 Ryan Mitchell with the Alabama Cooperative Extension System. Today I'm going to demonstrate an easy way to calibrate a backpack sprayer. Why calibrate a backpack sprayer, you may ask? When we provide herbicide prescriptions, the rates we prescribe are based on a ounces per acre or a percent volume. If you do not know how much fluid you're spraying, you're oftentimes going to exceed the amount of herbicide prescribed and that can cause problems. The method I'm going to demonstrate today is the 1-128 calibration method. Because there are 128 fluid ounces in one gallon, we can determine our sprayer output in gallons per acre based on the number of ounces it takes us to treat 1-128 of an acre. To calibrate a backpack sprayer, you're going to need your sprayer filled with clean water, boundary markers or pen flags, a long tape measure, a liquid measuring device, preferably in ounces, and it's always safe to have gloves and eye protection even though we're using water. Take one acre or 43,560 square feet and divide it by 128. You get 340 square feet or an 18.5 foot by 18.5 foot square. Mark the boundaries to clearly define the areas to be sprayed. It is important to set this up and terrain representative of what you will be treating, but while you're getting comfortable with your sprayer, it is okay to set this up in a parking lot or in a flat grassy area so you can learn your sprayer. Using a stopwatch or the stopwatch feature on your smartphone, measure the time required to spray the marked area with your sprayer. Spray at a comfortable pace and maintain a constant pressure. For backpacks, this may require some practice to become consistent at pumping as you spray. Repeat this process three times and calculate the average time required to spray the area. Next, you're going to use your sprayer to spray into a measuring container for the average time required to spray the area. Be sure to maintain the same constant pumping pressure as you did when you sprayed the 1,128th of an acre. Then measure how many fluid ounces of water are in the container. The amount is equivalent to your sprayer output in gallons per acre. For example, on average it took us 27 seconds to treat our area. After spraying clean water into the measuring container for 27 seconds, we ended up with 20 and a half ounces. This is equivalent to 20 and a half gallons per acre. Thanks for joining us today. I hope you learned something about calibrating a backpacks sprayer. If you have any questions, post them below. Thank you. Have a great day.