CH₄ dan CO₂ pada Lahan Sawah Berbeda Penggenangan dengan Pengukuran Closed Chamber dan IPCC

Abstract

Greenhouse gas emissions from paddy fields with different flooding systems produce varying amounts of CH₄ and CO₂, which need to be re-evaluated because IPCC calculations do not fully represent actual field conditions. Therefore, it is important to compare IPCC estimates with direct measurement methods such as Closed Chamber and titration to obtain results that are accurate for local conditions. This study aims to analyze the effect of water management systems (different flooding conditions) on CH₄ and CO₂ emission variability in paddy fields, to measure and compare CH₄ and CO₂ emissions using three methods (IPCC, Closed Chamber, and titration), and to examine the relationships between soil characteristics (pH, organic C, total N, and C/N ratio) and CH₄ and CO₂ emissions. The research was conducted in Tanjung Morawa District, Deli Serdang Regency, from July to October 2025. A survey method was applied to describe natural field conditions and analyze relationships among variables. Sampling points were selected using purposive random sampling based on flooding systems and rice varieties. The water management systems consisted of continuously flooded and intermittent irrigation fields. The rice growth phases observed were vegetative, generative, and harvest. CH₄ and CO₂ were measured using the closed chamber, titration, and IPCC approaches. The results show that the IPCC method produced CH₄ emission values approximately 1,39 times higher than the closed chamber method. Conversely, the closed chamber method generated CO₂ emissions about 69,19 times higher than the IPCC method. These differences arise from the fundamental approaches of each method: the IPCC method uses standard emission factors, making its estimates more conservative, whereas the closed chamber method measures fluxes directly and instantaneously, making it more sensitive to daily variations in the field. Flooded irrigation systems produced higher CH₄ emissions during the generative phase, while intermittent irrigation systems resulted in lower CH₄ emissions. CO₂ emissions showed the opposite pattern: intermittently irrigated rice fields produced higher CO₂ emissions, whereas flooded fields produced lower CO₂ emissions. Increased soil moisture content had a positive relationship with CH₄ emissions during the generative phase at approximately 72,2%. During the harvest phase, soil organic C and total N contents were negatively correlated with CO₂ at about 73,6% and 79,6%, respectively, while soil moisture content was positively correlated with CO₂ at around 52,5%. Rainfall showed a positive correlation with CO₂ emissions at approximately 87,2%, whereas the number of rainy days showed a negative correlation with CH₄ emissions at around 99,8%.