Made available in DSpace on 2017-07-25T19:31:00Z (GMT). No. of bitstreams: 1 Roberto De Carli.pdf: 2079271 bytes, checksum: 6ef44a2405637e03f847a58547e5b604 (MD5) Previous issue date: 2016-06-29 / Nitrogen is a nutrient with such a high contribution for agriculture, that various strategies are studied every year looking for enhancements of its use efficiency and reduction of its environmental impacts. This study hypothesis is that, the use of gypsum can change the soil’s nitrogen dynamic in the no-tillage system. So, the main objective of this study was to relate the dynamic of the labile compartments of C and N as indicators of fewer losses or lower efficiency of Nitrogen by the use of gypsum under a well-established no-till system. The objective was to relate the dynamics of labile compartments C and N as loss of reduction or efficiency indicators of N due to the use of gypsum in no-tillage system. The experiment was established in September 2012 on clay Oxisol in Ponta Grossa – PR, in a split-split plot completely randomized block design, with three replications. The sources of variation were used gypsum (plots), nitrogen (split-plots) and time (split-split plots). The corn sowing was done in September 2014. The treatments used in the plots were gypsum rates: a) absence of gypsum and b) 2.7 Mg ha-1 of gypsum applied surface. Treatments of subplots were: a) 0 kg ha-1 N; b) 80 kg ha-1 N; c) 160 kg ha-1 N and d) 240 kg ha-1 applied on corn at the V4 stage phenological (four leaves expanded). The time factor was inserted as split-split plots: a) 0 days after sowing (DAS); b) 34 DAS; c) 52 DAS; d) 87 DAS and e) 117 DAS. Within the first and the fifth time layers were sampled 0-5 cm, 5-10 cm, 10-20 cm, 20-40 cm and 40-60 cm. For intermediate times were sampled layers up to 20 cm. The variables analyzed were: a) Nitrate; b) hot water extractable organic carbon (HWEOC); c) permanganate oxidizable organic carbon (POXC); d) Total Organic Carbon (TOC) and e) Total Nitrogen (TN). It was also held for sampling density in the layers referred to only in the first season. Straw samples were collected for reading C and Total N was also evaluated the decomposition of crop residues. The corn production was studied in function of the treatments employed. The use of gypsum become an important tool to minimize the environmental impact nitrate leaching. In high fertility areas and therefore no chemical deterrents in depth to achieve high production ceilings, low doses of plaster do not provide increases in corn yields, but changes in labile compartments C are observed. In long term experiments changes should be seen in TOC and NT and consequently grain production in responses can be observed. / O nitrogênio é um nutriente de grande contribuição para a atividade agrícola, desta forma várias estratégias são estudadas cujo intuito é a maximização da eficiência associada à minimização dos impactos ambientais. O presente trabalho parte da hipótese que o uso do gesso agrícola altera a dinâmica do nitrogênio no solo em sistema plantio direto. Dessa forma o objetivo geral foi relacionar a dinâmica dos compartimentos lábeis de C e N como indicadores da redução de perda ou eficiência do N devido ao uso do gesso agrícola em sistema plantio direto de longa duração. O experimento foi implantado em setembro de 2012 em um Latossolo Vermelho distrófico argiloso em Ponta Grossa – PR. O delineamento experimental foi em parcelas sub-subdivididas com três repetições. As fontes de variação empregadas foram gesso agrícola (parcelas), doses de nitrogênio (sub-parcelas) e o tempo (sub-subparcelas). A semeadura do milho ocorreu em setembro de 2014. Os tratamentos empregados nas parcelas foram doses de gesso: a) ausência de gesso e b) 2,7 Mg ha-1 de gesso, aplicados em superfície. Os tratamentos que compuseram as subparcelas foram: a) ausência de N; b) 80 kg ha-1 de N; c) 160 kg ha-1 de N e d) 240 kg ha-1 aplicados no milho no estágio fenológico de V4 (quatro folhas verdadeiras expandidas). O fator tempo foi inserido como sub-subparcela, sendo que as avaliações foram realizadas em a) 0 dias após semeadura (DAS); b) 34 DAS; c) 52 DAS; d) 87 DAS e e) 117 DAS. Dentro da primeira e da quinta época foram amostradas as camadas 0-5 cm, 5-10 cm, 10-20 cm, 20-40 cm e 40-60 cm. Para as épocas intermediárias foram amostradas as camadas até 20 cm. As variáveis analisadas foram: a) Nitrato; b) Carbono extraído em água quente (C-AQ); c) carbono oxidado por permanganato (C-OXP); d) Carbono Orgânico Total (COT) e e) Nitrogênio Total (NT). Também foi realizada amostragem para densidade nas camadas referidas apenas na primeira época. Amostras de palha foram coletadas para leitura de C e N total, também foi avaliada a decomposição dos resíduos culturais. A produtividade do milho foi estudada em função dos tratamentos empregados. O uso do gesso se torna uma ferramenta importante para minimizar o impacto ambiental pela lixiviação de nitrato. Em áreas de alta fertilidade e consequentemente sem impedimentos químicos em profundidade para alcançar altos tetos produtivos, doses baixas de gesso não proporcionam incrementos na produtividade do milho, porém alterações nos compartimentos lábeis do C são observadas. Em experimentos que contemplem maior tempo, mudanças devem ser observadas nos estoques de COT e NT e consequentemente respostas em produção de grãos poderão ser observadas.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2017-03-14T12:34:58Z No. of bitstreams: 1 Uemeson Jose dos Santos.pdf: 2015027 bytes, checksum: 66a434524c6011a6eb2fb5eeb1227e57 (MD5) / Made available in DSpace on 2017-03-14T12:34:58Z (GMT). No. of bitstreams: 1 Uemeson Jose dos Santos.pdf: 2015027 bytes, checksum: 66a434524c6011a6eb2fb5eeb1227e57 (MD5) Previous issue date: 2016-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The land use in Caatinga has caused changes in their properties, as well as behavior and quality of organic matter. extractive character changes, agro pastoral and agricultural biome has taken this to an unsustainable condition, with profound changes in the dynamics and the stock C and its fractions, linked to changes in the microbial community that plays an important role in nutrient cycling in the soil. The objective of this study was to evaluate changes in soil C, its labile and recalcitrant but the activity and microbial diversity in soils under different vegetation covers and historical uses. seven areas were studied which consisted of native forest (F) without human action, forest with predominance of mimosa (AF) and the other with ipe (IP); three areas converted into farmland irrigated elephant grass (EG), irrigated corn (MI) and corn without irrigation (M); and a farmyard area (NF). They were collected in different areas samples at depths of 0-5, 5-10 and 10-20 cm, respectively. Evaluated the total stocks of C and N, water-soluble carbon (CSA) and the C cumulative mineralized after 32 days of incubation, the carbon oxidizable fractions (F1, F2, F3 and F4) and its fractions humic soil (C-FAH C-FAF and C-HUM), C microbial biomass, microbial quotient (qMIC) and structure the microbial community by phospholipid fatty acid analysis (PFLA). The conversion of the savanna for maize cultivation causes a decrease of 56 and 38% in stocks of C and N in the soil. The larger C stocks were observed in AF coverage, while for N, M stood out with lower stocks of this element and also below at all depths to the CSA. The C mineralizable showed linear behavior, observing a reduction in average C mineralized accumulated up to 21.03% in the intermediate depth. The AF, F and IP coverage had higher carbon content in oxidizable fractions for all depths evaluated. The AF area showed higher C levels in labile forms. The C of humic fractions showed inventories in C-FAF fractions and C-FAH 3.59 and 3.73 t ha-1, respectively for AF area; and 22.64 t ha-1 in C-HUM fraction for EG. The area with MI showed greater efficiency in the use of C for microorganisms at different depths. For CBM, coverage with F had a higher concentration, down to 78.32% in depth. Further total Pflas EG concentrations were observed in the area with a larger population of bacteria and fungi in relation to the predominance of gram positive bacteria over gram negative. F1 fractions, CSA and CHUN contributed most significantly to the increase in the stock of C and N soil. Areas converted agícola production, has the potential to change the fractions of COS and microbial activity, especially when it is making use of irrigation in these environments. The EG coverage was more efficient in the use of C and preservation of MOS, combined with a high microbial community, providing better soil quality. / A utilização do solo sob Caatinga tem ocasionado alterações nas suas propriedades, assim como no comportamento e na qualidade da matéria orgânica. Alterações de caráter extrativista, agropastoril e agrícola tem levado esse bioma a uma condição de insustentabilidade, com profundas alterações na dinâmica e no estoque do C e suas frações, atreladas às modificações na comunidade microbiana que exerce importante função na ciclagem de nutrientes no solo. O objetivo do trabalho foi avaliar as alterações no C do solo, suas frações lábeis e recalcitrantes além da atividade e diversidade microbiana em solos sob diferentes coberturas vegetais e históricos de usos. Foram estudadas sete áreas que consistiram em floresta nativa (F) sem ação antrópica, floresta com predominância de angico (AF) e outra com ipê (IP); três áreas convertidas em cultivos agrícolas de capim elefante irrigado (EG), milho irrigado (MI) e milho sem irrigação (M); e uma área de capoeira (NF). Foram coletadas nas diferentes áreas amostras nas profundidades de 0-5, 5-10 e 10-20 cm, respectivamente. Avaliaram-se os estoques totais de C e N, carbono solúvel em água (CSA) e o C mineralizável acumulado aos 32 dias de incubação, as frações oxidáveis do carbono (F1, F2, F3 e F4) e suas frações nas substâncias húmicas do solo (C-FAH, C-FAF e C-HUM), o C da biomassa microbiana, quociente microbiano (qMIC) e a estrutura da comunidade microbiana através da análise de fosfolipídeos de ácidos graxos (PFLA). A conversão da caatinga para o cultivo de milho ocasionou diminuição de 56 e 38% nos estoques de C e N no solo. Os maiores estoques de C foram observados na cobertura AF, enquanto para o N, o M destacou-se com menores estoques deste elemento, sendo também inferior em todas as profundidades para o CSA. O C mineralizável apresentou comportamento linear, observando-se uma redução na média de C mineralizado acumulado de até 21,03% na profundidade intermediária. As coberturas AF, F e IP obtiveram maiores teores de carbono nas frações oxidáveis para todas as profundidades avaliadas. A área AF apresentou maiores teores de C nas formas lábeis. O C das frações húmicas, apresentaram estoques nas frações C-FAF e C-FAH de 3,59 e 3,73 t ha-1, respectivamente para área AF; e 22,64 t ha-1 na fração C-HUM para EG. A área com MI demonstrou maior eficiência na utilização do C pelos microrganismos nas diferentes profundidades. Para o CBM, a cobertura com F obteve maior concentração, com redução de até 78,32% em profundidade. Maiores concentrações de PFLAs totais foram observadas na área EG, com uma maior população de bactérias em relação aos fungos e maior predominância de bactérias gram positivas em relação as gram negativas. As frações F1, CSA e a C-HUM contribuíram de forma mais expressiva para o aumento do estoque de C e N do solo. Áreas convertidas para produção agícola, tem o potencial de alterar as frações do COS e atividade microbiana, sobretudo quando faz o uso de irrigação nesses ambientes. A cobertura EG foi mais eficiente na utilização do C e preservação da MOS, aliada a uma alta comunidade microbiana, proporcionando melhor qualidade do solo.

No description available.

Soils are the largest pool of carbon (C) in terrestrial ecosystems and store 1500 Gt of C in their soil organic matter (SOM). SOM is a dynamic, complex and heterogeneous mixture, which influences soil quality through a wide range of soil properties. Labile SOM comprises a small fraction of total SOM (approximately 5%), but due to its rapid turnover has been suggested to be most vulnerable to loss following soil disturbance. This research was undertaken to examine the consequences of soil disturbance on labile SOM, its availability and protection in soils using the isotopic analysis of soil-respired CO₂ (δ¹³CO₂). A range of soils were incubated in both the short- (minutes) and long-term (months) to assess changes in labile SOM. Shifts in soil-respired δ¹³CO₂ over the course of soil incubations were found to reflect changes in labile substrate utilisation. There was a rapid depletion of δ¹³CO₂ (from a starting range between -22.5 and -23.9‰, to between -25.8 and -27.5‰) immediately after soil sampling. These initial changes in δ¹³CO₂ indicated an increased availability of labile SOM following the disturbance of coring the soil and starting the incubations. Subsequently δ¹³CO₂ reverted back to the initial, relatively enriched starting values, but this took several months and was due to labile SOM pools becoming exhausted. A subsequent study was undertaken to test if soil-respired δ¹³CO₂ values are a direct function of the amount of labile SOM and soil physical conditions. A range of pasture soils were incubated in the short-term (300 minutes), and changes in soil-respired δ¹³CO₂ were measured along with physical and chemical soil properties. Equilibrium soil-respired δ¹³CO₂, observed after the initial rapid depletion and stabilisation, was a function of the amount of labile SOM (measured as hot water extractable C, HWEC), total soil C and soil protection capacity (measured as specific soil surface area, SSA). An independent experimental approach to assess the effect of SSA, where labile SOM was immobilised onto allophane – a clay mineral with large, active surface area – indicated limited availability of labile SOM through more enriched δ¹³CO₂ (in a range between -20.5 and -20.6 ‰) and a significant (up to three times) reduction in HWEC. In the third study, isotopic measurements were coupled with CO₂ evolution rates to directly test whether equilibrium soil-respired δ¹³CO₂ can reflect labile SOM vulnerability to loss. Soils were sampled from an experimental tillage trial with different management treatments (chemical fallow, arable cropping and permanent pasture) with a range of C inputs and soil disturbance regimes. Soils were incubated in the short- (300 minutes) and long-term (600 days) and changes in δ¹³CO₂ and respiration rates measured. Physical and chemical fractionation methods were used to quantify the amount of labile SOM. Pasture soils were characterised by higher labile SOM estimates (HWEC; sand-sized C; labile C respired during long-term incubations) than the other soils. Long-term absence of plant inputs in fallow soils resulted in a significant depletion of labile SOM (close to 50% based on sand-sized C and HWEC estimates) compared with pasture soils. The values of δ¹³CO₂ became more depleted in 13C from fallow to pasture soils (from -26.3 ‰ to -28.1 ‰) and, when standardised (against the isotopic composition of the solid soil material), Δ¹³CO₂ values also showed a decrease from fallow to pasture soils (from -0.3 ‰ to -1.1 ‰). Moreover, these patterns in isotopic measures were in strong agreement with the amount of labile SOM and its availability across the soils, and were best explained by the isotopic values of the labile HWEC fraction. Collectively, these results confirm that labile SOM availability and utilisation change immediately after soil disturbance. Moreover, isotopic analysis of soil-respired CO₂ is a powerful technique, which enables us to probe mechanisms and examine the consequences of soil disturbance on labile SOM by reflecting its availability and the degree of SOM protection.