When looking at fertilizers and trying to decide which one to buy, you might notice an NPK label, followed by several numbers. Typically they’re written in a series such as 10-10-10, 20-20-20, 20-5-5, and so on.
If you’re haven’t really dealt with fertilizers in the past, all of that may seem Greek to you. However, the truth is that those numbers are actually pretty important – and it helps to know what NPK means, and what the numbers stand for.
“What Does NPK Mean?”
To put it simply, NPK stands for Nitrogen, Phosphorus, and Potassium – which are the three main components of complete fertilizers. Plants require these nutrients to grow, and each will affect them in different ways:
is mainly for leaf development and plays a role in its coloring and chlorophyll.
helps to promote root growth, and can also affect blooming and fruiting.
affects root growth and stem development, as well as the overall functions of the plant.
Due to the fact that each of these nutrients has a different role to play, it is important that you select a fertilizer that has the right quantities of the nutrients that your plant needs. For example, a leafy vegetable plant may require higher values of nitrogen as opposed to phosphorus. On the other hand, a flowering plant may require more phosphorus instead.
It should be noted that choosing the wrong fertilizer can be detrimental to some plants. For example, if you choose a fertilizer that is high in nitrogen but not phosphorus it may force the plant to focus on producing leaves as opposed to flowering.
“What Do the NPK Numbers Stand For?”
As you may have guessed, the NPK numbers represent the amount of each nutrient that is in the fertilizer in terms of Nitrogen(N)-Phosphorus(P)-Potassium(K). For example:
- 10-10-10 would mean the fertilizer contains 10% Nitrogen, 10% Phosphorus, and 10% Potassium.
- 20-20-20 would mean the fertilizer contains 20% Nitrogen, 20% Phosphorus, and 20% Potassium.
- 20-5-5 would mean the fertilizer contains 20% Nitrogen, 5% Phosphorus, and 5% Potassium.
It should be noted that some fertilizers may only contain one macro-nutrient, and may be labeled 10-0-0, 0-10-0, 0-0-10, and so on.
How to Choose
To choose the right fertilizer, you should not only take into account the type of plant – but also the soil. After all, plants absorb nutrients from the soil, and you’re going to be adding fertilizer to the soil and not the plants.
In short, the liquid NPK fertilizer that you choose should make up for any of the shortcomings of your soil to provide your plant with the nutrients it needs. If your soil is high in phosphorus and potassium but low on nitrogen, you should choose a fertilizer that is high in nitrogen.
Keeping that in mind, your first step should be to get your soil tested. Based on the results, you can decide which fertilizer is the best choice to supplement the nutrients it contains.