What do those fertilizer numbers mean?
Jackie, "Has anyone ever explained to you what these fertilizer numbers mean" I asked while holding up a bag of all purpose plant food.
"Nope" she replied with a slight grin on her face, while squeezing out her first pansy from a six pack.
"Well this is something that is important for every farmer or gardener to know." "Would you like me to explain
it to you?"
Jackie sat upright, gave me her full attention and said, "Ok."
At 11 years old, Jackie was a bright girl, however I knew I needed to explain what those fertilizer numbers meant without confusing her with to much information.
Here's how it went for me.
Numbers on a fertilizer bag or bottle represent the percentage of NPK in it.
The N, representing the first number stands for nitrogen.
The second number is a P, which stands for phosphate.
The third is a K, meaning potassium.
"Why is it not NPP instead?" She asked.
Knowing this was a good question but not wanting to confuse her further by a detailed explanation of the periodic table of elements, I stated, "You will learn this later on in school, but to help explain, scientists have a letter chart for different elements." "Like O is for oxygen or He stands for helium, which you know make balloons float." "So the letter for potassium in this chart is a K instead of a P."
"Oh....Ok" was Jackie's reply.
Knowing my class on fertilizer was not going to hold my only student's attention if it kept up in this manner,I moved cautiously forward.
"Don't worry too much about what the letters stand for."
"The important thing is how those numbers and letters help our plants grow"
This first number on this bag is a 5 meaning how much N is in here. Now N (nitrogen) helps the plant grow bigger and greener. For example, if you want a really lush, green lawn use fertilizer with a higher first number.
The second number is a 3meaning the amount of P in it. P (phosphate) helps the plants roots grow stronger while helping it produce more flower blossoms. So if you are looking for more roses on the rose bush, use a fertilizer with a higher second number.
The third number is a 3 which is the amount of K in it. K (potassium or what I call potash) is what I like to consider vitamins for plants. It helps plants overall health making them more disease resistant.
And if you looking for an organic fertilizer, these three fertilizer numbers will never add up to more than 15.
With this Jackie looked at my sister and said, "Your brothers a good teacher."
This response alerted me that class was over. The differences of chemical fertilizer vs organic or the importance of micro nutrients, would have to what for another time.
I had accomplished my goal of sharing the basics of fertilizer, we could all now get back to planting those pansies.
Jay - The Impatient farmer
For more information check out this page on plant nutrition