Characteristics of Inland, Transition, and Coastal Peatlands in Riau Province: Relationships between Degree of Decomposition and Chemical Properties of the Peat Materials with Oil Palm Biomass-Productivity
Karakteristik Gambut Pedalaman, Transisi dan Pantai di Provinsi Riau: Keterkaitan Tingkat Dekomposisi dan Sifat Kimia Gambut dengan Produktivitas Biomassa Kelapa Sawit
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Increased demand for palm oil derivative products (CPO, crude palm oil) causes the ever faster rate of and widespread land clearing for oil palm plantation area. Land clearing for this purpose is generally perfomed on peat swamps. In Riau Province, until year 2007, the use of peatlands for cultivating various plantation crop commodities have reached ±817.593 ha. Since peatlands are considered vulnerable to land clearing, this activity and its subsequent land management should be based on the nature and characteristics of the peat material which is largely determined by its formation physiography. Based on this background, this study aims to assess the relationship between the degree of decomposition and chemical properties of peatlands developed on fresh-water, brackish and marine physiography with biomass productivity of cultivated oil palm with age of <6 and >6 years in Riau Province. Field observations and sampling of the peat materials were conducted in January 2010. The results showed that the peat materials of Riau that developed on freshwater, brackish and marine physiography were at hemic decomposition degree. Based on the relationship between the degree of decomposition and the value of E400/E600 ratio, peat materials of the fresh-water, brackish and marine physiography cultivated for oil palm with age of >6 years were dominated by oldhemic decomposition degree (E400/E600 <5,0). Whilst, it was found in the brackish physiography with oil palm of age of <6 years peat materials with hemic decomposition degree (E400/E600 >5,0). This suggests that the degree of humification of the peat materials on oil palm cultivating lands with age of <6 years were lower than those with age of >6 years. The average organic-C content of the inland and transition peatlands were higher than those of the coastal one. The acidity was in moderate to high level in which the higher average values of pH-H2O and pH-KCl were found in transition and coastal peatlands. The average concentration of total N, P2O5 and K2O were also higher in the transition and coastal peatlands. The highest total biomass productivity of oil palm was found in the transition peatlands, both at the age of <6 and >6 years. The results of this study provides additional scientific facts that as compared to the coastal and inland ones, the transition peatlands provide as the best medium for the cultivation of oil palm, especially in Riau Province.