There are limited data for greenhouse gas (GHG) emissions from smallholder agricultural systems in tropical peatlands, with data for non-CO2 emissions from human-influenced tropical peatlands particularly scarce. The aim of this study was to quantify soil CH4 and N2 O fluxes from smallholder agricultural systems on tropical peatlands in Southeast Asia and assess their environmental controls. The study was carried out in four regions in Malaysia and Indonesia. CH4 and N2 O fluxes and environmental parameters were measured in cropland, oil palm plantation, tree plantation and forest. Annual CH4 emissions (in kg CH4 ha-1 year-1 ) were: 70.7 ± 29.5, 2.1 ± 1.2, 2.1 ± 0.6 and 6.2 ± 1.9 at the forest, tree plantation, oil palm and cropland land-use classes, respectively. Annual N2 O emissions (in kg N2 O ha-1 year-1 ) were: 6.5 ± 2.8, 3.2 ± 1.2, 21.9 ± 11.4 and 33.6 ± 7.3 in the same order as above, respectively. Annual CH4 emissions were strongly determined by water table depth (WTD) and increased exponentially when annual WTD was above -25 cm. In contrast, annual N2 O emissions were strongly correlated with mean total dissolved nitrogen (TDN) in soil water, following a sigmoidal relationship, up to an apparent threshold of 10 mg N L-1 beyond which TDN seemingly ceased to be limiting for N2 O production. The new emissions data for CH4 and N2 O presented here should help to develop more robust country level 'emission factors' for the quantification of national GHG inventory reporting. The impact of TDN on N2 O emissions suggests that soil nutrient status strongly impacts emissions, and therefore, policies which reduce N-fertilisation inputs might contribute to emissions mitigation from agricultural peat landscapes. However, the most important policy intervention for reducing emissions is one that reduces the conversion of peat swamp forest to agriculture on peatlands in the first place.
Data gas rumah kaca, terutama gas metana dan nitrogen, dari kegiatan pertanian skala kecil pada lahan gambut tropis sangat jarang diteliti. Tujuan penelitian ini untuk mengukur emisi gas CH4 dan N2 O dari pertanian skala kecil pada lahan gambut di Asia Tenggara dan mempelajari faktor-faktor lingkungan yang berhubungan dengan emisi kedua gas tersebut. Riset dilaksanakan pada empat tipe penggunaan lahan di Malaysia dan Indonesia. Fluks CH4 dan N2 O dan parameter lingkungan diukur dari pertanian hortikultura, kebun kelapa sawit, kebun campuran (karet dan jelutung), dan hutan sekunder. Emisi tahunan gas metana (kg CH4 per ha per tahun) sebesar 70.7 ± 29.5; 2.1 ± 1.2; 2.1 ± 0.6 dan 6.2 ± 1.9 dari lahan hutan, kebun campuran, kebun kelapa sawit, dan pertanian hortikultura. Dan emisi gas nitrogen (kg N2 O per ha per tahun) dari empat penggunaan lahan di atas adalah 6.5 ± 2.8; 3.2 ± 1.2; 21.9 ± 11.4 dan 33.6 ± 7.3. Ketinggian muka air tanah sangat mempengaruhi emisi gas metana, dan besarnya emisi tahunan gas metana meningkat secara eksponensial pada tinggi muka air tanah sebesar lebih dari −25 cm. Total nitrogen terlarut (TNT) dalam air tanah gambut sangat berkorelasi dengan emisi gas N2 O, membentuk hubungan sigmoid. Konsentrasi 10 mg N per liter menjadi faktor pembatas, ketika produksi N2 O berkurang. Pemerintah dapat menggunakan data baru emisi metana dan nitrogen untuk memperbaiki nilai faktor emisi untuk melaporkan emisi gas-gas rumah kaca skala nasional. Status hara, terutama dampak pemupukan, berperanan terhadap peningkatan emisi. Karena itu, pemakaian pupuk yang efisien dan pengurangan pemupukan perlu menjadi pertimbangan dan menjadi satu langkah penting untuk mengurangi emisi gas-gas rumah kaca. Yang terpenting adalah pencegahan perubahan hutan rawa gambut di Asia Tenggara menjadi penggunaan lain, seperti pengembangan pertanian, merupakan upaya prioritas untuk mengurangi emisi gas-gas rumah kaca dari lahan gambut.
Keywords: agriculture; crop production; emission factors; greenhouse gas fluxes; methane; nitrous oxide; peat swamp forest; tropical peatlands.
© 2023 The Authors. Global Change Biology published by John Wiley & Sons Ltd.