Abstract

MARQUEZ MOLINA, John Jairo; SAINATO, Claudia Mabel; HEREDIA, Olga Susana  and  URRICARIET, Alicia Susana. The contamination by feedlot activity in a typic argiudoll soil evaluated by means of geophysical methods. Cienc. suelo [online]. 2018, vol.36, n.2, pp.22-37. ISSN 1850-2067.

The livestock activity in feedyards can impact the environment by the management of the animals'excreta. The objective of the study was to evaluate the distribution of N and P concentrations in the soil of feedlots with different time of use and to analyze their impact on groundwater. The hypothesis was that, in the corral with longer time of animals'confinement, the concentrations of these elements in the soil are greater. In two feedlots with 1 and 12 years of use, an initial exploratory phase was carried out by geophysical surveys of electrical resistivity tomography (TRE) and electromagnetic induction (EMI) to characterize the contamination through the distribution of electrical conductivity (EC) of the saturated and unsaturated zone. The TRE lines were located approximately perpendicular to the topographic slope, following a gradient model. A soil - directed sampling grid was designed based on the EC map to evaluate sites with different EC anomalies at each topographic position (high, intermediate and low). Samples were extracted, with three replicates per site at intervals of 30 cm to a depth of 1.5 m. The concentrations of nitrates (N-NO₃ -, Pextractable (Pe) and soil profile moisture were determined. In phreatic groundwater, the concentrations of major ions were evaluated. High EC coincided with sites with accumulated manure and higher soil water content. The concentrations of N-NO₃ - increase towards the areas surrounding manure mounds. The Pe, would run off to the surroundings of these places. In the corral with 12 years of use, the EC and the accumulated mass of both elements, in the first meter of depth, were higher than in the corral with 1 year of activity. The depth of the water table and the fine texture of the soil could have contributed to attenuate the contamination of the groundwater, and favor surface runoff.

Keywords : electrical conductivity; nitrates; feedlot.

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