Fertilizers Chemistry : Types of Fertilizers used in agriculture

Fertilizers are compounds or mixtures applied to soil or plants to promote growth by supplying essential nutrients. In chemistry, fertilizers are broadly categorized based on their composition and nutrient content:

Inorganic Fertilizers: These fertilizers are manufactured from synthetic materials or naturally occurring mineral deposits. They are typically water-soluble and provide essential nutrients in forms readily available to plants. Examples include:

Nitrogen fertilizers: such as ammonium nitrate, ammonium sulfate, and urea.

Phosphorus fertilizers: like superphosphate, triple superphosphate, and diammonium phosphate.

Potassium fertilizers: such as potassium chloride, potassium sulfate, and potassium nitrate.

Compound fertilizers: which contain a combination of two or more primary nutrients (N-P-K), often in granular form.

Organic Fertilizers: These fertilizers are derived from natural sources, including plant materials, animal waste, compost, and other organic matter. They release nutrients slowly as they decompose and improve soil structure and fertility. Examples include:

Manure: from animals such as cows, chickens, and horses.

Compost: decomposed organic matter from food scraps, yard waste, and other organic materials.

Bone meal: made from crushed animal bones, rich in phosphorus.

Fish emulsion: derived from fish waste, a source of nitrogen and trace minerals.

Blood meal: dried and powdered animal blood, high in nitrogen.

Liquid Fertilizers: These fertilizers are dissolved in water and applied directly to plants or soil through irrigation systems or foliar spray. They can be either inorganic or organic and provide a quick nutrient boost to plants. Liquid fertilizers may contain a wide range of macro and micronutrients, depending on the formulation.

Slow-Release Fertilizers: These fertilizers are designed to release nutrients gradually over an extended period, providing a steady supply of nutrients to plants and minimizing nutrient leaching. They can be either inorganic or organic and are often coated or encapsulated to control nutrient release rates. Examples include sulfur-coated urea, polymer-coated fertilizers, and controlled-release fertilizers.

Specialty Fertilizers: These fertilizers are formulated for specific crops, soil types, or growth stages and may contain additional nutrients, growth stimulants, or soil amendments. Examples include micronutrient fertilizers, foliar fertilizers, starter fertilizers, and pH-adjusting fertilizers.

Each type of fertilizer has its advantages and limitations, and the choice depends on factors such as crop requirements, soil conditions, environmental considerations, and cost-effectiveness.

 Like living beings, they also need food for the growth of tree plants. In addition to water and air, tree plants also receive food as food. Trees plants take these substances from the ground.

The aqueous solutions of these substances reach the trees by capillary elevation where they are converted into other substances by various metabolic activities.

These other substances become part of tree plants. By continuously growing crops at one place, there is a shortage of those things in which the plants take food as food. In other words, by continuously growing the crop at one place, the fertility of the land there is reduced.

Some chemical substances made by artificial methods are added to the land to meet the shortage of the substances that the trees plant as food. These substances are called fertilizers, artificial manures or chemical manures.

Fertilizers Chemistry

Some of the major nitrogenous fertilizers are:

• Ammonium Sulphate: (NH₄)₂SO₄
• Ammonium nitrate: NH₄NO₃
• Calcium Ammonium nitrate: Ca(NO₃)₂.NH₄NO₃
• Basic Calcium Nitrate (Nitrate of Lime): Ca(NO₃)₂.CaO
• Calcium Cyanamide: CaCN₂
• Urea: NH₂CONH₂

Ammonium sulphate is made by the reaction of ammonia and sulfuric acid.

2NH₃ + H₂SO₄ → (NH₄)₂SO₄

To make ammonium sulphate in commercial quantities, the gypsum is finely ground and ground into water. Thus the NH₃ obtained in the solution or suspension is saturated with NH₃. After this, ammonium salfate is obtained by flowing CO₂.

2NH₃ + CO₂ + H₂O → (NH₄)₂CO₃

CaSO₄ + (NH₄)₂CO₃ → (NH₄)₂SO₄ + CaCO₃

Calcium carbonate is obtained in precipitated form. It is filtered and separated and after concentrating the remaining solution, crystals of ammonium sulfate are obtained.

It is also made from ammonium liqueur in commercial quantities. Ammonium liqueur is obtained as a side product in the process of making coal gas from coal. In this, ammonia gas is obtained by heating water and caustic lime.

2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃ + 2H₂O

• Importance of Biomolecules in Life || What are the 4 main biomolecules?
  
• Resonance effect or mesomeric effect || What is resonance effect with example?
  
• Valency of Elements || How to Find Valency || What is the Valency of the atom?
  
• Glucose Structure: Physical and chemical properties, Glucose Chemical Reaction
  
• Introduction of Inductive-Effect || How does Inductive Effect Work?
  

The ammonia gas thus obtained flows into an aqueous solution of sulfuric acid to obtain ammonium sulfate.

Ammonium sulfate is a white solid. It is soluble in water and contains 21.2% nitrogen and 24% ammonia.

Ammonium Nitrate (NH₄NO3)

It is made by reaction of ammonia obtained by Haber method and nitric acid obtained by Ostward method.

It is a very useful fertilizer.

NH₃ + NHO₃ → NH₄NO₃

Calcium cyanide(CaCN2)

It is made by flowing nitrogen gas on a fine powder of calcium carbide heated at 1100°C.

CaC₂ + N₂ → CaCN₂ + C

A mixture of calcium calcium cyanide and carbon is sold in the market as nitrolim. It is a good and cheap fertilizer. It is added while planting seeds in the ground. Under normal conditions, it reacts with water to form urea.

CaCN₂ + 3H₂O → Ca(OH)₂ + NH₂CONH₂

Urea(NH2CONH2)

Urea is made by reacting commercial quantities of ammonia and carbon dioxide at 125 – 150°C temperature and 200 atmospheric pressure.

2NH₃ + CO₂ → NH₂CONH₂ + H₂O

It is a major fertilizer. It is a white colored crystalline solid. It is soluble in water. It contains 44% nitrogen.

Phosphatic Fertilizers

Phosphorus is an essential ingredient of phosphatic fertilizers. In these, phosphorus is present as phosphate ion. Super phosphate of lime, phosphatic sintered and nitrophosphate are the major phosphatic fertilizers.

Super-Phosphate of Lime

Phosphorite and phosphate rock are the minerals of phosphorus. They mainly contain calcium phosphate. It is not available in water and cannot be used as fertilizer.

They are used to manufacture super phosphate of lime useful phosphatic fertilizer.

• How p-n Junction Diode works : Forward and Reverse Biasing
  
• Semiconductors : How Semiconductor works and Types
  
• X-Rays – Production, Properties, Wavelength and Uses
  
• Daily use Chemical Compounds and Their Properties
  
• Hard Water and Soft Water : Permutit and Anion Exchange Resins
  

Appropriate amounts of sulfuric acid, containing about 70% concentration of fine powder of phosphorite or phosphate rock, are reacted to form the superphosphate of lime. By doing this, a mixture of more soluble calcium di-hydrogen sulfate and calcium sulfate is obtained.

Ca₃(PO₄)₂ + 2H₂SO₄ → 2CaSO₄ + Ca(H₂PO₄)₂

Calcium di-hydrogen phosphate is also called calcium super phosphate or triple super phosphate. Adding appropriate amounts of water to a mixture of calcium di hydrogen phosphate and calcium sulfate. Calcium sulfate is converted into Gypsum(CaSO4.2H2O).

CaSO₄ + 2H₂O → CaSO₄.2H₂O

The mixture of calcium di hydrogen phosphate and gypsum thus obtained is called super phosphate of lime. This is a perfect phosphatic fertilizers.

Phosphatic Slag

The mixture of iron obtained in the form of slag in the metallurgy consists mainly of calcium phosphate and calcium silicate. This mixture is also used as a fertilizer.

Nitrophosphate

Nitrophosphate is made from phosphorite or phosphate rock in the same way as super phosphate of lime. The difference is that instead of sulfuric acid, nitric acid is used to make nitrophosphate. It is a better fertilizer as it provides both nitrogen and phosphorus.

Potash Fertilizers

In order to increase soil fertility, the need of potassium element in addition to nitrogen and phosphorus is also important. The fertilizer or fertilizer mixture in which the presence of these three elements is ensured is called NPK fertilizer.

Potassium nitrate, potassium chloride and potassium sulfate are the major potash fertilizers.