Drainage, mechanical compaction and water management are important land preparation and management practices in any agricultural development on tropical peatland. Drainage is prerequisite to create aerobic zone for better root growth for the crop. Mechanical compaction is essential to consolidate the peat, and which increase soil bulk density and moisture content. Drainage has been claimed to accelerate soil CO2 emission due to oxidative peat decomposition (OPD), contributing to peat subsidence. However, subsidence in tropical peatland for oil palm plantation is also due to mechanical compaction and consolidation more than carbon loss via peat oxidation (Melling et. al, 2008). Therefore, sole reliance on subsidence data for carbon emission alone is not correctly represented. Hence, more accurate data shall be obtained through direct measurement of the CO2 emissions through OPD and root respiration in order to better understand the net carbon emission of the tropical peatlands. This study is located in an oil palm (Elaeis guineensis) plantation of the 6-10 year-old palms on tropical peat in Sibu, Sarawak, Malaysia (2.11°S, 114.50°E). Groundwater level was controlled at 0.65 ± 0.09 m (mean ± 1 SD). The CO, efflux was measured continuously using an automated chamber system, consisting of 16 opaque chambers (40 cm high with a 25-cm internal diameter) and an infrared CO2 analyzer (LI820, Licor). Eight chambers were installed outside and inside the trench for each in May 2014 for the measurements of total soil respiration (TR) and OPD, respectively. The soil subsidence was measured using a tube, which was inserted vertically into the peat layer and anchored firmly in the underlying mineral substrate. This study provides the first estimate of annual carbon loss of 842 ± 465 and 724 ± 513 g Cm~2 yr~(-1) from the oil palm plantation based on continuous field data of TR and OPD obtained throughout a year, respectively.
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