Caracterização física de alguns solos de uma topossequência da ilha de Algodoal/Maiandeua-PA

Abstract

Knowledge of the physical properties of the soil, under natural conditions, is important so that one can evaluate the modifications that occur in the soil body, when it is used. In coastal areas, however, this knowledge has been little 52 considered, due to the low agricultural potential of these areas. A better knowledge of these soils shows that they can be sites of family farming, depending on the higher or lower percentage of pelitic sediments (silts and clays), as in the case of sandy-silt formations of the coastal plain of French Guiana and Suriname (Andreux, 1990). The objective of this work was to analyze some physical parameters of the soils, such as grain size, density and porosity. For this, three soil profiles were selected (P2, P3 and PS) from a topossequence on Algodoal/Maiandeua Island, municipality of Maracanã-PA, classified by Amaral (2000) as: Yellow Argissolo (P2), Sodic Fluvic Neosolo (P3), Hydromorphic Ferrocárbico Spodosolo (P4). Profile P2 occurs in an area of dry land, gently undulating relief, under restinga vegetation. Profile P3 is located in the depressional area of the topossequence, flat relief, under the influence of saline fields (apicuns). Profile P4 occurs under restinga vegetation and internal dunes. The granulometric data show that the soil material is predominantly sandy, and poor in clay, with some variation in silt content along the profiles. The clay content is low in the superficial horizons, and increases with depth. The bulk density presented lower values in the superficial layers of the three analyzed profiles. In the P4 profile, there were few differences between the values of density and porosity from one layer to another, with lower values than in the P3 profile. As for the total porosity, it was observed that its behavior in relation to soil density was inversely proportional.