Qualidade Estrutural da Camada Superficial de um Argissolo Vermelho-Amarelo sob Diferentes Usos

Abstract

The dairy farming is an alternative income of producers in southern Brazil. However, animal trampling and, or, the preparation can change the structural physical characteristics of the soil, damaging root growth and agricultural productivity. Physical parameters such as tensile strength, friability, soil bulk density, porosity, macroporosity, microporosity and penetration resistance have been used to assess the structural quality. The aim of this study was to quantify the tensile strength (TS), the friability (F), soil bulk density (Bd), total porosity (Pt), macroporosity (Ma), microporosity (Mi), the penetration resistance (PR) and the total organic carbon (TOC) content of an Alfisol under different uses and different positions in the landscape. The study was conducted in 2014, an agricultural property in the Pelotas city, RS-Brazil. The samples were collected in the layer from 0.00 to 0.10 m. To assess the tensile strength, 900 samples were selected per treatment, with a total of 2,700 aggregates. Samples with preserved structure were collected randomly using volumetric rings of 5 cm in height and diameter to assess the density, total porosity, macroporosity and microporosity and penetration resistance, totaling 135 samples. Using dried combustion method and with the aid of an elemental analyzer, the total organic carbon was quantified in 45 aggregates. The smallest and the largest TS, PR and Bd were found in the soil under fallow and pasture respectively. A significant inverse relationship between the TOC levels in relation to TS was verified. TS, PR, Bd and TOC were influenced by the use systems, featuring a reduced quality in proportion to the intensity of land use, featuring a reduced quality in proportion to the intensity of soil use. Only attributes PR and Bd in soil use under fallow and maize were sensitive in the evaluation of different positions in relief