Module 2: Plantation Maintenance
Please find information about important terms for the plantation management under this link.
1) General Notes on Chemicals
Warning! Herbicides, pesticides and other chemicals are often toxic to humans, animals and palms, and should be used sparingly and with care.
- Application of chemicals should always be carried out wearing full protective clothing including: Rubber gloves, boots, gas mask our mouth cover, safety glasses, rubber apron
- It is recommended that spraying is carried out only by workers who have followed a training session
- Spray equipment should be kept clean and in good shape
- Label every chemical container to say what is inside it (e.g. herbicide (with name), pesticide (with name), etc.)
- When preparing chemicals carefully follow the instructions on the package
Never store food in containers that were used for chemicals or fertilisers.
Herbicides can be sold as liquids or as powder. Liquid herbicides are often mixed at 0.5, 1 or 2 percent, which means 5, 10 or 20 ml per liter of water. Always prepare herbicide solution according to the instructions on the package. Ask others for help if you are not sure how to do it. Before getting started, make sure that the sprayer is properly calibrated so that it is clear how much water comes out of the sprayer every minute.
Common herbicides in oil palm
Herbicides are often divided into two groups: contact herbicides and systemic herbicides. These groups differ in their mode of action. Contact herbicides are toxic to the plant where they touch it. The most well-known contact herbicide is paraquat. Systemic herbicides move into the plant and are transported to the stem, roots, and other leaves. The most well-known systemic herbicide is glyphosate.
Some contact and systemic herbicides and their common brand name:
Proper protective clothing for herbicide spraying (but the left hand glove is missing!)
The mode of action of contact herbicides (left) and systemic herbicides (right). A contact herbicide kills the leaves it covers but is not transported into the stem or roots. Systemic herbicides are transported into the stem and roots and kill the entire plant.
2) Removing noxious and woody weeds
Noxious weeds are weeds that are unwanted in a plantation. Weeds can be noxious because they:
- Grow and/or spread very fast
- Are difficult to control
- Take up a lot of fertilisers
- Produce poisons in their roots to reduce the growth of other plants (allelopathy)
- Have spines or are dangerous in other ways
For an overview of common weeds in oil palm plantations, click here. All woody weeds are considered noxious weeds. If woody weeds or noxious weeds are allowed to grow, the weeding will take much time and there may be negative effects on the growth and productivity of the oil palms. Also, more fertilisers may be needed and harvesting will take longer and becomes less efficient, so the plantation becomes less profitable.
- Remove woody and noxious weeds from the plantation
- Make weeding easier and less time-consuming in the future
- Plantations are free of woody and noxious weeds
- A dense vegetation of soft weeds (legumes and Nephrolepis ferns) is maintained in the interrow
- In the beginning and at the end of the rainy season
- Shortly before applying fertilisers
- Shortly before the peak season (so that harvesting can be done more efficiently)
- When no rain is expected that day (otherwise the herbicide will be washed away)
- Every 3–4 months until all woody/noxious weeds are gone
- Then every 6 months if woody or noxious weeds have returned
Labour time required
- Manual inter-row weeding: 0.5 to 2 days per hectare, depending on the type and number of weeds
- Chemical weeding: 1 day per 3 hectares (when noxious weeds are still present)
Equipment and materials
- Manual weeding: chisel/spade, bush knife
- Chemical weeding: bush knife, knapsack sprayer, protective clothing, measuring cup (50–200 ml), clean water (50–100 L/ha), herbicide (glyphosate/gramoxone and Triclopyr, 0.5–2 L/ha), diesel, paint brush (for applying herbicides to woody stumps)
Every weeding activity should be recorded in a log book as shown in the example below.
3) Establishing a Cover of Soft Weeds
Create a closed cover of soft weeds in the plantation to:
- Prevent soil erosion
- Keep the moisture in the soil
- Prevent loss of soil organic matter
- Attract as many natural enemies of pests as possible
- Make access into the plantation easy
- Make weeding fast and easy
- Good cover of soft weeds everywhere in the inter-row
- Legumes established where possible
- Inter-row weeds slashed at knee height
- No noxious or woody weeds in the plantation
- At planting, or at the start of the rehabilitation process, after the noxious weeds have been removed
- Not during very strong rain or during the dry period
- Establishment of legume cover crop: once in the plantation lifetime
- Maintenance of weed cover: every six months
Labour time required
- Corrective phosphate application: 1 day per hectare
- Sowing legume cover crops or introducing soft weeds: 1–4 hours per hectare, depending on the extent of bare soil
- Slashing of inter-row vegetation: half a day per hectare
Equipment and materials
- Phosphate fertiliser: 500–1000 kg/ha
- Fertiliser measuring cup/bucket
- Bush knife
Cover plant seeds: usually 1–2 gram per 10 square meters (1–2 kg per hectare)
- Calopogonium caeruleum: 1–5 kg per hectare
- Calopogonium mucunoides: 1–3 kg per hectare
- Pueraria phaseloides (also known as Pueraria javanica): 3–4 kg per hectare
- Mucuna bracteata: 200–300 g per hectare
Every weed management activity should be recorded in a log book as shown in the example below.
Good cover of soft weeds (Nephrolepis ferns)
Good pruning is necessary for the most efficient use of fertilisers and to create an easily accessible plantation. Therefore the optimum number of leaves should be kept on the palms.
When pruning, remember:
- More fronds are better for production (palms can capture more sunlight)
- Dead or dying leaves hold nutrients which should be recycled
- If palms are tall it will be difficult to do good harvesting when there are many fronds
Pruned leaves decompose fastest when they are in touch with the soil and form an important source of food for palm roots. By stacking the fronds in a box shape, the nutrients and the organic matter are spread out, and the leaves decompose faster because the stacks are not too high. Stacking leaves also keeps them out of the harvester’s way, and helps to prevent soil erosion.
The appearance and organisation of oil palm leaves
The youngest leaves appear on the top and the older ones are at the bottom:
- The leaves grow in spirals of eight
- Leaf 1 is the youngest fully open leaf, on the top of the palm
- The leaf beneath Leaf 1 is Leaf 9 (1+8, because there are eight leaves on one spiral)
- The leaf below Leaf 9 is Leaf 17
- The leaf below Leaf 17 is Leaf 25, then Leaf 33, Leaf 41 and so on
About two new leaves appear per month. New leaves appear faster in young palms and slower in old palms. An ‘inflorescence’ (= a stalk with many flowers) is formed above each leaf, which can become male or female, or be aborted (no inflorescence at all). If the palm is stressed (e.g. by drought or lack of nutrients), more male inflorescences are formed and more inflorescences are aborted. Female inflorescences form bunches which are usually ripe about 16 months (32 leaves) after the supporting leaf has appeared and six months after the inflorescence has opened.
- Enable palms to capture the maximum amount of sunlight
- Ensure there is no waste of nutrients in unproductive fronds
- Enable fast, easy and complete harvesting
- Create a clean and efficiently organised plantation
- Conserve soil quality and nutrients
- Enable fast decomposition of pruned fronds
- Pruning only dead fronds in palms less than 4 years after planting
- Pruning down to 48–56 fronds per palm (or: 2–3 fronds below the last ripe bunch) for palms that are 5–7 years old
- Pruning down to 40–48 fronds per palm (or: 1–2 fronds below the last ripe bunch) for palms that are 8–15 years old
- Pruning down to ~40 fronds per palm (or: 1 frond below the last ripe bunch) for palms that are more than 15 years old
- Fronds butts are cut off close to the trunk
- Fronds are cut in two and stacked on the frond stack in a box-shape, with the bottom part behind the palms and the top part between the palms
- Shortly before the peak production season (so that harvesting can be done more efficiently)
- During the dry period (if possible)
- Twice per year
Labour time required
- Corrective pruning: 2 days per hectare
Equipment and materials
- Chisel (for shorter palms)
- Harvesting sickle (for tall palms)
- Axe, chisel or bush knife (to cut the frond in two)
Every pruning activity should be recorded in a log book as shown in the example below.