Functional Microbial Population on Oil Palm Rhizosphere in Riau Peatlands: Populasi Mikrob Fungsional pada Rhizosfer Kelapa Sawit di Lahan Gambut Riau

Oil palm growth in peatland may influence the presence of microbial populations. Root exudate is one of the organic compounds that is released by oil palm roots in the rhizosphere area where it can be used as a nutrient for microbes to survive in peatland. The study was conducted to study functional microbial population in the rhizosphere area of oil palm plantation aged <6, 9−15, and >15 years in Riau peatlands. The highest microbial populations were found in oil palm plantation aged <6 years at peat thicknesses of <3 and >3 m, which was respectively 10.3 x 106 and 5.7 x 106 CFU g-1. The highest cellulolytic microbial population was found in oil palm plantation aged <6 years at peat thicknesses of <3 and >3m, which was respectively 17.4 x 104 and 11.4 x 104 CFU g-1. The highest Azotobacter population was found in oil palm plantation aged >15 years at peat thicknesses of <3 and >3m, which was respectively 9.4 x 105 and 12.5 x 105 CFU g-1. The highest phosphate solubilizing microbial population was found in oil palm plantation aged <6 years at peat thicknesses of <3 and >3m, which was respectively 11.4 x 104 and 13.2 x 104 CFU g-1. The highest fungal population was found in oil palm plantation aged <6 years at peat thicknesses of <3 m and >3 m, which was respectively 11.4 x 104 CFU g-1 and 17.3 x 104 CFU g-1. The highest white-rot fungal population was found in oil palm plantation aged 9−15 years at peat thicknesses of <3 m and >3 m, which was respectively 8.7 x 103 CFU g-1 and 9.4 x 103 CFU g-1. In conclusion, the highest microbial population was dominantly found in oil palm plantation aged <6 years. Keywords: Microbial populations, oil palm plantation, peat thickness, rhizosphere areaPertumbuhan kelapa sawit di lahan gambut dapat mempengaruhi keberadaan populasi mikrob. Eksudat merupakan salah satu senyawa organik yang dihasilkan oleh akar sawit di rhizosfer, yang digunakan sebagai nutrisi bagi mikrob untuk bertahan hidup di lahan gambut. Penelitian ini dilakukan untuk mempelajari populasi mikrob fungsional pada rhizosfer kelapa sawit berumur <6, 9−15, dan >15 tahun di lahan gambut. Populasi total mikrob tertinggi pada ketebalan gambut <3 dan >3m ditemukan pada umur kelapa sawit <6 tahun masing-masing sebesar 10.3 x 106 dan 5.7 x 106 CFU g-1. Populasi mikrob selulolitik pada ketebalan gambut <3 dan >3 m 17.4 x 104 dan 11.4 x 104 CFU g-1 ditemukan pada kelapa sawit <6 tahun. Populasi Azotobacter tertinggi 9.4 x 105 dan 12.5 x 105 CFU g-1 ditemukan pada umur kelapa sawit >15 tahun pada kedua ketebalan gambut. Populasi mikrob pelarut fosfat pada ketebalan gambut <3 dan >3m tertinggi pada umur kelapa sawit <6 tahun, masing-masing 11.4 x 104 dan 13.2 x 104 CFU -1. Populasi jamur tertinggi pada kedua ketebalan gambut (<3 dan >3m) adalah 11.4 x 104 CFU g-1 dan 17.3 x 104 CFU g-1 terdapat pada kelapa sawit <6 tahun. Populasi White-rot fungi 8.7 x 103 CFU g-1 terdapat pada kelapa sawit 9-15 tahun dan 9.4 x 103 CFU g-1 pada kelapa sawit >15 tahun. Populasi mikrob tertinggi dominan pada kelapa sawit <6 tahun. Kata kunci: Populasi mikrob, kebun kelapa sawit, ketebalan gambut, rhizosfe