PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

The decrease in groundwater level (GWL) on peatlands, especially in the dry season, can lead to extensive peat drying and making it more vulnerable to the occurrence of wildfire. This research aimed to study the relationship between GWL fluctuations and water content on the surface of peatlands. The study was carried out in a 14 to 17 years old palm oil plantation and a secondary forest located in Siak, Riau Province, Indonesia. Field observations were carried out by installing a water level data logger and soil moisture sensor at a depth of 10 cm and 30 cm from the peat surface, recorded at an hour interval for one year. The results showed that GWL fluctuation was highly correlated to the peat water content in the 10 cm layer both in oil palm plantation (R2 = 0.65) and secondary forest (R2 = 0.67). The peat water content in the 30 cm layer showed a low correlation with GWL fluctuation down to -90 cm in oil palm plantation (R2 = 0.01), however, it was strongly correlated in secondary forests (R2 = 0.89). Water capillarity in peat soils was able to increase to up to 10 - 30 cm layers from the surface, ranging from 284 to 476% w/w. The capillary water could rise to 68 to 76 cm. The result of the General Linear Model analysis showed that there was a significant influence of land cover, GWL, and peat bulk density on soil water content. Oil palm cultivation activities on peatlands increase the peat bulk density, which in turn increases water capillarity and soil water content.