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Test the soil. Have your soil tested by your local USDA Cooperative Extension Service to determine pH and what nutrients, if any, your grass is missing, or test it yourself with a soil testing kit.
Once you know the pH, you can add organic matter, or fertilizer, to help balance it. Lawns prefer slightly acidic soils with a pH range of 6.5 to 7, but flowers, shrubs and trees vary in their pH preferences. Lime helps balance acidic soil, while sulfur helps with alkaline.
To find out the nutrient content of a fertilizer, look for the "NPK" number (NPK stands for nitrogen, phosphorus and potassium). A "5-6-5" NPK number, for instance, means that a fertilizer is 5 percent nitrogen, 6 percent phosphorus and 5 percent potassium with the remaining 84 percent representing filler material.
Spread it thin. Only use fertilizer sparingly or spread about half an inch of compost on your lawn at a time. Even though plant-based nitrogen is more easily absorbed, composts and organic fertilizers can still be applied too heavily, leading to nitrogen- and phosphate-heavy runoff.
Timing is everything. Avoid applying fertilizer before a downpour that will rinse it away before it gets absorbed.
Protect Yourself. Wear a mask if you're applying dusty fertilizers made with lime or any other fine particles you might inhale.
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