Assessment of methane emission from paddy rice cultivation in Nam Dinh province

Abstract

The study has been conducted to examine CH₄ emission from two paddy rice cultivation systems including two specific paddy rice crops (RL) and two paddy rice crops rotated with one another crop (RM) in Truc Hung commune, Truc Ninh district, Nam Dinh province. CH₄ emission was found peaking at 413.7 mg/m²/day in the RL system after 61-67 days of transplantation; while one in the RM system peaking at 540.6 mg/m²/day after 73-77 days of transplantation. The main reason for the difference was blamed on distinguished feritiser applications between RL and RM systems. Accordingly, the RL system which mainly applied inorganic fertilisers, so the plants easily absorbed the nutrients and grew faster, inducing earlier CH₄ emission peak. In contrast, the RM applied mainly compost which took a longer time for microorganisms to decompose and make nutrients available for crops. As a result, the CH₄ emission peak was delayed in comparison with the RL system. Therefore, the total emission of CH₄ in RM (2.668 tons CO₂e/ton rice equivalent) was higher than that in RL (2.194 tons CO₂e/ton rice, equivalent). These preliminary findings have demonstrated the effects of fertilisers and rice growth stages on CH₄ emission in the Red river delta. Further researches should be implemented to precisely evaluate CH₄ emission in cultivating conditions in Vietnam, in which N₂O emission should be included along with CH₄ emission.