How Much 10-10-10 Fertilizer to Apply to the Lawn?

NPK

• The three most important fertilizers are each listed on the bag in their percentage of the gross weight --- nitrogen, phosphorus and potassium (NPK). A 30-lb. bag of 10-10-10 fertilizer would have 3 lbs. each of the elements, while a 10-lb. bag would have 1 lb. each. A 30-lb. bag of 15-10-5 fertilizer would have 4.5 lbs. of nitrogen, 3 lbs. of phosphorus and 1.5 lbs. of phosphorus. The rest is filler that makes it easier to spread.

Testing

• Not all lawns need heavy fertilization. A lawn based on a rich topsoil with plenty of organic matter may only need a light application. This is especially true if the grass is mulched and left on the lawn. The surest way to know how much fertilizer to add to the lawn is to have the soil tested for both nutrients and pH balance. If the pH balance is too low or too high, then any fertilizer added is just wasted, since the nutrients will not be absorbed by the grass. Garden centers sell quick and easy home soil testing kits.

Grass Needs

• Different grasses have different nutritional needs. North Carolina State University lists the varieties of commonly planted grass on its website, and gives the amount of pounds of nitrogen that each grass requires. For example, bermudagrass needs 4 lbs. of nitrogen per every 1,000 square feet each year. On the other side of the chart, zoysiagrass only needs 1.5 lbs. per year. Four pounds of nitrogen equates to an application of a 40-lb. bag of 10-10-10 all-around fertilizer every year, while 1.5 lbs. equals 15 lbs. of a 10-10-10 mix.

Knowing the Grass

• Many types of grass listed by North Carolina State University require 2 to 3 lbs. of nitrogen, or 20 to 30 lbs. of 10-10-10 fertilizer every 1,000 square feet per year. Knowing what type of grass you have, along with knowing the soil makeup, will tell you specifically what amount of fertilizer to use. Warm-weather grasses and cool-weather grasses also have optimal times for fertilizing that are different from one another, so knowing which type of grass you have will also affect when you fertilize.