Role of Liming and Nitrogen Input in Determining Low Nitrogen Leaching Losses in Volcanic Soils

Livestock production based on grazing is the most important productive activity in southern Chile. Most grasslands are located on volcanic soils with unexplained low nitrogen (N) leaching losses.

A cutting field experiment was carried out between February 2008 and March 2010 on an Andisol of the Osorno soil series, testing liming (0 or 2 t CaCO₃ ha^− 1 yr^− 1) and N rate applied as inorganic fertiliser applied in two equal dressings (0, 200, 400 kg N ha^− 1 yr^− 1). Measurements of pasture yield, N uptake and N leaching losses were complemented with mineralization studies under field and laboratory conditions, and soil N abiotic retention.

Total N leaching losses were greater in the 400 kg N treatments (90 kg N ha^− 1, on average), with no differences between the liming treatments (10 kg N ha^− 1, on average; P > 0.05). Nitrogen addition resulted in 50% and 92% more dry matter yield in treatments receiving 200 and 400 kg N than the control (N-0) treatment. Potential N mineralization varied between 206 and 282 mg N kg^− 1 dry soil. The mineralization of more recalcitrant components of soil organic matter increased with both N and lime addition. Soil had a greater capacity to retain added N as ammonium (74% on average).

The natural acidic soil conditions did not prevent nitrification, neither N leaching losses, probably associated to occurrence of N abiotic immobilization processes. Lime addition could influence N mineralization in the long term, while N addition would influence it in both short and long term.