Get to Know Your Fertilizer

Did you know that there are 16 chemical elements that are absolutely essential for plant growth? The six most important elements are carbon, hydrogen, oxygen, nitrogen, phosphorous, and potassium.

The first three, carbon, hydrogen and oxygen, come from the air and water; the next three, nitrogen, phosphorus and potassium can be found in fertilizers. On the labels of many fertilizers you’ll see these three elements listed numerically by their percentage, and always in the same order. A label reading 20-40-35, for example, would mean 20 percent nitrogen, 40 percent phosphorus, 35 percent potassium. Fertilizers are rated by the ratio of these essential elements. To be considered a fertilizer there must be a minimum of 5 percent of one of these elements. If there is less than 5 percent total pure elemental Nitrogen, Phosphorus, or Potassium then the substance is considered a soil amendment.

Fertilizers consist of two main categories, natural fertilizers that come from substances such as bone meal or bat guano, and man made fertilizers that have been synthetically created.

Nitrogen
Nitrogen gives a deep, green color, and helps above-ground growth. Nitrogen deficiencies in the soil can usually be spotted by yellowing and wrinkling.

Phosphorus
Phosphorus is responsible for all areas of plant growth but is most commonly used to increase disease resistance. The usual visual signs of a lack of phosphorus are a deepening of the green color on the lower part of the plant, or a reddening.

Potassium
Potassium, or potash, is the third major nutrient. Its content usually increases in soils from East to West. It helps plants resist disease, manufacture oils and survive climactic changes. Potash deficiency is usually notes by brown edges.