.71 and 7.03 cm/hr at 30 and 150 cm depth, respectively. Comparison between the sampling scheme used and three-stage balanced designs revealed that at least two alternatives would be more effective in decreasing the variance of the mean, but they do not provide any degrees of freedom for the third stage. An apparent compromise was found to exist between the scheme used and the optimum unbalanced designs selected for efficient estimation of variance components for the majority of the measured parameters.
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