The number of fluid ounces you collect is equal to number ofgallons the sprayer would apply to 1 acre if you use it at thesame pressure and walking speed you used in the plot area.This quick conversion works since there are 128 fluid ounces in 1gallon of water. It doesn’t get much easier than this. Now allyou have to do is find out how much herbicide to add to thepump-up sprayer.How it appliesLet’s say your sprayer applies 25 gallons per acre. The rightrate for Trimec Classic is 4.0 pints, or 0.5 gallons, per acre.So divide 0.5 by 25 to get 0.02, or 2 percent.Multiply that by the sprayer capacity. A 2-gallon sprayer wouldhold 256 fluid ounces, and 256 times 2 percent would be 5.1ounces. So add 5.1 ounces of Trimec Classic to the sprayer. Thenfill it to the 2-gallon mark with water.Remember, you have to walk at the same speed, maintain the samepressure and hold the spray nozzle tip at the same height youused in the plot area.If you do these things, you’ll apply the recommended rate of theherbicide, control the target weed and, most important,drastically reduce the chance of injuring your turf grass.(Clint Waltz is an Extension Service turf scientist and TimMurphy an Extension Service weed scientist with the University ofGeorgia College of Agricultural and Environmental Sciences.) Mark off a plot 18.5 feet by 18.5 feet.Fill the sprayer to normal capacity with water.Pump the sprayer to the pressure normally used to applyherbicides.Spray water over the plot area while maintaining normal andconstant operating pressure.Record the time in seconds it takes to spray the plot area.Using the same constant pressure used in step 4, spray into abucket for the same time (number of seconds) it took to spray theplot area.Measure the volume of water in fluid ounces. Volume XXIXNumber 1Page 30/i> By Clint Waltzand TimMurphyUniversity of GeorgiaHand-held and backpack sprayers are extremely useful for treatingsmall turf areas infested with weeds. But they have to becalibrated to apply the recommended rate of a herbicide.Most herbicides used in turf grasses control weeds withoutinjuring the turf. But that depends on the rate applied. The rateis usually on the product label as the amount to be applied to 1acre or 1,000 square feet.For example, the highest recommended rate of Trimec Classic forBermuda grass and tall fescue is 1.5 fluid ounces per 1,000square feet.Applied at this rate and by the label directions, it will causeonly slight injury to labeled turf grasses. But if you applythree times that amount, some turf grasses would be yellow orbrown for weeks.If a sprayer isn’t calibrated, it can’t apply herbicides atrecommended rates.It’s simpleYou can use a number of methods to calibrate sprayers. One that’ssimple, easy to do and easy to remember is called the1/128th-acre method.In this method, you spray 1/128th of an acre. That’s 340.3 squarefeet. This figures out to 18.5 feet by 18.5 feet. Here’s how todo it.