Effect of stocking rate on ecological sustainability measured through standardized indicators in a system of outdoor pig production.

Outdoor pig production offers advantages with respect to investment costs, animal welfare, and reduced environmental impact. However, these systems, if not operated judiciously, can damage the environment. Environmental Impact Indicators are useful to identify, interpret and prevent such damage. Nitrate leaching and loss of vegetative cover are among the factors associated with mismanagement of the stocking rate that can affect the ecological sustainability of these systems. In Argentina little pertinent information is available. Thus, the aim of this study was to analyze the evolution of ecological sustainability, from the dynamics of vegetation and soil chemical characteristics, using standardized indicators. In the Swine Production Module of the Faculty of Agricultural Sciences (UNR), on a pasture implanted to fescue grass, the animals were divided among the treatments T1: low stocking rate during the growth phase; T2: high stocking rate during the growth phase; T3 low stocking rate during finishing; and T4: high stocking rate during finishing. The variables evaluated were vegetative characteristics (abundance, cover, biomass) and soil characteristics (nitrate and available phosphorus contents and pH). Normalization of the indicators was performed using ELANEM methodology. The indicators are represented in radial figures. Already by 5 Mo into the experiment T4 was observed to have caused displacement most distant from the ideal condition. Further studies are needed to determine the recommendable stocking rate and evaluate the indicators that best explain the environmental degradation. The radial figures proved useful to show how each indicator interacts and influences others.