Function of boron in oil palm

Boron (B) deficiency has been identified as the most common nutritional disorder in oil palm plantations around the world, and it is intensified in regions with alkaline, sandy soils and those subject to high rainfall volumes. Cultivation areas that have high productivity and are normally well-supplied with adequate doses of other nutrients, such as nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg), have high rates of vegetative growth. They are also areas with high B demands, thus requiring frequent supply of this micronutrient.

The critical function of boron in oil palm cannot be understated. Boron supports structural and metabolic processes, such as:

• Structuring cell walls
• Transporting carbohydrates in phloem vessels
• Forming complexes with sugars

In addition to functions related to floral biology, including pollen grain germination and pollen tube formation, there are fundamental biological processes that act directly on cluster productivity and consequent oil palm growth rate and yield. From a structural point of view, B is an essential constituent of membranes and cell walls of plants, acting directly in the formation of new tissues (meristems) of the aerial part and roots of the oil palm plant.

Boron deficiency symptoms to look for

In situations where severe deficiency occurs, there is complete inhibition of the development of new leaves, due to the disintegration of non-expanded leaf primordia. Palm plants are very sensitive to low concentrations of boron in the soil, and the onset of symptoms occurs very quickly on leaves, roots, and entire plants.

Leaves with boron deficiency symptoms show irregular expansion and malformations. Due to its low mobility in the phloem vessels of these plants, this nutrient results in the manifestation of symptoms first in young and growing leaves, with the leaflets in the distal section of the leaves being the most affected. The coloration often appears in a more intense green in the symptomatic leaves, with wrinkled appearance and shapes, showing rigidity and eventually brittleness.

Boron's impact on oil palm growth

Boron deficiency greatly affects reproductive growth, as the synthesis of cytokinins—phytohormones that promote cell division—is repressed and the germination of pollen grains associated with poor formation of pollen tubes prevent proper fertilization and embryonic formation. In roots, boron deficiency retards meristematic growth, and causes supra-optimal levels of auxins, which can inhibit cell division and induce increases in the enzyme auxin-oxidase. In the formation of tertiary and quaternary roots and loss of apical domain, boron deficiency causes a reduction in the differentiation of lateral roots that do not fully develop, forming clusters of short and thick roots.

These effects on the root system can reduce the uptake of water and other nutrients by palm plants, which will certainly impact the oil palm growth rate and yield. As a way of monitoring adequate B levels in the crop, periodic analysis of the plant tissue is recommended. These tests should be accompanied by assessments of the soil nutrient content, as well as frequent field checks, for the manifestation of deficiency symptoms in leaves and roots.

Symptoms of B deficiency in oil palm leaves
Source: Saldanha, 2016

Borate fertilizer for oil palm

The cultivation of oil palm is one of the agricultural crops with the highest consumption of fertilizers, as it has high levels of productivity and yield in oil production. Regarding development in the field, there are four phases, in which different nutritional needs and demands occur in each of them, namely:

I – Nursery phase

From planting germinated seeds to the seedlings planted in the field (10-18 months)
Adequate nutrition is essential to produce healthy and vigorous seedlings that can overcome the stresses caused at the time of transplantation. Therefore, boron's role in forming a robust root system with lateral rooting is a fundamental function of boron in oil palm. Foliar application of Solubor^® or in fertigation can be carried out on a fortnightly basis, ensuring a frequent supply of B.

II – Young immature phase

From planting in the field until the beginning of bunch harvesting (at approximately 3 years of age)
Nutrient demands during the first 6 months after planting are relatively low, as the seedlings go through a period of adaptation due to the stress generated in the transplanting stage, as well as the need to establish the root system. From year 2-4, a phase begins in which the plants have a high nutritional demand due to the formation of the aerial part and expansion of the root system. This is a stage where the palm plant has a high energy expenditure. Applications of Granubor^® can be carried out in this phase following this distribution scheme:

• Year 1: 60-90 g/plant of Granubor: Applications must be carried out in the 9^th month after planting the seedlings in the field
• Year 2: 90-160 g/plant of Granubor: The indicated doses must be divided into two applications, the first being carried out in the 18^th month and the second in the 24^th month after planting the seedlings in the field
• Year 3: 160-180 g/plant of Granubor: The applications must be carried out in the 31^st month after planting the seedlings in the field

Special attention should be given to the fertilizer application site. Since the root system is not yet fully developed, fertilizers must be applied in the projection area of the plant crown.

III – Young Mature Phase

From 4 to 9 years from planting

This is the period of greatest productivity for the oil palm culture. There is a great intensity in the formation of new leaves, aiming to guarantee the high rates of photosynthesis that the plant needs in this period of physiological maturity. At this stage, the root system reaches its maximum development, spreading between the lines of the crop, forming a dense network of roots. The proper borate fertilizer for oil palm and application is fundamentally important to meet the demand for vegetative development—frequent release of leaves and constant formation of new roots. It is also necessary to meet the demands of the reproductive phase, especially related to formation and germination of the pollen grain and the formation of the pollen tube. These are critical stages of oil palm floral biology. Applications of Granubor can be carried out in this phase following this distribution scheme:

• Year 4 – 9: 180-200 g/plant of Granubor: The indicated doses must be divided into two applications per year.

IV – Mature phase

From 9 or 10 years until the tree is replanted

At this stage, the plants reach the peak of physiological maturity. Special attention to leaf management is essential, giving priority to maintaining leaves exposed to the sun, aiming at maximizing photosynthesis.

• Year 9 onwards: 200-240 g/plant of Granubor: The indicated doses must be divided into two or three applications per year.

Note: The indications of doses, times, and form of application are suggestions based on agronomic recommendations indicated by the specialized technical literature. Diagnosis through soil and plant tissue analysis are recommended techniques for adjustments in the fertilization program. U.S. Borax always recommends consulting a professional agronomist regarding boron requirements.
 

Resources

• Crop guide: Oil palm
• Brochure: Boron in oil palm (PDF)
• Granubor
• Solubor

• Gutierrez-Soto, MV; Acuña, JT. 2013. Sintomas associados a deficiência de boro em palma de óleo (Elaeis guineenses, JACQ.) na Costa Rica. Agronomia Mesoamericana. 24(2): 441-449.
• Von Uexkull, HR; Fairhurst, TH. 1991. Fertilizing for high yield and quality The Oil Palm. International Potash Institute. Switzerland. WI-Bulletin No. 12.
• Viégas IJM, Müller AA. 2000. A cultura do dendezeiro na Amazônia brasileira. Belém: Embrapa Amazônia Oriental.