Want to learn the secrets of a properly fertilized lawn? Read on for 10 of the best ways to keep your lawn green and growing.

1. Do a soil test. You might be able to make a pretty good guess of when your grass seed lawn needs nitrogen—it will start to yellow and thin, giving weeds like clovers the chance to grow. But to know exactly how much nitrogen it needs, you need to do a soil test. A soil test will also be able to tell you when the levels of phosphorus and potassium levels are low and need to be replenished. You should do a soil test every 2 to 3 years and adjust your fertilizing accordingly.

2. Pick a fertilizer with the right ratio. Once you know what levels of nitrogen, phosphorus, and potassium you need to supply to your lawn, you can begin to shop for a fertilizer. Because phosphorus is most important when a lawn is establishing, you won’t usually need it to be a high percentage of the fertilizer unless your soil test recommends it. Fertilizers with the same ratios but greater amounts of nitrogen, phosphorus, and potassium in them will achieve the same results with less fertilizer.

3. Don’t scrimp on the insoluble nitrogen. Fertilizers that contain some insoluble nitrogen can be more expensive, but they are worth it. Insoluble nitrogen is a slow-release form, and is gradually available to your lawn over a long period of time. Always having some nitrogen available means that you lawn won’t have to be fertilized as frequently.

4. It’s all about timing. You should always apply fertilizer to an actively growing lawn, never when it is seasonally or drought dormant. For warm season grasses, you should fertilize in the late spring or early summer, just when the grass is reviving from its winter dormancy. Fertilizing too early in the spring can reduce the mass of the roots, and fertilizing too late in the fall can increase the chances of injury during the winter. Cool season grasses should be fertilized in the early spring and fall. Fertilizing during the summer would stress a cool season lawn as it tries to conserve energy, and can increase the possibility of disease. Both warm and cool season grasses should be fertilized every 8 to 10 weeks during their growing seasons.

5. Irrigate your lawn a few days beforehand. Give your lawn a deep irrigation 2 to 3 days before you fertilize, making sure that the grass blades are dry when you do begin to fertilize.

6. Don’t over fertilize. The general recommendation is that you should never apply more than 1 lb. of solid nitrogen per 1000 sq. ft. Applying too much fertilization takes a huge toll on the grass. The leaves grow too fast and the roots too slowly, making growth unsustainable. Thatch can build up, and the lawn becomes more susceptible to disease and cold. Extra fertilizer has the possibility of being leached into groundwater reserves, and too much quick-release fertilizer has the potential to burn the grass. Avoid all of these problems by reading the fertilizer bag label and applying the correct amount.

7. Back and forth, back and forth. Repeat (at a 90º angle). Two of the most popular lawn tools for applying fertilizers are drop spreaders and rotary spreaders. Although certainly more even than spreading fertilizer by hand, they too can miss areas, revealed by striped areas of lawn that haven’t greened up. The best way to make sure that you are spreading fertilizer evenly is to put your spreader on the lowest setting and pour in half of the fertilizer. Walk back and forth across the lawn in a horizontal direction until you have covered the entire area. Then refill the spreader with the other half of the fertilizer and walk back and forth across the lawn in a vertical direction.

8. Don’t pollute. Fertilizer gets a bad rap because it is extremely pollutive in excess, especially when it contaminates water. Don’t be a part of the problem: keep about 10 feet between your fertilizing path and any open bodies of water, and pick up any fertilizer granules that land on the sidewalk or pavement.

9. Lightly irrigate afterward. A brief irrigation will help the soil to absorb the fertilizer and prevent it from being washed or swept away. ¼" of water is about all you need. You want the fertilizer to stay within the root zone, and watering more than that could push the fertilizer past the root zone, where it can’t be accessed by the grass and could end up polluting groundwater.

10. Leave the grass clippings where they are. The rumor that grass clippings increase thatch isn’t true. Grass clippings are actually a valuable source of nitrogen for you lawn, and leaving them to become integrated into the soil will decrease the amount you have to fertilize.