Fertilizers Explained

Proper nutrition has long been touted as one of the keys to a long and healthy life. Interestingly, that’s as true of plants, trees, flowers and lawns as it is of people.

The main elements involved in proper plant nutrition are nitrogen (N), phosphorus (P) and potassium (K). Package labels indicate the ratio of the 3 main elements nitrogen, phosphorous and potassium. N-P-K is expressed in percentages: For example 10-6-6 contains 10 per cent nitrogen, 6 per cent phosphorus and 6 per cent potassium. These 3 elements each perform a specialized job.

Nitrogen: Promotes leafy growth and green colour.. Organic sources include blood meal, fishmeal.

Phosphorus: Promotes root growth and seed development. Organic sources include bone meal and mineral phosphates.

Potassium: Helps develop strong stems and roots and increases disease resistance. Organic sources include kelp and wood ash.

In addition to these primary elements which also include sulphur, magnesium and calcium, many fertilizers contain a variety of minerals such as iron, manganese, boron, zinc, copper, molybdenum, chlorine, nickel, sodium, cobalt and silicon. These are also essential for healthy plant growth and development.

Selecting a Fertilizer

There are various types of fertilizers available on the market. They include:

Balanced fertilizers - containing N, P and K.

Weighted fertilizers - NPK proportions are weighted heavily in favor of one or two of these to promote specific growth  

Specialty fertilizers - specially formulated for certain plants such as rose food, rhododendron and azalea food

Organic natural fertilizers break down slowly and naturally as in blood meal, cottonseed meal, and fish fertilizer

Slow-release fertilizers break down over extended periods and provide longer term benefits.

Points to remember when selecting your fertilizer.

Water-soluble fertilizers are quickly absorbed by plants' roots and also absorbed through the leaves. The disadvantage is that this application has a short term and immediate effect and consistent feeding is required.

Never apply fertilizer to a plant under water stress (when the soil is completely dry). Water plants before feeding. This is extremely important when using water-soluble products with very high nitrogen content like a 15-30-15 or 20-20-20.

Organics tend to be more environmentally friendly than chemical fertilizers. They are also less likely to burn plants and they improve overall soil condition. However, organic fertilizers are slower-acting, more bulky, and inclined to cost more than chemical fertilizers.

The advantages of chemical fertilizers are that they usually pack more of a nutrient punch, work faster and cost less. Unfortunately, chemical fertilizers burn plants more easily than the organic products and must be applied carefully and according to directions of the manufacturers label.

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