Fertilizer can be confusing when trying to figure out the numbers on the label as well as the correct type to use on your lawn. Here I will try to help you understand Fertilizers role in lawn care and discuss the numbers, and the types of ingredients. For the DO It Yourself (DYI) lawn care there are general guidelines developed but all experts agree, soil test, soil conditioning, proper watering are key factors to a healthy lawn and gardens.
Generally a high nitrogen fertilizer is recommended, such as a 3-1-2 or 4-1-2 (nitrogen - the first number, phosphorus - the second number, and potassium - the third number). The numbers are a ratio so an example of a 3-1-2 fertilizer would be 15-5-10. This translates to a fertilizer with 15% Nitrogen, 5% Phosphorus and 10% Potassium or Potash. These are the major nutrients that plants need and fertilizer provides. Two others often not provided by the soil is (S) sulfur and (Mg) Magnesium. Some types of nitrogen fertilizers are prone to volatize back into the atmosphere which is about 78% nitrogen.
There are other Micronutrients that turf needs as well but most are provided by the soil or irrigation water. Sometimes these “fertilizer” elements are present in the soil but not available to the plants. The best way to provide these Micronutrient fertilizer elements is through foliar feeding. These fertilizers are spoon fed to the Lawn and Ornamental plants and are adsorbed through the leaves and sometimes the bark. If they are applied to the soil as a dry granular fertilizer they could become bound up by the soil relatively quickly.
Macronutrients: N, K, Ca, Mg, P, S,
Micronutrients: Cl, Fe, B, Mn, Zn, Cu, Mo, and Ni
Typically your lawn would like several small applications of fertilizer per year. This would include Macronutrient commonly found in fertilizer.
Factors affecting fertilizers role in your lawn care program:
▪ Turfgrass Species
▪ Turfgrass use
▪ Soil test report
▪ Environmental conditions
Nitrogen Requirement from High to low
Hybrid bermudagrass ( highest)
St. Augustinegrass (sun)
St. Augustinegrass (shade)
Centipedegrass / Buffalograss (lowest)
Turfgrass use ranges from Athletic Fields to lawns.
Soil Testing gives an indication of what the soil type is, sandy, loam or clay as well as the available nutrients. Soil pH has an impact on general plant health and availability of nutrients.
Environmental Conditions include sun or shade, note that a St. Augustine Lawn in the shade requires less fertilizer than the same grass in full sun. Other environmental conditions include but not limited to slope (water run off), soil compaction, and drought stress.
Proper lawn care requires several small applications of fertilizer per year to achieve the desired maintenance levels.
Fertilizer is often applied at a rate to provide One (1) pound of nitrogen per 1,000 square foot (SF) of lawn. Care should be taken not to apply more than one pound per 1000 of quick release high nitrogen fertilizer in a single application. High levels of Nitrogen may cause excessive top growth, burn the grass and retard proper root development. Slow Release Fertilizers may be applied at rates higher than one pound of Nitrogen per 1,000 SF.
A slow release fertilizer is good for all outdoor plants. There are different type’s technologies to create slow release fertilizers. Polymer coated, Sulfur Coated Urea (SCU) and Water Insoluble Nitrogen (WIN). SCU types offer some advantage in that it includes sulfur that Lawns often need and is readily available in most stores. WIN typically breaks down over a period of time based on microbiological activity in the soil and soil temperature. WIN Nitrogen is not prone to mechanical damages from product handling, foot traffic or mowers. Excessive rain, mechanical damage or heat may cause the other slow release products to become quick release.
Some manufactures have created stabilized nitrogen. I believe this is not the same as controlled release but will leave that for another topic of debate. Lawns will thrive and be more weed free if fertilized several times per year. However, if I could only fertilize one time, do it in later summer or early fall between September 15 and October 15. The turf will survive the winter stronger; have a healthier root system and earlier green up. Also do not be in a rush to green up your lawn in the spring. After winter and growing conditions improve the lawn is going through a transition from dormancy. Applying a high nitrogen fertilizer to your lawn at this time can do more harm than good. Lawns and all plants respond to different spring conditions. Even with the warm weather we had in the winter in 2017, lawns respond to multiple environmental conditions when greening up, these include soil temperatures, moisture, air temperatures as well as the position of the sun in the sky.
The best rule of thumb is not to apply nitrogen fertilizer until the lawn requires three actual mowing. Weeds do not count, nor does the first mowing used to remove the winter stubble. Scalping in not part of proper lawn care.
Clearly some of the various constituents of the Fertilizer formulation will either be neutral, or raise or lower the pH of the soil. Bulk brand fertilizers are often blended the least expensive forms of each ingredient. These often work well but may not provide the best color or help condition the soil as much as other formulations. The best practice is to use a fertilizer that not only is a great plant food but also improves the soil conditions such as pH. For example, use a Nitrate Nitrogen on acidic soils and a Ammonia Sulfate on alkaline soils. Use care when using these fertilizers can burn the grass if applied improperly.
The Best Fertilizer has 40 to 50% slow release forms of nitrogen. Professional fertilizers are carefully blended with premium formulations that more closely matches the Lawn, soil and other environmental conditions.
General Lawn Care and Fertilizer
Keep in mind, Fertilizer is just one part of lawn care. It is part of a three legged stool, Mowing, watering and fertilization are all important to a great lawn. Proper mowing is the most important. Too little or too much water of fertilizer will often not harm the lawn as much as improper mowing. When I say that, I mean within reason because dumping a bag of fertilizer in one spot or a soaked yard for a long period of time will kill the grass. The key is balance, mow frequently at the height of cut that makes sense and does not remove more than 30 to 40% of the blade. Do not apply so much fertilizer that you must mow more frequently than you can manage, hence the beauty of slow release products. Water the grass in accordance to restrictions which are based on known turf requirements for a healthy stand of grass. Most southern lawns will need a half inch of water every 3 to 4 days in peak growing season, and several pounds of nitrogen or more depending on conditions, use and species of turf. Basically, the more you care for your lawn with high amounts of water and fertilize your lawn the more often you will need to mow it.