Reconnaissance survey of the soils of Bragatina region, Pará State, Brazil

Abstract

The soil called Bragantina Region is located in the Northeastern part of State of Pará, Brazil, between 1°26’ N and 1°40’ S latitudes and 47º24’ W Gr longitudes. It covers an area of 16,428 square kilometers corresponding to 1.3 percent of the State. It is the most crowded region of the State with a population density of 33.5 inhabitants per square kilometer and also is responsible for 50% of the whole agricultural output of the State. In this work the authors established the genetic classification of the soil of this Region. The purpose was to identify and delimit the main occurrences of the great soil groups which would have importance for a general evaluation of the resources of the region. The carrying out of this study contributes to the Survey of Pontencial Resources of the Brazilian Soils which is being carried out by Brazilian Soil Commission in South, Central and Northeast Brazil. An aerophotogrametric cartographic chart of the American Air Force with 1:200,000 scale was used for the soils survey. Delineation of soil types was made in partial areas of 0°30' both for meridian and for parallel. Sail identification was made by studying the morphological characteristics of profiles complemented by general observations in regard to topography, vegetative cover, parent material, climatic variation, drainage conditions and others. As to geology, Bragantina Region presents mainly tertiary and quaternary soils in which Pirabas, Pebas and Pará formations are distinguished, besides the stripes of low land on the rivers' banks. Vegetations appears as isolated spots of rain equatorial forest, capoeira (Bush vegetation) at various degrees of growth, fields, savannahs, marsh, beach and low land vegetation. Climate may be classified as Af type of Köppen (1948) classification with annual rainfall varying around 2,500 mm. Soil parent material is mostly constituted of quaternary sediments and topography as a rule is flat or slightly waved. In the area chosen for this study the following kind of soils were found: Yellow Latosol, Red-Yellow Latosol, Concretionary Latosol, Ground Water Podzol, Regosol, Low Humic Gley and Not Differentiated Hidromorphic Soils. These units are composed of separeted groups or associations of kinds of soils. For each group described in this work the authors presented general information as to its general concept, its description and variations, geographical distribution, parent material, topography, vegetation and climate and a detailed description of modal profiles, besides of her general information about its agricultural utilization. Chemical and physical analytical methods employed for the characterization of each unit were those approved in meetings and congresses held by the Brazilan Society and taken as classical and employed by national pedological institutions. Most of the techniques used were the same as those employed by the Instituto Agronômico de Campinas and the Food and Agricultural Technological Division of Ministry of Agriculture. This work includes a colored, 1:200,000 scale Soil Chart of Bragantina Region.