Potassium runoff and leaching losses in beef cattle production systems of southern Chile

Chilean livestock production is concentrated in the southern part of the country and is largely based on a direct grazing system that has intensified over the last 10 years because of new commercial trade agreements signed by the country. This more intensive land use has increased amounts of N, P, and K fertilizer use per hectare, as well as stocking rates, and the intensity of rotational grazing. The objective of this study is to quantify K losses in surface run-off and leaching from permanent pastures grazed with different stocking rates.

Potassium losses were evaluated in a closed beef cattle production system based on grazing at INIA Remehue between March and December 2005. The soil at the experimental site is a volcanic Andisol from the Osorno soil series (Typic Hapludands), which has 6% slope, more than 1 m in depth, high organic matter, and high K concentrations. The 30-year average rainfall for the area is 1,284 mm/yr. Animals at two stocking rates were managed under rotational grazing on a permanent pasture that had always been used for grazing beef cattle for 20 years. Fertilizer treatments included 67.5 kg N/ha and 69 kg P₂O₅/ha. No K fertilizer was added.

Little K losses via run-off and leaching (4 kg K/ha/yr, on average) were determined for this first year of evaluation. In total, 94% of the losses were a result of leaching. An increase in the stocking rate failed to have an impact on K losses from the system. Potassium losses represented only 6% of the K deposited in the soil by animals. The study will be completed with a second season of measurement in 2006/07. Chile-5