Several studies have shown that negative changes in physical attributes affect root growth and plant development. Thus, the objective of this work was to evaluate the impacts of forest-agricultural conversion on the physical-water attributes of the soil in the Amazon basin, southeastern Brazil. The study was carried out in Canutama - AM, in which areas of annatto, cupuaçu and guarana cultivation and a forest area were selected. Meshes of 90 m x 70 m, 90 m x 56 m and 54 m x 42 m were established, comprising 80 sampling points per layer. The points were georeferenced and the undisturbed soil samples were collected in volumetric rings to determine the physical and hydric attributes. data were submitted to descriptive statistics and multivariate analysis. It was observed that aspects such as the implementation time of the different use and occupation systems can be controlling factors for the restoration of these physical properties.

There is a lack of studies focusing on spatial variance of chemical attributes in Amazonas, Brazil. The objective of this study was to evaluate geo-statistics and sample density of chemical attributes in soils under sugarcane and agroforestry, Humaitá, Amazon state, Brazil. The research was carried out in the municipality of Humaitá, Amazon state, the areas were in meshes of 70 m x 70 m regularly spaced by 10 m, with 64 points per area, and then soil samples were collected in layers of 0.0-0.2 m and 0.4-0.6 m. We performed chemical analyses of the proprieties of soil. Then, it was applied descriptive statistics, geo-statistics and sample density techniques based on semivariogram coefficient of variation and range. As a result, we observed spatial dependence for most of the chemical proprieties in the two areas. Based on Cline, sugarcane presented a sample density of 237 (0.0-0.2 m) and 225 (0.4-0.6 m); and agroforestry had 356 (0.0-0.2 m) and 465 (0.4-0.6 m) points per hectare. Yet in the range sample density, sugarcane showed 30 (0.0-0.2 m) and 5 (0.4-0.6 m), whereas agroforestry areas had 23 (0.0-0.2 m) and 9 (0.4-0.6 m) points per ha.

The Amazon rainforest region presents a phytophysiognomy that ranges from savannas to cerrados, all of them intimately associated to climate and soil characteristics. Evidence has been given that plant growth and development are affected by soil quality and seasonality, thus making it crucial to understand them and how they are related to each other in order to grasp the dynamics of the whole ecosystem. In this context, the goal of this research was to assess how seasonality, soil attributes, and root system biomass are related in natural cerrado, cerradão, and forest areas in southern Amazonas State, in Brazil. Soil samples were collected during dry (June/2018) and rainy (December/2018) seasons from three different layers 0.00–0.05m; 0.05–0.15m, and 0.15–0.30m deep. In each area ten sampling points were randomly chosen. Two kinds of soil samples were collected: the first using 4.0 cm height by 5.1cm internal-diameter soil sample rings; and the second were intact soil lumps. Physical and Chemical soil attributes assessed were macro-porosity (MaP), micro-porosity (MiP), total porosity (TP), soil density (SD), aggregates texture and stability  (GMD and WAR), gravimetric humidity (HG), organic carbon (OC), exchangeable aluminum (Al3+), potential acidity (H+Al), sum of bases (SB), cation exchange capacity (CEC), and root biomass (RB). All data were analysed via Tukey t test and student T test to compare results between seasons and areas. Increasing vegetation density (cerrado < cerradão < forest) was followed by an increment in CEC and OC, showing the importance of these attributes to maintaining biodiversity in environments. In amazon cerrado, rainy season as well a sandier soil textures provided favourable conditions to the growth and development of plants’ root system. Soil attributes were little affected by seasonality, that had greater effect on MiP, TP, SD, and OC, leading to lesser values for these variables during rainy season.

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