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Redox Range with Minimum Nitrous Oxide and Methane Production in a Rice Soil under Different pH
Author(s) -
Yu Kewei,
Patrick William H.
Publication year - 2003
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/sssaj2003.1952
Subject(s) - nitrous oxide , incubation , chemistry , redox , oxidizing agent , soil water , soil ph , nitrogen , environmental chemistry , zoology , inorganic chemistry , soil science , biochemistry , environmental science , organic chemistry , biology
A Louisiana rice soil was incubated from the most oxidizing to the most reducing conditions that could be maintained. Four different pH levels were used. Nitrous oxide production initiated shortly after the incubation started under oxidized conditions. As the soil suspension became more reducing, a large amount of CH 4 was produced at a critical reducing point and increased exponentially with a further decrease of redox potential (E H ). The results indicated that there was no statistically significant difference between the theoretically predicted decrease of E H with increase of pH and the observed change of E H with pH for N 2 O production (60 mV, P = 0.932), and for significant CH 4 production (93 mV, P = 0.204), respectively. Consequently, the E H range with minimum N 2 O and CH 4 production shifted to lower values of the E H scale when pH increased. Global warming potential (GWP) contribution from the studied soil mainly comes from N 2 O production at moderately reducing conditions, and from CH 4 production under very reducing conditions. There was a slight production of CH 4 at high E H s soon after incubation started, but this CH 4 production was not a significant source of GWP from soils because of its small quantity and transient occurrence. If pH is neutral, the calculated E H range with minimum GWP is generally in the range of −150 to +180 mV. This redox window accounts for >40% of the entire E H range in this study, which makes appropriate management of irrigated rice fields possible that will minimize both N 2 O and CH 4 production.