Abstract:
The thesis was categorized into 2 parts, the first part subject to the influence of fertilizer and water management on methane emission from rice field at Inburi district, Singburi province during wet season. The rice strained SPR 1 (Oryza sativa var.) was cultivated for 112 days. The methane emission from the rice fields was collected using static box technique once a week during 21-1 12 days of the planting period. In this study 5 applications of fertilizers were: 1) No fertilizer 2) Supplement with basal, but not topdressing fertilizers 3) Supplement with both basal and topdressing fertilizers. These topdressing fertilizer were either urea (CO(NH$J, ammonium sulfate ((NHJ,SO>, or ammonium phosphate ((NHJ,PO>. The study on the influence of water management from rice field was categorized using 4 water management of regimes: 1) Flushing waters every 7 days at water level 5 cm 2) Flushing waters every 7 days at water level 2.5 cm 3) No water level above ground, and 4) Constant water level at 5 cm. The second part of this study was a laboratory investigation on anaerobic digestion of the Roi-Et soil series. Soil was incubated in an anaerobic condition for 112 days without organic carbon supplement, and with nitrogen source varied. There were 6 treatments: 1) Supplement with urea fertilizer 2) Supplement with ammonium sulfate fertilizer 3) Supplement with ammonium phosphate fertilizer 4) Supplement with mixed fertilizer (16-16-8) 5) Supplement with urea and ammonium phosphate fertilizer, and 6) No fertilizer. The methane emission fluxes from 5 fertilizer applications were in the range of 0.074-0.109 g~J3,Jm21d (0.744-1.086 kghald). The emission fluxes of methane in decreasing order were: urea > ammonium phosphate > ammonium sulfate > basal fertilizer only > no fertilizer. The emission fluxes were 0.109 g~~$m21d(1.087 Lgrndd); 0.092 gCH$m2/d (0.917 kglhald), 0.088 gCH/m21d (0.880 kwd), 0.084 gCH/m21d (0.840 kglhdd), and 0.074 gCH/m21d (0.744 kglhdd), respectively. The rice growth were in decreasing order of urea > ammonium phosphate > ammonium sulfate > basal fertilizer only > no fertilizer. The methane emission fluxes from 4 water management regimes were in the range of 0.087-0.109 (0.868-1.086 kglhdd). The emission fluxes of methane in decreasing order were: Constant water level at 5 cm >Flushing water every 7 days at water level 5 cm 7 Flushing water every 7 days at water level 2.5 cm > No water level above ground. The emission fluxes were 0.109 gCI4drn2ld (1.086 kglhdd), 0.099 gCH$m2/d (0.991 kglhdd), 0.093 gCH/m21d (0.927 kghld) and 0.087 gC~/m~/d(0.868 kglhafd), respectively. The rice growth were in decreasing order of: Constant water level at 5 cm > Flushing water every 7 days at water level 5 crn > Flushing water every 7 days at water level 2.5 cm >No water level above ground. The rice growth, represent by height, field density, air space in rice stems, and dry weight biomass that induced higher growth due to appropriate condition applied, led to higher methane emission. It is noted that the factors of fertilizer supplement influenced higher uncertainties than the factors of water management due to its broader ranges of methane emission fluxes. The study of anaerobic digestion of Roi-Et soil series in laboratory investigation without organic carbon supplement, and with nitrogen varied shown lower methane production than the experiments in the field due to the low of organic carbon. Fertilizer was essential for controlling methane production in paddy soil. Methane was emitted only fiom urea treatment and urea added ammonium phosphate treatment.