Spatio-kinetic variation of methane oxidizing bacteria in paddy soil at mid-tillering: effect of N-fertilizers
2003
Dubey, S.K.
Laboratory experiments were conducted to evaluate the variation of population size of methanotrophs (MOB) and CH4 oxidation pattern inflooded rice soils sampled at three spatial points (rhizosphere, bulk and baresoils). Rhizosphere soil had higher MOB population size (301.1 ×10(5) cells g−1 dry soil) than bulk (37.2× 10(5) cells g−1 dry soil) and bare soil (19.1 × 10(5) cells g−1 dry soil). The population size of MOB followed a decreasing trend with respect to fertilizer (urea ≤ NH4NO3 ≤ NH4Cl≤ control). The result indicated that rhizosphere soil presented the strongest CH4 oxidation activities, as shown by the highest values of the two kinetic parameters (Km(app) and V(max). K(m) and V(max) increased significantly from bare to bulk to rhizosphere soil in control and fertilized soil and ranged from 6.2 to 133.2μg g−1 dry soil and from 0.03 to 0.41μg h−1 g−1 dry soil,respectively. The differences in K(m) and V(max) among the three soils (rhizosphere, bulk and bare) in this study could be due to differential species composition of methanotrophic community and/or to conditioning of MOB under different soil micro environments. The present study has demonstrated a competitive inhibition effect of NH(4) (+)-N on CH4 oxidation.
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