Fertilizer Spreader Info

Two types of fertilizer spreaders are available for use on home lawns:  rotary and drop. They use entirely different principles to distribute granular materials.

Drop spreaders have a row of holes or metering ports across the full width of the bottom of the hopper. A shut-off bar is used to close the ports and to control the delivery rate by incrementally opening the ports.

Rotary spreaders have one metering port that drops the granules onto a rotating impeller that slings the granules in a pattern wider than the spreader.

Basic Patterns
A drop spreader will deposit a uniform rate of granules across the width of the hopper with no feathering of the edges of the pattern. A rotary spreader pattern is not uniform; the pattern will be heavier in the center and tapers toward the edge.

Overlapped Patterns
When operating a spreader you make multiple parallel passes across your lawn. With a drop spreader the pattern will be uniform if you space the patterns exactly with no skip or overlap. You do this by running the tire just inside the tire track from the pervious pass. Please be aware that with a drop spreader, an error of only an inch or two will result in a stripe with either a double rate or no fertilizer.

A rotary spreader the individual patterns will taper off and you must overlap the pattern somewhat. Because of the feathering at the edges, rotary spreader patterns are more forgiving of small errors in swath width. Nevertheless even properly overlapped patterns are seldom as uniformed as drop spreader patterns.

Swath Width
Drop spreaders have a narrow, fixed swath width. The swath width is the width of the hopper for all products.

Swath width varies with the product for rotary spreaders. The pattern is normally wider for larger or heavier granules. Some products will yield such poor patterns that a double overlap is required. The effective swath width for a homeowner rotary can vary from as little as 1 ½ - 2 feet up to 10 – 12 feet.

Ground Clearance
Many homeowners drop spreaders have only 2 – 4 inches of ground clearance. If the grass is a bit tall or if seed heads or weeds are sticking up, they will brush the bottom of the hopper. When there is dew on the grass, this rubbing will plug the metering ports, also affect uniformity.

Most rotary spreaders have much more ground clearance.

Pattern Consistency
Drop spreaders provide the same pattern with every product. Each granular product will yield a different pattern in a given rotary spreader.