How Does 10-10-10 Fertilizer Compare to 10-8-8?

Numbers

• The numbers on a bag of fertilizer represent the product grade, according to Best Organic Fertilizer, and they are percentages of the total. The most common fertilizer -- 10-10-10 -- is 10 percent nitrogen, 10 percent phosphorous and 10 percent potassium, also called potash. Each of these components adds a necessary nutrient to the soil. Compare that to 10-8-8, which has 10 percent nitrogen, 8 percent phosphorous and 8 percent potassium.

Soil Testing

• Having your soil tested by your county extension office is the best way to determine the nutrients your soil is lacking, noted Walter Reeves, the Georgia Gardener. Depending on what you are growing, the nutrient needs are different.

Growth Promotion

• Walter Reeves offers the phrase "up -- down -- all around" to remember what each fertilizer component does. The first number is the "up" number, or the one that promotes leaf growth. The second "down" number promotes the plant's roots. And, finally, the "all around" number represents the promotion of stress resistance.

Nitrogen

• Nitrogen, represented by a fertilizer's first number, or "up" number, helps grow foliage and lush blades of grass. Nitrogen is easily flushed from soil.

Phosphorus

• Phosphorus, the second number on a fertilizer's label is a root-growth stimulator. It stays for longer periods of time in the soil, assisting young plants to mature. Higher phosphorus numbers help grow fruit, flowers and seeds.

Potassium

• The final number, or "all around" number, is potassium, which strengthens a plant's stem. Potassium also assists the plant's resistance to weather changes and disease. Winterizing fertilizers have a high last number.