Understanding Fertilizer

Home gardeners at some point will turn to using a fertilizer.  If growing in containers indoors or outdoors, the use of a fertilizer is a must.  The reason being, the nutrients in the soil in the container become depleted by the growing plant so they must be replaced.  There are two main categories of fertilizers: organic and inorganic.  Many home gardeners concerned only with the vegetable/fruit yield or those growing ornamentals turn to inorganic fertilizers.  Those concerned about growing organic, pesticide free vegetables and fruits use only organic fertilizers on edible plants but may or may not use inorganic fertilizers on ornamental plants.  If they use inorganic fertilizers they are careful to not use them where any run-off could contaminate their organically grown fruits and vegetables.

Fertilizers are normally labeled organic if they are organic but inorganic fertilizers don't have any indication that they are inorganic.  There are three numbers on the label in the form of, for example 8-7-6.  This indicates the nitrogen (N)-phosphorus (P)-potassium (K) contents so using the example that fertilizer has 8% N, 7% P and 6% K.  Nitrogen is needed for the growth of leaves; phosphorus is for the growth of roots and fruit development; and potassium is for flower colour and size.  While you could use a general, all-purpose fertilizer (eg. 10-10-10) it is better to tailor the N-P-K to meet the needs of the plant.  If you are growing vegetables, a fertilizer higher in P is preferred for fruiting vegetables (eg. tomatoes, peppers) but a fertilizer higher in N is used for leafy vegetables (eg. lettuces, chards).  If you are growing flowering ornamentals then use a fertilizer with a higher K content.  In addition to N, P and K there are three additional macronutrients needed for healthy plant growth.  They are calcium, magnesium and sulfur (S).  These macronutrients are usually included in fertilizer compounds.  Sometimes the S content is indicated by a fourth number on the label in the form of N-P-K-S.  Fertilizers often contain micronutrients needed for healthy plant growth.  These are boron, chlorine, copper, iron, manganese, molybdenum and zinc.

Happy Gardening!

Garden Gnome
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