Manure plume modeling in feedlot pen soils

Abstract

The generation of large amounts of manure by confined cattle feeding operations (feedlot) in reduced areas is a concern due to its potential to act as pollutant for ground and surface water. Studies have revealed that leaching may occur in pen soils, with negative effects on water quality. The objective of this work was to develop a mathematical model for predicting manure plume vertical advancement in soil beneath feedlot pens. The study was carried out in feedlot pens situated in a Argentine region called the Sandy Pampa (Pampa Arenosa). Five areas or treatments were selected, four of which were located in pens (considerably impacted by beef cattle operations) with 1, 4, 8 and 15 years of use, and the remaining one in natural soil area as control. The soil in the study areas was morphologically characterized. Applying standard procedures, the following variables were quantified: gravimetric moisture content and chloride concentration in soil solution. Chloride ion was used as a tracer to estimate manure flux. Data of different chloride profiles adjusted to a first-order model, from which it was possible to predict the depth of penetration of the manure, and the factor of plume advance in the underlying soil. In addition, the dominance of flows was analyzed from the development of a flow number indicator (Nf), which could be useful for environmental regulatory purposes bringing a base for easy estimation of pollutant transport mechanism in water–soil systems.