By The Numbers: Using Fertilizer On Your Lawn

April 16, 2011

Many people think a beautiful lawn is unattainable, but that is not necessarily true. A good lawn can be achieved if you develop a good understanding of proper fertilization, watering, pest control and mowing.

Larry Williams, Horticulture Extension Agent in Okaloosa County, provides some basic facts relating to fertilizing a Florida lawn:

Many popular lawn fertilizers have too much nitrogen and too little potassium. A common example is 29‐3‐4. These numbers represent the percent nitrogen (N), phosphorus (P) and potassium (K), respectively. A 29‐3‐4 fertilizer has a lot more nitrogen (29%) than potassium (4%). Despite the fact it’s readily available, it’s not a good choice for a Florida lawn.

It’s better to select a fertilizer where the first and third numbers are equal or close to equal and the center number is very low. A few examples found locally include 15‐0‐15, 16‐2‐16 and 18‐0‐18.

You may be able to produce an attractive lawn for three, four, five years or so using a high nitrogen and low potassium fertilizer such as 29‐3‐4. But at some point in time, your lawn will begin to decline. This is the misleading part. When the lawn begins to deteriorate, most people blame mole crickets or something else. They never realize the true cause for the decline in their lawn. The excess nitrogen creates a nice green lawn short term (for a few years). But the lawn needs adequate amounts of potassium and other essential plant nutrients, which are not provided by a 29‐3‐4 or similar analysis fertilizer. As a result, the lawn declines with time.

Of the three primary nutrients (N, P and K), potassium is second only to nitrogen in utilization by lawns. Adequate potassium has been linked to reduced disease problems,
improved drought and cold tolerance and enhanced root growth.

Lawn grasses use much less phosphorus (center number) than nitrogen and/or potassium. Because of this and because phosphorus has been implicated as a cause for
problems in our surface waters, it’s recommended to base phosphorus rates on the results of a reliable soil test. In the absence of a soil test, select a fertilizer with 2% or less phosphorus. For a newly planted lawn, choose something like 8‐4‐8 or 10‐4‐10 when a soil test indicates a need for extra phosphorus.

Finally, look for slow release lawn fertilizers. It’s best to purchase a lawn fertilizer with at least half the nitrogen in a slow release form. Usually in very small print beneath the guaranteed analysis you can find a statement about the amount of slow release nitrogen. The words water insoluble, slowly available or slowly available soluble nitrogen or coated are types of slow‐release nitrogen.

Then, some calculations are necessary. If, for example a 10‐10‐10 fertilizer says it contains 5% slow‐release nitrogen, divide the 5% by the total percent of nitrogen (10% in this example) and multiply by 100 to get the percentage of nitrogen that is in slow-release form. In this example it is 5/10 x 100=50%.

Choosing a fertilizer with the right numbers is an important part of maintaining a healthy long lasting Florida lawn. For additional information on this topic, contact your
local UF/IFAS Extension Office or visit http://hort.ufl.edu/yourfloridalawn/ .

Comments

2 Responses to “By The Numbers: Using Fertilizer On Your Lawn”

  1. farmer on April 16th, 2011 3:08 pm

    Thanks Kay, Love it!!! Very interesting article too.

  2. Kay on April 16th, 2011 1:09 pm

    The way I like to remember it is :
    Put your thumb in an up position and say UP, then point your thumb down
    and say DOWN, then stick your finger up and circle the air.

    That means just like the numbers:
    Up – Down – All Around

    The first number is for the green you see.
    The second number is for the roots below ground
    The third number is for EVERYTHING.

    Anyway that’s the way I learned it and I have been able to remember
    what the numbers mean that way. Those numbers are on everything
    you buy that has something in it for your lawn or garden.

Written by William Reynolds · Filed Under FEATURE TOP STORY, Features, News