The calibration of turfgrass boom sprayers and spreaders  Page 11 
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The Calibration of Turfgrass Boom Sprayers and Spreaders 11 Figure 14. Pattern check for a rotary spreader. Place one box in the center with enough space on either side to allow the spreader wheels to pass through. Space the remaining boxes on 2foot centers to either side of the center box, as shown in Figure 14. All boxes must be identical in size, typically 1 to 2 inches deep, with an area of at least 1 square foot. There should be an oddnumber of boxes in the row covering 1½ to 2 times the anticipated effective swath width. Place a piece of cloth in the bottom of each box to keep particles from bouncing out. Pour some product into the rotary spreader and choose the setting recommended on the label. Make at least three passes over the boxes to obtain an accurate assessment of the distribution pattern. Be sure to operate in the same direction and position on every pass. Weigh the granules collected in each box and plot a distribution pattern, or pour the granules from each box into its own vial or small bottle. The vials must be identical in size and shape. When the vials are placed side by side in the same order as the collection boxes, a plot of the distribution pattern is visible, as shown in Figure 15. Figure 15. Rotary spreader distribution pattern in vials. Ideally the contents of the vials form a bellshaped curve that peaks in the center and descends evenly on each side. Determine which have onehalf the amount of product in the center vial. The distance between these boxes is the effective swath width. Use this figure to space spreader passes. For example, if the center vial has material that is 2 inches deep, and the vials from the 6foot positions (6 feet left of the spreader centerline and 6 feet right of the spreader centerline) have material 1 inch deep, the effective swath width is 12 feet. If it appears that the half rate falls between two boxes used in the test, take the midpoint between those boxes as half the effective swath width. For example, you estimate that the halfrate volume falls between boxes located 4 and 6 feet to the left and 4 and 6 feet to the right of center. The effective swath width is 10 feet (5 feet left and 5 feet right of the centerline). If the two boxes used to determine effective swath width do not contain the same amount of product (nonsymmetrical pattern), adjust the spreader to correct the pattern. Follow the manufacturer’s recommendation on pattern adjustment. Certain models allow you to block off part of the metering port(s) or move the drop point of the granules on the impeller. Checking the pattern over a paved area is a quicker, though less accurate, method to estimate the distribution pattern. Particle bounce and scatter make this method inexact, but it does reveal gross distribution errors. A rough estimate of the effective swath width can be made by measuring the central twothirds of the total swath. Measuring the Application Rate When selecting an area in which to check calibration, make certain that it is an acceptable application site, or plan to collect the granules in a device that prevents their contact with the ground. Be aware that repeated applications to the same area, as is common with calibration trials, can damage turf. Drop Spreader Several methods for checking the application rate of a drop spreader are described below. Be certain to walk at the desired speed before starting the flow of granules when crossing the starting point. At the finish point, stop the flow, but continue walking.
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Title  The calibration of turfgrass boom sprayers and spreaders  Page 11 
Full Text  The Calibration of Turfgrass Boom Sprayers and Spreaders 11 Figure 14. Pattern check for a rotary spreader. Place one box in the center with enough space on either side to allow the spreader wheels to pass through. Space the remaining boxes on 2foot centers to either side of the center box, as shown in Figure 14. All boxes must be identical in size, typically 1 to 2 inches deep, with an area of at least 1 square foot. There should be an oddnumber of boxes in the row covering 1½ to 2 times the anticipated effective swath width. Place a piece of cloth in the bottom of each box to keep particles from bouncing out. Pour some product into the rotary spreader and choose the setting recommended on the label. Make at least three passes over the boxes to obtain an accurate assessment of the distribution pattern. Be sure to operate in the same direction and position on every pass. Weigh the granules collected in each box and plot a distribution pattern, or pour the granules from each box into its own vial or small bottle. The vials must be identical in size and shape. When the vials are placed side by side in the same order as the collection boxes, a plot of the distribution pattern is visible, as shown in Figure 15. Figure 15. Rotary spreader distribution pattern in vials. Ideally the contents of the vials form a bellshaped curve that peaks in the center and descends evenly on each side. Determine which have onehalf the amount of product in the center vial. The distance between these boxes is the effective swath width. Use this figure to space spreader passes. For example, if the center vial has material that is 2 inches deep, and the vials from the 6foot positions (6 feet left of the spreader centerline and 6 feet right of the spreader centerline) have material 1 inch deep, the effective swath width is 12 feet. If it appears that the half rate falls between two boxes used in the test, take the midpoint between those boxes as half the effective swath width. For example, you estimate that the halfrate volume falls between boxes located 4 and 6 feet to the left and 4 and 6 feet to the right of center. The effective swath width is 10 feet (5 feet left and 5 feet right of the centerline). If the two boxes used to determine effective swath width do not contain the same amount of product (nonsymmetrical pattern), adjust the spreader to correct the pattern. Follow the manufacturer’s recommendation on pattern adjustment. Certain models allow you to block off part of the metering port(s) or move the drop point of the granules on the impeller. Checking the pattern over a paved area is a quicker, though less accurate, method to estimate the distribution pattern. Particle bounce and scatter make this method inexact, but it does reveal gross distribution errors. A rough estimate of the effective swath width can be made by measuring the central twothirds of the total swath. Measuring the Application Rate When selecting an area in which to check calibration, make certain that it is an acceptable application site, or plan to collect the granules in a device that prevents their contact with the ground. Be aware that repeated applications to the same area, as is common with calibration trials, can damage turf. Drop Spreader Several methods for checking the application rate of a drop spreader are described below. Be certain to walk at the desired speed before starting the flow of granules when crossing the starting point. At the finish point, stop the flow, but continue walking. 