Nutrients are defined as the raw materials that are assimilated by living organisms to promote growth, development, and reproduction. The types of nutrients required and the amounts in which they are consumed vary for the different plant and animal species. In general, nutrients include proteins, carbohydrates, fats, inorganic salts and minerals, and water. However, the term ‘nutrients’ is more commonly applied to essential elements such as nitrogen and phosphorus . Plants need at least sixteen essential elements to grow. They utilise oxygen , carbon, and water from air and soil. The primary macronutrients are nitrogen (N), phosphorus (P), and potassium (K). The secondary nutrients include calcium (Ca), magnesium (Mg), and sulphur (S). Micronutrients are absorbed in lesser amounts and include chloride (Cl), boron (B), iron (Fe), manganese (Mn), molybdenum (Mo), copper (Cu), and zinc (Zn). Some plants need some other elements, often called beneficial elements, such as cobalt (Co), nickel (Ni), silicon (Si), sodium (Na), and vanadium (V). Most of these elements are described in other chapters (Chapters 5 and 7); this chapter focuses mainly on nitrogen and phosphorus.