1. Objective: Students will identify how to interpret fertilizer labels.

2. What is fertilizer?
A material applied to supply essential elements

3. Major Ingredients
1. Most commercial fertilizers have 3 numbers on the front label, separated by dashes.
For example:
2. This is the fertilizer analysis or percentage by weight of the 3 major nutrients plants need:
nitrogen, phosphorus and potassium, in that order.
3. These are abbreviated as N-P-K.

4. Get out your Calculator and Analyze
1. If you purchased a 10 pound bag of fertilizer labeled , it would contain…
5% nitrogen
10% phosphorus
5% potassium.
The remaining 80% could be comprised of other nutrients and filler.
2. How many pounds of NP and K does it contain?
.5 lb. nitrogen
1 lb. phosphorus
.5 lb. potassium
The remaining 8 lbs could be comprised of other nutrients and filler.

5. 1st Number = Nitrogen
1. The first number gives the concentration of nitrogen in the product.
2. Nitrogen encourages foliage growth, among other benefits.
3. A fertilizer would contain 5% nitrogen by weight.
4. For every pound of fertilizer applied there is really only .05 pounds of nitrogen.
(The 10 pound bag mentioned would contain .5 lb. nitrogen)

6. 2nd Number = Phosphorous
1. The middle number refers to the concentration of phosphorous.
2. Phosphorous contributes to many fundamental plant processes such as rooting and setting flower buds.
3. A fertilizer would contain 10% phosphorous by weight or .1 pounds of phosphorous.
(The 10 pound bag mentioned above would contain 1 lb. of phosphorus.)

7. 3rd Number = Potassium
1. The final number states the concentration of potassium.
2. Potassium contributes to the overall health and vigor of plants.
3. Again, a fertilizer would contain 5% potassium by weight or .05 pounds of potassium.
(The 10 pound bag mentioned above would contain .5 lb. potassium.)

8. Complete Fertilizers
1. Fertilizers that contain all three major nutrients are considered complete fertilizers.
2. There are specialized fertilizers which are called incomplete because they lack one or more major nutrients such as a fertilizer labeled

9. Fertilizer Label
1. Some information is required by law to be on the fertilizer bags:
1. Net Weight
2. Brand and grade of fertilizer
3. Guaranteed analysis of each nutrient in fertilizer
4. Name and address of manufacturer

10. Other Valuable Information
Some manufacturers add the following on the bag as well:
% of water insoluble nitrogen
Potential acidity
Salt index
Source of carrier
% of minor elements
Calculation rates
How to calibrate spreaders

11. Reading a Fertilizer Label
P- 5 %
K- 11 %
Remaining 60% is other nutrients and filler.

12. Analyze This! What do you know from the bag?
P: 6 %
K: 12 %
Use: Lawn Fertilizer

13. Check for Understanding
1. Jack and Jill went up the hill and noticed the grass was very yellow. Which fertilizer would be best for them to use, , or ?
Why?
Nitrogen is used to help promote lush green foliage growth, the fertilizer is the highest in nitrogen.

14. Practice Reading the Label
In the boxes on your worksheet please provide the following information for each fertilizer placed on the tables around the class…
Net Weight
Brand and grade of fertilizer
Name of manufacturer
NPK percentage
One Secondary nutrient and %
One Micronutrient and %

15. Name of manufacturer, Brand and grade of fertilizer, Use, Net Weight, NPK percentage, One Secondary or Micronutrient and %