Compared with the commercial cultivation of apples, which started in the 1600s, the macadamia industry is considered as still in its infancy. The first commercial macadamia orchard was established in Australia only in 1880.

That would suggest farmers have a way to go to fine-tune the breeding of varieties for optimal kernel production and to develop ideal orchard management practices.

New innovations and techniques are, however, advancing rapidly, some of which are producing promising results on a third-generation avocado and macadamia farm in Mpumalanga.

When the Hearne family started expanding their farming set-up five years ago to incorporate a sizable macadamia business, they launched an immense planning strategy to drive efficiency, lower costs, maximise production and create a system that would be easy to manage for years to come.

Two aspects were critical in achieving this:

  • modularity – where the farm could be divided into manageable blocks and treated homogeneously, and
  • precision farming – where cultivars were given exactly what they needed, when they needed it, and not an ounce less or more.

The strategy has resulted in fast-maturing orchards producing bigger trees than age-equivalent trees on other farms, and fulfilled a key aim: to get into production sooner while producing a consistent farm average yield superior to industry norms.

Planting cover crops benefits the soil and increases organic matter.

But if they are planted directly under the trees the cover crops compete for water and nutrition and can hinder harvesting processes.

Danroc Farm CEO Justin Hearne said the use of weed mats coupled with low-flow fertigation was possibly one of the most interesting and effective innovations they had implemented.

“There were fundamentals we had to consider while developing the farm at such a speed and on such a scale. First, we would have needed significant quantities of herbicides and labour to control the weeds in the newly-planted orchards. It would have been a management nightmare. Weed mats were logical to eliminate herbicide usage and weed competition, while allowing for the retention of the moisture in the soil and to provide a clean surface from which to harvest,” he said.

Orchard preparation

Justin Hearne is a member of the Danroc team.

The orchard was prepared by creating ridges using soil and organic matter. Soil correction was carried out based on soil analysis. The weed mats were positioned over the ridge, and the trees planted in small holes made in the mat. Irrigation pipes were placed under the mat.

Hearne said the ridge and the weed mat had helped provide structure to the orchard and prevented tractors and other machinery from compacting and disturbing the soil around the main root zone of the trees. “The ridge is also essentially another layer of topsoil added to the existing substrate.”

Grass was planted between the rows as part of good establishment practice.

“We planted grass that grows relatively low to the ground and can be mown very short to allow for an easy harvest – similar to a cricket pitch,” he said.

When the grass in the interrow is mown, the cuttings are cast to the side, creating an additional organic zone half a metre from the weed mat. This area is also a no-drive zone and the soil here is ripped from time to time, with more organic matter added, to feed the trees’ roots.

“We fertilise intensively and precisely as we don’t want the weeds absorbing any of the nutrients or water and taking it way from the trees. Farming at this scale is a numbers game and we need to get the trees mature and into production as fast as possible, so eliminating competition aids this process. The precise application of fertiliser and the availability of that fertiliser and water to the trees alone is a big factor, contributing to the faster growth.”

From the perspective of sustainable production, Hearne emphasised the optimal use of water as a key priority. The weed mats, he said, allowed for minimal evaporation and only the trees were irrigated, not the weeds.

“This saves water and pumping costs.”

While the weed mats were a significant initial capital outlay, Hearne said they started becoming cost neutral after year five. This, he said, was due to the savings on labour and input costs. And the lifespan of the weed mats was long enough to get the trees to maturity, when the canopy would supress any weed growth or evaporation. By the time the irrigation pipes need replacing, the weed mats would have served their purpose, meaning they also would not hinder pipe management.

The trees in this orchard are three years old and bigger than most others of equal age. Justin Hearne attributes the faster growth to the management system.

An ideal orchard

Part of the drive towards greater efficiency and resource management is Danroc’s centralised cluster houses for irrigation and from where the fertigation is managed.

Low-flow drip irrigation means the power requirement is low compared with other methods and the whole farm can be irrigated at once. Further, there are optimal times during the day to fertigate, when the trees are most ready to take up nutrients.

And where possible, gravity is used to supply the water rather than using expensive pumps. In the newer blocks, solar powers the irrigation, rather than Eskom.

Hearne said between the weed mats and the low-flow irrigation technology, significant water savings were achieved.

“The nutrients and water are supplied exactly where they are needed. Micro-irrigation gets the trees irrigated more quickly, but there is a lot of evaporation and inefficient water distribution, so more water is required,” he said.

Precision farming – as the second cornerstone of the farming operation – has meant that each tree is GPS (Global Position system) mapped and monitored.

While establishing what the ideal tree density should be in the orchard is yet to be confirmed, the orchards are planted up to 8m x 3m and 8m x 4.35m to find what works the best.

To promote cross-pollination, every sixth line is planted up to a different cultivar from the rest on the block. The main varieties are A4, Nelmak2, and Beaumont, coupled with various pollinating varieties. While this does complicate the pursuit of uniformity, it is necessary to ensure optimal pollination and spread risk across nuts that crack out differently and offer varying quality. As for the ideal cultivar selection, Hearne says that is the million-dollar question.

“Macadamia varieties currently cultivated are deemed to be only three generations away from the wild trees. Apples, on the other hand, have a thousand generations of varieties between the wild plant and today’s commercially planted cultivars. We don’t know nearly enough yet about which cultivars do best in which environments and what their ideal production processes look like. Usually, you only get proper production data after a long period of research, and the industry is not there yet. It’s difficult in this day and age to say which cultivar will do best on which farm, which is why there has been a shotgun approach in the industry for the most part.”

Hearne believes that through plant breeding and cultivar selection there is massive scope to increase the performance of macadamia nut trees to get higher yields and better kernel recovery.

“But it’s a long term project that could take years,” he added.

This does put farmers – who are expanding their orchards – in a predicament, since production choices today will have a bearing on the business for many, many years to come.

To expedite their expansion, Danroc developed an on-farm nursery. Beaumont cuttings are taken and propagated, while other cultivars are grafted on to the Beaumont cuttings, which serve as the rootstock.

The cuttings go through a process of striking roots in an ideal, climate-controlled environment in the nursery. Almost half of them don’t make it to the next phase. Those that do are placed in the section of the nursery that closely mimics the orchard and provides an opportunity for the trees to “toughen up”. Here, the cuttings are fertigated and screens are manipulated to allow for maximum light distribution to promote growth.

The Beaumont cuttings are ready for planting  in the orchards within 10 to 12 months. Grafted-on varieties can take up to 14 months before they are ready to plant, whereas seed propagation could take 16 to 20 months. “We try to speed up the process as far as practically possible,” Hearne said.

And with the current crisis facing the industry, Hearne added that it was about driving systems efficiencies and doing more with less.