Electrostatic spraying of crops continues to become more popular in South America. This technique consists of inducing a static electric charge in each emitted drop, which causes it to be attracted to the plant that has a neutral charge. The air jet of the spray added to the high energy charge of the drops causes them to reach the plant very quickly, even before being volatilized. In addition, the fact that all drops are with electric charges of the same signal causes a repulsion between them. With this, it is possible to reach the plants in a more uniform way, even in more hidden regions.
In practice, this means higher spraying efficiency, savings in the use of pesticides and, consequently, greater efficiency in the application service, since the need for tank refueling is lower. In addition, by reducing the amount of pesticides used, the technology brings benefits to the environment.
Electrostatic spraying will typically produce fine drops with a diameter between 50 and 120 microns. Here are a few common questions related to drop size:
How important is the diameter of the drop?
Let’s compare two drop sizes: 220 microns and 80 microns. With the volume of a drop of 220 microns, we can make 21 drops of 80 microns. With 21 drops of 80 microns, you can cover 2.75 times more area than with a drop of 220 microns. In 1 liter of pesticide, we can get 180 million drops with a diameter of 220 microns or 3.8 billion drops with 80 microns, approximately 22 times more droplets generated with a smaller diameter, allowing the product to reach the target in more places. If we were to spray a flat area with only 1 liter of water, covering 100% of that area, when using the 220 microns, we would cover an area of 6.8m2 and with drops of 80 microns, we would cover 18.7m2. In this way, we almost have three times more coverage with fine droplets.
Why can’t we work with fine drops in conventional application?
Fine drops evaporate, are easily carried by the wind, suffer from thermal inversion, among other factors. Spray drift is probably the biggest concern. Studies show that up to 75% of conventional spraying is lost by drift or to the ground.
Why can we work with fine droplets in an electrostatic application?
Fine droplets with electric charge speed toward the target, which reduces evaporation loss. The force of attraction is so great that it can even overcome the turbulence of high winds.
Why is electrostatic spray coverage more uniform than conventional applications?
All drops are loaded with the loading table. Remembering that bodies loaded with the same charge repel each other, we can have drops that do not clash during their course to the target, causing drops to land side by side, instead of drop over drop as with conventional applications. Also, we must not forget that charged drops have so much force of attraction that even after they pass through a leaf or fruit, they are able to return and deposit on the back of the target.
One company, SPE, that offers electrostatic spraying systems in Brazil and has been working for three years with the technology. SPE has already installed thousands of these systems in South America, including many in Mato Grosso this past season. I learned about the technique last year, when we evaluated it after one of my clients had it installed in two John Deere 4630 sprayers. The cost is around R$ 1000 (US $ 330) per nozzle. We are applying with a volume of 30 liters per hectare product with the cone empty nozzle, where we had used 70 liters per hectare. And even reducing the volume of product we continue with good quality of application.