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Nitrogen is an essential nutrient for plant and animal life; however, its presence in concentrations exceeding assimilative capacities of receiving water bodies is undesirable. Therefore, the form and concentration of total nitrogen released in wastewater effluents is of great concern. During the course of this study, the nitrogen analysis was performed on the various unit processes of the Florida Technological University wastewater treatment plant. The average percent removal of nitrogen between plant influent and clarifier effluent was 30.5% during the month of August 1975. It is believed that the nitrogen removal is attributed to luxury uptake by the biomass through the plant. The clarifier effluent was highly nitrified containing an average ammonia nitrogen concentration of 0.76 milligrams per liter and a nitrate nitrogen concentration of 16.47 milligrams per liter. The extent to which nitrification took place was 93 - 98% with an average of 96.5% for the month of August.

Nitrogen deficiencies have long been acknowledged as a factor limiting the restoration of ecosystems destroyed by surface mining in the Appalachian Region of the U.S. The fundamental ecological structure and function common to intact terrestrial ecosystems are largely lacking in mine soils. Reliable guidelines for effective long-term restoration require a detailed understanding of the ecological processes occurring within the mine-soil system. The objective of this study was to determine the extent to which inorganic N fertilization, native topsoil replacement, or whole-tree wood-chip amendment affected the restoration and reforestation of an Appalachian mine-soil system through changes in C and ~ dynamics. Eighteen concrete tank lysimeters filled with mine spoils served as experimental microcosms to test hypotheses set forth in this study. Treatment effects on soil N and C pools, herbaceous biomass production, N uptake, N fluxes between pools, net leachate N losses, and early growth of pitch x loblolly hybrid pines were evaluated at regular intervals between July 1987 and October 1989. Inorganic N fertilization increased aboveground herbaceous biomass yield and N uptake by 87 and 71%, respectively, during the first growing season, but did not significantly affect yield or N uptake thereafter. During the first growing season, biomass production was 38% higher in the topsoil-amended mine soil than the unamended control. This resulted in an additional 17.4 kg N ha-1 sequestered in comparison to the control. Biomass yield was 270 and 19% lower in the wood-chip-amended mine soil than the unamended control after the first and third growing seasons, respectively. This resulted in 63 and 25% less N uptake, respectively, than the control. Survival of pitch x loblolly pine after two growing seasons was 90% in the N-fertilized mine soil and 71% with the fertilizer control treatment. This difference in survival was the result of lower water potential in the unamended mine soil during the growing season in which the trees were planted. Nitrogen fertilization did not significantly affect tree growth or nutrition. Pine survival after two growing seasons was 83, 98, and 60% for the unamended control, wood-chip, and topsoil treatments, respectively. By the end of the second growing season, the wood-chip treatment also resulted in greater tree height, ground-line diameter, and stem-volume index by 30, 49, and 203% respectively, when compared to the control. Increased survival and growth in the wood-chip-amended mine soil were directly related to higher soil water potential than the control or topsoil treatments. Total inorganic N leaching loss from N-fertilized mine soil was 47.64 kg ha-1 yr-1 higher than the control during the first growing season. However, N fertilization losses were not significantly higher during the remainder of the study period. Drainage was significantly higher during all three growing seasons in the wood-chip-amended mine soil. This resulted in lower N sequestering during the third growing season when precipitation was most abundant. Topsoil amendment did not significantly affect N leaching losses. Inorganic N fertilization did not significantly affect total organic C, total N, or N availability indices in the mine soil. Following topsoil addition, mine-soil total N was 294% higher than the unamended control. Wood-chip effects on the soil organic-matter pool were more gradual; however, by the end of the study, total N and total organic C were 18 and 95% higher, respectively in the wood-chip-amended mine soil than in the unamended control. Aerobic incubation of soil samples collected near the end of the second growing season showed that the topsoil and wood-chip amendments increased the N mineralization potential by 101 and 55%, respectively, in comparison to the unamended control. Furthermore, the mineralization rate constant of the wood-chip-amended mine soil was 44% lower than the control. This shows a slower rate of N turnover and more stable mine-soil N pool with the wood-chip treatment. This study shows that inorganic N fertilizer effects on N and C dynamics were rapid but transient. In contrast, the surface-applied amendments of native topsoil and whole-tree wood chips improved the potential for successful restoration of forests by increasing the N cycling capacity of the developing mine-soil system. / Ph. D.

1. Mechanisms of urea adsorption by soils Physically adsorbed urea may be easily desorbed by dilution. Chemisorbed urea existing primarily in the form of relatively stable soil organic matter-urea complexes may, in part, be slowly dissociated upon dilution. Differences between soil types with respect to urea adsorption were primarily related to organic matter contents; the effects of CEC, pH, and clay mineral content were found to be insignificant. Wet soils had a lower capacity for urea adsorption than dry soils. Considering the amounts of urea adsorbed it appears that soils have a weak affinity for the urea molecule. 2. Mechanisms of urea hydrolysis and volatilization in soils The biological or catalytic hydrolysis of urea is rapid and can be related to soil microbial activities. The reaction rate of the chemical hydrolysis of urea is very slow and insignificant in comparison with the biological or catalytic hydrolysis. Urea-nitrogen loss through ammonia volatilization may immediately follow urea hydrolysis and proceeds rapidly. Urea hydrolysis and ammonia volatilization from ammonium carbonate are first order reactions. 3. Mechanism of foliar absorption and subsequent utilization of urea The mechanism of foliar absorption of urea solution is suggested to be a simple physical diffusion phenomenon. The absorbing capacity of the foliage for urea solution is relatively lover during the day than during the night. It is suggested that rapid evaporation at high temperature and low humidity conditions may increase the concentration of the urea solution on the leaf thereby decreasing the rate of diffusion of foliar applied urea into the leaf. The absorbing capacity of the leaf for urea solution is independent of its position, but the younger leaves have a higher capacity to metabolize the absorbed urea. Urea in foliage cannot be translocated, but more than 90%of the absorbed urea can be rapidly and directly transformed into other soluble nitrogenous compound(s). The mechanism of the biochemical reactions and their related enzymatic systems are not yet known. Sucrose does not influence the urease activity, and no urease activity was detected in the tobacco leaves used. The reduction of urea injury from foliar applied urea solutions containing sucrose was associated with decreased urea absorption and increased urea utilization. A relationship was found to exist between the urea concentration in the leaf and the incidence of injury. Plasmolysis resulting from increased urea concentrations in the leaf may be the cause of foliage burning resulting from foliar application of urea. 4. Methodology The principle of the newly developed methods for the determination of urea in fertilizers, urine, and blood and the estimation of urease activity is based on the difference in electric conductivity of urea and ammonium carbonate produced from urea by urease in solution. These methods are rapid, simple and accurate. They have very wide testing ranges, and the values of the standard curves are constant at a specified temperature. Interference due to the presence of colored impurities are eliminated. However, these methods will not be applicable if heavy metal ions such as Ag, Hg, and the protein-destroying substances are present in the testing solution. / Ph. D.

M.S.

Free energy changes of oxidative inorganic nitrogen transformations in acid and basic media were calculated and interrelated. The free energy values of reactions involving nitrification were not always found to be in agreement with those reported in the literature. The primary reason for the deviations was that the pH of the medium had often not been considered in formulating these reactions. It was also found that thermodynamically, hyponitrous acid and nitrous oxide might well be intermediates in the process of nitrification. The existence of hydroxylamine as an intermediate between ammonia and/or ammonium ion and nitrite was not supported by the data obtained. It was shown that in acid solutions nitrite may thermodynamically undergo three reactions; it may decompose to nitric oxide, oxidize to nitrate or be reduced to nitrous oxide. In alkaline solutions nitrate seems to be the only product. Ammonia volatilization and water evaporation from the soils investigated followed different functions and may be independent of each other. The functions were not affected by differences in soil texture, soil water, speed and relative humidity of air flowing over the soil surfaces. Ammonia losses from finer-textured soils were proportional to their original soil pH's. Norfolk fine sandy loam, pH 6.7, lost most ammonia indicating that soil texture is also an important factor in ammonia volatilization. A linear relationship was observed between rate of ammonia applied (up to 600 ppm) and ammonia volatilized. The rate of ammonia volatilization followed a first-order reaction. Deviations from a first-order reaction were observed when higher levels of ammonia were applied. In regard to mechanisms of ammonia adsorption by soils it was found that at low concentrations, ammonia adsorption followed Langmuir's monomolecular adsorption theory. The differential slopes obtained for different sections of the curves were related to reactions involving "hydrogen", exchange sites and physical adsorption. The S-shaped curve obtained for high concentrations suggests the formation of polymolecular layers. Ammonia adsorption by neutral and basic soils also gave a typical Freundlich adsorption isotherm and furthermore closely simulated the behavior of a buffer medium. In fine-textured soils the amount of ammonia retained was inversely related to the original soil pH. The subsequent difference in adsorption capacity for ammonia between Yolo loam and Davidson clay, and between the buffer medium and Norfolk fine sandy loam seems to indicate that kind and amount of salt and/or weak acid may have a greater effect on ammonia adsorption than pH. Between texture groups, texture appears to exert a major influence on ammonia adsorption capacity. / Ph. D.

Fresh market broccoli (Brassica oleracea L. var italica) production is increasing in southcentral Virginia because it provides growers with a new economic opportunity while complementing the traditional tobacco-growing in that region. Little research data is available for vegetable fertilization on these southern Piedmont soils. The objectives of this study were to amend the current recommended nitrogen rates for broccoli production, and to measure plant N uptake and soil nitrate status throughout the growing season in order to develop an efficient N fertilization program for this emerging industry. A preliminary study in 1985 indicated no significant yield response to eight treatments varying in amount of total N applied from 56 to 290 kg N/ba. A more detailed study was conducted in 1986 with N treatments expanded as follows: main plot factor of base rate N at 0, 56, 112, and 168 kg N/ha, and 3 subplot factors of 0, 1, or 2 sidedressings at 56 kg N/ha each applied at 3 and 6 weeks after seeding. Yield differences for base rate N were significant at the first harvest only, while sidedressing effects on yield were significantly different for 3 of the 4 harvests and total yield. Nitrogen uptake during the first 32 days after seeding (DAS) was minimal, 0.17 kg N/ha/day, but increased to 8.05 kg N/ha/day during head formation (55 to 77 DAS). Initial soil nitrate status was 52 kg NO₃-N/ha in the top 25 cm and decreased to 10.6 kg NO₃-N/ha in the control plot by the end of the season. Total N uptake of broccoli with no fertilizer applied averaged 200 kg N/ha demonstrating the capability of these soils to supply N. These results suggest the current practice of applying the first sidedressing at 3 weeks after seeding may not be necessary. However, later sidedressings, prior to and during head formation, are recommended to maintain an adequate available nitrogen supply throughout the growing season. / M.S.

Graduation date: 1996

Some cyanobacteria strains have biofertilization and bioconditioning effects in soils. The objective of this study was to identify cyanobacteria with potential to improve the N fertility and structural stability of degraded soils and evaluate their effectiveness in soils of the Eastern Cape, South Africa. Isolation and characterization of the indigenous cyanobacteria strains with desirable properties was first to be undertaken because their effects are known to differ from strain to strain. Cyanobacteria strains 3g, 3v, and 7e were identified from 97 strains isolated from selected soils. Nostoc strains 3g and 3v had greater ability to produce exocellular polysaccharides (EPS) but low potential to fix atmospheric N2 (4.7 and 1.3 nmol C2H4 μg chl-1 h-1, respectively). On the other hand, strain 7e had the highest capability to fix atmospheric N2 (16.1 nmol C2H4 μg chl-1 h-1) but had the least ability to produce EPS. Evaluation of the strains was done in glasshouse studies starting with Nostoc strain 9v isolated from a Tanzanian soil, followed by the indigenous strains isolated from soils in Hertzog and Qunu, South Africa. Inoculation was done by uniformly applying cyanobacteria on the surface of potted soils at a rate of 6 g m-2. First harvest and soil sampling took place after six weeks, and the top 25 mm of the soil was mixed, replanted, and sampled again after a further six weeks (second harvest). Inoculation with Nostoc strain 9v increased soil N by 40 percent and 17 percent in Guquka and Hertzog soils, respectively, and consequently increased maize dry matter yields by 40 and 49 percent. Soil C increased by 27 percent and 8 percent in Guquka and Hertzog soils, respectively, and this increase was significantly associated with that of soil N (R2 = 0.838). Higher contents of soil C, soil N and mineral N, however, were found in non-cropped soils. Scanning Electron Microscopy (SEM) revealed coatings of EPS on soil particles and fragments of non-cropped inoculated soils, with iii other particles enmeshed in networks of filaments, in contrast to cropped and/or non-inoculated soils. The proportion of very stable aggregates was increased by inoculation but cropping with maize reduced the aggregate stability. Inoculating Hertzog soil with indigenous strains 3g and 7e increased the nitrate N in the first cropping by 49 percent and 69 percent respectively, in cropped soils. In the second cropping increases in mineral N were 41 percent and 43 percent in 3g and 7e inoculated soils, respectively. Maize dry matter yields were higher on inoculated soils both in the first and second harvest in response to the improved N status of the soil. Increases in aggregate MWD in cropped soil as determined by fast wetting, mechanical breakdown and slow wetting were 85 percent, 33 percent, 33 percent, respectively, for 3g inoculation, 64 percent, 41 percent, and 41 percent, respectively, for 7e inoculation and 60 percent, 24 percent, 50 percent for inoculation with 9v. In non-cropped soil, increases in MWD as determined by fast wetting, mechanical breakdown and slow wetting were 11 percent, 0 percent, 7 percent, respectively for 3g inoculation, 21 percent, 11 percent, and 7 percent, respectively for 7e inoculation, and 25 percent, 36 percent, and 19 percent for strain 9v inoculation. Scanning electron microscopy observations, which were confirmed by chemical results, revealed that inoculated soils had high EPS and filaments that encouraged soil aggregation and improved aggregate stability. Results of this study show that cyanobacteria strains isolated and selected for their ability to fix atmospheric N2 and produce EPS improved the fertility status and aggregate stability of degraded soils from South Africa.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy