Sustainable Oil Palm Farming / Removing noxious weeds

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Download: Module 3: Plantation Maintenance

Background

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, see Identifying noxious weeds. 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.

Goal

  • Remove woody and noxious weeds from the plantation
  • Make weeding easier and less time-consuming in the future

Standard

  • Plantations are free of woody and noxious weeds
  • A dense vegetation of soft weeds (legumes and Nephrolepis ferns) is maintained in the interrow

Timing

  • 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)

Frequency

  • 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) 1

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)

Who

Figure 13: This plantation needs to be weeded

Farmers and their families or hired labourers

How

Manual weeding

Manual weeding is an effective way to kill woody weeds. When weeding manually, no herbicides are used, so it is good for the other weeds and for the environment. However, manual weeding is labour-intensive, especially if the weeds have not been managed properly before.

Woody weeds and other noxious weeds can be removed manually as follows:

Step 1. Pull out as many of the noxious and woody weeds as possible. Make sure that most of the roots are also pulled out; if the weeds just ‘break off’ above the ground they will usually come back very fast.
Step 2. Cut the roots of the weeds that cannot be pulled out below ground level using a chisel or spade. Remove the weed and the roots from the ground.
Step 3. Large bushes or trees should be dug out completely.

Chemical weeding: herbaceous (i.e. non-woody) weeds

See Storing and spraying chemicals for notes on how to spray herbicides correctly. Herbaceous weeds can be removed using chemicals as follows:

Step 1. Identify the noxious weed species that need to be removed from Identifying noxious weeds. Do not simply spray all the weeds; this is bad practice, the soil will be degraded, it is a waste of herbicide and it is bad for the environment.
Step 2. Spray the noxious weeds with glyphosate or gramoxone:
  • Select a nozzle with a narrow cone to prevent spraying on soft weeds or the oil palms
  • Spray the herbicide over the leaves of the weeds from above
  • Remember that most herbicides work directly on the leaf and are not taken up through the roots. For the best result, try to get some herbicide on most of the leaves when spraying.
  • The right amount of spraying is when the leaves are wet but the water is not dripping off (then, it is too much!).
  • Do not spray all inter-row weeds but only the noxious ones
Step 3. If there are only a few Imperata cylindrica plants between the good weeds, they can be wiped with glyphosate solution instead of sprayed, using a sponge or piece of cloth.

Chemical weeding: woody weeds

All woody weeds are noxious weeds and should be removed from the plantation. Woody weeds often cannot be killed with normal herbicides. If they keep coming back, try the following:

For small woody weeds (no thick stems):

Step 1. After reading the label and putting on all necessary protective clothing, prepare the following solution:
  • 1% Triclopyr or a similar herbicide (= 100 mL per 10 L water)
  • 5% diesel (= 500 mL per 10 L water)

Prepare the solution by first mixing the triclopyr in diesel and then mixing the diesel with water. Note: the diesel may degrade the rubber components of the sprayer, so these need to be checked for leaks regularly, and a spare set is useful.

Put a nozzle on the sprayer that produces a narrow conical spray.

Step 2. Spray the woody weeds with the herbicide solution. If the woody weeds are all through the plantation, expect to spray about 3 L of Triclopyr per hectare. Usually it will be less (0.5—1 L). Note: Triclopyr is poisonous to humans and animals; use it with care and remember to wear gloves and other protective clothing.
Step 3. Spray the remaining noxious weeds (e.g. alang-alang) with glyphosate. Use Triclopyr only for woody weeds, as it is quite expensive.
Step 4. After one month, repeat the spraying with Triclopyr on the young shoots of the woody weeds that are still alive.

For large woody weeds (thick stems):

Option 1

Step 1. For each woody weed, scratch off some of the bark with a knife (an area of a few square centimetres is enough).
Step 2. Wipe/brush the scratched surface with a solution of 5% Triclopyr herbicide in diesel (no water is added, for example: 50 mL Triclopyr in 1 L diesel).
Step 3. If any young shoots appear on the trunks that were treated, repeat the treatment for these trunks after one month.

Option 2

Step 1. Cut the stems close to the ground. Make sure that fresh cuts are made on all woody stems.
Step 2. Apply a solution of 5% Triclopyr herbicide in diesel directly to the cut part of the stem (especially on the area just inside the bark). Make sure you apply the triclopyr less than 4 hours after cutting.
Step 3. If any young shoots appear on the trunks that were treated, repeat the treatment for these trunks after one month.

Data recording

Every weeding activity should be recorded in a logbook as shown in the example below.

Date Time Location Activity Input type Input amount Input costs Labour input Labour costs
People Hours
16/01/13 Field 3 Removing woody weeds Triclopyr

Diesel

1 L

5 L

180000

35000

1 4 40000

References

  1. I.R. Rankine, T.H. Fairhurst, Field Handbook: Oil Palm Series, Volume 3 – Mature, second ed., Potash & Phosphate Institute (PPI), Singapore, 1999.

Acknowledgements

The material from Removing noxious weeds is sourced from Smallholder Oil Palm Handbook and put together by Lotte Suzanne Woittiez (Wageningen Universit) and Haryono Sadikin, Sri Turhina, Hidayat Dani, Tri Purba Dukan, and Hans Smit (SNV) in August 2016. See Module 3: Plantation Maintenance for more information.

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