The N-P-K nutrients affects the plant growth differently, and therefore you need to choose the right blend depending on the result wanted.
These numbers represent the percentage by weight, of the most important nutrients. They are nitrogen-phosphorus-potassium (N-P-K). The percentages don’t equal 100 percent. That’s because there are other nutrients and filler product in fertilizer mixtures that helps to apply the nutrients evenly.
The higher numbers, like 20-20-20, means that you have to use less in your water than when using 5-5-5 e.g., in order not to have a too high concentration that burn the roots.
N Nitrogen make plants produce more chlorophyll that in turn let the plants grow with more speed. Also the green colour of the leaves will turn darker and healthier.
P Phosphorous aids in root development and increases flowering ability and bloom size.
K Potassium has many functions. It both help the plant protecting itself against diseases and aids in drought protection, as well as cold tolerance. Roots too are developed stronger and Potassium also helps in the process of photosynthesis.
Consider using a high-potassium fertilizer at the start of winter and summer to protect crops from temperature extremes or when insects and disease have caused damage to your bonsai or other plants.
So, what’s important is how much N and P and K there are in the fertilizer according to each other.