It is important to carry out weed control without delay on the harvesting paths
and palm circles of 2.5 m radius, to ensure good accessibility and crop recovery
especially loose fruit collection. Choice of spray equipment and herbicides must be
based on cost-effectiveness and labour productivity as well as safety to workers
and minimal impact to the environment. Herbicides that are quick acting and do
not destroy the root system of soft weeds should be used. Fimbristylis acuminata
with extensive surface root system is either encouraged or planted on peat roads
to reduce erosion and peat degradation (Lim 2003). Clean-clear weeding that
reduces the population of natural enemies (predators and parasitoids) against
leaf-eating caterpillars should be avoided as it may lead to outbreaks of nettle
caterpillars and bagworms.
18.5.5 Leaning and Fallen Palms
Palm leaning is one of the major problems of planting oil palms on tropical peatland.
Random leaning and in severe cases, fallen palms, are due mainly to peat subsidence.
The low bulk density of peat (0.10–0.15 gm/cm
3 ) and the less extensive root system
of oil palm planted in peatland are also contributory factors to leaning and fallen
palms. About 40–50% of the palms planted on peatland can lean at various angles
and directions at the age of about 7–8 years. The number of fallen palms increases
thereafter due mainly to excessive root exposure, desiccation and breakage caused
by the weight of the palms. Depending on the severity of leaning and fallen palms, a
yield reduction of 10–30% can occur due to root damage and poorer interception of
sunlight for photosynthesis. Different directions and degrees of palm leaning also
interfere with harvesting due to differential palm height.
A practical approach to rehabilitate leaning and fallen palms is to carry out soil
mounding to minimize root desiccation and promote new root development. The soil
for mounding the exposed roots of leaning palms should be taken from outside the
palm circles in order to prevent damage to the surface feeder roots (Lim and Herry
2010). To avoid palm leaning, proper compaction should be done at the time of
planting or replanting to increase the bulk density of the soil which enhances its
water holding capacity and is thought to reduce subsidence and palm leaning.
Alternatively, hole-in-hole planting method should be applied during replanting.
Good water management to maintain the water level at 50–70 cm (from water level
in collection drains) or 40–60 cm (groundwater piezometer reading) is crucial to
minimize peat subsidence and reduce palm leaning (Parish et al. 2019a).
18.5.6 Fire Prevention and Control
Peatland fires are a serious problem affecting oil palm plantations on peatland,
especially in Indonesia and Malaysia. Overcoming fire on drained and deforested
522
F. Parish et al.
and palm circles of 2.5 m radius, to ensure good accessibility and crop recovery
especially loose fruit collection. Choice of spray equipment and herbicides must be
based on cost-effectiveness and labour productivity as well as safety to workers
and minimal impact to the environment. Herbicides that are quick acting and do
not destroy the root system of soft weeds should be used. Fimbristylis acuminata
with extensive surface root system is either encouraged or planted on peat roads
to reduce erosion and peat degradation (Lim 2003). Clean-clear weeding that
reduces the population of natural enemies (predators and parasitoids) against
leaf-eating caterpillars should be avoided as it may lead to outbreaks of nettle
caterpillars and bagworms.
18.5.5 Leaning and Fallen Palms
Palm leaning is one of the major problems of planting oil palms on tropical peatland.
Random leaning and in severe cases, fallen palms, are due mainly to peat subsidence.
The low bulk density of peat (0.10–0.15 gm/cm
3 ) and the less extensive root system
of oil palm planted in peatland are also contributory factors to leaning and fallen
palms. About 40–50% of the palms planted on peatland can lean at various angles
and directions at the age of about 7–8 years. The number of fallen palms increases
thereafter due mainly to excessive root exposure, desiccation and breakage caused
by the weight of the palms. Depending on the severity of leaning and fallen palms, a
yield reduction of 10–30% can occur due to root damage and poorer interception of
sunlight for photosynthesis. Different directions and degrees of palm leaning also
interfere with harvesting due to differential palm height.
A practical approach to rehabilitate leaning and fallen palms is to carry out soil
mounding to minimize root desiccation and promote new root development. The soil
for mounding the exposed roots of leaning palms should be taken from outside the
palm circles in order to prevent damage to the surface feeder roots (Lim and Herry
2010). To avoid palm leaning, proper compaction should be done at the time of
planting or replanting to increase the bulk density of the soil which enhances its
water holding capacity and is thought to reduce subsidence and palm leaning.
Alternatively, hole-in-hole planting method should be applied during replanting.
Good water management to maintain the water level at 50–70 cm (from water level
in collection drains) or 40–60 cm (groundwater piezometer reading) is crucial to
minimize peat subsidence and reduce palm leaning (Parish et al. 2019a).
18.5.6 Fire Prevention and Control
Peatland fires are a serious problem affecting oil palm plantations on peatland,
especially in Indonesia and Malaysia. Overcoming fire on drained and deforested
522
F. Parish et al.