| Summary: | This study aims to comprehend the links between soil Eh and pH changes in eucalyptus biochar (BC) and rice straw
(RS) amended soils and CH4
emissions. Increased CH4
emission rates and high total CH4
emissions (TCH4
) were found in RS
soils. In contrast, higher concentrations of refractory lignin, fixed C and volatile matter in BC suppressed C mineralization
and terminal methanogenesis, resulting in low TCH4
. Eh in RS soils decreased more rapidly than in BC soils during the first
phase as a single exponential function. This indicated that RS is a fast electron donor for an instant electron acceptor
reduction and methanogenesis. During the second phase, Eh in BC soils decreased to very low values, probably because of
the higher concentrations of electron donating phenolic compounds coupled with terminal methanogenesis. Meanwhile,
hydrogen is consumed via electron acceptor reduction and methanogenesis simultaneously produce OH-
corresponded with
a rise of pH, a characteristic of reverse single exponential function.
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