Effect of water management and salinity stress on GHG emissions in rice cultivation | |
| Author | Eav, Kim Hong |
| Call Number | AIT Thesis no.EV-25-05 |
| Subject(s) | Greenhouse gases--Environmental aspects Water in agriculture |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | Global warming is accelerating due to increased greenhouse gas (GHG) emissions, with methane (CH4) being a highly potent contributor. Rice cultivation is a major source of CH4, especially under continuous flooding (CF), which creates anaerobic conditions favorable for methanogenesis. Alternate wetting and drying (AWD) has been introduced as a mitigation strategy to reduce emissions, while increasing soil salinity in many rice-growing regions adds complexity by inhibiting microbial processes responsible for both methane production and oxidation. This study assessed the effects of water management and salinity stress on CH4 emissions, CH4 consumption, CO2 emissions, and soil conditions in rice cultivation under four treatments: CF, CF+Salt, AWD, and AWD+Salt. The findings revealed that AWD increased aeration limiting acid accumulation in soil effectively (pH 6.93–6.98) than CF (6.83–6.84) and significantly enhanced CH4 consumption, reaching the highest average rate under AWD (19,830.53 mg/m2day). In contrast, salinity significantly increased electrical conductivity (up to 508.13 µS/cm) and suppressed both CH4 emissions and consumption to undetectable levels in CF+Salt and AWD+Salt. Average CH4 emissions occurred in CF (454.70 mg/m2day), while AWD reduced emissions to 263.25 mg/m2day. Methane emissions showed strong negative correlations with salinity (ρ = –0.84), EC (ρ = –0.87), nitrate (ρ = –0.76), and TOC (ρ = –0.78), while salinity and conductivity also significantly inhibited CH4 consumption (ρ = –0.58) and (ρ = –0.69) respectively. CO2 emissions were highest under AWD, 249.15 mg/m2day in average, indicating enhanced aerobic respiration. Biomass was greatest in CF (wet: 63.69 g; dry: 25.11 g) and lowest in AWD+Salt (wet: 30.28 g; dry: 12.39 g), reflecting the compounded effects of intermittent drying and salinity stress. These findings highlight that while AWD improves methane oxidation and reduces emissions under non-saline conditions, salinity remains a dominant limiting factor for both microbial activity and plant productivity. |
| Year | 2025 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Water Resources and Environmental Engineering (DWREE) |
| Academic Program/FoS | Environmental Engineering and Management (SET-EEM) |
| Chairperson(s) | Cruz, Simon Guerrero; |
| Examination Committee(s) | Ekbordin Winijkul;Shanmugam, Mohana Sundaram; |
| Scholarship Donor(s) | Loom Nam Khong Pijai (Greater Mekong Subregion) Scholarships; |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 2025 |