Farmer's Weekly (South Africa)
Latest technology improves macadamia quality output
Achieving the near impossible, Dian Pretorius reduced unsound kernel recovery in his macadamia crop from 6% to 1,7% over just one season, adding R1,7 million to his profit in the process. He spoke to Lindi Botha about the technology that helped him achiev
Macadamia farmer Dian Pretorius from Brondal, Limpopo watched as his unsound kernel recovery (USKR) percentage rose year after year. Averaging under 3% in the late 2000s, it steadily climbed to reach 5% and then over 6% in 2018, causing his profits to dwindle. Then, in a single year, Pretorius dramatically reversed the decline, so much so that he received a quality award at his local processor, Green Farms Nut Company, for the 2019 season.
In the macadamia industry, the 5% USKR mark is regarded as critical; once farmers exceed it, they very seldom recover. Instead, it tends to rise steadily thereafter.
Barry Christie, group agricultural technical manager at Green Farms Nut Company, notes studies where farmers’ USKR was measured over five seasons.
“In general, growers who ended under 5% USKR in 2018 came from a slightly higher USKR, whereas those that had 5% USKR or higher only got worse. It’s statistically unlikely to get out of the trend once you exceed 5%, unless you change something drastic.”
He adds that the orchard will never be completely free of pests, but once a farmer has a high pest load, it becomes difficult to manage.
“If you have 90% control of 10 insects, as opposed to 90% control of 100 insects, you’re that much better off. Once you get to a critical mass of pests, it becomes very hard to control.”
Knowing the make-or-break point all too well, Pretorius set about investigating his pest control
regime on his family’s farms spread across the Lowveld in the Brondal and Kiepersol areas.
The macadamia orchards, which cover 150ha, contain trees that vary in age from one year old to 15 years old, and of seven varieties: ‘788’, ‘816’, ‘Nelmak 2’, ‘Nelmak D’, ‘Beaumont’, ‘842’ and ‘849. A separate management programme is required for trees of each age, complicating matters. About 50ha are fully matured, while the rest are in varying ages of production.
Pretorius says that tree age is the main obstacle in management, and older trees, in particular, require considerable pruning.
As far as pests are concerned, stinkbugs are the main culprits behind high USKR, which prompted him to start his investigation by examining his chemical spraying programme.
SPRAYING
Reaching over
6% USKR was a wake-up call for Pretorius.
“Looking back at everything we did on the farm to reduce our
USKR, technology played the biggest role in reversing the bad quality,” he says.
Pretorius received his first eye-opener when he bought a drone and flew it over the spray cart while it was in operation.
“Previously, I’d walk behind the spray cart to check that the chemicals were being applied properly. From that vantage point, it appeared as if the entire tree was being covered. But when I looked at the drone footage, I could immediately see that we weren’t reaching the top of the trees.
“I also saw that the spray penetration wasn’t sufficient. Even at a row spacing of 7m and an inter-row spacing of 3,5m, I realised that I had to prune each tree heavily to open up the centre for better penetration.
applied chemicals at night; we did this to protect the bees in the orchards. But now I spray only at night, regardless of the time of year, because there’s less wind at night than in the day.”
Pretorius says that spraying at night had been problematic as he could not be present in the orchard all night long to monitor the process. With FarmTrack, he can check up on progress by smartphone, viewing the rows sprayed and the precise speed and location of the tractor.
“For those few hours when I’m not physically in the orchard, I can still see exactly what’s happening.”
According to Christie, night-time spraying has also significantly improved the efficacy of the process; pests can be more accurately targeted, as they tend to be stationary at night when the temperature is lower.
‘ CHECK WHETHER THE SPRAY PENETRATES THE TREES PROPERLY’
The cooler conditions also result in less evaporation of the chemicals, while the lower temperature and lack of sunlight ensure that the active ingredients in the chemicals stay effective for longer.
Pretorius has also achieved greater efficiency by reducing the volume of water in the spray tanks.
“We started with 2 000ℓ/ha and now we’re on 3 000ℓ/ha for the mature trees. We’ve done tests on 4 000ℓ/ha and 5 000ℓ/ha and this resulted in a lot of wastage. Much of the chemical just drips off the leaves and drenches the soil at these high rates. I use a mister to ensure that the droplet size is smaller, so it’s more likely to stay on the plant.”
He adds that he and his neighbour try to spray at more or less the same time; this helps prevent pests from retreating to adjacent orchards and then returning later.
Another weapon in Pretorius’s arsenal has been a weather station that he erected on the farm. This has had a major impact on reducing USKR, as his spraying programmes are better executed and more cost-effective.
“Previously, we would have a tractor driver arrive for his night shift, only to find that clouds had started gathering. He’d then sit and wait to see if it was going to rain and if the night shift should be cancelled. By 8pm, if it still hadn’t started raining, he would mix the chemicals in the tank. Then the first drops would begin falling, and he’d be forced to stop work, go back home and return the next day. By then I’d paid for a night’s work and lost a tank of chemicals, but nothing had been achieved.
“The weather station helps us monitor wind and rain predictions, and plan the best time for spraying.”
WINNING RESULTS
After just one season, Pretorius’s plan to remedy his high USKR has borne fruit. By taking his USKR from 6,5% in 2018 to just 1,7% in 2019, he added R1,7 million to his bottom line.