It's time to pick herbicide, fertilizer and the best method to apply them

The end of February is the time to prepare lawns for spring. This involves deciding when to apply herbicides and fertilizers, which herbicide or fertilizer to use, and how to apply these products.

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The time to apply pre-emergent herbicides is now, and we wait until the soil temperatures are consistently 65 degrees to fertilize. The soil reaches this temperature around the first of May. Which herbicide to use will depend on the weed species that need to be controlled, and the fertilizer recommendation will depend on the type of grass that is growing and what nutrients are available.

Having the soil tested will determine the type of fertilizer that is needed. The type of product purchased will determine the type of equipment that would be used to apply these products.

Herbicides and fertilizers are available as liquid and granular products. Both will do a good job if applied correctly. Most people find it easier to apply granular products, but the question is what kind of spreader to use? There are two types of spreaders that are used to apply herbicides and fertilizers --- drop spreaders and rotary spreaders.

These spreaders apply the product in different ways. The drop spreader has 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. A good drop spreader will evenly deposit the granules across the width of the hopper, delivering the same amount of product on the edge as in the center.

Drop spreaders also have the same pattern with every granular product. The drop spreader also can apply the products right up to the edge of flower beds, sidewalks, driveways and at the end of the lawn area.

The drop spreader does have some negatives as well. The first is its narrow, fixed swath width. To get uniform coverage, there should not be any skip or overlap in the swath. This requires running the tire just inside the tire track from the previous pass. If the track is off by an inch or two, it will leave a stripe that has no product applied or one with double the amount of product. I see this most often when fertilizers are applied, and there are yellow stripes in the lawn.

The second disadvantage is ground clearance. If the grass is too tall or if seedheads or weeds are sticking, they will brush the bottom of the spreader and mess up the even distribution of the product. If the grass is wet, this can cause plugging of the ports on the spreader. The last disadvantage is that drop spreaders require more force to push than rotary spreaders.

Rotary spreaders are the most popular spreaders used by homeowners. They can cover larger areas faster than a drop spreader. The rotary spreader has one to three ports that drop the granules onto a rotating impeller that slings the granules in a pattern wider than the spreader. The width of the pattern can be from 18 inches to 12 feet.

The weight of the product and the speed that the spreader is pushed will determine the width of the pattern, but the pattern will be heavier in the center and taper off on the edges. Overlapping the patterns will take care of the uneven distribution. Because of the tapering off, the patterns are more forgiving of small errors than drop spreaders. There won't be as many yellow strips. Rotary spreaders can handle larger granules than drop spreaders.

The biggest disadvantage with rotary spreaders is the risk to drift on to non-target areas. The most common of these is the product getting into flower beds or on sidewalks and driveways. Some brands of spreaders have adaptors that attach to the spreader that will block one side of the impeller so that these products are not applied to non-target areas.

For any type of spreader to work properly, it must be calibrated. The owner's manual should specify how to calibrate the model of spreader.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.