The “N-P-K’s” of Fertilizer

The “N-P-K’s” of Fertilizer – the three numbers on fertilizer – represents the value of the three macro-nutrients used by plants. These macro-nutrients are nitrogen (N), phosphorus (P) and potassium (K) or N-P-K for short. The higher the number, the more concentrated the nutrient is in the fertilizer. For example, numbers on fertilizer listed as 20-5-5 has four times more nitrogen in it than phosphorus and potassium. A 20-20-20 fertilizer has twice as much concentration of all three nutrients than 10-10-10.

The "M-P-K's" of Fertilizer

Here is how each of the macro-nutrients contribute to healthy plant growth:

N: Nitrogen, a nutrient which contributes to the vegetative development of all of a plant’s aerial parts.
P: Phosphorus, a nutrient which strengthens the resistance of plants and contributes to the root development process.
K: Potassium, a nutrient which contributes to flowering and fruit development.

Knowing the The “N-P-K’s” of Fertilizer can help you select one that is appropriate for the type of plant you are growing. For example, if you are growing leafy vegetables, you may want to apply a fertilizer that has a higher nitrogen number to encourage leafy growth.

There are three main types of fertilizers on the market : granular, soluble and liquid. The following explanations for each type will help you choose the fertilizer that suits your needs.

Granular fertilizers

This type of fertilizer comes in the form of dry granules. Often, granular fertilizers are formulated to slowly release nutrients. Granular fertilizers must be mixed with the soil or sprinkled around the base of plants. Most must be watered and take a few days to give results.
Formulation: dry granules
Use: trees and shrubs, vegetables, roses and flowers, grasses and lawns

  • Extended release
  • Easy to store
  • Fewer applications are required
  • Economical

Soluble fertilizers

This type of fertilizer comes in the form of water-soluble powders. It must be diluted in water before it is applied. It can be applied with a watering can or sprayer.

Formulation: water-soluble powder
Use: perfect for fast-growing plants such as flowers and vegetables, indoor plants, and plants grown in containers

  • Fast-acting
  • Quickly absorbed
  • Easy to measure and use
  • Does not burn roots

Liquid fertilizers

This type of fertilizer comes in the form of a liquid concentrate. It must be diluted in water before it is applied. Liquid fertilizers allow for even applications and are more efficiently absorbed by the soil.

Formulation: liquid
Use: lawns, vegetables, flowers, plants grown in containers, indoor plants

  • Easy to handle when mixing and applying
  • Easy dosage
  • Even applications
  • Immediate effect
  • Homogeneous mix

Before applying fertilizers to your garden or growing medium, it is always wise to have the soil tested first, using a good soil test kit.

To purchase highly recommended organic fertilizers in Canada, click here.

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