We all know that our crops and plants need a number of different chemical elements to grow and thrive well and luxuriantly. The most important are:crop picture
* Carbon, hydrogen and oxygen – Available from air and water and therefore in plentiful supply
* Nitrogen, phosphorus, potassium (a.k.a. potash) – The three macronutrients and the three elements you find in most packaged fertilizers
* Sulfur, calcium, and magnesium – Secondary nutrients
* Boron, cobalt, copper, iron, manganese, molybdenum and zinc – Micronutrients
Nitrogen, phosphorus and potassium are needed in the largest quantity by a plant. They are important because they are necessary for these basic building blocks. For example:
* Every amino acid contains nitrogen.
* Every molecule making up every cell’s membrane contains phosphorous (the membrane molecules are called phospholipids), and so does every molecule of ATP (the main energy source of all cells).
* Potassium makes up 1 percent to 2 percent of the weight of any plant and, as an ion in cells, is essential to metabolism.

Without nitrogen, phosphorus and potassium, the plant simply cannot grow. If any of the macronutrients are missing or hard to obtain from the soil, this fertilizer manwill limit the growth rate for the plant. In nature, the nitrogen, phosphorous and potassium often come from the decay of plants. The recycling of nitrogen from dead to living plants is the only source of nitrogen in the soil.
The goal of fertilizer is to make plants grow faster. We can supply the elements that the plants need in readily available forms to meet the plants need. Most fertilizers just supply nitrogen, phosphorus and potassium because their availability has the big limitation to growth. And the other chemicals are needed in much lower quantities and are generally available in most soils.
The numbers on a bag of fertilizer tell us the percentages of available nitrogen, phosphorus and potassium found in the bag. So 12-8-10 fertilizer has 12-percent nitrogen, 8-percent phosphorous and 10-percent potassium. In a 100-pound bag, therefore, 12 pounds is nitrogen, 8 pounds is phosphorous and 10 pounds is potassium. The other 70 pounds is known as ballast and has no value to the plants. Plants are factories that do all of the work to process the basic elements of life and make them available to us.