It's not just a matter of how you should apply fertilizer to your lawn but also when and how much. Applying the wrong amount of fertilizer at the wrong time can not only harm your lawn it could actual kill it.
You need to know what type of grass your lawn has so you will know when it grows best. Cool-weather grasses, like fescue and bluegrass, grow their best in cooler weather, like in the spring and fall, whereas grasses like Bermuda and zoysia grow better in the warmer summer months. These types of grasses go dormant in the fall and winter so if you apply fertilizer, you will make your lawn vulnerable to frost damage, which weakens it. So, it's best to give these grasses fertilizer only three or four times a year, in the summer months. With cool-season grasses it's the opposite: You fertilize two or three times in the fall and once in the spring.
When you buy fertilizer, you will see that it has a series of numbers on the bag. These indicate the proportion of nitrogen, phosphorus and potassium in the mix. For example, 22-3-14 fertilizer has 22 pounds (9.97 kg) of nitrogen, 3 pounds (1.36 kg) of phosphorus and 14 pounds (6.35 kg) of potassium in the 100-pound bag (45.4 kg). Nitrogen makes your lawn grow very quickly so you don't want it to do that in the depths of winter. The phosphorus helps the root growth, while the potassium is good for the overall health of the plant. Organic fertilizers usually do less damage if you give too much, compared to chemical fertilizers. Another natural way to feed your lawn is to just leave your grass clippings on the lawn instead of collecting them in the mower bag and disposing of them elsewhere.