How to Fertilize and Water-in With Rain

Fertilizer and working gloves on the grass
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Fertilize your lawn properly, and you'll be on your way to a healthy, dense stand of turf that maintains a deep green color and gives weeds a run for their money. First, choose a fertilizer that gives your grass what it needs, based on a soil test, and is suitable for your climate and the time of year when you're applying it. Next, choose a method for applying the fertilizer; the most common options are discussed here. The final step is watering-in the fertilizer to make sure it feeds the grass and doesn't get washed away. This can be done with rain or irrigation.

Choosing a Fertilizer Spreader

A broadcast or rotary spreader works well when you're fertilizing large lawn areas and is the most common type of spreader used by homeowners. Apply fertilizer around the edge of the lawn first, and then move back and forth across the interior area in straight lines. Overlap application strips slightly to ensure that you cover the whole lawn evenly with fertilizer.

A drop spreader is similar to a broadcast spreader but offers more controlled fertilizer distribution. While a broadcast spreader delivers fertilizer via a spinning wheel, a drop spreader simply drops it down thorough slots in the bottom of the spreader hopper; the granules fall right where you walk. As with a broadcast spreaders, overlap slightly on each pass to ensure you have adequate coverage.

A handheld broadcast spreader works like a broadcast spreader, but you hold the tool in one hand and use the other hand to turn a crank and fling out the granules. This is suitable for fertilizing small lawn areas. For best results, walk evenly and slowly, and be sure to overlap distribution patterns slightly with each pass. A small spreader like this also works really well when you have shady areas in your lawn that require a different fertilizer rate than the sunny sections.

Watering-In Standard Fertilizer

All fertilizers should be watered-in. This ensures that the product will be washed into the soil and become available to the grass through the roots. It's important to water-in with enough water—but not too much. Also, while standard fertilizers can be applied to dry or wet grass and can be watered-in immediately, fertilizers with weed killer typically should not be watered-in for 24 hours after application.

The best way to water-in fertilizer is to do it naturally, with rain. Try to time the application of fertilizer just before an expected rainfall of at least 1/4 inch. Rainfall typically provides good, even coverage over the entire lawn area (except under full trees), which can be difficult to achieve with lawn sprinklers.

However, you should plan to water-in with rain only when the rainfall is expected to be steady and not heavy or intense. Heavy or hard rain can easily flood the grass and wash the fertilizer off of the lawn and into the storm sewer system. From there, it typically gets washed into local waterways and contributes to water pollution.

If rain isn't expected, you can certainly water-in fertilizer with an irrigation system or even individual sprinklers. Take care to provide even coverage over the entire lawn, making sure you reach all areas. Fertilizer left on dry grass can burn the leaves (blades).

Watering-In Weed Killer Fertilizer

"Weed and feed" fertilizers that contain weed killer must stay on the grass longer than standard fertilizers to allow time for the herbicide to be absorbed by the weeds. Typically, you should water the grass just before applying these fertilizers, or apply them in the morning when the grass is still wet with dew. The moisture helps the fertilizer granules stick to the weed leaves.

Don't apply weed killer fertilizer when rain is expected within 24 hours. Rain, or watering-in too early, is fine for the grass, but it washes the product off the weed leaves, so the weed killer can't do its job. To be safe, it's best to apply the fertilizer when the weather is sure to be dry for a day or more. Then, simply water-in with sprinklers after 24 hours.

Natural Fertilizer Needs No Watering-In

Grasscycling refers to letting grass clippings lie on the lawn after cutting. These clippings can provide up to 25 percent of your lawn's fertilizer needs, saving you time and money. One hundred pounds of lawn clippings can yield up to three to four pounds of nitrogen, an important component of lawn fertilizers.

Cut grass left on the lawn doesn't need to be watered-in like conventional fertilizer. You simply let it dry up and decompose naturally with no additional care. You also don't need a specialized mulching mower to grasscycle, although you might want to replace your current mower blade with a mulching blade, which cuts grass into small pieces so they decompose quickly. Most new mowers these days are designed for mulching grass clippings.