RESUMOObjetivou-se caracterizar, por meio de espectroscopia no infravermelho com transformada de Fourier (IVTF), possíveis mudanças na natureza química de ácidos húmicos (AHs) extraídos de amostras de Latossolo (0-10 cm) do Campo Experimental da Embrapa Meio Ambiente, em Jaguariúna (SP). Os dados foram obtidos após seis cultivos de milho e a aplicação de doses variáveis de lodo de esgoto de Barueri (LB) (base seca), conforme os tratamentos avaliados: LB0, LB1, LB2, LB4 e LB8, sendo 0, 1, 2, 4 e 8 vezes a necessidade de N para o milho. Como referência, foi amostrada uma área sob mata. Foram obtidos espectros de ácidos húmicos e do lodo de esgoto utilizado no experimento, e calculados os índices de hidrofobicidade (IH) e de condensação (IC) nas amostras de ácidos húmicos. Foram notadas pequenas alterações na natureza química de AHs de áreas tratadas com lodo de esgoto, em relação à testemunha. Os AHs apresentam grupos aromáticos, -OH fenólicos, -COOH, estruturas alifáticas, carboidratos e impurezas minerais. O uso contínuo de elevadas doses de LB reduziu a concentração de C-alifático e o grau de condensação dos ácidos húmicos, o que sinaliza que há frações orgânicas

As amigas-irmãs Adriana Guirado, Emily Ribeiro, Ingrid Horak, Virginia Damin pelos conselhos, apoio, bons momentos de descontração....Amo vocês!!! Aos meus pais pelo amor incondicional, orações, confiança, apoio e exemplo de vida a seguir; a minha jóia rara Heloisa pelos sábios conselhos, amizade....não existira sem vocês.Amo Aos meus familiares: avós, tios e tias, primos e primas por sempre me incentivarem a lutar pelos meus objetivos. A todas as pessoas que colaboraram, direta ou indiretamente, para realização dessa pesquisa. Muito obrigada! ABSTRACT Changes in the soil carbon stocks due to agricultural land use in the Southwest Amazonian Land use changes such as conversion of natural ecosystems to agro ecosystems are shown to cause alterations in the transformations of soil organic matter (SOM), as well they are responsible for crescent emissions of greenhouse gases (GEE), therefore representing around 20% of total GEE emissions. Over the last 30 years, land deforestation has occurred more intensively in the deforestation arc of Amazonian, particularly in the States of Rondônia and Mato Grosso. The main objective of this research was to evaluate variations in the soil carbon stocks, due to land conversion of native forest to pastures in the Southwest Amazonian region. The specific objectives were to measure some chemical and physical soil attributes, carbon stocks and the remaining soil carbon, through isothopic technique, from the native forest and that incorporated by land use to pastures. Study site (7° and 18° S; 50° and 67° W) was located in the States of Rondônia and Mato Grosso. Soils used in this study were Latosols, Argisols and Neosols, which cover 75% of the total area of both States. The choice of sampling areas was based on a preliminary division of total area in 11 biogeoclimatic region, followed by randomized selection of cities. Soil samplings were realized during June/July 2007, according to five treatments: native forest (forest, savanna and cerradão) (NA), pasture (PA) under different managements, perennial crops (PE), areas under no tillage (PC) and tillage management (PD). Experimental design was randomized with five replications. Soil samples were collected in the following soil layers: 0-5, 5-10, 10-20 and 20-30 cm. Results showed that PD decreased pH in the deeper soil layers. For all treatments ∆ pH illustrated a dominance of negative charge. Soil density was found to be highest in the degraded pastures. Carbon contents showed a positive correlation with the clay+silt contents for all soil layers in the different land uses. In the 0-30 cm layer, PC management showed a tendency to increase soil carbon stocks (51,46 Mg ha-1), followed by PD (48,76 Mg ha-1), PA (46,75 Mg ha-1) and PE (46,75 Mg ha-1), although significant differences among study sites were not found. In the forest, δ 13 C values showed a variation from-28 to-26‰ in the soil depth; while in the pasture δ 13 C variation was lower than in the forest (-22 a-24 ‰), probably due to the presence of remaining carbon from the fores...

Resumo -O objetivo deste trabalho foi avaliar o efeito da aplicação contínua de doses crescentes de lodo de esgoto sobre os teores de carbono (C) associados à fração leve (C-FL) e à fração pesada (associado à areia -C-areia; associado ao silte -C-silte -e associado à argila -C-argila) de matéria orgânica em amostras de Latossolo. O experimento foi instalado em 1999, em Jaguariúna, SP, e os dados foram obtidos após a sexta aplicação de lodo de esgoto com doses acumuladas em base seca -0, 30, 60, 120 e 240 Mg ha -1 -, após seis cultivos subseqüentes de milho. Os tratamentos foram: testemunha, sem adição de lodo (L0); aplicação de lodo de esgoto para fornecer uma (L1), duas (L2), quatro (L4) e oito (L8) vezes a dose de nitrogênio requerida pelo milho. Como referência, foi amostrada uma área sob mata nativa, adjacente ao local do experimento. O acréscimo nas doses de lodo de esgoto aplicadas aumenta de modo linear os teores de C orgânico, C-silte e C-areia, e não interfere nos teores de C-argila. À medida que se aumenta a dose de lodo de esgoto até 120 Mg ha -1 , há acréscimo no teor de C-FL no solo. Em relação ao C orgânico, os teores de C associado aos compartimentos avaliados de matéria orgânica do solo têm a seguinte ordem de contribuição: C-FL

<p>Land-use change (LUC) is one of the main responsible for the loss of soil organic matter (SOM) in the form of CO₂ to atmosphere. The aims of the present study were i) evaluate soil C stocks due to coffee cultivation time after LUC and ii) evaluate the use of the organic compost from the by-product of bean processing as a source of SOM. The study was performed in dystrophic red latosol in the municipality of Patrocínio, MG, Brazil. Two evaluations were performed; i) three coffee (<em>Coffea arabica </em>L. var. Icatú Vermelho) growing areas with different implantation times (8, 15 and 37 years) in relation to Cerrado <em> stricto sensu <em> (reference); and ii) area cultivated with coffee (<em> C. arabica </em> var. Bourbon Vermelho) that received organic compost for four years. Soil was sampled in layers 0-5, 5-10 and 10-20 cm. In the first study, the C stock (0-20 cm) was higher under native vegetation (67 Mg C ha^-1) in relation to the coffee growing (63 Mg C ha^-1), however, did not differ significantly and showed subtle loss rates of 0.12; 0.06 and 0.02 Mg C ha^-1 year^-1 for 8, 15 and 37 years, respectively. In the second study, the organic compost applied to the soil increased the C stock (0-20 cm) to 4.6 Mg C ha^-1 and showed an accumulation rate of 1.15 Mg C ha^-1 year^-1. Thus, it is concluded that C stocks is reduced in the soil due to LUC, however, the application of organic compost increased the supply of organic material, favoring the maintenance and even increasing the stock in the soil.</em></em></p>