METHANE EMISSION FROM PLOTS WITH DIFFERENCES IN FERTILIZER APPLICATION IN THAI PADDY FIELDS

Methane emission rates from plots with differences in fertilizer application (no fertilizer: NF-, chemical fertilizer: CF-, and organic materials: OM-) in 3 typical Thai paddy fields (fresh water alluvial, acid sulfate, and low humic gley paddy fields) were measured every week throughout the rice-growing period. The CH4 emission rates from the NF- and CF-plots in the paddy field with acid sulfate soil were much lower than the CH4 emission rates from similar plots in other countries, while those from the paddy field with low humic gley soil were much higher. The CH4 emission rates from these plots in the paddy field with fresh water alluvial soil corresponded to the lower reported values. The CH4 emission rates from the OM-plots in Thailand were within the ranges of reported values or higher. Methane was mainly emitted in the first half of the growth period in Thailand irrespective of the plots, in contrast to reports stating that CH, emission was higher in the second half of the growth period in the temperate region. The total amount of CH4 emission (g C m-2) during the rice growing period ranged from 4 to 59 in the fresh water alluvial paddy field, 0.6 to 17 in the acid sulfate paddy field, and 21 to 35 in the low humic gley paddy field, respectively.