APM Factsheet Number 01: January 2024
A practical guide to optimizing macadamia yield
Drawing from extensive experience in macadamia cultivation and data analysis, this guide outlines key strategies for substantial yield improvements in macadamia farming. Implementing these recommendations may be challenging, but they offer cumulative benefits and long-term success.
A practical guide to optimizing macadamia yield
Download our comprehensive guide to top-tier results in macadamia farming.
Core Principles for Exceptional Results
We assert that perfect management of the following areas should lead to top-tier results in macadamia farming:
1. Irrigation Management
Implement accurate irrigation scheduling to maximize oxygen to maintain soil moisture at 60-90% of maximum water holding capacity, especially in the 0-30 cm soil layer. Sprinkler systems are recommended over drip irrigation for optimizing nutrient release through microbial decomposition of mulch.
Figure 01. Soil Moisture Dynamics for Macadamia Cultivation: These schematic tracks soil moisture levels over time in a macadamia orchard planted in sandy soil. It illustrates key moisture thresholds such as field capacity, the point at which free drainage occurs, and the refill point where irrigation is needed to avoid stress. The leveling off of the moisture curve indicates the onset of plant stress due to insufficient water, underscoring the importance of timely irrigation to maintain soil moisture above the wilting point and ensure adequate oxygen levels for optimal tree health. GRAPHICS: Schoonover, J & Crim, J. (2015)
2. Canopy and Light Control
Maintain canopy volume by intercepting 85-90% of sunlight (43,000 m³ per hectare for an 8 x 4 m spacing). This involves managing tree height and row spacing (2.1 meters) to maximize light penetration whilst considering and balancing pest and disease risks. Lidar and drone technologies can be instrumental in this management.
Figure 02. This schematic graph elucidates the critical relationship between canopy volume, light interception, and macadamia yield for an 8 x 4 m tree spacing scenario. It emphasizes that maintaining a canopy volume around 43,000 m³ is vital for achieving the highest possible yield without compromising manageability. At this volume, growers can expect manageable levels of pest and disease incidence, along with improved pollination efficiency, beneficial insect activity, and optimal ground cover that prevents erosion while ensuring ease of access for orchard management. In contrast, canopy volumes exceeding this threshold may increase humidity and decrease light availability within the orchard, which could lead to more challenging pest and disease conditions, poorer pollination, and overall reduced ground cover, ultimately complicating maintenance and potentially impacting yield negatively.
Comparative Analysis of Tree Management Strategies: This table delineates the structural and productivity metrics of two tree management setups with varying row widths. It contrasts the physical attributes such as tree height, working rows, and canopy dimensions, alongside productivity measures like the volume of hedge rows and required nut density for achieving an optimal yield of 6 metric tons per hectare. The 10-meter wide setup features larger volumes and fewer rows, while the 6-meter wide setup requires a higher density of nuts per cubic meter of canopy, illustrating the trade-offs between space utilization and yield concentration in agricultural planning.
3. Pollinator and Cross Pollination
The key to this is to have 4 cultivars. Have small and big nut cultivars that flower at the same time so you can get the benefit of cross pollination and bigger nut genetics boosting smaller nut cultivars and overall yield.
Figure 03. Assessing Cultivar Diversity Impact: The boxplot depicts the association between the total kernel recovery percentage (TKR%) and the number of cultivars per farm, offering insights into how cultivar variety might affect overall kernel recovery.
Figure 04. Synchronized Blossoms: This schematic represents a guideline for flowering times of various macadamia cultivars within the Bundaberg region. Each peak corresponds to the bloom intensity of a cultivar, showing how their flowering periods overlap, crucial for planning cross-pollination strategies to enhance pollination success and optimize yield. In cooler areas these times may shift and/or extend.
Long-Term Strategies for Sustainable Growth
We assert that the most successful long-term strategies for sustainable growth in macadamia farming are:
4. Soil Health and Nutrition
Aimfor optimal soil health by ensuring maximum drainage and porosity, maintaininga minimum of 3% organic matter for preferred sandy soils, and balancing soil cations(Ca, Mg, K, Na). Regular annual applications of compost (1kg compost/squaremeter of midday shaded canopy) and mulch is necessary. Monthly applications of lowsalt index and low phosphorous fertilizer (little and often), along withcontinuous management of interrow vegetation, will promote the rhizosphere andthus earthworm activity and improve soil structure and fertility.
Figure 05. Soil Moisture Dynamics for Macadamia Cultivation: These schematic tracks soil moisture levels over time in a macadamia orchard planted in sandy soil. It illustrates key moisture thresholds such as field capacity, the point at which free drainage occurs, and the refill point where irrigation is needed to avoid stress. The leveling off of the moisture curve indicates the onset of plant stress due to insufficient water, underscoring the importance of timely irrigation to maintain soil moisture above the wilting point and ensure adequate oxygen levels for optimal tree health.
5. Integrated Pest and Disease Management
Aimfor optimal soil health by ensuring maximum drainage and porosity, maintaininga minimum of 3% organic matter for preferred sandy soils, and balancing soil cations(Ca, Mg, K, Na). Regular annual applications of compost (1kg compost/squaremeter of midday shaded canopy) and mulch is necessary. Monthly applications of lowsalt index and low phosphorous fertilizer (little and often), along withcontinuous management of interrow vegetation, will promote the rhizosphere andthus earthworm activity and improve soil structure and fertility.
Figure 06. Promoting Ecological Balance: A praying mantisstands guard among macadamia leaves, symbolizing the strength of natural pestcontrol within Integrated Pest Management (IPM). This approach is compromisedby aggressive insecticides, which can disrupt this balance and harm beneficialpredators essential for the health of macadamia orchards.
6. Harvesting and Post-Harvest Management
Ensurerapid processing of harvested nuts to avoid quality degradation, with a focuson maintaining ventilation (min 1m/s through bed depth) in storage bins toreduce risks of mold and rancidity.
Figure 07. Promoting Ecological Balance: A praying mantisstands guard among macadamia leaves, symbolizing the strength of natural pestcontrol within Integrated Pest Management (IPM). This approach is compromisedby aggressive insecticides, which can disrupt this balance and harm beneficialpredators essential for the health of macadamia orchards.
Figure 08. Figure 8 presents a positive ventilation systemwith fans, which is designed to push air through the nuts. The key in such asystem is to ensure that the intake air for the fans is fresh and not theexpelled air that has already absorbed moisture from the nuts. This is becausemoist air has a higher humidity and a lower capacity to absorb water, making itless efficient for drying. If fans were to recirculate this humid air, it wouldlead to a slower drying process, increased energy consumption, and potentiallycreate conditions favourable for mould growth or nut spoilage. To avoid this,the system should be designed so that the fans pull in fresh, ambient air fromoutside the shed. This air has not been in contact with the moist nuts andtherefore is drier and more capable of absorbing moisture. The expelled air,now carrying the moisture from the nuts, should be directed away from theintake of the fans to prevent it from mixing with the fresh air. This ensures acontinuous flow of dry air and maintains the efficiency and effectiveness ofthe drying process. The use of temperature and humidity sensors, as shown inFigure 5.7, helps to monitor the drying conditions and ensure that the airwithin the bins remains at optimal drying conditions Source: Macadamias: Anoverview and Guide to Preservation Principles and Engineering Practice 2nd Ed. Dorran Bungay.
Innovative Approaches for Yield Enhancement
Aim for optimal soil health by ensuring maximum drainage and porosity, maintaininga minimum of 3% organic matter for preferred sandy soils, and balancing soil cations(Ca, Mg, K, Na). Regular annual applications of compost (1kg compost/squaremeter of midday shaded canopy) and mulch is necessary. Monthly applications of lowsalt index and low phosphorous fertilizer (little and often), along withcontinuous management of interrow vegetation, will promote the rhizosphere andthus earthworm activity and improve soil structure and fertility.
Figure 09. Sustainable Macadamia Cultivation: Harmonizingthe Elements - This illustrative guide captures the essence of macadamiafarming, emphasizing the interconnectedness of critical factors like soilhealth, climate, and biological cycles. It highlights the role of non-structuralcarbohydrates in plant energy balance, underlining their importance alongsidesoil moisture, organic matter, soil chemistry, and cross-pollination.Integrated with seasonality, these elements form the backbone of a productiveand eco-conscious macadamia orchard, steering growers towards excellence witheach harvest cycle.
Innovative Approaches for Yield Enhancement
Aim for optimal soil health by ensuring maximum drainage and porosity, maintaininga minimum of 3% organic matter for preferred sandy soils, and balancing soil cations(Ca, Mg, K, Na). Regular annual applications of compost (1kg compost/squaremeter of midday shaded canopy) and mulch is necessary. Monthly applications of lowsalt index and low phosphorous fertilizer (little and often), along withcontinuous management of interrow vegetation, will promote the rhizosphere andthus earthworm activity and improve soil structure and fertility.
Note: These ideal qualities assume that macadamia growers will manage the soil to maintain optimal conditions, including regular applications of organic matter to improve soil structure and fertility, use of microjet irrigation for efficient water delivery, and appropriate fertilization to meet the nutrient requirements of the trees. Regular soil testing is also recommended to monitor and adjust these properties as needed.
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