Periodic maintenance of spray equipment is required for accurate application of pesticides and fertilizers. Avoiding the replacement of poorly functioning parts and performance of the system often results in a misapplication, usually to a greater than acceptable degree. When improperly adjusted equipment is used, turf can be damaged, pests may not be controlled sufficiently, and the environment can be contaminated, all of which are unacceptable. Performing a simple spray check is well worth the time and effort, and most sports turf managers could really use an easy-to-follow procedure. Following are some simple, yet important, steps that can improve the efficiency of spray equipment.
- Before each spray application, a visual inspection should be performed. A good starting point is to fill the tank with water and check for leaks. Look at all parts of the system including the hoses, fittings and tank. Next, start the spray unit and pump. Check to see if water is circulating in the tank as a result. Continue to look for leaks, this time focusing on the pump, but also the hoses, fittings and other parts of the system that may begin to leak due to the action of the pump. Even a small leak is problematic, in that they often become larger as the spray operation progresses. The next step is to turn on the spray boom and look for seeping water in the hoses that lead to the boom or nozzle hoses.
- As the unit is spraying, make a general observation of visual differences; sometimes it’s pretty obvious which nozzles are working well, in other cases the differences or inefficiencies are more subtle. Actual measurement is the only real way to know.
- Replace nozzles that have obvious irregular spray patterns, using the same style and output volume of the other ones. Measurements of the distance between the ground and each nozzle, as well as between nozzles, should also be taken. Gross differences should then be corrected.
Basic physical adjustments
- After the overt and obvious flaws have been corrected, it’s time to move on to physical adjustments and maintenance. Start with removing and cleaning the main in-line filter. Likewise, remove and clean (replace if necessary) the screen behind each nozzle. Remove the nozzles and engage the pump to flush out any undissolved particles or other debris, and then reinstall the nozzles. Adjust the sprayer pressure to the optimal operating pressure for the specific type of nozzle being used. Make sure the spray pattern stays in line with the boom and other nozzles.
- To measure pressure, attach a pressure gauge to nozzle caps and observe the reading for system pressure at the nozzle. This procedure measures differences between the observed pressure at the normal pressure gauge location and actual nozzle pressure. Again, repairs may be necessary.
- Nozzle discharge tests can be an eye-opening experience. To determine the output of sprayer nozzles, place a stationary bottle under each nozzle and begin spraying. Collect spray output at various time intervals such as 15 seconds, 45 seconds and 1 minute. After each time interval, compare the output from adjacent nozzles. It’s common for small volume disparities to exist; if they are greater than 5 to 10 percent, replace those nozzles and retest.
- When it comes to accurate nozzle output, the number stamped on the nozzles provides important information. The numbers are four or five digits. The first set of numbers refers to the spray angle of the nozzle; the second is the intended output in gallons per minute. A 11005 spray tip has a spray angle of 110 degrees and an output of .5 gallon per minute.
- To measure subtle differences, set the proper PSI for the nozzle on the boom and engage the spray flow for one minute. Collect the water from each nozzle and compare them by dividing the total ounces collected by the number of ounces in a gallon (128). For example, if the boom is fitted with 11005 tips and 80 ounces of water is collected, divide 80 by 128 for an actual gallons per minute flow of .625. Then, subtract the actual gallons per minute from the intended output to determine the difference. In this example, the intended output of .5 is subtracted from the .625 actual output to indicate that a .125 difference exists.
- Finally, divide the difference in actual gallons per minute by the intended delivery of the nozzle to determine the percent error. Dividing the difference in the actual gallons per minute, .125, by the intended output, .5, reveals that an error of 25 percent exists. Sometimes, what appears to be a subtle difference isn’t really all that subtle after all. In this case, the nozzle should be replaced. Generally, if more than one nozzle is off by more than 10 percent, it’s wise to replace all the nozzles on the boom.
Cost of misapplication
- The costs of misapplication are real in terms of pest control and actual application cost. Pest control failures due to the inaccurate delivery of active ingredients increase the likelihood of the need for repeat treatments, which can lead to immediate and long-term dissatisfaction. In addition, actual application costs may be affected, especially in cases where spray volumes exceeding label or intended rates were delivered.