Carbon induced subsoil denitrification of 15N-labelled nitrate in 1 m deep soil columns
1999
Clough, T.J. | Jarvis, S.C. | Dixon, E.R. | Stevens, R.J. | Laughlin, R.J. | Hatch, D.J.
Nitrate in soils is potentially a contaminant of groundwater and can also be denitrified to form nitrous oxide (N(2)O), a global warming gas that is also involved with stratospheric ozone depletion. The objective of this work was to examine the fate of (15)N-labelled NO(3)- when it was injected into the subsoil (80 cm) in the presence of carbon. Gas fluxes from the soil surface and gas concentrations in the soil profile were monitored for 38 d. On average, after this time only 13% of the (15)N-labelled N was present as NO(3)- with immobilisation (54%), entrapment in soil pore space (7%), dissolution of N in soil water (2%), gas fluxes from the soil column surface (N(2)O < 1%, N(2) 1.8%) and unaccounted for (15)N (20%) making up the remainder of the (15)N balance. As (15) N-labelled N gases diffused from the zone of denitrification towards the soil surface the ratio of N(2)O-N:(N(2)O-N + N(2)) decreased (range of 0.90 to 0.17).
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