EFFECT OF THE STOCKING RATE AND LAND SLOPE ON NITROGEN LOSSES TO WATER ON A GRAZED PASTURE OF SOUTHERN CHILE

Most of the studies on nitrogen (N) leaching have been carried out on cut grass, and there is a lack of information on beef grazed grasslands. The objective of this study was to quantify N runoff and leaching losses in beef production systems with two different immediate stocking rates (63 and 191 Holstein Friesian steers ha(-1) day(-1)) and two land slopes (4 and 12%). Runoff and leachate samples were analyzed from 2004 to 2006 for total N, nitrate and ammonium. No significant differences for the total N losses were found between treatments (p > 0.05), which were low ranging from 0.9 to 26.8 kg N ha(-1) yr(-1). The main pathway for the losses was leaching, which contributed >99% of the total N lost. The main form of N leaching was nitrate-N (>84%). Nitrate-N concentration in runoff samples was high, averaging 14 to 31 mg L-1. We suggest that these low N losses could be related the low N fertiliser inputs in the pasture and to the N adsorption properties of volcanic soils and, so that further research is required on this subject.