Many lawn care companies and applicators select granular products as part of their program or even as a complete program. Proper selection, maintenance, calibration and use of granular applicators can reduce costs and maximize the results expected from the chemical being applied. Most granular spreaders are of two types: drop (gravity) and rotary (centrifugal). A discussion of each follows.
The typical drop-type spreader (Fig. 10) has a full-length agitator mounted on the spreader axle. The agitator rotates over a series of openings in the bottom of the spreader hopper, and granules exit the hopper through these openings. The size of the openings can be adjusted to obtain different rates of application. Because all the fertilizer falls within the wheel base, slight overlapping of the wheels with each pass is necessary to ensure uniform coverage. Common problems associated with drop spreaders include:
However, drop spreaders are generally more precise than rotary spreaders and deliver a better pattern. In addition, because the granules drop straight down a short distance, there is less chemical drift and pattern distortion. To avoid nonuniform spread when turning corners, always turn off the spreader while making turns. This means that you should treat the strips at both ends of the area first. This allows you to start in this strip and turn the spreader on as you cross the start line.
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| Fig. 10. Drop-type spreader. |
With rotary spreaders (Fig. 11), granules drop out of one or more adjustable openings at the bottom of the hopper onto a rotating plate and are spread in a semicircular arc. Rotary spreaders cover a wider swath than drop spreaders. Therefore, they are preferred by applicators servicing large lawns and golf courses.
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| Fig. 11. Rotary-type spreader. |
Common problems associated with rotary spreaders include:
Although rotary spreaders are generally less precise than drop spreaders in terms of uniformity of distribution, with proper calibration and operation they too provide satisfactory results. The problem with uniform distribution of granules can be corrected by proper overlapping of adjacent swaths. Always try to minimize drift of small particles when using rotary spreaders.
Rotary spreaders throw material three to four feet in front of the spreader. The operator is another three to four feet behind the spreader hopper. This means that when the material finally reaches the turf, it is six to eight feet in front of the operator. It is essential then that the operator run a border along the edges of the area being treated so that there is enough room to maneuver the spreader for the next pass. This technique also eliminates the possibility of pesticides reaching non-target areas.
Much attention is currently being given to non-target application of fertilizers and pesticides. Because rotary spreaders throw material six to eight feet wide, materials will likely be spread on sidewalks, driveways and patios. To prevent such non-target applications, operators must use extreme caution around non-target areas. Some spreaders have shut-off valves to limit the spread of materials to the right of the operator. The use of this shut-off valve along with some commercially available deflectors used to divert any other material will prevent non-target applications to the right of the applicator.
Remember to open and close the spreader at the beginning and ending of each pass. Start walking before opening the lever and close it before stopping. Keeping the spreader open while turning around will cause a misapplication because the impeller plate is driven by one wheel. Therefore, the impeller stops when turning one direction, but turns faster than normal in the other direction. Always hold the spreader handle at the proper height to keep the impeller level.
Do not operate spreaders traveling backward. The pattern with rotary spreaders will be skewed and the delivery rate of drop spreaders will be different.