Matéria orgânica e sua relação com os atributos do solo em áreas sob conversão de floresta em cultivo no sul do Amazonas.

Abstract

Soil quality and sustainability of agricultural production environments are the subject of frequent studies, and when it comes to environments located in the Amazon biome, the concern is constant to use conservation management and soil practices in order to maintain or increase quality and fertility soils that are naturally poor in general. Within this context, soil organic matter is a fundamental factor in the maintenance of these environments, since the anthropic disturbance of a natural system usually causes more losses than carbon gains and may lead to soil degradation. The objective was to fractionate the organic matter of the soil and evaluate its relationship with the soil attributes in environments with forest / cultivation transformation, in Amazonian conditions, aiming to investigate the impacts of vegetation transformations on the soil attributes in the southern region of Amazonas. The study was conducted in the municipality of Canutama, located in the south of the state of Amazonas, where chemical and physical attributes were evaluated in four different environments, namely the cultivation of guarana, cupuaçu, annatto and a forest area at three depths 0.00-0.05, 0.05-0.10 and 0.10-0.20 m, and the sampling was made in the form of meshes with 32 points. The physical attributes evaluated were Sd, WPD, WGD, aggregate class < 1.00 mm, 1.00 - 2.00 mm and > 2.00 mm, MaP, MiP, TP, GM, textural analysis (sand, silt and clay). The chemical attributes analyzed in the four areas were pH, Al3+, H+ + Al3+, K+, Ca2+, Mg2+, P, BS, t, T, V% and m%. Chemical fractionation in the 0.00-0.05 and 0.05-0.10 m layers were also performed, quantifying the fulvic and humic acid fractions and the humine, and the particle size fractionation of the soil organic matter at the three depths. TOC, OCp and OCam are defined. Descriptive statistics tests were performed, means were compared by Tukey test at 5% probability and then performed multivariate analysis using the principal component analysis technique. According to the results, it is concluded that in the present study the conversion of the forest area to crops caused chemical and fertility and physical changes in soil attributes; to humine was the fraction of the most abundant soil organic matter in all studied environments; the quality of humus in the areas of guarana, cupuaçu and annatto cultivation in the depth of 0.00-0.05 m and under depth 0.05-0.10 m in the guarana and cupuaçu area was better than when compared to the forest area; multivariate statistics with was efficient in distinguishing the best attributes that define the environments; The organic matter fractions that had the greatest influence of the management were acid fulvic in the 0.00-0.05 m layer and OCp in the 0.10-0.20 m depth, since it was the fractions that best distinguished the forest from the environments cultivated.