Fertilization will cause your lawn to have a thick and healthy carpet of grass, meaning the root system strong. This will allow your lawn to absorb water quicker, especially during bad rainy weather. This decreases the muddy spots and flooding in your lawn. Without proper fertilization, no matter how much you mow and water, the grass will definitely lose its healthy and lush growth and would instead turn brown as the weather becomes hotter. Fertilization may seem simple and easy to do, but there are different types of fertilizer needed and especially on how to effectively apply them. Leave all that to professional lawn care.