PALAVRAS-CHAVE Atributos do solo Floresta nativa Milho Pastagem KEYWORDS Soil attributes Native forest Corn PastureRESUMO: O conhecimento dos danos provocados pelos diferentes sistemas de manejo é essencial para melhorar a qualidade física do solo. Assim o objetivo deste trabalho foi avaliar os atributos físicos do solo em áreas sob diferentes sistemas de usos na região de Manicoré, AM. Foram delimitadas três áreas, com os seguintes usos do solo: área cultivada com milho, área cultivada com pastagem e área sob floresta nativa. Foram coletadas 32 amostras de solos nas profundidades de 0,0-0,10 m em cada uma das três áreas estudadas. Os atributos físicos avaliados foram: textura, resistência do solo a penetração, umidade do solo, macroporosidade, microporosidade, porosidade total, densidade do solo e de partícula e estabilidade dos agregados. Foram realizadas análises de variância uni e multivariadas e os resultados dos diferentes sistemas de usos foram comparados pelo teste de Tukey a 5% de probabilidade. Os sistemas de usos alteram os atributos do solo, especialmente a densidade do solo, macro e microporosidade do solo, resistência do solo a penetração e volume total de poros. A maior percentagem de agregados com maiores diâmetros foi encontrada no sistema de uso com pastagem. O uso das técnicas multivariadas mostrou-se eficiente na distinção de ambientes sobre os sistemas de usos estudados. ABSTRACT: Knowledge of the damage caused by different management systems is essential to improve the physical quality of the soil. So the aim of this study was to evaluate the soil physical properties in areas under different uses systems in the region of Manicoré, Amazonas

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Inceptisols are poorly developed soils with original material characteristics and high or low base saturation depending on th e environment in which they developed. This study aimed to evaluate the spatial variability of chemical pedoindicators in an Inceptisol under different management systems. The study was carried out in three agricultural areas cultivated with cassava, sugarcane and an agroforestry system, with cultivation time of 15, 8 and 17 years, respectively. All the areas investigated were located in Southern Amazonas state, Brazil. In these areas, a square mesh was established measuring 70.00 x 70.00 m, with cross points spaced 10.00 m apart and a total of 64 sampling points in each grid. Soil samples were then collected at a depth between 0.00 and 0.10 m to determine organic matter, pH, calcium, magnesium, potassium, available phosphorus, potential acidity, sum of bases, cation exchange capacity and base saturation, in addition to magnetic susceptibility in all the samples, using 10 cm 3 of soil. Data were analyzed using multivariate, descriptive and geostatistics. It was found that magnetic susceptibility may be a pedoindicador for areas under cassava cultivation, potential acidity for the agroforestry environment, and pH for areas under sugarcane cultivation. The agroforestry area had higher data heterogeneity, since a nugget effect was encountered for all the properties analyzed. Based on the scaled semivariograms, the lower range values indicate greater spatial variability in the sugarcane and agroforestry systems, due to the specificities of the management system.

Abstract. Soil position in the landscape reveals its history of formation and genesis. Therefore, the landscape is the combination of features of the surface of the earth with subsurface components (parent material), while the soil is a three-dimensional, dynamic natural body inserted in the landscape. This research aimed to study the soil-landscape relationship in a sandstone-gneiss topolithosequence in Amazonas, Brazil. The study was carried out along a 9.253-meter transect from the top downwards the softer slope. Soil profiles were selected in five landscape compartments (top, upper third, lower third, transport foothill, and deposition foothill). Morphological, mineralogical, physical, chemical, and ray diffraction characterizations were performed. Soils had different morphological, physical, chemical, and mineralogical attributes due to the variations of the geological substrate and landscape position. The mineralogy of the clay fraction is composed of kaolinite, goethite, hematite, and gibbsite, with goethite being the predominant iron oxide. A sand fraction dominance was observed in relation to the other fractions in all the profiles, being related to the alluvial nature of the parent material, with the highest values occurring in the lower third. The separation of the landscape into geomorphic surfaces and identification of the parent material were effective for understanding the variation of soil attributes along the landscape.

The crop systems adopted in the Amazônia region have been studied several times in terms of the variability and to indicate the soil attributes more sensitive to the different crops. Thus, the objective of this work was to apply multivariate techniques in order to identify the chemical attributes most sensitive to environmental changes in different crop systems in Western Amazonia, Brazil. The research was conducted in five rural properties located in the Humaitá city region, Western Amazonia, Brazil. There were selected four environments with natural characteristics (Native Forest - NF) and five cropping systems (Grazing, Cassava, Açaí, Agroforestry and Reforestation). In the selected areas, soil samples were collected at depths layers of 0.0-0.05 m; 0.05-0.1 m and 0.1-0.2 m and the following chemical analyzes were performed: pH in water, Ca2+, Mg2+, K +, Resin-P, phosphorus bio-available particulate (Pbp), OC, Al3+, H++Al3+ and from these results SB, T, t, m% and V% were calculated. Multivariate statistical techniques were used to verify similarities between the crop systems in the attempt to relate the crops grown and the chemical attributes. The multivariate analysis was essential in the crop systems distinction, as well as to describe the relationship with the chemical properties. The results demonstrate and reinforce the existing variability between crop systems, with emphasis on the variation in crop systems, compared to natural environments.

Converting natural ecosystems into agro-ecosystems often reduces soil organic carbon content by decreasing carbon input, as well as by increasing erosion losses and organic matter decomposition rate. This study aimed at evaluating carbon stocks, soil aggregate stability, and spatial variability of some other attributes in soils of Southern Amazonas state. The study was carried out on areas with archaeological dark earth (ADE), under rainforest, pasture, agroforestry environments, sugarcane, and cassava. We collected disturbed and undisturbed soil samples from 64 points in a regular spacing of 10 m at 0.0-10 cm depth. From these samples, we determined the stock of organic carbon (STOC), organic carbon (OC), organic matter (OM) content, soil aggregate stability (SAS), and soil bulk density (SBD). Data analysis included univariate, multivariate, and descriptive statistics. The STOC was higher in ADEs and the adjusted semivariograms pointed out a greater spatial variability for soils under pasture and cassava crop. Kriging maps of principal component analysis scores proved a positive correlation between the studied variables and terrain slope, with higher values for lower lands.