A good fertility program for your turf grass lawn is essential for eye-catching dark green grass and optimal growth that can endure for years. But it does not have to be complicated, and in fact the simpler it is, the better. What is important is that it is well planned and that your grass fertilizer is properly suited for your specific growing region.
Most grass fertilizer sold on the market have some mixture of the three most needed nutrients utilized by grass, and most all plants for that matter. N-P-K. Nitrogen, Phosphorous, and Potassium. Grasses require about 16 basic nutrients for growth but these are historically the most deficient of the nutrients and excluding carbon, hydrogen, and oxygen (which grasses pull from air and water), grasses utilize more N,P, and K than any other nutrient. Most of the other basic nutrients are available to the grass from the soil, water and air, but nitrogen, phosphorous, and potassium are macro-nutrients and are the most abundantly needed.
When you look at a fertilizer bag, these are what the three numbers in sequence that you see represent. They represent the analysis of that particular fertilizer in percent by weight of that product. For example, a 25 lb. fertilizer bag has an analysis of 16-4-8. This means that this particular grass fertilizer is 16% nitrogen by weight, 4% phosphorus by weight, and 8% potassium by weight. A 25 lb. bag would therefore contain 4 lbs nitrogen, 1 lb. Phosphorus, and 2 lbs potassium. This is a simple calculation that will help you to determine how much fertilizer to buy when you know how many pounds of each nutrient you must apply to the grass or soil.
How to Determine Fertilizer Requirements
To apply 1 pound of nitrogen per 1,000 sq ft: Divide 100 by the first number on the fertilizer bag to determine the amount of product to be applied per 1,000 sq ft.
Example: If using a 16-4-8 fertilizer, 100 divided by 16 equals 6.25. Therefore, 6.25 pounds of fertilizer per 1,000 square feet will provide 1 pound of nitrogen per 1,000 square feet.
To apply 0.5 pounds of nitrogen per 1,000 sq ft: 50 divided by the first number on fertilizer bag equals the amount of product to be applied per 1,000 sq ft.
Example: If using a 15-15-15 grass fertilizer, 50 divided by 15 equals 3.33. Therefore, 3.33 pounds of fertilizer should be applied per 1,000 square feet to deliver 0.5 pounds nitrogen per 1,000 sq ft.
Repeat the same calculations for phosphorous and potassium requirements. Visit the Spreading Lawn Fertilizer post to see this step done in action.
Some grass fertilizer will also contain some of the other essential nutrients for growth such as, calcium, iron, zinc, sulfur, magnesium, and others. These are called micro-nutrients and are just as important as N,P, and K but are used by grass in very small amounts. Depending on your region and what nutrients are deficient in your turf grass, a grass fertilizer that also has micro-nutrients may produce great results in your lawn.
When planting grass seed in virgin ground or a newly renovated parcel of land, it is always a good idea to take a soil sample of the area and have it analyzed for nutrient levels and soil texture. The soil texture will help you with what kind of soil amendments are needed to be added to improve soil structure. (More information on the Soil Preparation section on Planting Grass Seed page). The nutrient levels analysis will let you know what nutrients are lacking in the soil. With this information you can determine what blend of grass fertilizer you need apply and at what rate, or how much you need to apply per 1000 ft2 or per acre. Ideally you want to take 10 to 12 random samples 3 inches deep and mix them together. From this composite sample, take out 1 pint of soil for testing.
When planting grass seed you typically want a fertilizer that has a high amount of phosphorous because one of phosphorous’ attributes is that it stimulates seedling development. This is a general rule but as stated above, a good soil analysis will take the guess work out the equation and save you a lot of time and money down the road. After your grass has been established, then you can adopt a fertility program that is designed to maintain your lush, green lawn.
When planning for a general fertility program, a well balanced, complete grass fertilizer like a 15-15-15 or 16-16-16 is your best option. Again depending on special soil conditions or your specific growing region, a different fertilizer analysis may be more suitable, but for the most part a 15-15-15 or 16-16-16 is a pretty good starting point. This fertilizer blend is simple and widely available and it provides a balanced flow of the three most abundantly used nutrients. Adding micro-nutrients with this blend is also recommended.
Below is a chart with suggested fertilizer requirements for a few different grass species. These recommendations are based off the annual nitrogen requirement for each grass because nitrogen is the most common deficient nutrient in grass and must be applied on a regular basis for vigiorous growth. But if you apply your nitrogen from a well balanced grass fertilizer with a good pack of micro-nutrients, you should not encounter any other major deficiency problems. You DO NOT want to apply a full years application in one single application. This would be a bad idea. Instead you want to spread out your applications over the months that your grass is in optimal growing conditions. For example, common bermuda grass nitrogen requirement is about 4-5 lbs nitrogen per year. You would want to spread about 1 lb. nitrogen per month during the months of March through September because this is when bermuda grass is most actively growing and when nitrogen can be utilized most.
|Suggested Maintenance Fertilization for Grass Lawns|
|Grass||Total Pounds Nitrogen / 1000 ft2 / year|
|Bermuda Grass (Common)||4-5|
|Bermuda Grass (Hybrid)||5-6|
|Zoysia Grass||1 1/2 – 2|
|St. Augustine Grass||2 1/2 – 3|
|Perennial Rye Grass||2 1/2 – 3|
|Tall & Fine Fescue||2 1/2 – 3|
|Kentucky Blue Grass||2 1/2 – 4|
For keeping your grass green through some of the cooler weather when grass is growing much slower, apply a fertilizer that contains iron. Iron based fertilizers are beneficial in promoting good turf color during colder temperatures.