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Drop Spreader Calibration

Drop spreader basics

Drop spreaders provide a simple and accurate tool for homeowners to apply dry or granular products to their lawns. True to their name, drop spreaders allow a solid material, such as fertilizers and pesticides, to fall through holes at the base of the hopper onto the ground below. Drop spreaders are not only simple to operate but can allow greater control over where a product is placed compared to broadcast spreaders. However, many homeowners are not sure how to properly calibrate drop spreaders. By following these simple steps below, you can calibrate your drop spreader.

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Drop Spreader Calibration

Step 1: Check the drop spreader to make sure the hopper is clean and dry and that the drop spreader is working properly. Any necessary repairs should be completed prior to calibration and operation of the drop spreader.

Step 2: Measure the inside width of the hopper.

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Step 3: Determine the calibration area. For example, if the drop spreader has a width of 3 feet, mark with flags a length of 100 feet. This would give a calibration area of 300 square feet (3 feet x 100 feet = 300 square feet). This is important in determining later steps. Make sure the calibration area is large enough to maintain a comfortable walking speed.

Step 4: Based on the product being applied, determine the rate of product that you need to apply. This rate will be used to determine the amount of product that you will need to capture in the calibration area. For example, a fertilizer with an analysis of 20-0-0 and recommended rate of 1 pound of nitrogen per 1,000 square feet will require 1.5 pounds of fertilizer to be applied in the 300 square foot calibration area to achieve the recommended rate of 1 pound of nitrogen per 1,000 square feet. If you need a refresher on fertilizer or pesticide calculations, see publications 3624-YY, 3624-ZZ, and 3624-FFF, to learn how to complete these calculations.

Step 5: Make sure the hopper is closed before placing the product into the hopper. Make sure the product is evenly distributed across the hopper and that the product is at a sufficient depth to complete the calibration.

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Step 6: Attach a catch pan or trough underneath the drop spreader hopper to catch the product being applied during calibration when the base of the hopper is open.

Step 7: Most drop spreaders have dials or slides that control the orifice size that the product drops through at the base of the hopper. It may be labeled with numbers or letters. Familiarize yourself with the dial or slide settings before choosing a setting to begin the calibration process. Make sure to write down your setting prior to each time across the calibration area. This will help to better determine how to adjust settings as you complete calibration.

Step 8: Move to the calibration area. Begin walking well behind the first marker of the calibration area in order to attain a comfortable walking or traveling speed. It is important to maintain a constant speed during calibration. Turn the lever to release the product from the hopper into the catch pan below as you cross the first calibration marker. Make sure to use the lever to close the hopper as you cross the second calibration flag or end of the calibration area.

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Step 9: Carefully remove the catch pan located beneath the hopper and weigh the amount of product released as you traveled the calibration area. If the amount of product equals the weight calculated in Step 4, then the drop spreader is calibrated for the product and speed used in calibrating the drop spreader.

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Step 10: If the product weight is not equal to the amount calculated in Step 4, then change the orifice size with the control dial or slide. Remember to write down the new setting. Then repeat the calibration steps until the amount of product in the catch pan equals the amount calculated in Ste 4.

Tip: In order to apply products accurately, you must calibrate for each product. The size of the product will affect calibration. Also consider calibrating your drop spreader frequently to ensure proper calibration.

Download here: Louisiana Home Lawn Series: Drop Spreader Calibration 3624-OOO

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