Last week I wrote about the importance of mowing. This week, allow me talk about how to fertilize appropriately. Selecting the right formulation of fertilizer can help your turfgrass stay lush, green and healthy during the growing season. There are many fertilizer formulations available for homeowners. Not all are created equal. The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) extension recommends using a fertilizer with a 1:1 or 2:1 ratio of nitrogen to potassium. For example, 15-0-15 and 16-0-8 would be a 1:1 formulation. A 20-0-10 would be a 2:1 formulation. The numbers do not have to be exact. A palm fertilizer with a formulation of 8-2-12 would be good. However, a formulation of 32-0-5 or 20-0-0 would be way off base. The appropriate formulation is important for many reasons.
The first number of a fertilizer bag is nitrogen (N). Basically, nitrogen greens your lawn and produces shoot growth. Too much nitrogen is not be a good thing. Excessive nitrogen will stress turf and attract pests. The middle number is phosphorus (P). Phosphorus is very abundant in Florida soils. In some parts of the state, they actually mine it. Having said that, you really do not need to be too concerned with (P) in your turf fertilizer. The last number is potassium (K). Think of potassium as giving vitamins to your roots. Potassium helps root development and will help turf in times of stress, such as drought or a freeze.
Now that you have selected the right formulation, do you know if it is slow-release? UF/IFAS recommends using a fertilizer that has 15% or more slow-release. Have you ever seen a turf fertilizer bag that states clearly on the front of the bag how much slow release it has in it? I rarely do. There are several terms in which you can find out if you have a slow-release fertilizer or not. Let us look at a formulation of 15-0-15. On back of the bag, you may notice a small box called “Guaranteed Analysis.” This is a breakdown of what is in the fertilizer. Look at the components that make up the total nitrogen. You are looking for a word called water-insoluble. Water-insoluble is slow-release. Therefore, a bag that has 15% total nitrogen will be broken down in the guaranteed analysis box. For example, it may have 2.56% ammoniacal nitrogen, 1.38% nitrate nitrogen, 3.56% urea nitrogen and 7.50% water-insoluble nitrogen in its formulation. Add all of these up and it will total 15%. The 7.50% water-insoluble is slow-release. Since 7.50% is half of 15, then that bag has 50% slow-release nitrogen in its formulation. That formulation would fit UF/IFAS guidelines.
If you do not see water-insoluble, look down at the bottom of the guaranteed analysis box and you will see a paragraph titled “Derived from.” If you see words like “Polymer coated,” then that means it is slow-release as well. A bag of 8-2-12 fertilizer containing 5.4% polymer coated urea in its total nitrogen would contain almost 70% slow-release nitrogen. Reading and understanding fertilizer labels can be daunting and frustrating. Most people ask me if I have a favorite trade name. Truth is you really cannot go by trade names. You have to go by what is in the bag and if that fertilizer is what you need for that particular plant species. I would also highly recommend doing a soil test. Contact our local county extension office for materials and instructions.
UF/IFAS Extension in Hernando County provides solutions for your life. Extension programs are open to all persons without regard to race, color, sex, age, disability, religion, or national origin.