Dinâmica da matéria orgânica e fertilidade do solo em sistemas agroflorestais e outras coberturas vegetais em comunidades indígenas do Alto Solimões Amazonas

Abstract

Seeking to know the potentialities of the agroflorestry systems and other vegetable coverings better in indigenous communities of Alto Solimões, Amazonas, this work had as objectives to characterize the quality of the organic matter through analyses of chemical division, quantifying the values of acid húmico, acid fúlvico and humina, to evaluate the effect of those systems of use of the earth and other vegetable coverings in the distribution of the light fractions (FLL and FLI) of the organic matter, to quantify the concentrations of carbon of the organic matter in the heavy fraction (silte, clay and it sands), in the layers of 0-10, 10-20 and 20-30 cm of the soil and to determine the total stock of carbon and nitrogen in the depth of 0-30 cm of the soil in primary forest (FP), old secondary forest (FS), young secondary forest (CAP), agroflorestry systems (SAF), copping (RÇ) and pasture (PAS). The chemical division was based on differences in the solubility of the substances húmicas in solutions acid or alkaline. The light-free fraction (FLL) and fraction light intra-attachés (FLI) of the organic matter of the soil, it was removed by flotação in dense solution of iodeto of sodium (NaI) before and after supersonic sound waves application with centrifugação aid. The division granulometric of the heavy "fraction" or organo-mineral was led by humid (sands) and (silte and clay). The values of carbon and nitrogen were analyzed in each one of the fractions and the stocks of carbon and nitrogen they were calculated in agreement with Bayer et al. (1996) and Lobato et al. (2004). This datas were submitted to the variance analysis, for verification in each depth, of the effects of the systems of use of the earth. The comparisons of the averages were made by the test of Tuckey to 5% of probability. The pasture estokes significantly more carbon than the primary forest and there was not significant difference in the stock of nitrogen, among the studied systems. The chemical division of the organic matter allowed to separate the value of acid húmico, acid fúlvico and humina and the highest fertility of the soils of the area in study, it guaranteed better process of humificação of the organic matter of the soil of the systems of use of the earth. The distribution of the light fractions (FLL and FLI) of the organic matter it showed that the Agroflorestry Systems accumulated the largest amount of FLL and the Primary Forest accumulated FLI. The concentrations of carbon of the organic matter in the heavy fraction (silte, clay and it sands), they differed significantly just in the layer of 20-30 cm of the soil between the Pasture and the Yang Secondary Florestry, for the fraction silte and clay.