Guaranteed analysis

The label on all fertilizer bags is required to show the percentage by weight of nitrogen, available phosphate and soluble potash. This is called the guaranteed anaylsis of the fertilizer.

  • The first number is Nitrogen (N), which promotes overall grass shoot growth.
  • The second number is available Phosphate (P₂O₅), which promotes strong root growth.
  • The third number is soluble Postash (K₂O), which helps grass withstand stress, drought or disease.

For example, a 24-2-8 fertilizer has 24% nitrogen, 2% available phosphate and 8% soluble potash. Nitrogen, phosphate and potash are also sometimes referred to as N-P-K.

To understand how much of each nutrient is being applied to your lawn, you must multiply the weight of the fertilizer bag by the percentage of each nutrient. For example, a 30 lb. bag of fertilizer rated 24-2-8 contains:

N: 24% x 30 lbs = 7.2 lbs. Nitrogen
P: 2% x 30 lbs = 0.6 lbs. Available Phosphate
K: 8% x 30 lbs = 2.4 lbs. Soluble Potash