Module 4: Fertiliser Application
Oil palms require sufficient nutrients, in the right balance, to produce good yields and to stay healthy in the long term. While the soil provides some nutrients, it is often not in the right balance and there are generally not enough nutrients to sustain oil palm growth and productivity. Nutrients are also lost when the fruit is harvested and carried away, and immobilised in growing oil palm trunk and roots.
Removal and immobilisation of nutrients on mineral soils:
To provide sufficient nutrients for good oil palm growth and fruit production, it is necessary to apply fertilisers.
Some important things to understand in relation to oil palm production and the application of fertilisers are:
- Key nutrients which all oil palms need are nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg).
- Oil palms often also need small quantities of boron (B).
- On peat soils, it is usually necessary to fertilise with copper (Cu) and zinc (Zn).
- Other nutrients, such as calcium (Ca), sulfur (S), manganese (Mn), iron (F) and chlorine (Cl) are important but it is usually not necessary to supply them as fertiliser.
- If present in too large quantities, nutrients can poison the oil palm.
- Soil organic matter can be increased through good management, and is very important for soil quality and the efficient use of fertiliser
- Fertilising oil palms is very expensive; it takes up about 60 percent of overall costs!
- If fertilising is done in the wrong way, up to 50 percent of the nutrients can be lost, which means a lot of money is spent on fertilisers that don’t reach the palms and don’t increase the yield.
- Fertilisers should be applied efficiently and effectively, according to the ‘4 R’ principle: right type, right amount, right place, right time
Palms of different ages need different amounts of fertiliser. The fertiliser needs of palms not only depend on the palm’s age, but also on:
- Soil type (especially mineral or peat soils)
- Soil fertility (nutrients and organic material in the soil)
- Planting material
- Current yields
When deciding on how much fertiliser to apply, it is useful to get advice from one or more of the following:
- Extension workers;
- Cooperative experts;
- Excellent farmers in the area;
- Nearby plantation companies (while estate fertiliser rates may be very high, they can give a good idea of the ‘nutrient balance’ needed under the local conditions, which is the ratio between N, P, K and Mg. Companies may also be able to give information about the best type of fertilisers and the best timing of application);
- Handbooks and other available materials;
- By conducting your own experiment.
Conducting your own experiment to assess fertiliser needs
Yield increase after fertiliser application can be tested on small plots with at least 36 palms.
Early effects can usually be seen after six months to one year and should include:
- Larger bunches
- Different colour of ripe bunches
- Nutrient deficiency symptoms reduced/disappeared
- Denser canopy (larger leaves)
If the experiment is continued for 3 years, full effects can be seen which should include:
- Better yields
- More bunches
- Larger bunches
- Nutrient deficiency symptoms disappeared
- Denser canopy (larger leaves)
- Taller palms with bigger trunks at the top
It is necessary to keep good track of the fertiliser applications and the yield to decide if the experiment is successful! If the fertilisers are effective, they can be used in the entire plantation.
Before applying fertilisers it is necessary to make sure that the following plantation conditions are in order:
- Drainage and soil conservation are fully done;
- Maintenance is up to standard;
- Noxious weeds have been removed.
The information in this chapter will help you decide which type and what quantities of fertilisers you need to apply to your plantation and how to do it correctly.
Fertilisers can make up 60 percent of the total costs of producing palm oil so it is important to apply fertilisers efficiently.
Different fertilisers have different concentrations of nutrients. To know how much fertiliser to apply, it is necessary to know the nutrient concentration of the fertiliser.
Nutrient content of the most important fertilisers:
Please find the general fertiliser recommendations here under this link.
Further information: Exceptionally rich soils
Fertiliser application and lack of money
If not enough money is available to buy all the recommended fertilisers, do not leave out the more expensive fertilisers but follow these recommendations:
- Apply fertilisers correctly and in several rounds, so that losses are as small as possible.
- If there are any deficiency symptoms, give priority to applying the fertilisers which are needed to correct the deficiency.
- Do not save on potassium (K) and nitrogen (N) fertiliser, as these nutrients are most important for oil palm and do not stay in the soil for long.
- Magnesium (Mg) is important, but as long as there are no deficiency symptoms, you may decide to reduce application or apply the cheapest fertiliser type (e.g. dolomite).
- If enough phosphorus (P) was applied in the past, it is acceptable to apply less for one year, or to use a cheaper fertiliser type (e.g. rock phosphate).
- If the palms do not show deficiency symptoms, it is acceptable not to apply boron (B) for one year. However, in the next year application will be necessary again, especially in plantations with good production.
- Keep in mind that if too little fertiliser is applied now, yield will go down two to three years later. Fertilisers are a necessary investment and buying them should be a priority.
Nutrient Deficiency Symptoms
Healthy oil palm leaf
A healthy oil palm leaf is dark green, strong and flexible. In fully mature palms (more than 10 years after planting) the leaf is 5–8 m long and has leaflets up to 1.20 m long.
Nutrient deficiency symptoms in oil palms can occur as a result of the following:
- Not enough nutrients are applied;
- Nutrients are applied in the wrong way;
- Nutrients do not reach the palms because of the conditions in the plantation (e.g. waterlogging, soil erosion, or competition with weeds).
What follows is a description of the key types of nutrient deficiencies and their symptoms in oil palms.
Immature palm with N deficiency symptoms
Nitrogen (N) Deficiency
- Leaflets turn an overall light green or yellow colour, starting in the older leaves.
- In severe cases, leaflets may curl up and die, starting at the tip and edges.
- Also in severe cases, the rachis and the midribs of the leaflets turn bright yellow or orange. This type of yellowing often happens when palms are in low-lying areas or swamps that are flooded during part of the year and have a high water table.
- Weeds under the palms sometimes also show a pale green or yellow colour.
Palm with tapered trunks
Phosphorus (P) deficiency
- P deficiency does not tend to show up clearly in oil palm leaves although in some cases the leaves may be shorter (‘stunted’) and bunches smaller.
- Trunks have a pyramid-shape which is wider at the bottom and much thinner at the top.
- P deficiency can show in the weeds by:
- The presence of Melastoma malabathricum and/or Dicranopteris linearis;
- The presence of Imperata cylindrica with purple-coloured leaves;
- Poor growth of legume cover crops (which need a lot of phosphorus).
Potassium deficiency symptoms
Potassium (K) deficiency
- Yellow or orange spots with irregular shapes appear on the leaves, starting in the older leaves. If the leaves are held up to the sun, the light shines through the spots.
- Later, the spots turn orange and grow until they fuse together.
- In severe cases, K deficiency shows as an overall yellowing of the older leaves (especially on acid sands or peat soils) giving the appearance of the whole crown turning yellow.
- ‘White stripe’, a straight white line on both sides of the mid-ribs of the leaflet, sometimes is a sign of too much N and not enough K and B, although this may also be genetic.
Magnesium (Mg) deficiency
- Leaflets on older leaves that are in direct sunlight get an even olive green to orange/yellow colour, starting at the tip of the leaflet;
- Typically only leaflets in full sunlight turn yellow, but not the shaded leaflets and young leaves;
- In severe cases, the leaflets become bright yellow and die, starting at the edge and tip of the leaflets.
Boron deficiency – crinkled leaf
Boron (B) deficiency
- Leaves are crinkled and dark green;
- Leaflet tips sometimes fold sharply;
- New fronds get shorter and shorter so the top of the palm crown appears flattened;
- Sometimes the tip of the leaf is completely missing
“Peat yellows” – a sign of copper or zinc deficiency
Copper and zinc deficiency
Copper and zinc deficiencies are to be expected in peat soils only. It is very rare to find deficiencies in mineral soils.
- The youngest leaves become yellow at the tips of the leaflets, but the mid-ribs stay green;
- In severe cases, the leaflets die off from the tips inward;
- New fronds become shorter and shorter.
Types of fertilisers
Warning: Fake fertilisers are a common problem in many countries. Be careful when buying fertilisers, especially from someone you don’t know.
When buying fertilisers, stick to the following guidelines:
- Buy from a trusted person;
- Do not buy fertilisers that are extremely cheap or from an unclear origin (these are likely to be fake);
- Check if the fertilisers are in good condition (i.e. dry, clean, correct colour);
- Check if the bags look good and have been closed correctly with a straight stitch and the same colour thread for all bags;
- Check if the soluble fertilisers (i.e. all fertilisers other than rock phosphate and dolomite) actually dissolve when a handful is thrown into a bucket of water. If the grains sink to the bottom and don’t dissolve after stirring the fertiliser is probably fake;
- If KCl (MOP) or urea is dissolved when put in water, the water temperature should go down, so the water should get colder;
- Check the smell of KCI – good quality KCl doesn’t have a particular smell.