May 1997

An Easy Calibration Method for Boom Sprayers

David M. Kopec, Extension Turfgrass Specialist

Proper calibration of the boom sprayer is essential in golf course management. It is necessary to deliver the proper amount of product, within the necessary solution delivery range (gallon per acre, or gallon per thousand square feet). There are several formulas used to calibrate boom sprayers.

Listed below is an easy way to calibrate a boom sprayer. You don't need any equations, just a clear head, common sense, a notepad and a simple hand held calculator.

Power Boom Sprayers

Power boom sprayers are used for large turf areas. Either liquid fertilizers, fungicides, herbicides, wetting agents or insecticides can be applied using the power boom sprayer.

The same rules apply to calibrating boom sprayers as the hand pump sprayers, only now you have more control and more nozzles. Here are the steps to follow.

I. Determine the Delivery Rate
Nozzle size (orifice size) spacing between nozzles, operating pressure and ground speed will determine the solution delivery rate (gallons per acre, or gallons per 1000 ft2). Without a lot of math, here is the easy way to calibrate a boom sprayer.

Pre-check list.
(1) Make sure all nozzles screens are clean and all nozzles are the same size and are not plugged. Make sure the same size nozzles are used on the entire boom.

(2) Make sure all line fittings are water tight under operating pressure

(3) Place a catch can under each nozzle and run water through the nozzle for one minute. Measure the amounts. Volumes should not be either more or less than 10% in difference. Replace nozzles and/or screens which exhibit high or low outputs. Select a steady and constant RPM on the pump and a steady regulator pressure when you perform the nozzle test.

Spray Volume Calibration
(1) Measure the width of the boom in feet (example 18').

(2) Measure a straight line distance in feet (300').

(3) Set the RPM and gear selection to a specific setting.

(4) Measure the time in seconds it takes to travel the straight line distance of 5400' (18'x300'). Do this in two directions and get an average. Example: 90 second average.

(5) Stop the sprayer.

(6) Place a large container under each nozzle and spray (at the same line pressure) for 90 seconds.

(7) Add the total amount of water from all nozzles. Example: 8.8 gallons was collected from 18 nozzles at 35 psi for 90 seconds. Note: If the containers are too small, spray for 45 seconds and multiple by 2. This will give the same amount for 90 seconds of operation.

(8) Figure out the gallons per acre delivery from the information in numbers 4 and 7.

8.8 gallons ----------------- 5400 ft2

(x) gallons ----------------- 43,000 ft2

Solve for (x) . (8.8 x 43.000)/5400

(x) = 70.07 or 70 gallons per acre

To convert to gallons per 1000 ft2, divide this by 43.

70 ÷ 43 = 1.62 gallons per 1000 ft2.

These values are your "solution delivery rates!

(70 gpa) or (1.62 gallons 1000 ft2)

II. Determine the Product Rate
From Section I, we know that at a specific rpm/gear speed combination (constant ground speed), at a specific line pressure (35 psi), we are delivering 70 gallons per acre. Now we need to figure out how much pesticide is needed for each gallon of the final solution.

We need to spray Bromxynil 2E liquid herbicide to 10 acres of turf which is severely infested with burr clover weeds. The label rate calls for 2 quarts of product per acre (1.5 ounces per 1000 ft2). How much do we put in the spray tank?

(1) Our solution delivery rate is 70 gallons per acre, determined earlier.

(2) Amount of product per gallon of solution is calculated as follows.

2 qts. product = 0.0285 quarts per gallon of water

70 gallons per acre

or easier

1892cc = 27cc per gallon of water

70 gallons per acre

Remember: 1 quart equals 946cc and two quarts equal 1892cc.

III. Estimating the Total Amount of Gallons Needed to Spray the Area
From Section I, we know that our final delivery solution rate is 70 gallons per acre (1.63 gallons per 1000 ft). Using this information, we can estimate how much water we need in the tank to spray the 10 acre turf area in question.

70 gpa ----------------- 1 acre

(x) ---------------------- 10 acres

Solver for (x) . (70 x 10) / 1 = 700 gallons

So, a 350 gallon sprayer would need to be filled twice. A 250 gallon sprayer would need to be filled three times. And a 100 gallon sprayer would need to be filled seven times. Each gallon of water will receive 27cc of Bromxynil.

Products mentioned are used for discussion purposes only and does not imply endorsement. Exclusion of similar products is not intentional, not does it imply product efficiency.

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