Sustainable Oil Palm Farming / Establishing a ground cover

Download: Module 3: Plantation Maintenance

Goal

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

Standard

• 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

Timing

• 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

Frequency

• 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—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

Figure 14: Mature plantation with a vigorous cover of Calopogonium caeruleum

Figure 15: Good cover of soft weeds (Nephrolepis ferns)

Who

Farmers and their families or hired labourers

How

Application of phosphate fertilisers

If there are many noxious weeds in the plantation (alang-alang,melastoma, dicranopteris) the soil is likely to be phosphorus-deficient. Beneficial weeds such as ferns and legumes grow better in phosphorus-rich soils.

To help the good weeds grow and reduce the growth of noxious weeds it is useful to apply phosphate fertilisers as follows:

• 500 kg/ha soluble P fertilisers (TSP, SP—36)
• 500—1000 kg/ha reactive rock phosphate

Spread the P fertiliser evenly throughout the plantation, mostly in the inter-row and over the frond stack.

Establishing legume cover plants or other soft weeds

Table 3: List of the most common legume cover crops and some of their properties

Name	Shade tolerance	Sowing practices	Other properties
Calopogonium caeruleum	Very tolerant	Needs scarification	Very productive; tolerant of heavy shade; Figure 14
Mucuna bracteata	Tolerant	Needs to be sown in a seedbed and then planted; benefits from inoculation	Good N fixation; good soil cover; prevents soil erosion
Calopogonium mucunoides	Somewhat tolerant	Needs scarification	Pioneer species; short life span
Pueraria phaseloides	Somewhat tolerant	Needs scarification	Grows quickly; very palatable for livestock

Legume cover crops are best sown at the time of land preparation, when all the other weeds have been cleared. If there are many weeds, then the legumes may still grow, but selective weeding will become very difficult. In plantations where clear-weeding was a normal practice, legume cover crops can be sown directly after spraying. For sowing or planting legume cover crops, follow the steps below:

Step 1.	Select the appropriate legume cover crop (see Table 3). They can also be mixed to increase the chances of successful establishment.
Step 2.	Scarify the seeds, if necessary. Scarification is required to remove the hard outside of the seeds, so that the seeds can germinate faster and simultaneously. Scarification can be done mechanically (with sandpaper), by using 70% sulphuric acid or by using hot water . The sulphuric acid method is the most common and the most effective one, but the acid may not be widely available and is a dangerous chemical, which is also difficult to dispose of after use. Therefore the mechanical scarification or the hot water treatment are recommended. For mechanical scarification, use the following approach: Place the seeds on a table between two pieces of sandpaper Make small rounds with the sandpaper, first one way and then the other There is no need to rub off the complete outside of the seeds; there just need to be some deep scratches for the water to enter For scarification with hot water, try the following with a small batch of seeds : Heat water to boiling in a pan Take the pan from the fire and let the water cool down to 75°C (check the temperature using a cooking thermometer) Add the seeds to the water and stir for 3 minutes Remove the seeds and rinse them with cold water, or leave the in the hot water to cool overnight Sow the seeds on the next day, or sun-dry them immediately to prevent rotting or germination The optimum temperature and soaking time vary from species to species; if the germination is not good, then it is recommended to try different temperatures and find out what works best
Step 3.	Broadcast the seeds in the plantation, on bare soil or in an area that was recently weeded. Start with a small area to see if the legumes are able to establish effectively.

Apart from sowing legume cover crops, the population of Nephrolepis ferns can also be increased (Figure 15). To achieve this, pull the ferns from the trunks of the palms (roots and all) and throw them in the inter-row. Some of them may establish and start growing. The application of empty fruit bunches promotes the growth of Nephrolepis ferns.

Slashing inter-row vegetation at knee height

• Every six months slash all inter-row vegetation at knee height using a bush knife.
• Note: in some plantations it is considered a good practice to let the ferns in the frond stack area grow over 1 meter tall.

Date	Time	Location	Activity	Input type	Input amount	Input costs	Labour input		Labour costs
							People	Hours
16/01/13		Field 3	P fertiliser application	Rock phosphate	1000 kg	1500000	2	4	80000
20/01/13		Field 3	Sowing legumes	Legume seed	2 kg	400000	2	4	80000

Acknowledgements

The material from Establishing a ground cover 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.