Agronomist notebook: Why getting higher macadamia yields should never be a hard nut to crack

Friday July 10 2020
notebook img

A farmer picks macadamia in a farm in Nyeri County in this past photo. Macadamia farming is less labour-intensive compared to other crops such as coffee or tea. PHOTO | FILE | NATION MEDIA GROUP


As the global macadamia market starts to open up with the resumption of cargo flights, one of the challenges farmers must strive to overcome for higher yields is breakage of tree stems.

Normally, the stems break when there is a heavy downpour or when it is too windy.

Macadamia is an evergreen tree that grows to a height of about 20 metres and has a wider ecological suitability. 

A number of varieties are planted locally, but one must select that which is well-adapted to their ecological conditions.

Grafted varieties start to produce fruits after three to four years from planting, hence have a shorter maturity period compared to non-grafted ones.

Mature fruits consist of cream to white seed, enclosed in a hard brown shell.


Macadamia farming is less labour-intensive as compared to other crops such as coffee or tea.

The crop can be propagated through either vegetative materials or seeds. The tree requires deep, well-drained soils and areas that receive adequate rainfall.

Good access to sunlight facilitates production of healthy nuts. Thus, when planting, one should ensure that the trees are not congested as this cuts off access to sunlight and other required conditions, eventually resulting in decreased production.

The tree should be sheltered against strong winds to avoid breakages.

The breakages can also be controlled by maintaining a good structure of the tree.

Pruning should be done during the early stages of growth, before flowering and after harvesting.

This should be done in a slanting manner while ensuring that the pruning shear is well disinfected to prevent spreading pests and diseases.

Damaged branches should also be pruned to stop the spread of diseases. The overall goal of pruning is that it results in increased yields.


Mulching should be done frequently to preserve moisture and other nutrients.

Some farmers experience premature dropping of nuts, which in most cases is a result of inadequate nutrient uptake, especially during the dry season. 

To curb this, proper fertilisation should be done depending on the soil nutrients available.

Pest and disease infestation increases when the plant has stress, lowering the production of the fruit.

This is very common especially when the crop is growing in very poor soils. Defoliation of leaves results in nuts dropping and low-quality fruits.

This can be managed by ensuring that the crop receives adequate nutrients and water to set and grow the nuts.

During heavy rainfall, inadequate pollination takes place, which results in flower abortion or even the nuts fall off prematurely.

An extended dry season can lead to the dropping of the tree, especially if it is planted in sandy soils that dry quickly. 

Most trees planted in sandy soils thus concentrate their energy on few number of nuts they can support during dry season. Good watering is thus crucial.

Mechanical damages due to wind can result in fruits and flower abortion thus plant border trees to curb the situation.

Diseases such as downy mildew result in the shedding of the leaves, lowering production. To curb the disease, maintain high level of farm hygiene.

Pests such as black aphids cause the nuts to drop. During the flowering stage, avoid using chemicals since they kill beneficial insects leading to inadequate pollination.

Ripe nuts can easily be identified by their colour and texture. In most cases, unripe nuts are usually sticky and should not be harvested.

The nuts should be harvested when the skins begin to crack. Mature nuts are usually chocolate brown and easily drop off. Weeding is key to facilitate easy collection of the nuts.