Links between emissions of nitrogen and sulfur gases from acid sulfate soils: field evidence

Field scale emissions of nitrous oxide, nitrogen oxides and sulphur dioxide, measured by micrometeorological techniques, were examined to investigate a suggestion from laboratory studies that reduction of nitrate by pyrite could explain the very large emissions of nitrogen gases and sulphur dioxide from acid sulphate soils (ASS). All three of the target gases were emitted simultaneously from a bare ASS in the field, as they were in laboratory experiments in which nitrate solutions were added to pyrite or pyritic soil. However, the presence of a crop made it difficult to decide if chemodenitrification was at work in the field because of effects on soil evaporation and possible foliar absorption of emitted gases. The possibility remains that reaction between nitrate and pyrite might contribute to very high N2O emissions from ASS. More work on bare field soils is needed.