1.5 bar pressure, sealed tight as mentioned previously and
incubated again for 24 hours. Prior gas sampling the incubated
samples were shaken for 1 minute to expel CH4 in soil
aggregates into the headspace, and 1 ml gas sample was
taken from the headspace of incubation bottle by using an
air-tight syringe. The concentration of CH4 in the gas
samples was analyzed using gas chromatograph
(Shimadzu GC2014), detector temperature 200o C (FID),
injection port 150o C, oven 180o C, stainless steel column
2 m length packed with unibead C. Carrier gas is He and
retention time is 2.25 minutes. To calculate the CH4
production the equation by Setyanto et al. (8) was used.
Labile organic carbon (LOC) was analyzed by 33 mM
permanganate-oxidation (KMnO4) method (9).The pH and
EC of flooded water were measured fitting to CH4 and
labile carbon analysis by using pH and EC meters,
respectively. SO4
2- content in soil was extracted with
KH2PO4 and analyzed using turbidimetric method.
2.3 Statistical analysis
The data collected was analyzed statistically
using Analysis of Variance (ANOVA) technique and
treatment means were compared by using Duncan’s
Multiple Range Test (DMRT) with SAS statistical
program.