Fertilize Your Yard Responsibly

Dale Armstrong, Coordinator Florida Yards & Neighborhoods, Pinellas County Extension

It’s that time of year when homeowners start thinking about fall fertilization of their lawn and landscape. This year Pinellas County residents may give a little more thought to fall fertilization since this was the first summer that the new county ordinance prohibited the application of fertilizers containing nitrogen (N) and phosphorus (P).

As a reminder, the Pinellas County Fertilizer Ordinance contains a “black-out” period between June 1 and September 30 when fertilizers containing nitrogen and phosphorus may not be used. The reasoning is that if N and P are not applied during the rainy season then these nutrients cannot be carried by stormwater to pollute our surface waters and groundwater. Excessive N and P in our surface waters are responsible for harmful algae blooms and undesirable growth of aquatic vegetation. For additional information about the fertilizer ordinance please see the link at the end of this article.

So, if you decide to apply fertilizer during the fall, how do you do it responsibly? If you are hiring someone to fertilize for you, the responsible thing to do is to ensure they are a state-certified fertilizer applicator, which becomes mandatory after January 19, 2011 in Pinellas County. Ask to see their license. If you plan to fertilize your own yard you should educate yourself about how to properly select and apply the product. Following are some important factors to consider if you are going to apply fertilizer yourself:

• First, do a rough measurement of your turfgrass area to determine approximate number of square feet. Fertilizer application rates are calculated based on pounds of nitrogen per thousand square feet. Once you have calculated how many square feet you will be fertilizing you can determine how much fertilizer to purchase.

• Since you will be buying a fertilizer with at least 50% slow release nitrogen as required by the Pinellas County Fertilizer Ordinance and recommended by University of Florida Institute of Food and Agricultural Sciences, you will use table 1a in this fact sheet: “Figuring out Fertilizer for the Home Lawn”. Table 1a is for application of 1 pound of nitrogen per thousand square feet.

• Looking at table 1a you will see that the number of pounds of fertilizer you purchase varies depending on the percentage of nitrogen (the first of the three numbers listed) in the bag. A 15-0-15 formula has 15% nitrogen, no phosphorus, and 15% potassium.

• The higher the percentage of nitrogen, the less fertilizer you will be spreading. Referring to table 1a you will see that for a 15% N fertilizer the application rate is only 6.5 pounds per 1,000 square feet. So, on a lawn that is 3,000 square feet, for example, you would purchase a 20 pound bag of 15-0-15 because 3 times 6.5 equals 19.5 pounds total fertilizer needed. Since several fertilizer formulas may be available you may want to take table 1a with you when shopping.

• It is very important to keep fertilizers and all other pollutants off of hard surfaces like driveways, sidewalks, and roads so rain runoff will not carry them into storm drains. Remember, only water (nothing else) down the storm drain.

I suggest you read the instructions on the fertilizer bag, the Pinellas County Fertilizer Ordinance, and the fertilizer fact sheet for additional tips and instructions about responsible fertilization. A healthy lawn can be maintained by using the correct quantity of fertilizer and by applying it properly and at the right time of the year. By following these instructions you will also be protecting the environment from the detrimental effects of nutrient runoff and leaching.

Additional Resource
Pinellas County Fertilizer Ordinance http://www.pinellascounty.org/environment/pageshtml/pdfs/Fertilizer-Ordinance-Brochure.pdf