Fertilizer and St Augustine grass make a great combo.
When good cultural practices are combined with proper fertilization applications through the entire growing season, the end result is a healthy, vigorous carpet of grass.
To sustain a healthy lawn, one that can handle environmental stresses like drought, plus compete with grass fungus and disease, gray leaf spots, brown patches, root rot lawn weeds & pests, insects like the southern chinch bug and sod webworm attacks, proper fertilization practices and fertilizer amounts play a dominant role.
In today’s world of “green” many states, counties and cities are passing laws, regulations and ordinances governing fertilizer application and best practices in applying fertilizers to lawns.
These regulations, laws, and ordinances are designed to reduce the pollution potential of water resources due to the application of excess fertilizer, resulting in fertilizer runoff and other cultural practices. However, even with these limitations, homeowners can still maintain a healthy lawn.
In the case of St Augustine grass care, fertilization plays a big role to make it look at its best and come up with a beautiful lawn.
St Augustine grass is a warm season type of lawn grass with medium to high difficulty of maintenance. It spreads with the help of above ground stolons, also called runners.
The warm-season grass is a popular choice in tropical and subtropical regions that creates a thick, carpet-like sod. It crowds out other types such as bermuda grass, argentine bahiagrass and centipede grass.
Among its many cultivars include:
- Floratam St Augustine grass
- Palmetto St Augustine grass
- Captiva, known for it resistance against southern chinch bag
- Sapphire, famous for its blue-green colored leaves
The sod-propagating grass has high drought and shade tolerance level. It grows its best in a tropical setting and occurs often in marshes, lagoons, and shorelines where moisture is always present.
Soil Test For The Best Fertilizer Results
The results of the soil test will “tell” you the soil pH and what the nutrient levels are of the 16 essential elements needed for proper growth and appearance.
If any of these essential elements are missing or low in the soil, they can be “adjusted” through fertilizer applications.
16 Essential Elements Required by Lawn Grasses
|From Air/Soil||From Soil|
The big 3 macronutrients – nitrogen (N), phosphorus (P), and potassium (K) are the ones we see posted on fertilizer bags, and needed by St Augustine grass in the greatest quantities.
The other macronutrients, magnesium, calcium, and sulfur are required as well but in smaller quantities.
Don’t think micronutrients are not important, they are essential but in much smaller quantities.
Check with your local extension office for information and instructions on taking a soil sample and submitting them for a lab for a detailed soil analysis. This will help in selecting the best fertilizer for St Augustine grass for your yard.
Why is a Soil Test Important?
The more you know the better choices you can make on the type, amount of fertilizer, ratio, and analysis of the yard fertilizer you select for your St Augustine.
For example, in Florida where the St Augustine grass plant is the most popular grass-grown, most soils hold sufficient levels of phosphorous.
The best way to determine the level of phosphorous in your soil is with a soil test. Phosphorous is the P in N-P-K on a fertilizer bag… the second number. Once a lawn is established, phosphorous is not needed very often.
This is why when a homeowner examines most of the labels of lawn fertilizers in Florida, they find low amounts or ZERO phosphorous on the bag.
The State of Florida has also mandated in Florida Rule (5E-1.003) fertilizer application rates. The rule states that the amount of nitrogen fertilizer applied cannot exceed 1 pound per 1000 square feet of turf grass for any application.
For information on determining how much fertilizer this equals, refer to our article on understanding “NPK in Fertilizer and What Is In The Bag?”.
Selecting Lawn Fertilizers for St Augustine Grass
So, what is the best fertilizer for St Augustine grass?
When selecting a St. Augustine grass fertilizer, keep in mind ones containing slow release nitrogen provide a longer lasting, slower feeding to your grass. Plus, the slow release nitrogen generally is considered safer for the environment and your lawns.
Many fertilizers are known by their formulation or make up, such as 6-6-6 or 12-4-8.
Fertilizer mixes containing N, P and K are called complete fertilizers which are used on many turfgrasses. The numbers on the fertilizer bag label indicate the percentage of each of these nutrients.
For example, a 12-4-8 fertilizer mixture, contains 12% Total Nitrogen, 4% Available Phosphorus and 8% Soluble Potash. So 100 pounds of 12-4-8 would contain 12 lbs of nitrogen total, 4 lbs of available phosphate, and 8 lbs of potash.
For a quick green and rapid growth soluble forms of nitrogen are used in many complete fertilizers. Below are some soluble forms of nitrogen:
- ammonium nitrate
- ammonium sulfate
- calcium nitrate
- potassium nitrate
Slow-release sources of nitrogen:
- Isobutylidene diurea
- Sulfur-coated urea
St. Augustine like most turfgrasses are very efficient at absorbing nitrogen. For this reason, St. Augustine needs more frequent and higher rates of nitrogen compared to the other nutrients.
Good growth and color often is achieved with a 70/30 ratio of soluble nitrogen and slow-release fertilizer sources.
A ratio of 3-1-2 (N-P-K) is a good overall fertilizer mix for the St Augustine lawn.
But, you will also find mixes of lawn fertilizers like a 26-2-14, 26-2-11, 15-0-15, and 10-5-10 fertilizer for St Augustine, in states like Florida where soils contain adequate amounts of phosphorous and little or no phosphorous may be required for the lawn.
Many homeowners assume a high quality grass must be dark green and fast-growing. However, often excess nitrogen leads to dark green color, excessive growth and thatch.
This can result in grass needing to be mowed more frequently, and potentially nitrogen leaching into the ground water.
Although the third element in N-P-K – Potassium the K, plays the influencing role in root growth. It is second to nitrogen in the requirements needed in a total fertilization program to obtain optimal growth.
Should you use an Organic or Inorganic (chemical) Fertilizer?
There is much discussion on which fertilizer type is best – organic or inorganic fertilizer. Both have advantages and disadvantages. Grass cannot tell the difference.
When To Fertilize St Augustine Grass
When fertilizing St Augustine grass, fertilizer should be applied 2-6 times during the year from spring green-up through fall, unless you live in south Florida.
Watch out in applying fertilizer too early in the spring growing season, especially in northern areas where late-season frost may damage new tender growth. The same holds true in fertilizing late in the year after growth has become less active.
The southern part of Florida where year round temperatures are warmer, St Augustine grass grows year round and the fertilizer program continues year-round as well.
As you move up the state to Central Florida (Orlando area) the first application of lawn fertilizer should be done around early April. The last fertilizer application of the season should occur around mid-October.
Moving to the northern region (Ocala north and across the southern US) the first application of lawn fertilizer should be done around mid-April or about 3 weeks after the grass begins to turn green.
The last fertilizer application of the season in the north should occur around the end of September. As you move farther north final applications should end earlier.
Beware: Keep in mind when applying fertilizer, never use more fertilizer per application than the recommended rate of 0.5 of soluble nitrogen per 1,000 sq foot. Applying too much can result in lawn fertilizer burn.
Related Reading: St. Augustine Grass Lawn Maintenance Schedule
Final St Augustine Fertilizer Tips
When storing fertilizer always store in a location where the fertilizer will stay dry. Never store near fuels or pesticides.
When applying fertilizer with a broadcast spreader for example, many times fertilizer “prills” will find their way to the driveway or sidewalk.
It is best to sweep the prills up or use a leaf blower, rather then using irrigation or a hose to wash the fertilizer away with water. This helps prevent fertilizers unique ability to find its way into water supplies.
For best results in “growing” a great looking St Augustine lawn, start by getting a soil test. Apply fertilizer to your lawn according to the recommendations of the soil test, follow the label, mowing 1/3 of the grass blade and irrigate when rain does not supply enough water.
If you are unsure of the fertilizer analysis, ask a lawn professional. Following these basics will help you grow a lawn of St. Augustine grass lawn the neighbors will envy.