How to Fertilize a Lawn

A green and vibrant spring lawn is a homeowner's dream, and fertilizing properly is crucial to keeping your lawn bright and well nourished. Without the proper nutrients, your lawn will not thrive and can more easily be infested by pests or diseases. Whether you're fertilizing for the first time or are an avid pro, fertilizing gives your lawn the nutrition it needs to grow greener and healthier.

The only accurate way to determine how much fertilizer you need is to have your soil tested. Soil testing by a local county extension or university identifies base levels of phosphorus and potassium, two key nutrients for lawn growth. Soil tests for nitrogen are often inaccurate, because it leaches easily from the root area, so the facility may not perform a nitrogen test.

It is important to create an accurate soil sample to get accurate fertilizer recommendations. To get a soil sampling kit by mail, contact to your county extension office.

Garden trowel

Ruler (optional)

Small knife

Clean pail

Large spoon

Plastic bag (from soil sampling kit)

Dig into the ground with a garden trowel. Cut a triangular sample of soil from the area and set it aside.

Press the trowel into the soil at the edge of the hole you created, and remove a thin soil sample, approximately 1/2 inch thick.

Measure a 1-inch strip, using a ruler if necessary. Cut the sample into a strip measuring 1 inch by 1/2 inch with a small knife.

Move around your lawn, removing at least 10 samples of the same size from several areas.

Place all the core samples into a clean pail, and use a large spoon to mix them together thoroughly to create an accurate composite sample. Once it's mixed, place the sample in the plastic bag provided by your county extension and return the sample.

Once you receive results for your soil sample, you'll know which nutrients your lawn is in need of and can choose a fertilizer that contains the right nutrients. Review the fertilizer bag and the analysis statement that explains the percentage of each nutrient in the product. For example, a 16-8-5 fertilizer contains 16 percent nitrogen, 8 percent phosphorus and 5 percent potassium. If your soil is low in potassium and phosphorus, you might choose a 20-5-10 or similar fertilizer, depending on your soil test results.

A high-quality, dry, granular fertilizer ensures that your lawn gets adequate nutrients. For best results, choose a slow-release chemical fertilizer. Slow-release fertilizers contain high amounts of nutrients and release nitrogen into the soil over long periods of time for consistent nutrition. They are also safer, because they won't burn your lawn even when applied at high rates. On the other hand, less expensive fast-release fertilizers will quickly make your lawn greener, but they are more likely to burn your lawn and you must apply them more frequently.

There's one exception to this rule -- in cooler drier climates, fall applications of combination products with slow- and quick-release nitrogen are useful for strengthening grass and preparing it for cooler temperatures.

Applying fertilizer on a hot day can increase the risk of burning your lawn. Do not apply fast-release fertilizers in temperatures above 85 degrees, and apply all fertilizers on cooler days.

Although it's tempting to fertilize your lawn in the spring, applying fertilizer in late summer or fall creates a healthier lawn. If you apply fertilizer in early spring, your lawn will quickly become green as you encourage top growth, but this will make the grass weaker once summer heat and other stresses arrive.

Fertilize between late August and early November, depending on the climate. If you live in a cooler area, fertilize several weeks before the ground typically freezes, while the soil is still warm enough for grass roots to absorb nitrogen and other nutrients. If you live in a warmer climate, like southern Florida, you can fertilize throughout the year while following your product's instructions. This will help grass grow, resist summer stress and diseases and become greener in early spring without the problems quick top growth can cause.

Do not over-apply fertilizer. It can damage your grass and the environment. Always follow the application rates on your fertilizer package.

Water your lawn several days prior to fertilizing to help protect your grass.

Immediately

after you fertilize, water in the fertilizer. Use a sprinkler or

garden hose to remove excess fertilizer, reduce the potential for burning and make soluble nutrients available

to grass roots. 

Fill your spreader near a driveway or other paved area to avoid burning and for easy cleanup in case of a spill.  

Drop spreaders offer the most precision and even application. Their main downfall is that they can give lawns a striped appearance without careful attention. Rotary spreaders are less precise -- they distribute fertilizer in many directions, but they will save you time and will not create striping.

To use either type of spreader, measure your lawn and then carefully follow the instructions on your fertilizer package to determine how much fertilizer to use. Fill the hopper with half of the proper amount of fertilizer for your lawn's area. Move the drop spreader over your lawn in one direction. Turn off the spreader when you make a turn or complete a pass. To avoid striping, try to overlap wheel marks with each row. Once you've fertilized in one direction, fill the hopper with the remaining half of the fertilizer and apply it at a right angle to the initial direction.

Fertilizing by hand is the least expensive method of applying fertilizer, but it's also the least accurate. Uneven application is likely and the possibility of burning your grass is higher. Fertilizing by hand also takes longer, so a spreader may be worth the investment. Generally, hand application is not recommended. If you do fertilize by hand, scatter fertilizer as evenly as possible in one direction and then the other. Drag a rake over the area in each direction to improve distribution and ensure that the fertilizer reaches the grass roots. Wear gloves to protect your hands.