Low nitrogen leaching losses following a high rate of dairy slurry and urea application to pasture on a volcanic soil in Southern Chile

Dairy slurry is an important plant nutrient source. However, mismanagement (e.g. high application rate) can lead to nutrient losses to the wider environment. There are few data on slurry management and its effect on nitrogen (N) losses specific to Southern Chile, although existing studies suggest that N leaching on volcanic Chilean soils might be expected to be low. The objective of this study was to evaluate the effect of heavy dairy slurry application on N leaching losses and compare it with an inorganic fertiliser on a volcanic soil of Southern Chile. A field experiment was carried out at the Agricultural Research Institute, Remehue Research Centre, on a volcanic soil of Southern Chile (40°35′S, 73°12′W) from March 2008 to March 2010. There were two N application treatments, with a target application rate of 400 kg N ha−1 yr−1 as either dairy slurry (S) or urea (U) split into four even applications over the year. Additionally, a control (C) treatment with no N addition was included. N leaching was measured using ceramic suction cups (3 per plot), with samples taken every 100 mm of drainage during the drainage season. Despite the high N rate and application time, N leaching losses were small with no significant differences between treatments in either year (P > 0.05). Concentrations of NO3−–N for each sampling period never exceeded c. 5.5 mg L−1 and annual mean values were below 0.5 mg L−1 for all treatments. Cumulative N leaching losses were small at 1.4 and 1.2 kg ha−1 yr−1 (C), 2.8 and 4.2 kg ha−1 yr−1 (S) and 2.4 and 3.3 kg ha−1 yr−1 (U) for 2008 and 2009, respectively. We suggest that this could be explained mainly by the unique N retention properties of volcanic soils in Southern Chile and/or gaseous N losses.