Variabilidade das concentrações de metais e propriedades físicas do solo em área com fertirrigação

Abstract

The use of swine effluents as liquid fertilizer is a common agricultural practice in the northwest region of the state of Rio Grande do Sul. Considering that the activity may cause an eventual impact to the environment where it is applied, this study aims to analyze the chemical and physical properties of soils where pig manure is applied as liquid fertilizer and compare their characteristics with others in the area where this practice does not occur. For this, soil samples from two agricultural zones in the municipality of Pinheirinho do Vale - RS were analyzed. Samples were collected at five sampling sites, at depths of 0, 50 and 100 cm. For each location, the concentrations of chemical elements (cadmium, cobalt, copper, chromium, manganese and zinc) were determined using the atomic absorption spectrometry technique, in addition to physical parameters (saturated hydraulic conductivity and granulometry). The results obtained indicated that the soil of area 1 (with application of swine manure) presented average values ​​of 34% of clay, 41% of silt and, only, 25% of sand, being classified as clayey loam. In area 2 (without application of swine manure) the soil presented average values ​​of 18% clay, 46% silt and 36% sand, being classified as frank. The saturated hydraulic conductivity was 1.4 x 10-5 cm.s-1 for area 1 and 2.4 x 10-4 cm.s-1 for area 2. Regarding the analysis of soil chemical parameters, the results indicated values ​​above those established by current legislation, and the elements Copper and Cadmium showed values ​​above at all points and depths analyzed. There was a significant difference between the areas only for the depth of 1 meter for the elements Zinc, Cobalt and Manganese. It follows from this that the use of liquid swine manure did not alter the natural quality of the soil, where some elements may be of natural origin in the environment (local geology). For some chemical elements, leaching by the profile and/or translocation of the clay fraction in depth occurred.