Fertilizer Application Rates
There are three primary nutrients found in fertilizer, each represented by the following letters:
(N) nitrogen
(P) phosphorous
(K) potassium
When reading a fertilizer bag the nutrients are represented by three numbers.
A fertilizer label which reads “28 -14 - 5” really means 28% of the contents is N, 14% is P, and 5% is K. The rest is 52% inert (or inactive) material.
To determine the actual pounds of nutrient in each bag, multiply % of nutrient by pounds (weight) of bag
Example: Suppose the soil test recommended that you apply 100 lbs of nitrogen per 1000 square feet.
Using the 28-14-5 fertilizer formulation above, you would need to apply 357 pounds per 1000 square feet.
100 lbs of nitrogen divided by 28% (.28) = 357 lbs of fertilizer
How many 50 lb bags will you need to purchase?
357 lbs of fertilizer divided by 50 lb bag = 7. 14 bags (7 bags)
Source: Nola M. Wilson, Small farm Extension Agent, Marion County Extension.
Modified by: Roy Beckford, Agriculture/Natural Resources Agent, Lee County Extension
