Estudo dos atributos do solo e qualidade da água do rio sob açaizais nativos na Amazônia oriental.

Abstract

The açaizeiro (Euterpe Oleracea Mart.) is native to the Brazilian Amazon whose natural habitat is hydromorphic soil ecosystems that drain twice a day. The objective was to evaluate the floodplain systems by means of the chemical, physical and biological attributes of hydromorphic soils in areas of native açaizais, in addition to the chemical characteristics of the water quality of the Tocantins river in order to contribute to the maintenance, preservation and proper management of these ecosystems. The study was developed in three areas of native açaizal on the Saracá Island belonging to the Municipality of Limoeiro do Ajurú, in the region of Baixo Tocantins. Ten soil samples with deformed structures were collected in the rainiest period in each area and another 10 samples in the least rainy period in each area and 20 undisturbed samples per area at a depth of 0-10 cm. The deformed samples were used to determine the physical characteristics of the soil and the deformed samples were used for the analysis of texture, chemical and biological attributes of the soil and micronutrients and the chemical quality of the river water was also analyzed in two pluviometric periods. Regarding the physical-hydric attributes of the hydromorphic soil, the three floodplain areas presented a silty-white texture, soil moisture above 0.1 gg-1 in potential critics and soil aggregation index greater than 85% with more than 60% of aggregates belonging to the size class> 2mm, already taking into account the chemical attributes of the soil and water in the two pluviometric periods, the levels of iron in the soil were higher in the less rainy period whereas manganese decreased in the same period. Calcium showed values above 4 cmolc dm-3 in both periods and magnesium greater than 2 cmolc dm-3 whereas phosphorus varied from 4 to 15 mg dm-3 and potassium varied from 0.09 to 0.19 mg dm-3 in relation to the two periods. Aluminum was less than 0.30 cmolc dm-3 in the evaluated periods. The levels of metals found in the river water of the three areas are in accordance with the reference values established by CONAMA, only the iron in the rainiest period in the central floodplain obtained a higher value. However, in relation to biological attributes, the metabolic coefficient found was less than 7.59x10-3 mg kg-1 in the three areas, while the biomass carbon was greater than 70 mg kg-1 and the soil respiration greater than 100 mg CO2 kg-1. The soil of the three floodplain ecosystems has physical, chemical and biological characteristics with natural and favorable conditions for the production and maintenance of native açaí groves and the quality of the river water considered suitable for consumption by local riverside dwellers.