(i) Macronutrients These are generally present in plant tissues in large amount (in excess 10 m mole of dry matter). The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium and magnesium.
(ii) Macronutrients Micronutrients or trace eleifients, are needed in very small amount (less than 10m mole of dry matter). These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.
(iii) Beneficial nutrients The elements which are not essential for plants, hut their presence are beneficial for the growth and development. Such, element are called beneficial elements.
(iv) Toxic elements Any mineral ion concentration in tissues, that reduces the dry weight of tissues by about 10% is considered toxic. For example, Mn inhibit the absorption of other elements.
(v) Essential elemehts The macronutrients including carbon, hydrogen,oxygen, nitrogen,
phosphorus, sulphur, potassium, calcium and magnesium, which are required directly for the growth and metabolism of the plants and whose deficiency produces certain symptoms in fhe plants are known as essential elements.