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Effects of N‐fertilisation on CH 4 oxidation and production, and consequences for CH 4 emissions from microcosms and rice fields
Author(s) -
KRÜGER MARTIN,
FRENZEL PETER
Publication year - 2003
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.2003.00576.x
Subject(s) - microcosm , paddy field , methane , agronomy , topsoil , nitrogen , environmental science , environmental chemistry , chemistry , biology , soil water , soil science , organic chemistry
The world's growing human population causes an increasing demand for food, of which rice is one of the most important sources. In rice production nitrogen is often a limiting factor. As a consequence increasing amounts of fertiliser will have to be applied to maximise yields. There is an ongoing discussion on the possible effects of fertilisation on CH 4 emissions. We therefore investigated the effects of N‐fertiliser (urea) on CH 4 emission, production and oxidation in rice microcosms and field experiments. In the microcosms, a substantial but short‐lived reduction of CH 4 emission was observed after N‐addition to 43‐d‐old rice plants. Methane oxidation increased by 45%, demonstrated with inhibitor measurements and model calculations based on stable carbon isotope data (δ 13 CH 4 ). A second fertilisation applied to 92‐d‐old plants had no effect on CH 4 emission rates. The positive effect of additional N on methanotrophic bacteria was also found in vitro for potential CH 4 oxidation rates in soil and root samples from the microcosm and field experiments, indicated by elevated initial oxidation rates and reduced lag‐phases. Fertilisation did not affect methane production in the microcosms. In the field, the effects were diverse: methane production was inhibited in the topsoil, but stimulated instead in the bulk soil. Stimulation occurred probably in the anaerobic food chain at the level of hydrolytic or fermenting bacteria, because acetate, a methanogenic precursor, increased simultaneously. Combining field, microcosm and laboratory experiments we conclude that any agricultural treatment improving the N‐supply to the rice plants will also be favourable for the CH 4 oxidising bacteria. However, N‐fertilisation had only a transient influence and was counter‐balanced in the field by an elevated CH 4 production. A negative effect of the fertilisation was a transient increase of N 2 O emissions from the microcosms. However, integrating over the season the global warming potential (GWP) of N 2 O emitted after fertilisation was still negligible compared to the GWP of emitted CH 4 .