Spatial variation in the capacity of soil for CH4 uptake and population size of methane oxidizing bacteria in dryland rice agriculture

摘要

The pattern of methane (CH4) oxidation and population size of methane oxidizing bacteria (MOB) were studied in three different soils (rhizosphere, bulk and bare) of a dryland rice (Oryza sativa L. cultivar Narendra-118) field. The rhizosphere soil exhibited the strongest CH4 oxidation activity and bare soil the weakest. MOB population size was significantly higher in the rhizosphere (671.0 x 10(5) cells g(-1) soil) than in the bulk (569.0 x 10(5) cells g(-1) soil) or the bare soil (49.2 x 10(5) cells g(-1) soil), and NH4+-N concentration was highest in the bare soil (6.74 mu g g(-1) soil) followed by the bulk (5.58 mu g g(-1) soil) and rhizosphere soil (4.02 mu g g(-1) soil). Half saturation constant (K-m) and maximum oxidation rate (V-max) decreased significantly from the rhizosphere to bulk to bare soil and ranged from 84.01 to 5.81 mu g g(-1) dry soil and 0.62 to 0.05 mu g h(-1) g(-1) dry soil, respectively. The rice rhizosphere not only supports a larger population of MOB but also contributes substantially to the capacity of soil for CH4 uptake, leading to a predictable spatial pattern in CH4 sink strength within the dryland rice ecosystem. [References: 28]