The mineral elements are usually classified into two categories:
(1) macronutrients and (2) micronutrients.
These elements are required in large amounts and form the plant constituents, constitute from 0.5% to 3.0% of the dry weight of the plant. Macronutrients include CARBON, HYDROGEN, OXYGEN, NITROGEN, PHOSPHORUS, POTASSIUM, CALCIUM, MAGNESIUM and SULPHUR.
These elements form an integral part of complex organic molecules and some of these elements help in the functioning of enzyme systems. If these essential elements are deficient in the soil, then the plants exhibit characteristic symptoms of the deficiency.
Carbon (C), Hydrogen (H) and Oxygen (O)
These are essential for plant growth and make up 96% of the weight of a plant.
Nitrogen is an essential constituent of proteins, nucleic acids, chlorophyll. Nitrogen is present in the atmosphere as an inert substance. It is brought to the soil and converted to soluble nitrates either by asymbiotic or symbiotic nitrogen fixation. Its deficiency causes relatively uniform loss of color in leaves and reduces lateral breaks. Nitrogen Deficiency appears first on older growth.
Phosphorus (P) and sulphur (S) are derived from rocks during weathering.
It is essential for respiration and cell division. It Promotes root formation and growth and highly mobile in plant. With its deficiency plants stunted and leaves appear to be darker green than normal.
Sulphur or Sulfur (S)
It is structural component of some amino acids; not mobile in plant; and contributes to smell and taste of vegetables. Sulphur deficiency symptoms are: leaves appear to be pale green with dead spots; yellowing of the young leaves; veins lighter in color than the adjoining area; roots and stems are small
It activates some enzymes and be a part in the synthesis, besides promoting the disease resistance of plants. Magnesium is mobile within plants. Deficiency symptoms of Magnesium are: yellowish or reddish color of leaves while veins of leaves remain green; leaf margins may curl; appearance of dead spots on leaves
It activates enzymes; concentrates in meristems. Potassium is highly mobile in plants. Plants with adequate potassium can help them overcome drought stress and winter hardiness. It also helps plants by increasing disease resistance and strengthening cell walls structure. Deficiency symptoms of Potassium are: yellowing of leaves; shortened internodes; dead spots on older leaves and often mottled
Calcium mobility in plants is limited. Calcium is an essential part of middle lamella and involved in movement of substances through cell membranes. Calcium is essential element for the growth of shoot and root tips. It reduces the toxicity of aluminum and manganese in plant roots. Deficiency symptoms of Calcium are: inhibition of bud growth, as terminal bud often found dead; young leaves often appear to be hooked at tip; tips and margins of leaves are dried up and dead; roots can turn rot or dead.