The essential elements can be divided into macronutrients and micronutrients. Nutrients that plants require in larger amounts are called macronutrients. About half of the essential elements are considered macronutrients: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. The first of these macronutrients, carbon (C), is required to form carbohydrates, proteins, nucleic acids, and many other compounds; it is, therefore, present in all macromolecules. On average, the dry weight (excluding water) of a cell is 50 percent carbon, making it a key part of plant bio-molecules. Micronutrients: are needed in very small amounts. Their adequate concentrations in plants are generally below the 100 parts per million (ppm) level. The essential micronutrients are zinc (Zn), iron (Fe), manganese (Mn), boron (B), chlorine (Cl), copper (Cu), molybdenum (Mo), cobalt (Co), vanadium (V), sodium (Na), and silicon (Si). Deficiencies of the last four minerals are very rare. Sodium is probably essential for only a few plants indigenous to saline soils. Silicon may be considered more of a secondary or macronutrient but it is ―quasi-essential in that it has been shown to enhance growth in certain laboratory experiments but plants grown in its absence still thrived. Silicon is second only to oxygen in its abundance in soil because most soil mineral are silicates or aluminosilicates.

Source: Shankar IAS