A adição ao solo de resíduo vegetal de elevada relação C/N no sistema \"cana crua\", afeta o equilíbrio entre os processos de entrada e saída do N no sistema solo-planta-atmosfera. Assim, a presença da palhada modifica o agrossistema fazendo-se necessários ajustes no manejo da fertilização nitrogenada. Nesse sentido, quatro estudos foram desenvolvidos com os seguintes objetivos: (i) Avaliar as características produtivas e nutricionais da cultura da cana-de-açúcar de modo a identificar a fonte e a dose de N de maior eficiência agronômica; (ii) Quantificar a recuperação do N proveniente do fertilizante pela cana-de-açúcar; (iii) avaliar o potencial de inibição do íon cloreto na nitrificação no solo; (iv) avaliar as taxas de mineralização e imobilização do N-fertilizante e a sua interação com o Nnativo do solo. Em campo, foi conduzido um experimento em Latossolo Vermelho distróficocom cana-de-açúcar. O delineamento experimental foi o de blocos casualizados, com quatro repetições e nove tratamentos, com as fontes nitrogenadas: sulfato de amônio, YaraBela NitromagTM, nitrato de amônio e ureia na dose de 100kg ha-1 de N, cloreto de amônio, nas doses de N: 50, 100, 150 e 200 kg ha-1, e controle. Foram instaladas microparcelas com aplicação das fontes marcadas no isótopo 15N na dose de 100 kg ha-1 de N. Os fertilizantes nitrogenados foram aplicados manualmente, sobre a palhada. Posteriormente, amostras do solo coletadas previamente foram incubadas aerobiamente por um período de 21 dias. O delineamento experimental foi o inteiramente casualizado com quatro repetições e os tratamentos constaram da combinação de sulfato de amônio ou cloreto de amônio, na dose de 100 mg kg-1 de nitrogênio, com cloreto de potássio na dose de 100 ou 200 mg kg-1 de cloro. Avaliou-se, também, doses de cloreto de amônio (50, 100 e 200 mg kg-1 de N). As formas de N-mineral foram determinadas por meio de sistema de análise por injeção em fluxo. Amostras de solo foram, também, incubadas aerobiamente por um período de 20 semanas. O delineamento experimental foi o inteiramente casualizado com três repetições e seis tratamentos, constituindo-se um fatorial 3x2 (Namídico, N-amoniacal ou sem N versus com ou sem resíduo de cana). As fontes nitrogenadas (enriquecidas com 2% em átomos de 15N) foram aplicadas superficialmente no solo na dose de 100 mg kg-1 de N e o resíduo de cana-de-açúcar incorporado na dose de 5,2 g kg-1. O fornecimento de doses de N na forma de cloreto de amônio resultou em decréscimo de produtividade de colmos e açúcar. As fontes nítrico/amoniacais promoveram maior atividade da enzima redutase do nitrato nas folhas da cana-de-açúcar, porém, não apresentaram influência no acúmulo total de N. O aproveitamento do N-fertilizante pela cana-de-açúcar foi da ordem de 60% nos estádios iniciais, reduzindo-se para aproximadamente 20% próximo à fase de maturação. O íon cloreto reduziu a concentração de nitrato no solo devido a ação do ânion na reação de nitrificação. A incorporação de resíduo de cana-de-açúcar ao solo promoveu maiores taxas de imobilização do N e a aplicação de sulfato de amônio resultou em maior mineralização do N nativo do solo comparado a ureia. / The addition of plant residue with high C/N ratio to the soil in a \"green cane\" system affects the balance of input/output processes of N in a soil-plant-atmosphere system. Thus, the presence of straw modifies the agroecosystem requiring adjustments in management of nitrogen fertilization. Accordingly, four studies were developed to: (i) evaluate the nutritional and productive characteristics of sugarcane crops to identify the source and N rates of greater agronomic efficiency; (ii) quantify the sugarcane N recovery from fertilizers; (iii) assess the potential inhibition of chloride ion in reaction to soil nitrification, (iv) evaluate mineralization and immobilization rates of fertilizer-N and their interaction with the native soil N. We conducted a field experiment on a Typic Hapludox with sugarcane, in the 2009/2010 harvest. The experimental design was a randomized block with four replications and nine treatments with nitrogen sources: ammonium sulfate, YaraBela NitromagTM, ammonium nitrate and urea at 100 kg N ha-1, ammonium chloride at N doses: 50, 100, 150 and 200 kg ha-1 and control. Microplots were installed with application of nitrogen sources labeled 15N at 100 kg N ha-1. Nitrogen fertilizers were applied manually over straw. Subsequently, previously collected soil samples were incubated aerobically for 21 days. The experimental design was completely randomized with four replications and the treatments consisted of ammonium sulfate or ammonium chloride at 100 mg N kg-1 with potassium chloride at a chlorine dose 100 or 200 mg kg-1. We also evaluated doses of ammonium chloride (50, 100, and 200 mg N kg-1). Forms of mineral-N were determined by Flow Injection Analysis (FIA) system. Soil samples were incubated aerobically for 20 weeks. The experimental design was completely randomized with three replications and six treatments, comprising a 3x2 factorial (amidic-N, ammonium- N or without N versus with or without cane residue). Nitrogen sources (enriched with 2 atom% 15N) were applied to the soil surface at a N dose of 100 mg kg-1 and residue sugarcane incorporated at 5.2 g kg-1. The N supply in ammonium chloride form resulted in decreased yield of sugar and stalks. Nitric-ammonium sources promoted higher activity of nitrate reductase in sugarcane leave; however, they did not affect total N accumulation. The sugarcane recovery of fertilizer-N was approximately 60% in early stages, dropping to about 20% near the maturity stage. The chloride ion reduced nitrate concentration in soil due to the anion action in the nitrification reaction. The sugarcane residue incorporation to the soil showed higher N immobilization rates and the use of ammonium sulfate resulted in higher N mineralization rates of native soil N compared to urea.

A adição ao solo de resíduo vegetal de elevada relação C/N no sistema \"cana crua\", afeta o equilíbrio entre os processos de entrada e saída do N no sistema solo-planta-atmosfera. Assim, a presença da palhada modifica o agrossistema fazendo-se necessários ajustes no manejo da fertilização nitrogenada. Nesse sentido, quatro estudos foram desenvolvidos com os seguintes objetivos: (i) Avaliar as características produtivas e nutricionais da cultura da cana-de-açúcar de modo a identificar a fonte e a dose de N de maior eficiência agronômica; (ii) Quantificar a recuperação do N proveniente do fertilizante pela cana-de-açúcar; (iii) avaliar o potencial de inibição do íon cloreto na nitrificação no solo; (iv) avaliar as taxas de mineralização e imobilização do N-fertilizante e a sua interação com o Nnativo do solo. Em campo, foi conduzido um experimento em Latossolo Vermelho distróficocom cana-de-açúcar. O delineamento experimental foi o de blocos casualizados, com quatro repetições e nove tratamentos, com as fontes nitrogenadas: sulfato de amônio, YaraBela NitromagTM, nitrato de amônio e ureia na dose de 100kg ha-1 de N, cloreto de amônio, nas doses de N: 50, 100, 150 e 200 kg ha-1, e controle. Foram instaladas microparcelas com aplicação das fontes marcadas no isótopo 15N na dose de 100 kg ha-1 de N. Os fertilizantes nitrogenados foram aplicados manualmente, sobre a palhada. Posteriormente, amostras do solo coletadas previamente foram incubadas aerobiamente por um período de 21 dias. O delineamento experimental foi o inteiramente casualizado com quatro repetições e os tratamentos constaram da combinação de sulfato de amônio ou cloreto de amônio, na dose de 100 mg kg-1 de nitrogênio, com cloreto de potássio na dose de 100 ou 200 mg kg-1 de cloro. Avaliou-se, também, doses de cloreto de amônio (50, 100 e 200 mg kg-1 de N). As formas de N-mineral foram determinadas por meio de sistema de análise por injeção em fluxo. Amostras de solo foram, também, incubadas aerobiamente por um período de 20 semanas. O delineamento experimental foi o inteiramente casualizado com três repetições e seis tratamentos, constituindo-se um fatorial 3x2 (Namídico, N-amoniacal ou sem N versus com ou sem resíduo de cana). As fontes nitrogenadas (enriquecidas com 2% em átomos de 15N) foram aplicadas superficialmente no solo na dose de 100 mg kg-1 de N e o resíduo de cana-de-açúcar incorporado na dose de 5,2 g kg-1. O fornecimento de doses de N na forma de cloreto de amônio resultou em decréscimo de produtividade de colmos e açúcar. As fontes nítrico/amoniacais promoveram maior atividade da enzima redutase do nitrato nas folhas da cana-de-açúcar, porém, não apresentaram influência no acúmulo total de N. O aproveitamento do N-fertilizante pela cana-de-açúcar foi da ordem de 60% nos estádios iniciais, reduzindo-se para aproximadamente 20% próximo à fase de maturação. O íon cloreto reduziu a concentração de nitrato no solo devido a ação do ânion na reação de nitrificação. A incorporação de resíduo de cana-de-açúcar ao solo promoveu maiores taxas de imobilização do N e a aplicação de sulfato de amônio resultou em maior mineralização do N nativo do solo comparado a ureia. / The addition of plant residue with high C/N ratio to the soil in a \"green cane\" system affects the balance of input/output processes of N in a soil-plant-atmosphere system. Thus, the presence of straw modifies the agroecosystem requiring adjustments in management of nitrogen fertilization. Accordingly, four studies were developed to: (i) evaluate the nutritional and productive characteristics of sugarcane crops to identify the source and N rates of greater agronomic efficiency; (ii) quantify the sugarcane N recovery from fertilizers; (iii) assess the potential inhibition of chloride ion in reaction to soil nitrification, (iv) evaluate mineralization and immobilization rates of fertilizer-N and their interaction with the native soil N. We conducted a field experiment on a Typic Hapludox with sugarcane, in the 2009/2010 harvest. The experimental design was a randomized block with four replications and nine treatments with nitrogen sources: ammonium sulfate, YaraBela NitromagTM, ammonium nitrate and urea at 100 kg N ha-1, ammonium chloride at N doses: 50, 100, 150 and 200 kg ha-1 and control. Microplots were installed with application of nitrogen sources labeled 15N at 100 kg N ha-1. Nitrogen fertilizers were applied manually over straw. Subsequently, previously collected soil samples were incubated aerobically for 21 days. The experimental design was completely randomized with four replications and the treatments consisted of ammonium sulfate or ammonium chloride at 100 mg N kg-1 with potassium chloride at a chlorine dose 100 or 200 mg kg-1. We also evaluated doses of ammonium chloride (50, 100, and 200 mg N kg-1). Forms of mineral-N were determined by Flow Injection Analysis (FIA) system. Soil samples were incubated aerobically for 20 weeks. The experimental design was completely randomized with three replications and six treatments, comprising a 3x2 factorial (amidic-N, ammonium- N or without N versus with or without cane residue). Nitrogen sources (enriched with 2 atom% 15N) were applied to the soil surface at a N dose of 100 mg kg-1 and residue sugarcane incorporated at 5.2 g kg-1. The N supply in ammonium chloride form resulted in decreased yield of sugar and stalks. Nitric-ammonium sources promoted higher activity of nitrate reductase in sugarcane leave; however, they did not affect total N accumulation. The sugarcane recovery of fertilizer-N was approximately 60% in early stages, dropping to about 20% near the maturity stage. The chloride ion reduced nitrate concentration in soil due to the anion action in the nitrification reaction. The sugarcane residue incorporation to the soil showed higher N immobilization rates and the use of ammonium sulfate resulted in higher N mineralization rates of native soil N compared to urea.

Reconstruction studies of seasonal rainfall utilizing stable isotope based proxy approach suffer from the limitations of time resolutions. Conventional methods and archives limit the achievable resolution to annual scales. However, high resolution reconstruction (seasonal to sub-weekly scale) can be achieved in proxy records where growth rates are high enough to leave spatial signatures in an organically or inorganically deposited layer such as growth bands. In this study, aragonitic skeleton of the gastropod Lissachatina fulica (Bowdich, Giant African Land Snails) is investigated with an aim to achieve sub-weekly scale reconstruction of the Indian monsoon rainfall. These terrestrial gastropods are native of Africa and highly invasive. Their evolution in the geological time period dates back to the Pliocene and is presently distributed across the tropical belt. They exhibit a high growth rate in the presence of water and high relative humidity in the environment. As a result, they are ideally suited for the task of palaeo seasonality reconstruction. The isotopic patterns recorded in their growth bands reveal composition of environmental water at seasonal time scales. In vitro studies were carried out on L. fulica to estimate their growth rates and growth responses to changes in the physical conditions within the culture chamber. The Indian monsoon rainfall exhibits characteristic dry spells that are generally sandwiched between periods of active phases of high rainfall during the South West monsoon season. These dry spells are typically characterized by rainfall with low intensity. Isotope fingerprinting of the rain water at daily time resolution, covering the years of 2007-10 exhibited distinct isotopic ratios for the dry and wet spells. Dry spells were clearly demarcated in the record with isotopically enriched signature. In addition, the study indentified the role of three distinct moisture sources on δ18O of rain water at Bangalore, India. The variability in the oxygen isotopic composition of the Indian monsoon rainfall is predominantly controlled by this source moisture variability at inter annual time scales, while temperature and amount of rainfall tend to dominate the variability in the precipitation isotopes at seasonal and weekly scales. Simultaneous isotopic analyses of both rainwater and shell carbonates growth bands were undertaken to understand their relationship to aid in high resolution reconstruction. Carbonate found in the growth bands of the gastropods, which is precipitated under equilibrium condition from rainwater, preserves the signature of rainfall. This provides an opportunity to reconstruct rainfall parameters (i.e. amount and moisture sources) knowing the variability in shell carbonates. Stable isotopic ratios measured across the growth bands of live shell specimens collected from the southern and eastern Indian regions (Bangalore and Kolkata, respectively) were compared with the rainfall isotope ratios at these two locations; signature of dry spells were clearly identified from the study of isotopic composition in the growth bands of the gastropod specimens. The approach was also extended to older samples from historical archives from eastern Indian region (Kolkata, East India). Individual specimens belonging to the same species of gastropod, which were collected during the monsoon season of the year 1918 were used for reconstructing the seasonal pattern in monsoon rainfall over the region. The record of variation in the isotopic composition seen in the shell was compared with the rainfall data from Indian Metrological Division observatory at Kolkata station. The year 1918 was characterized as a major drought year and the signature of dry period was seen preserved in the specimen. The work under taken in this thesis will widen the scope of seasonality reconstruction using terrestrial shell fossils from palaeo records, which have been rarely investigated in paleoclimate studies from the perspective of understanding the seasonal precipitation variability.

Reconstruction studies of seasonal rainfall utilizing stable isotope based proxy approach suffer from the limitations of time resolutions. Conventional methods and archives limit the achievable resolution to annual scales. However, high resolution reconstruction (seasonal to sub-weekly scale) can be achieved in proxy records where growth rates are high enough to leave spatial signatures in an organically or inorganically deposited layer such as growth bands. In this study, aragonitic skeleton of the gastropod Lissachatina fulica (Bowdich, Giant African Land Snails) is investigated with an aim to achieve sub-weekly scale reconstruction of the Indian monsoon rainfall. These terrestrial gastropods are native of Africa and highly invasive. Their evolution in the geological time period dates back to the Pliocene and is presently distributed across the tropical belt. They exhibit a high growth rate in the presence of water and high relative humidity in the environment. As a result, they are ideally suited for the task of palaeo seasonality reconstruction. The isotopic patterns recorded in their growth bands reveal composition of environmental water at seasonal time scales. In vitro studies were carried out on L. fulica to estimate their growth rates and growth responses to changes in the physical conditions within the culture chamber. The Indian monsoon rainfall exhibits characteristic dry spells that are generally sandwiched between periods of active phases of high rainfall during the South West monsoon season. These dry spells are typically characterized by rainfall with low intensity. Isotope fingerprinting of the rain water at daily time resolution, covering the years of 2007-10 exhibited distinct isotopic ratios for the dry and wet spells. Dry spells were clearly demarcated in the record with isotopically enriched signature. In addition, the study indentified the role of three distinct moisture sources on δ18O of rain water at Bangalore, India. The variability in the oxygen isotopic composition of the Indian monsoon rainfall is predominantly controlled by this source moisture variability at inter annual time scales, while temperature and amount of rainfall tend to dominate the variability in the precipitation isotopes at seasonal and weekly scales. Simultaneous isotopic analyses of both rainwater and shell carbonates growth bands were undertaken to understand their relationship to aid in high resolution reconstruction. Carbonate found in the growth bands of the gastropods, which is precipitated under equilibrium condition from rainwater, preserves the signature of rainfall. This provides an opportunity to reconstruct rainfall parameters (i.e. amount and moisture sources) knowing the variability in shell carbonates. Stable isotopic ratios measured across the growth bands of live shell specimens collected from the southern and eastern Indian regions (Bangalore and Kolkata, respectively) were compared with the rainfall isotope ratios at these two locations; signature of dry spells were clearly identified from the study of isotopic composition in the growth bands of the gastropod specimens. The approach was also extended to older samples from historical archives from eastern Indian region (Kolkata, East India). Individual specimens belonging to the same species of gastropod, which were collected during the monsoon season of the year 1918 were used for reconstructing the seasonal pattern in monsoon rainfall over the region. The record of variation in the isotopic composition seen in the shell was compared with the rainfall data from Indian Metrological Division observatory at Kolkata station. The year 1918 was characterized as a major drought year and the signature of dry period was seen preserved in the specimen. The work under taken in this thesis will widen the scope of seasonality reconstruction using terrestrial shell fossils from palaeo records, which have been rarely investigated in paleoclimate studies from the perspective of understanding the seasonal precipitation variability.