Plants require 16 essential nutrients to grow. These are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), Iron (Fe), manganese (Mn), boron (B), molybednum (Mo), copper (Cu), zinc (Zn) and chlorine (Cl). Carbon, Hydrogen and Oxygen are mostly derived from light and water, and therefore we have very little control over them. The others are obtained primarily from soil. Often the soil does not hold enough of these nutrients in the quantities required. Furthermore, these nutrients may have been leached away by water, or used up by previous plantings. As a result, the nutrients in your soil may need periodic replacement through the use of fertilizer.
WHAT IS FERTILIZER?
Any material that replaces one or more of the required nutrients can be considered a fertilizer. Fertilizers are often classified as being either organic or inorganic. Organic fertilizers are derived from living or once living material, while Inorganic ones are usually comprised of man-made compounds.
Fertilizers come in many different chemical compositions. They can be identified by examining the 3 numbers that are written on the label. These numbers identify the percentage of Nitrogen (N), Phosphorus (P) and Potassium (K) contained within the product. The rest of the product may contain some of the other essential nutrients and filler material.
WHICH FERTILIZER DO I WANT?
For best results, you must choose a fertilizer that best matches its intended application. That is, it contains the most appropriate mix of the N - P - K nutrients. Each of these nutrients assists plant growth in a different way:
Is the main nutrient for new, green growth. Plants that are almost all leaf (such as lawn grasses) need plenty of nitrogen, so the first number is especially high in fertilizers for lawns because grass must continously renew itself after mowing. The higher the number, the more nitrogen the fertilizer provides.
Promotes root development which helps strengthen plants. It also increases blooms on flowers. Lots of phosphorous is great for bulbs, perennials, and newly planted trees and shrubs. They depend on strong roots, so fertilizers meant for these plants often have high middle numbers.
This nutrient enhances the overall growth and health of plants and aids in process of flowering. It helps plants withstand very hot or cold weather and defend against diseases. Fertilizers meant for fall, such as Winterizer, also contain extra potassium to help prepare plants for cold weather.