Fertilize Appropriately
(See pages 10-14 in FY&N Handbook)

any trees and landscape plants demand little or no fertilizer once they are established and mature. In fact, fertilizers can be hazardous to the health of your yard and the environment when they are misused.

When over-applied, fertilizers aggravate insect and disease problems and force excessive growth which must be mowed or pruned. Excess fertilizers can run off yards into waterways or leach into aquifers, polluting drinking water.


How much fertilizer should you buy?

It's spring, and Bob and Jane want to fertilize their lawn. Here are the steps they take to determine how much fertilizer to buy:
  • They measure their lawn area and calculate square feet:
    Back yard: 60 X 50 feet = 3000 sq. feet
    Front yard: 50 X 40 feet = 2000 sq. feet
    Total square footage = 5000 square feet
  • They shop for fertilizers which contain slow-release nitrogen and find two products priced the same, a 10-2-10 and a 16-4-8. The 16-4-8 contains 16% nitrogen (N), 4% phosphorus (P), and 8% potassium (K). The 10-2-10 contains 10% N, 2% P, and 10% K.
  • They use this simple formula to determine the application rate of each fertilizer:
    100 divided by to % N = the amount of fertilizer to spread over 1000 square feet
  • Therefore, 100 / 10 = 10 lbs. per 1000 sq. feet (for the 10-2-10) and 100 / 16 = 6 lbs. per 1000 sq. feet (for the 16-4-8)
  • Their 5000 square foot lawn would require 50 lbs. of 10-2-10 (5 X 10), but only 30 lbs. of the 16-4-8 (5 X 6).
  • Both products contain 40 lbs. of fertilizer. Bob and Jane save money by purchasing one bag of 16-4-8 instead of two bags of 10-2-10. 
  • Before spreading the fertilizer, they calibrate their fertilizer spreader to apply 6 pounds per 1000 square feet. (Hint: This information is available from the spreader's manufacturer or the Cooperative Extension Service.

The Fertilizer Label:

Florida law requires that fertilizer manufacturers supply a label with every bag of fertilizer. 

There's a wealth of information on the label once you understand how to interpret it. The FY&N Handbook helps to demystify much of the information you will find.

Use fertilizers in which 30% or more of the nitrogen is in a slow- or controlled-release form.

Fertilizer Facts:

1. Fertilizer is not plant food.

Food to a plant is the sugars it makes through photosynthesis. Fertilizer nutrients are used in this process, but a lawn or plant growing poorly in too much shade will not grow better if fertilized.

2. The Truth about"100% Organic."

The "100% Organic" claim often refers only to the nitrogen in the bag, furthermore, the nitrogen can be derived from natural products such as manure or it can be from synthetic chemicals such as urea. Read the label to determine where the "organic" nitrogen is coming from.

3. Buy nutrients, not fertilizer.

Many fertilizers contain a number of plant nutrients even though only one or two may be needed. What plant response do you want – greener growth? More flowers or fruits? Know which nutrients will provide these responses and buy only those.


Fertilize only as needed to maintain the health of lawns and landscape plants. If plants show signs of stress, such as yellow leaves or stunted growth, identify the problem before applying fertilizer. Do not exceed the rate of 1 pound of nitrogen per 1,000 square feet per application.
Credit: 2 inches
Use slow-release fertilizers. Buy fertilizers that contain 30% or more of the nitrogen in slow- release forms. 
Credit: 2 inches
Use iron (ferrous sulfate or chelated iron) instead of nitrogen to make your lawn green during the summer. 
Credit: 1 inch

____Total inches

Slow-release Fertilizers

When fertilizer nutrients are in slow release" forms, they are available to plants over a longer period of time and less nutrients are wasted or lost as pollutants. Look for these terms on the product or fertilizer tag:

Timed-release, slow-release or controlled-release.

Water insoluble nitrogen, activated sludge, sulfur-coated urea (SCU), IBDU, ureaform (UF), nitroform, or polymer-, plastic-, or resin-coated urea.


Table of Contents Introduction What is A Florida Yard? Right Plant, Right Place Water Efficiently Maximize Mulch
Recycle Yard Waste Fertilize Appropriately Manage Yard Pests Responsibly Reduce Stormwater Runoff Provide for Wildlife On the Waterfront
Return to Florida Yardstick Workbook Return to FYN Publications