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Direct Measurement of Denitrification Loss from Soils: II. Development and Application of Field Methods
Author(s) -
Ryden J. C.,
Lund L. J.,
Letey J.,
Focht D. D.
Publication year - 1979
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/sssaj1979.03615995004300010020x
Subject(s) - denitrification , soil water , nitrous oxide , chemistry , acetylene , nitrogen , environmental chemistry , environmental science , soil science , organic chemistry
A method was developed for the direct measurement of denitrification N loss from field soils. The method was based on the observation that in the presence of acetylene (C 2 H 2 ) concentrations of 0.1 to 5.0% (vol/vol) the sole product of denitrification in soils was nitrous oxide (N 2 O). Sustained C 2 H 2 concentrations of approximately 0.4 to 1.6% were induced in the atmosphere of a field soil by supplying C 2 H 2 through probes inserted into the soil to a depth of 1 m. The time required to establish these C 2 H 2 concentrations ranged from 15 to 30 min. The concentrations could be maintained for at least 17 hours during which C 2 H 2 was supplied at 2.8 liters/hour. Essentially, no increase in 30 N 2 concentration was detected under closed soil covers installed at C 2 H 2 ‐treated field locations which had received 15 N‐NO 3 . At locations without C 2 H 2 treatment an average 30 N 2 enrichment of 14.2% relative to air was observed. Production of 15 N‐labeled N 2 O and N 2 at locations with and without C 2 H 2 treatment was very similar, and essentially 100% of the 15 N evolved at C 2 H 2 ‐treated locations appeared as N 2 O. Direct measurements of N 2 O fluxes from an irrigated, fertilized Haploxeroll at locations with and without C 2 H 2 treatment were made using a previously established method. Net denitrification N fluxes, measured as N 2 O flux from C 2 H 2 ‐treated locations ranged from 0.5 to 80 g N/ha per hour. Peak N fluxes were between 30 and 80 g N/ha per hour and usually occurred 30 to 60 hours after irrigation had ceased. Total denitrification loss during 123 days was 51.2 kg N/ha with the total fertilizer application being 335 kg N/ha. Dinitrogen/nitrous oxide ratios, determined from the difference in N 2 O evolution at sites with and without C 2 H 2 treatment, ranged from 0 to 1 during the first 12 to 24 hours of each denitrification cycle after which the ratio gradually increased to values of 10 to 20 towards the end of each cycle. The average value was between 5.6 and 7.4. The methodology provides a technique for direct monitoring of denitrification N loss in situ.