Factors influencing methane emissions in rice paddies using alternate wetting and drying method

BACKGROUND AND OBJECTIVES: Addressing global food security, rice is one of the fundamental food sources, particularly in Southeast Asia where traditional flooded rice cultivation is a major methane source. Conventional techniques encourage anaerobic breakdown in saturated soils, resulting in methane emissions, where effective water management being a significant determinant. The study objectives were to investigate rice cultivation under different alternate wetting and drying water management practices, while measuring methane concentration using the closed chamber method.METHODS: This study investigated methane emissions from irrigated rice under five water management treatments, with the control being continuous flooding (Treatment ۱), maintained at ۵ centimeters. The alternate wetting and drying methods exhibited differences in the initial water depth with. Treatment ۲ followed the Thailand standards with ۵ centimeters water depth, while Treatment ۳, ۴, and ۵ applied alternate wetting and drying depths of ۱, ۱۰, and ۲۰ centimeters, respectively. The study was carried out in the rice cultivation season utilizing lysimeter systems. The methane flux was measured weekly together with other environmental parameters.FINDINGS: Rice treatments showed differences in water use and methane emissions. The application of alternate wetting and drying at ۱ and ۵ centimeters has led to a reduction in irrigation water usage by over ۴۰ percent. Rice growth generally increased through the growth stages, with no significant differences. methane emissions varied. Treatment ۵ and ۱ produced the highest methane fluxes (۱۹.۸۸ ± ۱.۰۲ and ۱۷.۴۵ ± ۱۰.۶۷ milligram per square meters per hour, followed by Treatment ۴, while ۲ and ۳ showed the lowest emissions (۷.۳۷ ± ۳.۲۹ and ۳.۰۶ ± ۲.۳۵ milligram per square meters per hour). During the heading stage, methane emissions were at their peak, as plant biomass, root exudates, and aerenchyma had fully matured. Under alternate wetting and drying conditions, higher dissolved oxygen and oxidation-reduction potential were also seen.CONCLUSION: Water level is the controlling factor for methane emissions in rice paddies. During the heading stage, methane emissions were at their peak, as plant biomass, root exudates, and aerenchyma had fully matured. While frequent wetting drying cycles promoted oxygen diffusion and methane oxidation. The study revealed that employing the alternate wetting and drying technique is a viable approach to managing water resources, leading to improved water-use strategy and a reduction in methane emissions during rice farming.

کلیدواژه ها:

Methane (CH۴) emission ، Alternate wetting and drying (AWD) ، Rice paddies ، Water Conservation.