Top tips to grow the best quality macadamia nuts

South Africa is the largest producer of quality macadamia nuts globally. According to Allan Sutton, Valley Macadamia Group chairman, China’s insatiable demand for South African macadamias is due to a hard-earned reputation for superior quality. In a long chain of processes to get quality macadamias from farm to fingertips, stringent checks and balances are essential at every stage. For farmers, growing the best quality macadamia nuts starts in the soil and ends with the right choice of processor.

Here are a few top tips to ensure quality throughout the farming cycle.

Soil preparation
Macadamia trees flourish in a wide variety of soil types across South Africa. The preferred soil depth for macadamia trees is 1m and soil should be well drained and free of restrictive layers. Also consider soil characteristics such as fertility, water retention, organic content and pH levels. Macadamia trees are tolerant of acid soils and a soil pH of 5.0 to 5.5 is ideal. Soil pH levels should be analysed and corrected before planting to ensure an optimal environment for root development. Growers should also sample and analyse the soil every two years to monitor soil fertility over time.

Climate and altitude
Macadamia tree growth and nut quality is heavily reliant on climate and altitude. Macadamias flourish between 16 and 25°C but extended exposure to temperatures over 30°C can harm new growth and cause premature nut shedding during early development. Nut quality is also superior when grown at an altitude of 600m or lower. Altitudes above 600m tend to reduce the quantity of grade one kernels and total nut production.

Planting distances
Give each tree its due time in the sun. Macadamia cultivars have different growth patterns and specific planting and fertilisation guidelines to ensure optimum growth. These are broadly categorised as being either spreading or upright growers. Upright varieties require less space and are best suited to close-planted orchards. Commonly used planting distances are 4m between trees and 8m between rows for upright varieties, and 5m between trees and 9m between rows for spreading varieties.

Although the fine lateral roots of macadamia trees are efficient in absorbing nutrients, trees need to be fertilised regularly to ensure good growth. However, it is advised to wait one year for recently planted trees to become well established. Fertilisers should be applied evenly from 0,2m from the stem to 0,5m from outside the drip area or the surface area below the leaf canopy. Macadamia trees are sensitive to root damage and fertilisers should be followed by light irrigation.

Rainfall and irrigation
All macadamia production areas in South Africa have a rainfall between 800 and 1,200mm per year. From September to March, macadamia trees are most sensitive to a shortage of moisture. To safeguard against periodic droughts and ensure a better yield, it is essential to provide supplementary irrigation, particularly during critical development periods.

Wind protection
Macadamia wood is very brittle and prone to wind damage. Wind protection can be provided in the form of fast-growing rows of trees. To ensure structural strength against wind damage, narrow crotch angles between the stem and the side branches should be pruned to get stronger crotch angles between 45 and 60 degrees during the first two to three years.

Macadamia nuts drop to the ground naturally when they are mature. To preserve nut quality while on the ground, ensure that the area underneath the trees are clear of grass, leaves and branches. Nuts must be collected at least once a week to limit potential damage caused by mould and rodents.

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