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Denitrification in Soil Aggregates Analyzed with Microsensors for Nitrous Oxide and Oxygen
Author(s) -
Højberg Ole,
Revsbech Niels Peter,
Tiedje James M.
Publication year - 1994
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/sssaj1994.03615995005800060016x
Subject(s) - denitrification , denitrifying bacteria , nitrous oxide , chemistry , acetylene , environmental chemistry , oxygen , soil respiration , organic matter , nitrogen , soil water , environmental science , soil science , organic chemistry
Denitrification in soil microenvironments is difficult to study by conventional techniques. By use of O 2 and N 2 O microsensors, it was possible to study the spatial distribution of oxygen respiration and denitrification in soil aggregates kept at field capacity. Aggregates with diameters of 20 to 25 mm often contained anaerobic centers but exhibited only low rates of denitrification due to a limiting availability of electron donors. Addition of organic matter such as clover leaves or tryptone to the surface of the aggregates greatly stimulated respiratory activity and caused anoxia and high rates of denitrifying activity within the organic hot‐spot and in the underlying soil. Due to imbalance between N 2 O production and N 2 O reductase activity, the creation of a hot‐spot led to an initial accumulation of N 2 O even when acetylene was absent. Denitrification within the center of a hot‐spot rapidly became limited by the diffusional supply of NO − 3 , even when the underlying soil contained 5 m M NO − 3 , and such hot‐spot centers depleted of NO − 3 served as sinks for N 2 O while N 2 O concentrations of up to 400 µ M were building up immediately below. The bulk N 2 O production rate of the soil was thus the result of a net production in some microenvironments and simultaneous net consumption in other microenvironments.