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O objetivo deste trabalho foi avaliar atributos químicos do solo, quantificar os teores e os estoques de C e N, e avaliar a qualidade química da matéria orgânica do solo em sistemas de colheita de cana-de-açúcar com ou sem queima da palhada. Áreas cultivadas com cana-de-açúcar foram avaliadas com ou sem queima da palhada, aos 6 e aos 12 anos após a última reforma do canavial. Além disso, também foram avaliadas uma área de vegetação nativa e outra cultivada por 19 anos sem queima. O teor de C no solo das áreas sem queima foi superior ao daquelas queimadas e inferior ao da área com vegetação nativa. O estoque de C a 0,0?0,3 m de profundidade, na área queimada, foi 22% menor do que o na área sem queima, aos 6 anos, e 43% menor, aos 12 anos. Os maiores graus de humificação ocorreram na área sem queima por 19 anos; e os menores, na área com vegetação nativa. Os solos cultivados apresentaram maior concentração de grupos fenólicos e carboxílicos nos ácidos húmicos. A fertilidade do solo aumenta em áreas de cana-de-açúcar sem queima, em razão da matéria orgânica do solo mais humificada e da maior quantidade de grupamentos carboxílicos e fenólicos. Made available in DSpace on 2019-04-26T00:45:34Z (GMT). No. of bitstreams: 1 Atributosquimicosequalidade.pdf: 410548 bytes, checksum: e566f204f2ccd521efccc4ba7749bfa5 (MD5) Previous issue date: 2016

In March 2013, 40 leading experts from across the world gathered at a workshop, hosted by the European Commission, Directorate General Joint Research Centre, Italy, to discuss the multiple benefits of soil carbon as part of a Rapid Assessment Process (RAP) project commissioned by Scientific Committee on Problems of the Environment (SCOPE). This collaboration led to the publication of the SCOPE Series Volume 71 "Soil Carbon: Science, Management and Policy for Multiple Benefits"; which brings together the essential scientific evidence and policy opportunities regarding the global importance of soil carbon. This short communication summarises the key messages of the assessment including research and policy implications.

O trabalho objetivou apresentar dados atuais sobre os acúmulos de C no solo e potenciais reduções de emissão de GEE para a atmosfera nos principais agrossistemas no Brasil, incluindo os envolvidos na produção de biodiesel, cana-de-açúcar, mudanças do uso da terra na Amazônia e pastagens. Made available in DSpace on 2018-11-23T23:45:08Z (GMT). No. of bitstreams: 1 TropicosemCienciadoSolov.9p.1472015.pdf: 22010833 bytes, checksum: 51d1d501d1b5d7a8f9280ae383e1c335 (MD5) Previous issue date: 2015-12-09

The objective of this study was to quantify the soil greenhouse gas (GHG) balance after the conversion of native vegetation (NV) to pasture and agricultural land and the conversion of agriculture to crop-pasture rotation (CPR) by evaluating changes in C stocks and N2O and CH4 fluxes. Soil sampling was carried out in March 2007 and April 2009 and GHG fluxes were sampled nine times between April 2007 and March 2009. The conversion of NV to pasture and agriculture decreased soil C stocks, with loss rates ranging from 0.25 to 0.64 Mg C ha(-1) yr(-1), respectively. The implementation of CPR in,agriculture areas increased soil C stocks by 0.60 Mg ha(-1) yr(-1). N2O emissions were higher in CPR and lower in NV. Emission of 1.03 kg CH4-C ha(-1) yr(-1) was observed in pasture, while in other areas consumption of CH4 was observed. The net GHG emission from the soil, including all GHG expressed in C-equivalent, indicated that the conversion of NV to pasture and agricultural land results in emissions of 0.54 and 0.72 Mg C ha(-1) yr(-1), respectively. In contrast, the adoption of CPR in areas under crop succession was a sink of 0.36 Mg ha(-1) yr(-1). Among the evaluated land use changes, only the implementation of CPR proved to be a good strategy to mitigate soil GHG emissions in Brazilian Cerrado.

Thee effects of land-use change (LUC) on soil carbon (C) balance has to be taken into account in calculating the CO2 savings attributed to bioenergy crops(1-3). There have been few direct fieldmeasurements that quantify thee effects of LUC on soil C for the most common land-use transitions into sugar cane in Brazil, the world's largest producer(1-3). We quantified the C balance for LUC as a net loss (carbon debt) or net gain (carbon credit) in soil C for sugar-cane expansion in Brazil. We sampled 135 field sites to 1 m depth, representing three major LUC scenarios. Our results demonstrate that soil C stocks decrease following LUC from native vegetation and pastures, and increase where cropland is converted to sugar cane. The payback time for the soil C debt was eight years for native vegetation and two to three years for pastures. With an increasing need for biofuels and the potential for Brazil to help meet global demand(4), our results will be invaluable for guiding expansion policies of sugar-cane production towards greater sustainability.

The greenhouse gases concentration in the atmosphere have significantly increased since the beginning of the Industrial Revolution. The most important greenhouse gases are CO2, CH4 and N2O, with CH4 and N2O presenting global warming potentials 25 and 298 times higher than CO2, respectively. Most of the N2O emissions take place in soils and are related with agricultural activities. So, this review article aimed at presenting the mechanisms of N2O formation and emission in agricultural soils, as well as gathering and discussing information on how soil management practices may be used to reduce such emissions. The N2O formation in the soil occurs mainly through nitrification and denitrification processes, which are influenced by soil moisture, temperature, oxygen concentration, amount of available organic carbon and nitrogen and soil C/N ratio. Among these factors, those related to soil could be easily altered by management practices. Therefore, understanding the processes of N2O formation in soils and the factors influencing these emissions is fundamental to develop efficient strategies to reduce N2O emissions in agricultural soils.

The Brazilian Amazon and Cerrado are among the principal agricultural frontiers of the world, and have attracted global attention because of their potential to be a source or sink of atmospheric CO2. However, accurately quantifying alterations in soil organic carbon (SOC) due to land-use changes remains to be a major challenge. Using a meta-analysis, our objective was to evaluate tillage effects on SOC stocks in Brazil's Amazon and Cerrado biomes. Two approaches: (1) the classical SOC annual change rate which provides only an arithmetic average of SOC changes, and (2) the rate of annual change adjusted from management factors derived according to the Intergovernmental Panel on Climate Change (IPCC) SOC methodology, which allows a temporal dataset adjustment, were used. Regardless of approach, conservation technologies such as no-tillage (NT) and integrated crop-livestock (ICL) systems were identified as viable options for SOC sequestration, increasing it between 9 and 16%. One exception was adoption of NT in the Amazon forest, where SOC decreased by 9% over 20 years. Comparing results of the two approaches showed substantial differences between them. For conversions from NT to ICL or from native vegetation to full tillage (FT), the IPCC-based approach produced SOC stock estimates that were 65 and 47% lower, respectively, than with the classical approach. The IPCC approach also identified modeling covariate effects and was influenced less by outliers, thus reducing the risk of under or overestimating soil management effects on SOC.

Soils of a large tropical area with differentiated landscapes cannot be treated uniformly for ecological applications. We intend to develop a framework based on physiography that can be used in regional applications. The study region occupies more than 1.1 million km(2) and is located at the junction of the savanna region of Central Brazil and the Amazon forest. It includes a portion of the high sedimentary Central Brazil plateau and large areas of mostly peneplained crystalline shield on the border of the wide inner-Amazon low sedimentary plain. A first broad subdivision was made into landscape regions followed by a more detailed subdivision into soil regions. Mapping information was extracted from soil survey maps at scales of 1:250000-1:500000. Soil units were integrated within a homogenized legend using a set of selected attributes such as taxonomic term, the texture of the B horizon and the associated vegetation. For each region, a detailed inventory of the soil units with their area distribution was elaborated. Ten landscape regions and twenty-four soil regions were recognized and delineated. Soil cover of a region is normally characterized by a cluster composed of many soil units. Soil diversity is comparable in the landscape and the soil regions. Composition of the soil cover is quantitatively expressed in terms of area extension of the soil units. Such geographic divisions characterized by grouping soil units and their spatial estimates must be used for regional ecological applications.

SUMMARY: Pasture is the main form of land use in Amazonia. Over time the pasture grass loses vigor and yields decrease, indicating a certain degree of degeneration. The main causes of degradation are lack of pasture maintenance and subsequent weed infestation, the choice of regionally unsuitable forage species and excessive grazing. The main purpose of this study was to evaluate the impact of different recovery managements on soil chemical properties and grass yield of a degraded pasture in Rondônia. For this purpose, an experiment was installed in October 2001, consisting of five treatments: C = control; HA = harrowing + NPK + micronutrients; HE = Herbicide + NK + micronutrients; R = No-tillage rice + NPK + micronutrients; and S = No-tillage soybean + PK + micronutrients. The following N, P and K sources were used: ammonium sulfate for N, calcined phosphate for P and potassium chloride for K. The experiment was arranged in a randomized block design with four replications. The shoot dry matter yield of the grass was analyzed as of the 35th month of experimentation, in a dry and a rainy period. Phosphorus fertilization resulted in significant increases in Ca2+ and Mg2+ and increasing trend of P in the topsoil in the initial months of the experiment in treatments HA and S and increases in Ca2+ and P (trend) in the treatment R. The cumulative production of Brachiaria brizantha, from Sep/2004 to Mar/2005, was 30,025, 28,267 and 27,735 kg ha-1 shoot dry matter in the treatments HA, R and S, respectively. These values differed significantly from treatments C and HE, with 17,040 and 17,057 kg ha-1, respectively. It was concluded that phosphorus fertilization associated to pasture reform was effective to raise the dry matter yield of Brachiaria brizantha. Rice or soybean under no-tillage is recommended as a practice of pasture recovery, due to the residual effect of fertilization. Resumo: As pastagens consistem no principal uso da terra na Amazônia. Com o tempo de utilização do pasto, a gramínea perde o vigor e reduz a produtividade, caracterizando algum estado de degradação. Entre as principais causas de degradação estão a falta de manutenção do pasto e consequente infestação de plantas invasoras, a escolha de espécies forrageiras inadequadas à região e o pastejo excessivo. O objetivo principal desta pesquisa foi avaliar o impacto de diferentes manejos de recuperação sobre os atributos químicos do solo e a produtividade da gramínea numa pastagem degradada em Rondônia. Para atingir esse objetivo, foi instalado, em outubro de 2001, um experimento composto de 5 tratamentos: T = testemunha (controle); G = gradagem + NPK + micronutrientes; H = herbicida + NK + micronutrientes; A = plantio direto de arroz + NPK + micronutrientes; e S = Plantio direto de soja + PK+ micronutrientes. As seguintes fontes de N, P e K foram utilizadas: sulfato de amônio para N, termofosfato para o P e cloreto de potássio para o K. O delineamento experimental foi em blocos ao acaso, com quatro repetições. A produção de matéria seca da parte área da gramínea foi analisada a partir do trigésimo quinto mês de experimentação, englobando um período seco e outro úmido. A adubação fosfatada propiciou incrementos significativos de Ca2+ e Mg2+ e tendência de aumento de P na camada superficial do solo nos primeiros meses de condução do experimento nos tratamentos G e S e incrementos de Ca2+ e P (tendência) no tratamento A. A produtividade acumulada de Brachiaria brizantha, obtida entre os meses de set/2004 e mar/2005, foi de 30.025, 28.267 e 27.735 kg ha-1 de matéria seca da parte aérea, nos tratamentos G, A e S, respectivamente, as quais diferiram significativamente dos tratamentos T e H: 17.040 e 17.057 kg ha-1, respectivamente. Concluiu-se que a adubação fosfatada, associada à reforma da pastagem, foi efetiva no incremento de produção da matéria seca de Brachiaria brizantha. O plantio direto do arroz ou da soja é aconselhável como prática de reforma de pastagens, por propiciar o efeito residual da adubação.

The intensive land use invariably has several negative effects on the environment and crop production if conservative practices are not adopted. Reduction in soil organic matter (SOM) quantity means gas emission (mainly CO2, CH4, N2O) to the atmosphere and increased global warming. Soil sustainability is also affected, since remaining SOM quality changes. Alterations can be verified, for example, by soil desegregation and changes in structure. The consequences are erosion, reduction in nutrient availability for the plants and lower water retention capacity. These and other factors reflect negatively on crop productivity and sustainability of the soil -plant-atmosphere system. Conversely, adoption of "best management practices", such as conservation tillage, can partly reverse the process - they are aimed at increasing the input of organic matter to the soil and/or decreasing the rates at which soil organic matter decomposes.

Land-use change for human settlement and agricultural purposes, especially pasture establishment, has caused major impacts on the Amazon Basin's environment. Development of strategies for reformation and restoration of already degraded pastures constitutes the main goal of the authors' research work. For some of this work, a homogeneous area of land in terms of soil characteristics was selected at Nova Vida ranch in Rondônia state to conduct a multidisciplinary experiment, which included agronomic, environmental and economic analyses. Since July 2001, the authors have monitored five treatments: control, herbicide, tillage, no-till rice and no-till soybean, arranged in four blocks. Early results on carbon and nitrogen stocks, nitrogen mineralization, trace-gas fluxes, dissolved organic carbon and microbial biomass are briefly presented.