Abstract:The aim of this research was to know the impact of planting leguminous cover crops (LCCs) of Mucuna bracteata and Calopogonium mucunoides in oil palm plantation on peatland on reducing CO 2 emissions. Atmosphere temperature, peat surface temperature, in-closed chamber temperature and peat surface CO 2 fluxes were monitored on two adjacent experimental plots. The first experimental plot was on the newly opened peat surface (NOPS) and another was on the eight years planted oil palm land (EPOL). The closed chamber techniques adopted from International Atomic Energy Agency (IAEA) (1993) were implemented to trap CO 2 emissions emitted from 24 treatment plots at the 1st, 3rd and 6th months observations. Average CO 2 fluxes observed on no LCCs plots in the NOPS site were 61.25 ± 8.98, 33.76 ± 2.92 and 33.75 ± 3.45 g/m 2 h , while in the EPOL site were 55.38 ± 15.95, 29.90 ± 5.32 and 27.70 ± 4.62 g/m 2 h at the 1st, 3rd and 6th months monitoring, respectively. Average CO 2 fluxes observed on the planted M. bracteata plots in the NOPS site were 68.2 ± 24.5, 12.88 ± 3.70 and 10.40 ± 1.28 g/m 2 h, whereas in the EPOL site were 54.04 ± 6.70, 11.45 ± 2.00 and 9.33 ± 3.49 g/m 2 h at the 1st, 3rd and 6th months monitoring, respectively. Average CO 2 flux observed on the planted C. mucunoides plots in the NOPS site were 66.5 ± 23.7, 15.41 ± 1.51 and 9.74 ± 2.55 g/m 2 h, while in the EPOL site were 47.00 ± 5.00, 9.34 ± 1.23 and 10.52 ± 4.80 g/m 2 h at the 1st, 3rd and 6th months, respectively. P-value for the experimental sites was 0.008 (< 0.05), indicating the significant difference in the level of CO 2 fluxes between the sites. P-value for the treatments in the experimental plots was 0.000 (< 0.05), indicating markedly different level of CO 2 fluxes among treatments. P-value for the age of M. bracteata and C. mucunoides planted on the experimental plots was 0.000 (< 0.05), indicating the significant difference in the level of CO 2 fluxes due to the enhanced LCCs age performing at the increase of shading effects. The comparison of CO 2 fluxes among experimental plots shows that planting M. bracteata and C. mucunoides on the peatland could reduce CO 2 emission.