Estimating impacts of alternate wetting and drying on greenhouse gas emissions from early wet rice production in a full-dike system in An Giang Province, Vietnam, through life cycle assessment

The contribution of alternate wetting and drying (AWD) to mitigating soil methane (CH4) emissions from rice (Oryza sativa L.) cultivation is well known, but the trade-off among soil CH4 emissions reduction, rice yields and agronomic management is less clear. This study carried out a structured interview and life cycle assessment to explore the influence of AWD on life-cycle greenhouse gas (LC-GHG) emissions, yields and agronomic management in An Giang Province, Vietnam, which is the 5th-largest rice producer in the world. Farmers in An Giang Province were trained in a course that introduced them to AWD as a technological package known as ‘one must do, five reductions’. All farmers interviewed who attended the course reported that they were implementing AWD (AWD farmers), whereas interviewed farmers who did not attend the course reported that they did not implement AWD (non-AWD farmers). The present study showed that yields were almost identical among the AWD and non-AWD farmers. Irrespective of the water management, on-site burning was practised as straw management by >75% of farmers. Due to the influence of the technological campaigns, AWD allowed farmers in An Giang Province to reduce LC-GHG emissions without decreasing yields significantly and with lower use of fertilizers (nitrogen and phosphate) and seeds. Furthermore, the results suggest that a reduction in the use of fertilizer and seed does not reduce yields significantly for either AWD or non-AWD farmers, but careful straw management is required to avoid an increase in LC-GHG emissions.