Premium
Field Evaluation of Four Methods for Measuring Denitrification
Author(s) -
Aulakh M. S.,
Doran J. W.,
Mosier A. R.
Publication year - 1991
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1991.03615995005500050023x
Subject(s) - denitrification , acetylene , soil water , chemistry , flux (metallurgy) , nitrogen , atmosphere (unit) , evaporation , environmental chemistry , analytical chemistry (journal) , soil science , environmental science , physics , organic chemistry , thermodynamics
Reliable and direct monitoring of in situ denitrification N loss will aid understanding of the N cycle and development of efficient agricultural management systems. The objective of this research was to evaluate four approaches for measuring denitrification in the field. A method using coated CaC 2 as a source of acetylene (C 2 H 2 ) to block N 2 O reduction was compared with two existing C 2 H 2 methods and a 15 N method. Use of CaC 2 granules in soil around gas‐measuring chambers produced soil atmospheric C 2 H 2 concentrations comparable to those observed with continuous C 2 H 2 flow through diffusion tubes, which were sufficient to inhibit N 2 O reduction for a 48‐h period. Acetylene concentrations in the soil atmosphere exceeded 1.0 mL L −1 and completely inhibited the reduction of N 2 O to N 2 , giving N 2 O‐N recoveries of 105 ± 7% of total denitrification. Daily denitrification rates (two gas samplings each day) and total N emissions over 4 d were comparable for 15 N chamber, C 2 H 2 ‐inhibition chamber, and CaC 2 ‐C 2 H 2 ‐inhibition chamber methods but were five‐ to sevenfold higher for the C 2 H 2 inhibition method using intact soil cores. Where N‐gas flux was measured four times daily in chambers and intact soil cores, denitrification rates were associated with daily changes in soil temperature and decreases in soil water‐filled pore space (WFPS) in chamber soils due to evaporation/percolation. Either of three chamber methods may be used for measuring field denitrification, provided daily variation in gas‐N flux is considered in choosing sampling times. To avoid overestimation of denitrification using the acetylene‐inhibition soil‐core method, fresh intact soil cores should be taken daily to simulate field soil physical conditions, especially soil WFPS.