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Factors Controlling Ammonia and Nitrous Oxide Emissions from Flooded Rice Fields

John R. Freney and Owen T. Denmead
Ecological Bulletins
No. 42, Trace Gas Exchange in a Global Perspective (1992), pp. 188-194
Published by: Oikos Editorial Office
Stable URL: http://www.jstor.org/stable/20113120
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Factors Controlling Ammonia and Nitrous Oxide Emissions from Flooded Rice Fields
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Abstract

We have determined the importance of several cultural and environmental factors on ammonia volatilization and nitrous oxide emission from rice fields in experiments conducted in Australia, China and the Philippines. Ammonia loss has been determined in the field by micrometeorological methods. Investigations in which ammonium bicarbonate, ammonium sulfate or urea were incorporated into the soil or broadcast into the floodwater indicate that the important variables controlling ammonia loss are the ammoniacal nitrogen concentration, the pH and temperature of the floodwater, and windspeed; other factors exert their influences through effects on those primary variables. Nitrogen losses from volatilization have varied from 0 to 56% of the nitrogen supplied. Our studies have also shown that some ammonia is emitted to the atmosphere from the leaves of rice plants, but these emissions appear to represent only a small part of the nitrogen budget of the crop, probably less than 5% of the nitrogen applied. Nitrous oxide emissions from temperate and tropical rice fields were studied with chamber techniques. Investigations in two cultural systems, a rotation involving pasture legumes and bare fallow, which produced an appreciable nitrate build-up before the field was flooded, and a system in which a rice field received applications of urea or ammonium sulfate some weeks after flooding, suggest that the emission of nitrous oxide is controlled by the time of flooding relative to nitrate production.

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