Have you ever been standing in the fertilizer section at the garden store and wondered what the numbers on the bags meant? It can feel like information overload, especially when you’re first getting into gardening. Numbers?! I don’t want numbers in my gardening! No worries, my friend.
This post is going to break down what those numbers are, what they mean, and why they are important to the health of your garden.
What do the numbers mean?
The numbers refer to the levels of macro nutrients available in a bag of fertilizer. In order, the numbers represent the availability of nitrogen, phosphorus, and potassium (also called potash). The higher the number is, the more concentrated that nutrient is in a fertilizer. For example, a 10-5-5 has twice the amount of nitrogen than phosphorus and potassium. A 20-20-20 has twice as many nutrients as a 10-10-10, etc.
Fertilizers can also contain only one macro nutrient, for instance,these bags would be labeled something like 10-0-0.
If you want to get really specific, you can also find out how many pounds of a nutrient are available by multiplying the weight of the bag by the number of your preferred nutrient as a decimal. So, if you have a 20 pound bag of a 10-0-0 fertilizer you would multiply 20 (the weight of the bag) by .10 (decimal form of nitrogen available) for a total of 2 pounds of nitrogen per bag of that fertilizer.
Why these nutrients though?
Nitrogen, phosphorus and potassium are the nutrients plants require the greatest amount of (the ‘macro’ part of macro nutrients). These nutrients are vital to plant growth and vitality. Here are some of the major roles these nutrients play:
Nitrogen: part of chlorophyll. Makes plants leaves green and is a major key to photosynthesis. Nitrogen converts suns energy into sugars that help with leaf and stem growth. If the leaves of your plants are turning yellow, you probably have a nitrogen deficiency.
Phosphorus: Vital to flower, fruit and root development. Also helps with photosynthesis, as well as creating starches for strong stalks and stems. If fruits lack development or taste slightly acidic – you’re short on phosphorus.
Potassium: Also referred to as potash. Improves overall health, helps disease and pest resistance. If leaf tips curl, or you have yellowing veins in the leaf stems you may need some potassium.
Hopefully this helps clear up any questions you had about what N/P/K meant and how to use the numbers. If you have any questions leave them below and I will be sure to answer them for you!