LIVESTOCK PRODUCTION AND DIFFUSE POLLUTION IN A VOLCANIC SOIL

Abstract

In developed countries, intensive grazing has been related to waterpollution. The results of several projects carried out on a volcanicsoil of the Osorno soil series on beef grazing production systems haveshown that grazing management did not increase total nitrogen (N) andphosphorus (P) transfer and losses. Due to the high water infiltrationcapacity of the soil, runoff was < 1% of total drainage, therefore, Nand P losses in runoff were small. Nitrogen leaching losses were high (3up to 71 kg N ha(-1) yr(-1)). Nitrogen loss in runoff was mainly lost asDON (c. 50%) while N leaching losses were mainly as nitrate (c. 70%).Total P losses ranged between 1 and 22 g P ha(-1) yr(-1) and theyincreased with increasing field slopes. Phosphorus was mainly lost asreactive P (c. 70%). Total losses were greatly affected by incidental Nand P losses associated to spring N and P fertilizer application, sothat grassland managements should consider this constrain for grazedareas in southern Chile. Research should be carried out in moreintensive production systems (e. g. dairy farms) where N and P ratesused are higher and applied during different times of the year, with apotential impact for the wider environment.