Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1974. / Bibliography: leaves 160-167. / xiv, 167 leaves ill

CAPES / A adubação nitrogenada é freqüentemente observada como um eficiente fator nutricional fornecido a planta visando melhorar a produção de espécies forrageiras, necessitando ser entendido o comportamento do nitrogênio (N) no sistema. O experimento foi conduzido na área do Instituto Agronômico do Paraná (IAPAR) na estação experimental de Pato Branco, com objetivo de avaliar a dinâmica do N no sistema solo-planta em pastagem de Brachiaria plantaginea. O delineamento experimental foi o de blocos ao acaso com duas repetições. Os tratamentos foram arranjados em parcelas subdivididas. Nas parcelas foram alocados os períodos e nas sub-parcelas a combinação das três doses de N e duas intensidades de pastejo (Massa Alta e Massa Baixa), perfazendo seis tratamentos em esquema fatorial. As doses de N foram compostas de 0, 200 e 400 kg.ha-1 de N e as intensidades de pastejo preconizadas em massa baixa (MB), com 1.500 kg de MS.ha-1, e massa alta (MA) com 3.000 kg de MS.ha-1 em pastejo com lotação contínua e taxa de lotação variável. Utilizaram-se caprinos, meio sangue Bôer, com cinco meses de idade e peso médio de 21 Kg de peso vivo (PV), para definir as massas de forragem (MF) preconizadas. Avaliou-se a produção acumulada e total de biomassa aérea de papuã nos períodos experimentais, os índices nutricionais de nitrogênio, fósforo e potássio, também a curva de diluição, eficiência e recuperação do nitrogênio e o comportamento do nitrogênio no solo. A produção de forragem de B. plantaginea foi maior na dose intermediaria de N (200 kg de N.ha-1), atingindo uma produção de 19.834 kg de MS.ha-1, 31% a mais que no tratamento que não recebeu adubação nitrogenada. Os teores de N encontrados nas plantas que receberam adubação nitrogenada apresentaram valores superiores aos preconizados como críticos, resultando em conteúdos adequados deste elemento na planta, e, ao contrário, as plantas cultivadas sem adubação nitrogenadas apresentaram teores inferiores ao crítico, apontando desta forma que a curva de diluição de N é uma ferramenta adequada para diagnose de nutrição nitrogenada em pastagens. A máxima produtividade foi limitada pela falta de fósforo indicada pelo baixo índice de fósforo obtido conforme os teores do elemento na pastagem e a absorção de K aumentou com a adubação nitrogenada apresentando índices satisfatórios do elemento. A dose de 200 kg de N.ha-1 demonstrou-se a mais eficiente com taxas de recuperação de N superiores em 63% em relação a dose de 400 kg de N.ha-1. Não foi observada lixiviação das formas de nitrogênio inorgânicas estudas (nitrato e amônio) no perfil do solo e observou-se maior quantidade de nitrato e N-Mineral na menor massa de forragem após completada a quantidade de N proposta. / Nitrogen fertilization is usually noticed as an efficient nutritional factor offered to the plant with the aim to improve its production, being necessary to understand the nitrogen behave (N) in the system. The experiment was carried out at the Agronomist institute of Paraná (IAPAR), experimental unit of Pato Branco with the aim to evaluate the dynamic of N in the soil-plant system of a Brachiaria plantaginea. The experiment was laid out as random block design with two replications. The treatments were arranged in a split-plot model. At the plots were allocated the periods and at the sub-plots the combination of three levels of nitrogen and two grazing intensities (High mass and Low Mass), making six treatments in a factorial scheme. The levels of nitrogen used were composed of 0, 200 and 400 kg of N.ha-1 and the grazing intensities characterized by the low forage mass (LM) with 1.500 kg of DM.ha-1 and high forage mass (HM) with 3000 kg of DM.ha-1 in a continuous stocking rate. Were used goats half blood Boer with five months old and average life weight of 21 kg of live weight (LW) at the beginning of the experiment with the aim to adjust the forage mass (FM) wanted. Was evaluated the accumulate and total forage production of the papuã aerial biomass at the experimental periods, the nutritional indices of nitrogen, phosphorous and potassium and also the dilution curve, efficiency of N recovery and behave of nitrogen in the soil. The Brachiaria plantaginea forage production was higher at the nitrogen intermediate level (200 kg of N.ha-1), reaching an production of 19.834 kg of DM.ha-1, 31% more then treatment without nitrogen. The N levels found in the plants that received nitrogen fertilization showed higher values than the ones recognized as deficient, resulting in adequate contents of this element in the plant and, in the other hand, the plants cultivated without nitrogen showed levels below the one recognized as sufficient, showing with that the dilution curve of N is an adequate tool to diagnose the forage nitrogen nutrition. The highest production was limited by the lack of phosphorous showed by the phosphorous indices obtained according to the pasture element levels and the absorption of K increased with the nitrogen application, showing satisfactory level of the element. The 200 level of N.ha-1 showed to be the most efficient with recovery N levels 63% higher than the 400 kg.N.ha-1. There was no inorganic (NO3 - e NH4 +) N leaching found in the soil profile and was noticed higher quantities of NO3 - and mineral-N at the lower forage mass after finishing the total N applied.

CAPES / A adubação nitrogenada é freqüentemente observada como um eficiente fator nutricional fornecido a planta visando melhorar a produção de espécies forrageiras, necessitando ser entendido o comportamento do nitrogênio (N) no sistema. O experimento foi conduzido na área do Instituto Agronômico do Paraná (IAPAR) na estação experimental de Pato Branco, com objetivo de avaliar a dinâmica do N no sistema solo-planta em pastagem de Brachiaria plantaginea. O delineamento experimental foi o de blocos ao acaso com duas repetições. Os tratamentos foram arranjados em parcelas subdivididas. Nas parcelas foram alocados os períodos e nas sub-parcelas a combinação das três doses de N e duas intensidades de pastejo (Massa Alta e Massa Baixa), perfazendo seis tratamentos em esquema fatorial. As doses de N foram compostas de 0, 200 e 400 kg.ha-1 de N e as intensidades de pastejo preconizadas em massa baixa (MB), com 1.500 kg de MS.ha-1, e massa alta (MA) com 3.000 kg de MS.ha-1 em pastejo com lotação contínua e taxa de lotação variável. Utilizaram-se caprinos, meio sangue Bôer, com cinco meses de idade e peso médio de 21 Kg de peso vivo (PV), para definir as massas de forragem (MF) preconizadas. Avaliou-se a produção acumulada e total de biomassa aérea de papuã nos períodos experimentais, os índices nutricionais de nitrogênio, fósforo e potássio, também a curva de diluição, eficiência e recuperação do nitrogênio e o comportamento do nitrogênio no solo. A produção de forragem de B. plantaginea foi maior na dose intermediaria de N (200 kg de N.ha-1), atingindo uma produção de 19.834 kg de MS.ha-1, 31% a mais que no tratamento que não recebeu adubação nitrogenada. Os teores de N encontrados nas plantas que receberam adubação nitrogenada apresentaram valores superiores aos preconizados como críticos, resultando em conteúdos adequados deste elemento na planta, e, ao contrário, as plantas cultivadas sem adubação nitrogenadas apresentaram teores inferiores ao crítico, apontando desta forma que a curva de diluição de N é uma ferramenta adequada para diagnose de nutrição nitrogenada em pastagens. A máxima produtividade foi limitada pela falta de fósforo indicada pelo baixo índice de fósforo obtido conforme os teores do elemento na pastagem e a absorção de K aumentou com a adubação nitrogenada apresentando índices satisfatórios do elemento. A dose de 200 kg de N.ha-1 demonstrou-se a mais eficiente com taxas de recuperação de N superiores em 63% em relação a dose de 400 kg de N.ha-1. Não foi observada lixiviação das formas de nitrogênio inorgânicas estudas (nitrato e amônio) no perfil do solo e observou-se maior quantidade de nitrato e N-Mineral na menor massa de forragem após completada a quantidade de N proposta. / Nitrogen fertilization is usually noticed as an efficient nutritional factor offered to the plant with the aim to improve its production, being necessary to understand the nitrogen behave (N) in the system. The experiment was carried out at the Agronomist institute of Paraná (IAPAR), experimental unit of Pato Branco with the aim to evaluate the dynamic of N in the soil-plant system of a Brachiaria plantaginea. The experiment was laid out as random block design with two replications. The treatments were arranged in a split-plot model. At the plots were allocated the periods and at the sub-plots the combination of three levels of nitrogen and two grazing intensities (High mass and Low Mass), making six treatments in a factorial scheme. The levels of nitrogen used were composed of 0, 200 and 400 kg of N.ha-1 and the grazing intensities characterized by the low forage mass (LM) with 1.500 kg of DM.ha-1 and high forage mass (HM) with 3000 kg of DM.ha-1 in a continuous stocking rate. Were used goats half blood Boer with five months old and average life weight of 21 kg of live weight (LW) at the beginning of the experiment with the aim to adjust the forage mass (FM) wanted. Was evaluated the accumulate and total forage production of the papuã aerial biomass at the experimental periods, the nutritional indices of nitrogen, phosphorous and potassium and also the dilution curve, efficiency of N recovery and behave of nitrogen in the soil. The Brachiaria plantaginea forage production was higher at the nitrogen intermediate level (200 kg of N.ha-1), reaching an production of 19.834 kg of DM.ha-1, 31% more then treatment without nitrogen. The N levels found in the plants that received nitrogen fertilization showed higher values than the ones recognized as deficient, resulting in adequate contents of this element in the plant and, in the other hand, the plants cultivated without nitrogen showed levels below the one recognized as sufficient, showing with that the dilution curve of N is an adequate tool to diagnose the forage nitrogen nutrition. The highest production was limited by the lack of phosphorous showed by the phosphorous indices obtained according to the pasture element levels and the absorption of K increased with the nitrogen application, showing satisfactory level of the element. The 200 level of N.ha-1 showed to be the most efficient with recovery N levels 63% higher than the 400 kg.N.ha-1. There was no inorganic (NO3 - e NH4 +) N leaching found in the soil profile and was noticed higher quantities of NO3 - and mineral-N at the lower forage mass after finishing the total N applied.

An incubation technique was used to examine carbon mineralization and inorganic nitrogen accumulation in samples of Douglas-fir and alder forest floors developed over soils derived from granitic, ultrabasic and limestone parent materials in western British Columbia and Washington. Samples included L, F, and H or Hi horizons of Douglas-fir mor, raw moder, mull-like moder and mull forest floors and alder typical moder forest floors. Carbon dioxide production by the forest floor materials provided an estimate of gross carbon mineralization and an approximate indication of gross nitrogen mineralization. Comparison of inorganic nitrogen accumulated and gross carbon mineralized indicated that a large fraction of the mineralized inorganic nitrogen is immobilized by the microbial population and (or) lost to denitrification. The Hi horizons (organic horizons containing considerable incorporated mineral matter) accumulated more inorganic nitrogen than did the L and F horizons. Alder forest floors accumulated more inorganic nitrogen than did Douglas-fir forest floor materials. Alder L horizons tended to accumulate ammonium nitrogen while the F and Hi horizons accumulated nitrate nitrogen. Douglas-fir mor forest floors were distinguished from their mull and moder counterparts by slower decomposition and less inorganic nitrogen accumulation, and by largely accumulating ammonium nitrogen in all horizons. Irregular nitrogen accumulation curves, for some samples of Douglas-fir L and F horizons were probably due to denitrification losses. Incubation conditions favoring nitrification, with no plant sinks to remove accumulated inorganic nitrogen, may have favored denitrification losses. / Land and Food Systems, Faculty of / Graduate

Understanding the redistribution and fate of N is essential for justification of Best Management Practices (BMP). This project was conducted on a Hecla fine sandy loam (sandy, mixed, Aquic Haploboroll) soil at the BMP field site near Oakes, North Dakota. One objective of this investigation was to evaluate the residence times of N03- -N in 20 undisturbed lysimeters and its infiltration time through the soil profile to tile drains. Corn (Zea mays L.) was fertilized with 135 kg N ha -1 as ¹⁵N-enriched urea plus 13.5 and 48.1 kg N ha -1 preplant for 1993 and 1994, respectively. Urea-N was band applied to 20 and 10 undisturbed lysimeters at 2.0 and 5.93 atom percent (at %) ¹⁵N in 1993 and 1994, respectively. Average resident times of N03- -N in the lysimeters was 11.7 months. Lysimeter and tile drainage indicate the presence of preferential pathways. Residence times of N03- -N depend on frequency and intensity of precipitation events. Another objective was to determine what portion of the total N in the crop was from applied urea-N and what portion was from the native soil-N. Nitrogen plots received ¹⁵N enrichments of 4.25 and 5.93 at % ¹⁵N in 1993 and 1994, respectively. At the end of the 1993 and 1994 growing season, 41.5% and 35.7% of the labeled fertilizer N remained in the soil profile, while the total recovery of applied ¹⁵N in the soil-plant system was 86.2% and 75.4%, respectively. Low recoveries of applied N may have been the result of soil or aboveground plant biomass volatilization, or denitrification or preferential flow processes. Further research needs to be conducted with strict accountability of gaseous loss and the mechanism(s) responsible. / U.S. Bureau of Reclamation

No description available.

No description available.

No description available.

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.