March 1999 Volume VI, Issue 3

Fertilizer Series No. 3

David M. Kopec, Extension Turfgrass Specialist

The Universal Fertilizer Application Equation

In the previous two issues, we discussed various fertilizer terms and how to determine the costs of fertilizer in terms of cost per lb. of nutrient.

Listed below is the universal fertilizer application. This equation tells you how much total fertilizer is required to make an application at a selected fertilizer rate for any sized lawn.

To use the equation, you need to know the following information.

* Fertilizer analysis or grade (Examples include 10-6-4, 21-7-14, 13-0-50, etc.).

* Target application rate (the amount of fertilizer you wish to apply). This is usually expressed in terms of lbs. of -N- per 1000 ft 2 , but can be any other element selected. (Examples include 0.50 or 1.25 lbs. of -N- 1000 ft 2 ).

* The area of the lawn in square feet.

The equation is as follows:

Total fertilizer needed


Desired rate in lbs./1000 ft 2


Lawn size(sq. feet)

% content of fertilizer


We want to apply a 21-7-14 fertilizer to a 6500 square foot lawn. The application rate is 0.50 lb. ( 2 lb.) of nitrogen per 1000 square feet.

Substituting into the equation:

Total fertilizer needed


0.50 lbs.


6500 ft 2



Thus you need 3250/210 = 15.5 lbs. of this fertilizer to apply 2 lb. -N-/1000 ft to the 6500 square foot lawn.

Let's try one more example:

We want to apply 1.25 lbs. of -N- to a 2200 square foot lawn after a summer de-thatching of the bermudagrass. The fertilizer is a 33-0-0 (ammonium nitrate).

Total fertilizer needed


1.25 lbs.


2200 ft 2



This equals 2750/330 = 8.3 lbs. of fertilizer product is required to fertilize the lawn at the desired rate of 1.25 lbs -N-/1000 ft using a 33-0-0 fertilizer.

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