What Is the Role of Drop Size in Agricultural Chemical Spray Equipment

1. What Is the Role of Drop Size in Agricultural Chemical Spray Equipment? Spray drift of agricultural chemicals away from the target sites is a very costly problem faced by commercial as well as private applicators. When a pesticide spray drifts from the targeted area, it results in a variety of challenges and problems, such as: Damage to susceptible off-target sites Lower rate of spray application on the targeted sites, significantly reducing the effectiveness of pesticides Wastage of money, chemical spray, and resources, Contamination of the environment, such as water pollution and illegal pesticide residues Understanding the Dynamics of Drop Size in Spray Drift of Agricultural Sprays When a chemical solution is sprayed through a nozzle, it gets divided into droplets that are ideally spherical or nearly spherical in shape. The size of these droplets is indicated in microns. Droplets that are too small (smaller than 100 microns) are highly prone to drift. Plus, they are so tiny that one can’t see them readily unless these drops are present in higher concentrations like fog. Thus, for smaller droplets, drift is more affected by the turbulent air instead of gravity. Particle drift of spray equipment refers to the actual movement of spray particles away from the intended application area. While several factors affect particle drift, the initial size of the droplets plays a bigger role. Small droplets when fall through the air slowly, they are swayed away by the moving air. Meaning, the longer the droplets stay in the air, the greater the potential of drift.

2. Unless particles are electrostatically charged, gravity and air resistance both act upon the droplets coming out of spray equipment and greatly affect their speed and movement. The speed of droplets is typically reduced by the air resistance that leads to the breakdown of droplets. Once the initial speed of droplets slows down, the droplets continue to fall due to the gravitational pull. With lower heights, the initial speed might be sufficient enough that the droplets reach the target area before particle drift occurs. Besides, small droplets also evaporate much quicker than large droplets, leaving minute particles of the chemical in the air. As the pressure in the spray equipment increases, the percentage of small droplets in the spray also increases. When the proportion of small droplets in the spray is higher, the potential for spray drift onto off-target sites also increases significantly. Ideally, most of the volume of spray chemical should be contained in larger droplets. Larger droplets are heavier, and therefore, they are less affected by wind and evaporation. They maintain a downward velocity longer than smaller ones. However, these coarse sprays can also sometimes lead to reduced coverage and control. Thus, the use of droplet size categories seems to be the most practical approach. Agricultural nozzles are designed to generate a range of droplet sizes, commonly known as the droplet size spectrum. The volume median diameter (VMD) is typically used to characterize the droplet size spectra. VMD is the droplet size in microns at which half of the spray volume consists of larger droplets and half the spray contains smaller droplets. While VMD is useful for a general composition of droplet spectra, it is not effective to measure drift potential as it indicates an average droplet size. The more effective way to measure the spray drift potential is to evaluate the percentage of spray volume in small droplets that are more prone to drift. Therefore, the use of drop size measurement equipment becomes essential

3. when it comes to creating highly effective and affordable agricultural spray equipment. Source: https://www.enurga.com/dropsize.htm