Robby --- it's just one of the mirco-nutrients essential to plant life ... or any life, for that matter.
About Nutrients
Nutrients are divided into two main groups: non-mineral and mineral.
Non-Mineral Nutrients:
The Non-Mineral Nutrients are hydrogen, oxygen, & carbon.
These nutrients are found in the air and water.
In a process called photosynthesis ("doing things with light"), plants use energy from the sun to change carbon dioxide and water into starches and sugars. These starches and sugars are the plant's food.
Since plants get carbon, hydrogen, and oxygen from the air and water, there is little farmers and gardeners can do to control how much of these nutrients a plant can use.
Mineral Nutrients:
The 13 mineral nutrients, which come from the soil, are dissolved in water and absorbed through a plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers to add the nutrients to the soil.
The mineral nutrients are divided into two groups:
macro nutrients and micro nutrients.
Macro nutrients
Macro nutrients can be broken into two more groups:
primary and secondary nutrients.
The primary nutrients are nitrogen, phosphorus, and potassium. These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.
The secondary nutrients are calcium, magnesium, and sulfur. There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is usually found in sufficient amounts from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.
Micro nutrients
Micro nutrients are those elements essential for plant growth which are needed in only very small (micro) quantities . These elements are sometimes called minor elements or trace elements. The micro nutrients are boron, copper, iron, chloride, manganese, molybdenum and zinc. Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micro nutrients (as well as macro nutrients) to growing plants.
There ... your horticulture lesson for the day ...