Browsing by Author "Lewis, Sandra Tracey"

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    Assessing the relationship between soil reduction and methane emission in Texas rice fields
    (1995) Lewis, Sandra Tracey; Sass, Ronald L.
    Reduction processes and methane emissions have been observed in six rice fields along a sand-clay-silt gradient for one growing season. Variations in reduction processes occurred by depth and upon field draining, as well as among fields of differing soil sand content. Analysis at four 2.5 cm-intervals revealed that greater microbial activity appears to be occurring close to the surface of the soil, and decreases with depth. This may be due to greater substrate availability through decomposition of organic matter from roots and dead plant material at that location. Also, it was observed that the re-entry of oxygen upon field draining decreases the amount of reduction occurring, as well as the levels of methane emitted. In this study, greater amounts of emitted methane were measured from the sandy soil extreme. Reduction processes, however, were found to be similar in both clayey and sandy soils.
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    The use of redox measurements to study methane mitigation options in Texas rice paddies
    (1996) Lewis, Sandra Tracey; Sass, Ronald L.
    Redox measurements were used to study whether different mitigation options affect methane emission and production by altering the electrochemical environment in rice paddy soil. These mitigation options include field drainage, use of different cultivars, and changing soil texture. Results indicate that the redox potential (Eh) is an accurate indicator of whether or not methane is produced. Also, the timing of methane production and emission was found to be dependent upon the reduction of iron and subsequent increase of the ferrous ion concentration. Field drainage is a mitigation option that successfully lowers methane emission rates by increasing the Eh. By studying the other mitigation options, it was found that once sufficiently negative Eh values are reached, different non-redox parameters control the actual amount of methane emitted.