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

Purpose: 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.

Methods: 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.

Results: 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).

Conclusions: 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.