1. Mark off a rectangular area of 10 feet by 43.6 feet ?EUR??,,????'?????<
2. Using only water, spray this area in your usual manner. Record the time it takes to make this application and be sure to calibrate for each person who may use the sprayer.
3. With only clean water in the spray tank and the gun stationary, start spraying at the pressure you intend to use. Catch and measure the output from the gun for the same amount of time required to treat one-tenth of an acre.
4. Calculate the output by multiplying 100 times the number of gallons or 0.78 times the number of ounces collected. This gives a spray rate in gallons per acre.

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Parish says that after arriving at a suitable overall rate, you need to mix the chemical properly for that rate. Multiply the recommended rate per acre by the area to be sprayed to determine the amount of material you need and mix the appropriate amount of material with the correct amount of water.

For larger lawns or small pastures, you might use a small tractor for applying your fertilizers and pesticides.

Parish says boom-type lawn sprayers that are mounted on vehicles are calibrated in the same way as agricultural sprayers. ?EUR??,,????'?????<

1. Measure the spacing between adjacent nozzles.
2. Mark off a test-run area on the lawn 200 feet long by using flags, stakes or something else you can see.
3. Drive the sprayer through the 200-foot test run at normal operating speed and time how long it takes to go between the marks. There?EUR??,,????'?????<
4. Put clean water in the spray tank and with the spreader stationary, start spraying at the pressure you intend to use. Catch and measure the output from one nozzle for the same amount of time required to cover 200 feet in the previous step.
5. Calculate the output by multiplying the nozzle output in ounces by 20.4 and then divide by the spacing between the nozzles in inches. This will give you a spray rate in gallons per acre.

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The engineer notes that using this method requires none of the calculations of sprayer ground speed in miles per hour or nozzle output in gallons per minute required by many other calibration methods. This method assumes all nozzles are equally spaced and of the same size.

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Herbicide misapplication, in even small amounts, can result in lawn injury such that pictured above.

Calibrating Spreaders

In addition to liquid pesticides, granular pesticides also have to be applied at the correct rate. If the rate is too low, you may not get turf response; if you overapply, you waste material and risk turf damage. Calibrating your spreader is also necessary to help assure that your spreader delivers the correct rate of material.

Why Does a Spreader Need Calibration?

First, it is important to calibrate new spreaders. The hard knocks a spreader gets during shipping can change calibration. Also, many spreaders are shipped unassembled. The way the spreader is bolted together can affect calibration, so it is necessary to calibrate after assembly. Even if you buy your spreader already assembled, don?EUR??,,????'?????<

Also, different products may have granules of different sizes and densities.

Not all spreaders can be calibrated. In the past, only the highest quality lawn spreaders provided for recalibration by the user. Now, many models of both drop and rotary spreaders can be calibrated. If your spreader allows recalibration, you should take advantage of that feature.

One reason to calibrate your spreader annually is because material may have shifted, such as screws loosening, resulting in a different output.

How Do You Calibrate a Spreader?

To find out if your spreader can be calibrated and how to do it, consult your spreader operator?EUR??,,????'?????<

The most common way of calibrating drop spreaders consists of aligning a mark on the hopper bottom with the front edge of the shut-off bar while the rate mechanism is set at the calibration setting. In either case, if the mark is not aligned with the edge of the port or the edge of the shut-off bar, you will need to move an adjusting screw that is typically located either on the bottom of the rate dial or the bottom end of the control cable. Move the adjusting screw until the proper alignment is obtained.

Older homeowner spreaders and some current professional spreaders use a special calibration gage (or a drill bit) to measure the opening of the metering port(s) at a specific setting. If the port opening is not correct, the rate scale is adjusted until the opening is correct.

High quality backpack sprayers are widely available and a popular choice for many groundskeepers. They are versatile and can be very effective, but the success is contingent on steady output and walking speed. Calculating one?EUR??,,????'?????<

You can also follow these steps:

1. Mark out a test strip of 440 square feet (approximately 1/100th of an acre).
2. Weigh your granular product before and after you apply.
3. Subtract the difference to get the amount applied, then multiply by 100 to get the amount you need per acre.
4. Adjust your equipment and repeat the test until you have the correct setting for the required amount per acre.

Calibration is an easy way to improve the metering performance of your spreader. It takes only a couple of minutes and helps you apply the recommended amount of material to your lawn. You should check your spreader?EUR??,,????'?????<

This information is reprinted with permission from the Louisiana State University website: www.lsuagcenter.com.