Fertilizers

Dr. Mudassar Altaf, Associate Professor of Chemistry, Department of Higher Education, Government of the Punjab, Pakistan

Contents:

• Definition of fertilizer
• Fertilizers of ammonium salts
• Fertilizers of nitrate salts
• NPK fertilizer
• Nitrogen, potassium, phosphorous roles in plants growth

Fertilizer: Definition

 “The natural or manufactured substance added to soil for supplying essential nutrients to plants required for their healthy growth”are called fertilizers. These substances enhance the fertility of the plants, trees, and crops; hence, a better yield of crops, fruits and flowering is obtained.

Fertilizers of Ammonium Salts:

There are various ammonium salts that are manufactured in industries as fertilizers. These are the sources of nitrogen, an essential element for amino acids and proteins. These are:

• Ammonium nitrate NH₄NO₃: It provides 35% nitrogen; and having its appearance of white or grayish-white spherical prills (beads, granular).
• Ammonium sulphate (NH₄)₂SO₄: It provides 21% nitrogen; and having its appearance of white or off-white granules or crystals.
• Ammonium chloride NH₄Cl: This fertilizer provides 26% nitrogen; and available in white or slightly-yellow granules or crystals.  
• Ammonium phosphate NH₄​H₂​PO₄​: This is also called ‘monoammonium phosphate (MAP)’; it provides 11% nitrogen; and available in white, off-white, grey, or brown spherical prills.
• Diammonium phosphate (NH₄​)₂​HPO₄​: This is also called ‘diammonium phosphate (DAP)’; it provides 18% nitrogen; and available in yellow, black, light or dark brown grains due to raw material impurities.

Fertilizers of Nitrate Salts:

These fertilizers contain nitrates (NO₃^–) ion in their salts which are the sources of nitrogen for plants. These are:

• Ammonium nitrate NH₄NO₃.
• Calcium nitrate Ca(NO₃)₂.
• Calcium ammonium nitrate (CAN); it is a mixture of CaCO₃ and NH₄​NO₃.
• Sodium nitrate NaNO₃; also known as Chile saltpeter.  Its etymology is Latin ‘sal’ meaning ‘salt’ and ‘petra’ meaning ‘rock’. Chile is a country in south America; because, it was obtained historically from this region. So, it gives meaning of ‘salt rocks of Chile’.
• Potassium nitrate KNO₃.

NPK Fertilizer:

It is a mixture of nitrogen, phosphorus, and potassium. NPK is a mixture of various salts to fulfill the needs of these elements. For example, urea [CO(NH₂)₂], DAP and potassium chloride (KCl) in various ratio.

Roles of N, P & K in Plants’ Growth:

• Nitrogen: It promotes chlorophyll synthesis in leaves.
• Phosphorus: It is essential for seed formation, flowering and root growth.
• Potassium: It is important for water regulation, disease resistance, and plant strength.