groundwater level, experimental reports suggested that sago palm growth would be
decreased under permanently submerged conditions or waterlogged land (Flach
1977; Shimoda and Power 1990; Takaya 1983).
In the peat soil area, the groundwater level shall be controlled to remain within
25 cm below the ground surface in order to avoid land subsidence and irreversible
damage from excessive drainage in the large-scale sago plantation (Jong 2015b). As
some studies reported, the level of soil water table has a comparatively great
influence on the growth of sago palm. Maintenance of the appropriate soil water
table level is important for sago palm growth. A plantation in Riau Islands has
adopted a closed system of water canals at its plantation, punctuated by floodgates at
the appropriate positions. The groundwater level is maintained at about 18 cm below
the ground surface on average throughout the year (Jong 2015b). The movement of
groundwater decreases and stagnates (oxidation-reduction potential of À15 mV) in
the dry season with some deluging rainfall. This is important for minimizing
leaching losses of the applied fertilizer (Jong 2015b).
17.4.1 Leaf, Trunk, and Root Growth under Higher GWL
Flach (1977) found that the rate of leaf emergence slows in sago palm seedlings
examined under waterlogged conditions. Jong (2006) described that the growth of
sago palm tends to be poor where the groundwater level is high. This tendency is
understandable based on our empirical knowledge. In tropical peat soils with an
average water table of 57–68 cm, the number of leaves and the diameter at breast
height of sago palms 8 years after the trunk formation are smaller than those in the
areas of lower water table (Hashimoto et al. 2006). In the report by Sim et al. (2005),
the sago palms growing in peat soil with a water table depth of 40–50 cm did not
form trunks. Kakuda et al. (2015) introduced Sasaki’s unpublished data on a positive
correlation between the groundwater level in the range of 52–89 cm below the
ground surface and the number of leaves, breast height diameter, as well as trunk
height increase rate (Fig. 17.7), which constitute the growth parameters for sago
palms at the trunk formation stage. This result indicates that sago palms grow better
at a higher groundwater level, the different tendency of which shown by other
reports would suggest that the growth of sago palm under different water level is
influenced by various factors such as growth stage (phase), level of water table and
duration, etc. (see the following section about photosynthesis). In a study of 9-yearold sago palms at a large-scale cultivation site in Sarawak, Malaysia, they formed
healthy trunks in areas with peat soil whose depth was up to 1.5 m and exhibited
growth inhibition as well as mass withering in areas with peat soil whose depth was
1.5–3.0 m (Sim et al. 2005).
Omori et al. (2002) examined the root growth of sago palms for 1 year after
transplantation in the soil with a low water table of 40–50 cm below ground surface
and a high water table of 0–30 cm below ground surface. As the result, the root dry
weight and length were smaller in the soil with a higher groundwater level. However,
17 Sago Palm in Peatland
489
decreased under permanently submerged conditions or waterlogged land (Flach
1977; Shimoda and Power 1990; Takaya 1983).
In the peat soil area, the groundwater level shall be controlled to remain within
25 cm below the ground surface in order to avoid land subsidence and irreversible
damage from excessive drainage in the large-scale sago plantation (Jong 2015b). As
some studies reported, the level of soil water table has a comparatively great
influence on the growth of sago palm. Maintenance of the appropriate soil water
table level is important for sago palm growth. A plantation in Riau Islands has
adopted a closed system of water canals at its plantation, punctuated by floodgates at
the appropriate positions. The groundwater level is maintained at about 18 cm below
the ground surface on average throughout the year (Jong 2015b). The movement of
groundwater decreases and stagnates (oxidation-reduction potential of À15 mV) in
the dry season with some deluging rainfall. This is important for minimizing
leaching losses of the applied fertilizer (Jong 2015b).
17.4.1 Leaf, Trunk, and Root Growth under Higher GWL
Flach (1977) found that the rate of leaf emergence slows in sago palm seedlings
examined under waterlogged conditions. Jong (2006) described that the growth of
sago palm tends to be poor where the groundwater level is high. This tendency is
understandable based on our empirical knowledge. In tropical peat soils with an
average water table of 57–68 cm, the number of leaves and the diameter at breast
height of sago palms 8 years after the trunk formation are smaller than those in the
areas of lower water table (Hashimoto et al. 2006). In the report by Sim et al. (2005),
the sago palms growing in peat soil with a water table depth of 40–50 cm did not
form trunks. Kakuda et al. (2015) introduced Sasaki’s unpublished data on a positive
correlation between the groundwater level in the range of 52–89 cm below the
ground surface and the number of leaves, breast height diameter, as well as trunk
height increase rate (Fig. 17.7), which constitute the growth parameters for sago
palms at the trunk formation stage. This result indicates that sago palms grow better
at a higher groundwater level, the different tendency of which shown by other
reports would suggest that the growth of sago palm under different water level is
influenced by various factors such as growth stage (phase), level of water table and
duration, etc. (see the following section about photosynthesis). In a study of 9-yearold sago palms at a large-scale cultivation site in Sarawak, Malaysia, they formed
healthy trunks in areas with peat soil whose depth was up to 1.5 m and exhibited
growth inhibition as well as mass withering in areas with peat soil whose depth was
1.5–3.0 m (Sim et al. 2005).
Omori et al. (2002) examined the root growth of sago palms for 1 year after
transplantation in the soil with a low water table of 40–50 cm below ground surface
and a high water table of 0–30 cm below ground surface. As the result, the root dry
weight and length were smaller in the soil with a higher groundwater level. However,
17 Sago Palm in Peatland
489