By Erdal Ozkan, Ohio State University
This is the time of the year you must complete shopping for nozzles because the spraying season is just around the corner. Although nozzles are some of the least expensive components of a sprayer, they hold a high value in their ability to influence sprayer performance. First, nozzles meter the desired amount of liquid sprayed per acre. Second, nozzles help us spray the liquid uniformly over the width of the sprayer boom. Third, nozzles influence droplet size, affecting both target coverage and spray drift risk. For these key reasons, you need to make sure your sprayer is equipped with the right kind and size of nozzles, and they are still performing within the acceptable range of performance they delivered when they were new.
If you were happy with your nozzles last year, and if you are not switching to a new pesticide, all you need to do this spring before the spraying season is to check the flow rate of each nozzle to make sure the nozzles are not worn out. You will need to compare the flow rate of your nozzles with the flow rate of new nozzles of the same type and size at the same pressure. You can find information on the flow rate of new nozzles in nozzle catalogs or company web sites. A deviation of 10% between flow rates of your nozzles and the new nozzles is considered as acceptable. If the difference is greater than 10% of the new nozzle flow rate, it is time to get rid of the old nozzles and replace them with new nozzles.
Whether you are using the nozzles you already have on the boom, or getting new nozzles, there are some new issues you will need to consider before the start of the sprayer season. Typically, we take into account many important factors including: sprayer operation parameters (such as application rate, spray pressure, travel speed); application type (broadcast, band, directed, air assisted); target crop (field crops, vegetables, vineyard, shrubs and trees, etc.); and spray drift risk.
Are you aware of specific nozzle “requirements” on Labels?
In the past, the labels on chemicals gave some vague and general statements when referring to application equipment. For example, we used to see (it is still the same for many chemicals) on labels statements such as: “use spray equipment to provide thorough coverage of the canopy”. There was no help with explaining what “thorough coverage” is, and how to achieve it. Then, we saw labels giving us more specific recommendations on nozzles; such as: “use nozzles that provide medium spray quality”, or “do not use nozzles that produce droplets in coarse or larger spray qualities”. Most recently, the labels of the most talked-about 2,4-D or Dicamba herbicides include very specific requirements on which nozzle or nozzles must be used when spraying these products. For example one of these products requires using only ONE type and size of nozzle. Simple interpretation of this requirement is that you would be violating the label if you use any other type or size of nozzle. So, it is your responsibility to comply with the label recommendation.
Why are specific nozzles required by manufacturers of 2,4-D and Dicamba Herbicides?
Although manufacturers of these products claim that the new formulations containing 2,4-D or Dicamba are more resistant to drift of these active materials due to high volatility characteristics of similar products used decades ago, they are still extremely concerned about the physical drift of these products in droplets. Therefore, since these products are systemic in nature, they should work even when large size droplets are used during spraying. With this in mind, the manufacturers of these products have decided on recommending specific nozzles that produce droplets that are in the category of “Extra Coarse”, or “Ultra Coarse”. Physical drift of such large droplets will likely reduce the risk for drift to minimum. Although there are many nozzles that can provide these desired droplet size classes at certain pressures, at this point you are advised to choose exactly the nozzles identified on their labels.
Act now if you will be switching to new nozzles.
If you are going to use one of the new 2,4-D or Dicamba herbicides this year, it is very likely that you do not have on the boom the specific nozzles required by the manufacturers of these herbicides. That means, you will need to purchase the recommended nozzles and put them on the boom. Since many growers would want to do that, there may be short-term shortages of these nozzles in stores from which you purchase nozzles. So, act now and get the nozzles you need before experiencing potential problems with availability of these nozzles.
Keep several types of nozzles on the boom
It is very likely that you will be using your sprayers to spray a variety of pesticides during the growing season. Remember that one specific type of nozzle will not be best for all applications. For this reason, it is best to have several types and sizes of nozzles on the boom so that you can switch to the “best” nozzle choice for a given spraying job. As shown in the pictures below, there are various types of sprayer components and setups you can buy to configure your boom so the new set up allows you to easily switch from one nozzle to another instantly.
Some final thoughts
Nozzles are typically the least costly items on a sprayer, but they play a key role in the final outcome from a spraying job: achieving maximum efficacy from the pesticide applied while reducing the off-target (drift) movement of pesticides to minimum. Pesticides work well if the rates on labels are achieved during application. This can be achieved only if the right nozzle type and the proper size of the nozzles are on the sprayer, and the sprayer is operated properly.
Although the Apps and tables in catalogs may expedite the nozzle size selection process, it is best to understand the process and the math nozzle manufacturers use to generate the values listed in tables, and to generate nozzle recommendations in their Apps. A new Ohio State University Extension Publication, entitled “Selecting the Best Nozzle for the Job” gives step-by-step guidelines for selecting the most appropriate spray nozzle for a given application situation.