Atributos do solo, estoque de carbono e erodibilidade em áreas sob diferentes usos no assentamento São Francisco, Canutama, Amazonas

Abstract

Over the years, the occupation and replacement of before forested areas by agricultural areas without proper knowledge and non-observance of technical criteria has been one of the main problems in the Amazon region. The present work had as objective to evaluate the soil attributes, erodibility and carbon stock in areas under different uses in the São Francisco, Canutama, AM settlement. Were established meshes according to the dimensions of cultivation, then samples were collected at the crossing points of the meshes, at depths of 0,00-0,05; 0,05-0,10; and 0,10-0,20 m, with 80 sampling points in each area, totaling 240 samples per area. At each sampling point, were collected samples with a structure preserved clod-shaped were collected in the depths evaluated, to determine the physical attributes and chemical, making a total of 960 samples in the four evaluated areas. After the determination of the physical, chemical, erodibility and organic carbon attributes, the data were submitted to univariate and multivariate analysis, and the comparisons of the means of the variables within each studied environment were analyzed by the Tukey test at 5%, using the computational program Statistica 7. To complement the work, a geostatistical analysis was performed, which was used to identify the distribution and spatial pattern of the studied variables, defining theoretical semivariogram models, in order to evaluate spatial dependence and generate kriging maps. The process of conversion of forests into cultivated areas without proper management caused negative changes in the physical attributes of the soil. The areas cultivated with guaraná and urucum presented more advanced stage of degradation of soil physical properties; The attributes that suffered the most changes in forest conversion in cultivated environments were: density (Ds), macroporosity (MaP), microporosity (MiP), porosity (Pt), soil penetration resistance (RSP) and aggregate stability index IEA); Through the multivariate analysis, it was possible to verify that the greatest alterations of the physical attributes for the studied areas occurred in the depths 0.00-0.05 and 0.05-0.10 m; The multivariate analysis of soil chemical attributes is adequate to identify the nutrients that present the greatest alteration after the process of forest / agricultural conversion. The changes in chemical attributes were more pronounced in the superficial layers (0.00-0.05 m and 0.05-0.10 m), this result demonstrates the importance of above-ground biomass in nutrient cycling. The conversion process influenced soil aggregation, evaluated by increasing clay fraction dispersion and decrease in values weighted mean diameter (WMD), geometric mean diameter (DMG) and aggregate classes> 2.00 mm; The attributes evaluated in the respective areas studied were within the limits of the degree of spatial dependence, presenting dependence ranging from moderate to strong; At each sampling point, were collected sample with a structure preserved clod-shaped were collected in the depth evaluated, for determination of soil texture and organic carbon, for a total of 320 samples in the four evaluated areas; In the multivariate analysis, the forest and cupuaçu areas presented similar behavior, with values of organic carbon (CO), carbon stock (EC), silt, clay and classes of aggregates 2 - 1 mm, <1mm and IEA, above average; The areas cultivated with guaraná and urucum presented greater predisposition of the soil to erosion in furrows (Krwepp) and entressulcos (Kiwepp). The areas of cupuaçu and forest presented high silt values, favoring erodibility conditions (factor K). In contrast, they showed high values of critical strain of shear, fact that signal resistance to the beginning of the erosive process; Geostatistics integrated with the multivariate analysis helped to understand the behavior of the erodibility factors, after the process of native forest / cultivated areas conversion.