LIVESTOCK PRODUCTION AND DIFFUSE POLLUTION IN A VOLCANIC SOIL

Abstract

In developed countries, intensive grazing has been related to water pollution. The results of several projects carried out on a volcanic soil of the Osorno soil series on beef grazing production systems have shown that grazing management did not increase total nitrogen (N) and phosphorus (P) transfer and losses. Due to the high water infiltration capacity of the soil, runoff was <1% of total drainage, therefore, N and P losses in runoff were small. Nitrogen leaching losses were high (3 up to 71 kg N ha-1 yr-1). Nitrogen loss in runoff was mainly lost as DON (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 they increased with increasing field slopes. Phosphorus was mainly lost as reactive P (c. 70%). Total losses were greatly affected by incidental N and P losses associated to spring N and P fertilizer application, so that grassland managements should consider this constrain for grazed areas in southern Chile. Research should be carried out in more intensive production systems (e.g. dairy farms) where N and P rates used are higher and applied during different times of the year, with a potential impact for the wider environment.