Fertilize Your Lawn Now

If you have not fertilized your turf then now is the time to make the first application of the year. Selecting a fertilizer is the first step. Most of the retail garden centers should have a product which will fit your needs. When you look at the fertilizer bag you will see three large numbers on the front of the bag. The first number stands for percent nitrogen (N), the second stands for the percent phosphorous (P) and the third stands for percent potassium (K). In other words if the product is a 16-2-16 then a 100 pound bag would have 16 pounds of nitrogen, 2 pounds of phosphorous and 16 pounds of potassium. The other 66 pounds consists of some sort of filler like sand. You have probably noticed that the middle number which represents phosphorous is quite low. The reason for this is that most soils in central and north Florida have an ample amount of phosphorous already in the soil. Adding addition phosphorous is usually not necessary and can easily runoff into our waterways encouraging exotic plant growth.

We recommend selecting a turf fertilizer which has nitrogen in a 1:1, 2:1 or a 3:1 ratio with potassium (third number) and 30-50% slow release nitrogen. Acceptable products include Scotts Turf Builder for Southern Lawns (32-0-10) which has 50% slow release nitrogen, and a 3 to 1 nitrogen/potassium ratio; and Lesco 24-2-11 fertilizer which contains at least 50% slow release and has 2:1 nitrogen/potassium ratio. It is important to have no less than a 3:1 nitrogen/potassium ratio as potassium is important for building strong roots which increase turf tolerance to stresses. There are other acceptable products on the market, but space prevents listing any more. And there are more inexpensive products available which have a greater than 3:1 nitrogen/potassium ratio such as one sold locally with a 29-0-4 ratio which we don’t recommend due to low potassium.

You will find stacks of weed and feed products at the retail garden centers right now. We do not recommend weed and feed products because weed killer applications should be made in mid-February to be most effective followed up with a second application before April 15^th. Mid-February would be much too early to apply a turf fertilizer in a weed and feed product since most turfgrass is still somewhat dormant at this time. Fertilizer applied in mid-February has the potential to leach and run off into our waterways during a substantial rain event. The correct time to apply turf fertilizer in central Florida is at the end of March. However herbicides in a weed and feed product applied at this time would be applied too late to control many germinating weeds. So, weed killers should be applied in mid-February with a second application before April 15^th and fertilizer should be applied at the end of March to be most effective and Florida-Friendly.

Let’s say that you have selected the Scotts Turf Builder for Southern Turfgrasses (32-0-10) or the Lesco 24-2-11 for your lawn fertilizer. The next question is how much to apply? The University of Florida and Polk County require that not more than one pound of nitrogen be applied per 1000 square feet of turfgrass per application if the product has 30-50% slow release nitrogen and 1/2 pound nitrogen if the product has less than 30% slow release nitrogen.

You have these bags of formulated fertilizer (32-0-10) and (24-2-11) so how much of the product in this bag equals one pound of nitrogen. This can be calculated by dividing 100 by the percent nitrogen in the bag (32% and 24% nitrogen) – 3.3 pounds of the 32% nitrogen product and 4.2 pounds of the 24% nitrogen product equals one pound of nitrogen.   A 50 pound bag of the 30% nitrogen product will cover about 15,000 square feet of turfgrass  and a 50 pound bag of the 24-2-11 will cover about 12,000 square of turfgrass applied at one pound of nitrogen per 1000 square feet of turf. Applied at 1/2 pound nitrogen the bag would cover twice the square footage - 30,000 and 24,000.

Next you are going to have to determine how many square feet of turfgrass you have in your landscape. Square feet is determined by multiplying width by the length. A tape measure or roll-a-tape would be handy tools to help make this calculation. Let’s say your front turfgrass is an area which is 150 feet long and 35 feet wide. Thirty-five multiplied by 150 equals 5250 square feet of turf area. The correct amount of 30-0-10 product for 5250 square feet calculates out to be 17 pounds based on the product being applied at 3.3 pounds per 1000 square feet. (3.3 pounds 30-0-10 X 5250 square feet turf divided by 1000 square feet =’s 17.3 pounds.)

Next you will need to calibrate the output of your rotary spreader. We have already determined that 3.3 pounds of 32-0-10 fertilizer needs to be applied per 1000 square feet to equal one pound of nitrogen per 1000 square feet. An area smaller than 1000 square feet needs to be selected to practically calibrate the spreader.  Lay out a small area something like 200 square feet, an area 10 feet wide (assuming the spreader throws five feet to each side) and 20 feet long, and cover with plastic. This area would require 1/5 (0.2) of the recommended fertilizer for 1000 square feet or 3.3 pounds divided by 5 which equals 0.66 pounds. Set the spreader output level at a medium opening. Fill the spreader half full with fertilizer and pass over the 200 square foot area. Pour the expended fertilizer from the plastic sheeting into a container and weigh. Adjust opening until 0.66 pounds is expended per pass over the 200 square feet test area. It may be a good idea to calibrate the spreader at 1/2 the above rate and cover the turfgrass twice in different directions to minimize missed areas.