Phosphorus losses in surface run-off from grazed permanent pastures on a volcanic soil from Chile

Reactive (RP) and organic phosphorus (OP) losses from grazed paddocks were determined on a volcanic soil during 2004 and 2005. Paddocks were grazed by Holstein Friesian steers (3.5 steers ha -1 ) and received N (67.5 kg ha -1 ) and P fertilizer (30 kg P. ha -1 ). Total losses ranged between 4 and 15 g P ha -1 year -1 and were greatly affected by incidental P losses associated with spring P fertilizer application. Reactive P constituted 90% of the total losses on average. Due to the high water infiltration capacity of the soil, run-off was < 1% of total drainage, therefore, phosphorus losses in run-off were small.