GHG emissions (CO2, CH4 and N2O) from tropical peatland cropland drainage ditches

Drainage of tropical agricultural peat has a significant impact on enhancing GHG emissions from oxidised soils. Across Malaysia and Indonesia for example, an estimated 16.6–27.9% of emissions come from peat soils with the conversion of peat swamp forest to oil palm plantation. While there is now a significant body of evidence demonstrating emissions from tropical peat soils under differing drainage regimes (especially for oil palm and acacia plantations), very little attention has been given to the emissions from the drainage networks associated with these complexes. Of these soil-based emissions, the majority of work has focused on CO₂ and CH₄ with minimal focus on N₂O emissions. For drainage ditches there is an even greater knowledge gap. There are, to our knowledge, no studies exploring all three GHGs from agricultural drainage ditches in the tropics. Therefore, here we present data showing the first combined emission factors for all three GHGs derived from surveys over the dry season within smallholder agricultural systems (vegetable and oil palm) in Malaysia. These will be linked to water chemistry, flow rate and aquatic DOC variability. This work demonstrates the importance of inclusion of these emission factors in overall land use emissions reporting and in the management of the drainage ditches for emissions reduction.