SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/282941
April 2014 | SportsTurf 37 www.stma.org place it with a new tip that is the same style and output volume. • Consistency with this calibration technique is dependent on how evenly the operator can spray an 18.5 feet by 18.5 feet area. This can be performed on a concrete or asphalt driveway/parking lot to observe how evenly the surface dries. The angle of a nozzle's spray pattern and the height at which it is held from the ground de- termine the width of the spray pattern. Try different spray heights and observe the drying rate. A uniform drying rate indicates uni- form coverage. Nozzle height can be adjusted to control excess streaking. Once your application techniques are consistent, then you can begin calibrating your backpack or hand-held sprayer. • Constant pressure must be maintained for consistent applica- tion rates. High pressure equals more product being applied per unit area as well as higher drift potential, while lower pressure equals less product per unit area. Few hand-held and backpack sprayers contain pressure regulators. Pressure fluctuations can be prevented by instal- lation of a pressure gauge or spray management valve (SMV) or constant flow valve (CFV) on the spray handle or boom. Spray rates and patterns will be more consistent, drift potential can be reduced, and calibration is easier. If a pressure regulator is not an option, fairly even pressure can be maintained if the hand pump is operated by a constant number of pumps per minute. It is not necessary to know the exact pressure output to calibrate a sprayer, but the pres- sure must be kept constant throughout calibration and application. Keep in mind that each operator will have a different walking speed and will regulate pressure differently. Therefore, it is important to calibrate a sprayer for each operator. CALIBRATION PROCESS The amount of spray applied to an area will depend on walking speed, pressure, spray swath width, and the spray tip selected. If you change any one of these, the amount of spray applied changes and the sprayer must be calibrated from the beginning. There are several different ways to accurately calibrate a sprayer. The process being outlined in this bulletin is based on the 128th Acre Calibration Method. The spray collected from a single nozzle measured in fluid ounces directly converts to gallons per acre re- gardless of the number of nozzles. Because there are 128 fluid ounces in a gallon, the fluid ounces collected from 1/128th of an acre will equal gallons of solution per acre. Remember: Collect materials needed to calibrate the sprayer: • Sprayer • Correct spray tips (if using more than one, the tips are identical) • Measuring tape • Water • Flags or turf paint • Measuring container (measurement in fluid ounces) • Stopwatch Step 1: Determine application pressure and timing. Mark off an area 18.5 feet by 18.5 feet. Turf paint or flags can be used to establish boundaries. Fill the sprayer tank ½ full of clean water. Use only clean water during calibration. Never add pesticides to a sprayer until it is prop- erly calibrated and ready for use. Pump to the normal operating pressure to simulate the average spray situation. Walk at a comfortable, steady speed while spraying to achieve uniform coverage. Maintain consistent pressure while spraying. Measure the time in seconds it takes to uniformly spray the 18.5 feet by 18.5 feet area. Record the time. Example: It took 46 seconds to spray the 18.5 feet by 18.5 feet area. Step 2: Measure nozzle output Nozzle flow rate is the amount of liquid sprayed from the nozzle in a given amount of time. Operate the sprayer with water in the tank at the desired pressure. Using a stopwatch and measuring cup marked in fluid ounces, collect water from the nozzle for the time (in seconds) it took to spray the predetermined area. Record the amount collected. Repeat this process 2-3 times to get the average nozzle output. Note: Application rates can be highly variable with backpack or hand-held sprayers. Simple adjustments can be made to ensure a consistent application rate. To increase application rates, the opera- tor can increase pressure and to decrease application rates, the oper- ator can decrease pressure. Example: The first amount collected after 46 seconds is 44 fluid ounces. The second amount collected after 46 seconds is 45 fluid Photo courtesy of Michael Goatley, Jr., Ph.D. 1 acre = 43,560 square feet 1/128th of an acre = 340.31 square feet 1/128th of an acre = 18.5 feet by 18.5 feet 1 gallon = 128 fluid ounces