Garden Tips
Plant Nutrition and Fertilization

December 2009
By Sally Pfeifer

Many people confuse plant nutrition and plant fertilization. Nutrition refers to the plant's needs and uses of basic chemical elements. Fertilization is the term used when these materials are supplied to the environment around the plant. A lot must happen before a chemical, supplied in a fertilizer, can be taken up and used by the plant. Reading up on Plant Physiology can help improve our gardens.

Plants need 17 elements for normal growth. Among these, carbon, hydrogen, and oxygen are found in air and water. Nitrogen, potassium, magnesium, calcium, phosphorus, and sulfur are found in the soil.

Testing the soil in our garden beds is a good place to start. Then we know what we are dealing with. After finding out what the soil needs, we can add fertilizer and composts. If you want to add general compost and fertilizers, you can get them at a garden center.

All fertilizers are labeled with three numbers that indicate the guaranteed analysis or grade of the major nutrients: nitrogen (N) for green leaves, phosphorus (P) for flowers and potassium (K) for the general well being of the plant. For example, a 10-10-10 ratio indicates a balanced fertilizer.

If your soil testing says you need more nitrogen, buy the fertilizer with the most nitrogen , e.g., 20-10-10. If your test says you need more phosphorus, look for a high number in the middle, e.g., 10-20-10. For more potassium, you might want a 10-10-20.

Note: You can find soil testing kits at local garden centers. Uconn's Soil Nutrient Analysis Laboratory ( also provides information on soil testing.
In addition, several times each year the Laboratory offers free soil pH testing along with limestone recommendations to the general public. Bring ½ cup of soil for a free pH test to The Connecticut Flower and Garden Show in Hartford, February 19 – 22, 2009.

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