Peter Dörsch

Liming of acidic agricultural soils has been proposed as a strategy to mitigate nitrous oxide (N 2 O) emissions, as increased soil pH reduces the N 2 O/N 2 product ratio of denitrification. The capacity of different calcareous (calcite and dolomite) and siliceous minerals to increase soil pH and reduce N 2 O emissions was assessed in a 2‐year grassland field experiment. An associated pot experiment was conducted using homogenized field soils for controlling spatial soil variability. Nitrous oxide emissions were highly episodic with emission peaks in response to freezing–thawing and application of NPK fertilizer. Liming with dolomite caused a pH increase from 5.1 to 6.2 and reduced N 2 O emissions by 30% and 60% after application of NPK fertilizer and freezing–thawing events, respectively. Over the course of the 2‐year field trial, N 2 O emissions were significantly lower in dolomite‐limed than non‐limed soil ( p < .05), although this effect was variable over time. Unexpectedly, no significant reduction of N 2 O emission was found in the calcite treatment, despite the largest pH increase in all tested minerals. We tentatively attribute this to increased N 2 O production by overall increase in nitrogen turnover rates (both nitrification and denitrification) following rapid pH increase in the first year after liming. Siliceous materials showed little pH effect and had no significant effect on N 2 O emissions probably because of their lower buffering capacity and lower cation content. In the pot experiment using soils taken from the field plots 3 years after liming and exposing them to natural freezing–thawing, both calcite ( p < .01) and dolomite ( p < .05) significantly reduced cumulative N 2 O emission by 50% and 30%, respectively, relative to the non‐limed control. These results demonstrate that the overall effect of liming is to reduce N 2 O emission, although high lime doses may lead to a transiently enhanced emission.