When applying any type of pesticide through a boom sprayer, the most important item to consider - even more important than the selection of pesticide or fertilizer - is to ensure the sprayer is calibrated correctly. When I recommend a herbicide to kill an undesirable weed, I often get asked, "How much product should I add to the tank?"
Unfortunately, it isn't that easy when broadcast spraying an entire field. The label on pesticides provide use rates for application - typically listed as a volume or mass of product/area (Ex: fluid ounces/1000 ft2, fluid ounces/acre, pints/acre, quarts/acre, pounds/acre). The only way to apply the pesticide at the label rate is to apply it with a calibrated sprayer.
The goal of calibration is to determine what volume of water is applied over a given area. Typically, the units are given in gallons/acre. In general terms, we want to determine how many full tanks are required to spray the entire field. I hear of many people using 20-25 gallon tanks attached to an ATV. In this case, one would likely need to fill up multiple tanks in order to spray the field. You can imagine the negative effects of not knowing this - all of the pesticide needed to cover the entire field is added to the first tank, the tank runs out of water after only covering one-third of the field, then 3x the desired rate has been applied. While this is not only illegal, over-applying these products can severely damage desirable turf (especially herbicides).
To calibrate a sprayer follow the instructions given in the video below. One thing they do not mention is that it is important to maintain constant speed - ideally around 3 MPH. If there is a speedometer on your vehicle, use it!
Also, if your nozzle spacing is not included in the video, here is a chart that provides calibration distances for various nozzle spacings:
Once the sprayer is calibrated and you know how many gallons of water cover an acre of turf, it is time to determine how much product to put in each tank. Follow the simple formula below which was taken from Practical Math for the Turfgrass Professional:
Some advice for spraying:
Purchase and add blue indicator dye to the spray tank to ensure you are getting adequate spray coverage. It is very difficult to see where you last sprayed! Overlapping too much applies more product than the label intended, which could lead to turf injury.
Spray in straight lines - it is easier to ensure proper coverage when spraying straight lines.
Wear proper PPE - refer to the label of the pesticide you are spraying for recommended PPE
If you need help with any specifics, my contact is below!
Keep raking!