A rotary spreader is a type of spreader that throws fertilizer, seed, pesticides or herbicides out in a circular pattern around the spreader. The other type of spreader used in these applications is a drop spreader. By understanding how each type of spreader works, you can determine if a rotary or drop spreader will best meet your needs.
A rotary spreader has at least one metering port. This port is responsible for flinging granules onto the ground. The granules drop through the metering port and onto an impeller that rotates as the spreader is pushed. This action causes the granules to be flung outward from the spreader.
The flinging action of a rotary spreader makes even application a problem. The granules are dispersed in a heavier concentration toward the center of the spreader, and become thinner as they land further away. For this reason, when you are applying a product with a rotary spreader, it is important to overlap your path as you go. This allows the areas that receive a lighter application to receive an additional layer of product.
It does take some practice to determine exactly how much you should overlap the application with a rotary spreader. These spreaders will broadcast heavier or larger granules in a larger arc than lighter weight or smaller granules. Trial and error are often necessary to determine the best application method with this type of spreader.
With the difficulty of precise application with a rotary spreader, it may seem difficult to determine why someone would choose these. Rotary spreaders have many positive attributes. They typically have a higher ground clearance than drop spreaders. If the bottom of the spreader drags against the grass or ground, not only does it interfere with the distribution of the product, but it also can clog the ports that release the granules. Rotary spreaders are an excellent choice for areas with tall grass or uneven ground.
Rotary spreaders are also easier to push than drop spreaders. If you have a lot of ground to cover, a rotary spreader is a time and labor saving choice. The difficulty that you will run into with uneven application from a rotary spreader is most noticeable when applying herbicides or pesticides. If you are broadcasting seeds or fertilizing, the application differences may not even be noticeable.