There are three major plant nutrients listed as three numbers on the package: nitrogen for green leafy growth; phosphorous for rooting, blooming, and fruiting; and potassium for disease resistance and other health issues. Let us look at lawn fertilizers. A basic lawn fertilizer is 28-4-4. This formulation has a lot of nitrogen and encourages green leafy growth, which is what you want from a lawn. Suppose you are seeding or sodding your lawn. In this situation you want to use more phosphorous to encourage the roots to grow, a new lawn formula is 9-13-7.