February 7, 2022
Spring is just around the corner and soon it will be time to get equipment ready for the 2022 season. Along with tillage and planting equipment, sprayer equipment preparation also needs to be considered. What are some key things to keep in mind when setting up the sprayer for this season?
Aside from sprayer calibration, nozzle selection is the biggest factor that may impact sprayer and pesticide performance. To determine which nozzles to use, the type of sprayer, the purpose for an application, and which pesticides are to be used are important considerations. Prior to any pesticide application the applicator must review the label for that product (Figure 1). The label is the legal document that pesticide applicators are required to follow by law.
Under “Directions for Use”, specific sections, such as Spray Drift Management, Aerial Application Equipment, and Ground Application Equipment provide important application information and must be read and followed to properly apply the respective chemistry (Figure 2).
Figure 1. First page of Roundup PowerMAX® label.
Figure 2. Specific sections in the label provide information regarding application equipment including nozzles.
Please review the application section of the pesticide label for the product you plan to apply to determine the type of nozzle that should be used. There are 4 components of nozzle selection worth noting:
Spray Patterns: Flat fan, cone, and streaming nozzles are available from most nozzle companies. Flat fans are the most common and form a “V” pattern when used. The center of the fan has the heaviest output so when combining nozzles on a boom, the nozzle manufacturer will provide nozzle spacing and height recommendations to achieve an even application. Often used for directed spray applications, cone nozzles create a circular output pattern that is designed to be used at higher pressures. Streaming nozzles are often used with fertilizer applications and true to its name provides output in a single stream instead of a flat or circular pattern. Most pesticide applicators for agriculture use flat fan nozzle patterns.
Spray pressure: Flow rate of the fluid from the nozzle varies based on pressure in the sprayer system. This is usually measured in pounds per square inch (PSI) or gallons per minute (GPM). Higher pressure increases flow rate and may impact droplet size. The pressure may be adjusted to increase or decrease nozzle output and most nozzles have a manufacturer recommended pressure use range.
Nozzle size: The size of the nozzle orifice helps determine the droplet size which is a critical factor in pesticide applications. Droplet size has a huge impact on how easily the droplets may drift; larger drops don’t drift as far as smaller ones. Again, refer to the pesticide label for recommendations. In general, larger droplets are often recommended for systemic herbicides because the pesticide is absorbed and translocated to the roots. Non-systemic or contact herbicides tend to recommend smaller droplet sizes to increase coverage on the target weed. In addition to the physical hole size on the nozzle, changes in pressure can impact droplet size and ultimately drift potential. There are a lot of size options available ranging from extremely fine to ultra-course with about 6 sizes in between depending on the manufacturer. General or specific nozzle size recommendations are usually found in the label as noted above.
Nozzle types: Nozzle type impacts performance in a big way.
Air induction or flat fan nozzles are the most used in pesticide applications.
Air induction nozzles are often used when drift reduction is important. They use two orifices to meter flow and impact the pattern of the spray particles. They can be used at lower pressure and incorporates more air into the system to increase droplet size, thus helping to reduce drift.
Flat fan nozzles can be used over a range of pressures and are often used when more surface coverage is important.
Flood nozzles are the most basic nozzle type and may be greatly impacted by pressure variations.
When nozzle selection is complete, sprayer calibration is important for delivering the desired application rate (quantity and uniformity) across the spray boom. Before calibrating, the sprayer tank and lines should be properly cleaned. The lines should be checked for leaks and each nozzle removed to clean the nozzle screens to rule out any output variation from physical barriers.
One simple calibration method is the 1/128th of an acre method. Depending on nozzle spacing, one can determine how long it takes to cover that distance. For example, with a 30-inch nozzle spacing, 1/128th of an acre can be covered in 136 feet. Set flags to mark 136 feet and determine the time it takes to cover that distance. If it takes 32 seconds, park the sprayer, fill with water, set the desired pressure, and collect the water from a nozzle for 32 seconds. Since there are 128 oz/gallon, if 13 oz are collected in 32 seconds, the output rate would be 13 gallons/acre. Staying within nozzle pressure rate ranges, tweak the pressure up or down to get the desired output rate. The step should be repeated across the nozzles to verify output across the boom.
There are several calibration methods and most University Extension Services and nozzle manufacturers have documents that can be referenced to determine appropriate sprayer calibration. At the end of the day, regardless of the method used, the important thing is knowing that your sprayer is calibrated correctly.
Uncalibrated sprayers may be delivering too much or too little product. Over applying a pesticide can impact crop safety, be economically inefficient, and may be a potential environmental hazard. Under application may decrease the effectiveness of the pesticide and could be economically inefficient. Therefore, take time on a nice day and properly calibrate the sprayer to help maximize the potential for a successful growing season.
Legal Statement
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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