“Efficiency of spraying will become increasingly important on high-value crops as the demand for food production rises and integrated pest management practices improve,” says Marius Ras, Specialist Consultant at Rovic Leers.
“While agricultural chemicals are softer than before, it still has large impact on the environment. One wants the highest amount possible to land on the target and not in the atmosphere or on the ground.”
To this end, Rovic Leers commercialized their EVENFLOW® and Variable Air Momentum (VAM) technology two years ago and the success of their approach has convinced them to offer it to growers in Europe and the Americas.
The EVENFLOW® turret, designed according to flow dynamic analysis (photos supplied by Rovic Leers)
Many sprayers tend to move the spray-laden air right through the target, which is the result of an oversupply of air speed, in the process not getting the full value of the application on the target.
“The goal is to replace the static, dry air within the tree canopy with spray-laden air, with none of it ending up on the other end of the tree, nor falling short of the tree,” he explains. He has been studying the relationship between ground speed and air momentum for decades since his Masters engineering degree.
“It’s that fine balance that you’re trying to obtain. The concept is not unknown, but not yet employed to its optimal effect. The EVENFLOW® technology allows this and it answers to the SYNCROFLOW® conditions.”
Balancing air momentum with ground speed
Employing the exact required air momentum for a pre-specified volume of tree canopy, taking into account the growth architecture and density along with the ground speed, allows the spray-laden air to displace the dry static air within the tree canopy and for the air with atomized liquid to come to rest within the tree, not spraying through the canopy and losing the chemical due to drift.
“The results are outstanding,” he says; they have spent six years in R&D and field trials in South Africa. “We have found a proven increase in recovery of the active ingredients on the target – up to three times more than conventional sprayers, and hence less environmental contamination due to drift or runoff.”
Rovic Leers, established in 1927, well-known agricultural equipment manufacturer and agent in South Africa
Employing Rovic Leers’ patented Variable Air Momentum (VAM) technology, the ROVIC EVENFLOW® can be used at varying ground speeds whilst spraying in an orchard. The change in ground speed of the sprayer and the changing requirement of the trees, depending on tree architecture and density, are adjusted on the sprayer to attain a balance between maximum allowable speed or as much as 50% slower. The higher the speed, the more air volume is necessary to replace the dry air and vice versa, and is achieved with VAM®.
The EVENFLOW® designed air velocity profile, which is the velocity at which the sprayed air needs to be projected towards the tree, is of equal importance and is similarly also adjusted to the tree shape, so that there aren’t parts of the tree that gets too little or too much air momentum.
“This is the only machine that reaches this delicate balance and it does this through our Variable Air Momentum patent,” he continues.
The ground speed is adjusted for different commodities and their tree canopy: hence an apple orchard, for instance, requires a different ground speed (average 6 - 8km/h) and a different air volume to a denser crop like macadamias (average 2.5 - 4km/h), and the VAM system allows for all of these variables.
To supply sufficient air momentum within a macadamia orchard planted at 10m x 6.5m height x 4m tree depth, the fan has to supply 48,000m3 air at 2.9km/h. This results in the exact right air momentum and air velocity profile to replace the static dry air within the canopy with sprayed air, just enough for it to settle on the target.
Their comparative trials have shown better and more even deposition as a result of their patented ROVIC EVENFLOW® technology
Moreover, the top part of the EVENFLOW turret, designed according to flow dynamic analysis, projects the spray at a slight angle to the rear, while the bottom part projects the spray towards the front, not impacting at a 90-degree angle on the foliage, and improving penetration.
In this way there is a slight time delay between the bottom and top spraying of the same tree, creating conditions for better deposition.
Please see video on following link: https://youtu.be/0RK-ujUsGXc