Fertilizers

1. Introduction

Fertilizers are chemical substances that supply essential plant nutrients directly or indirectly to improve soil fertility and crop productivity. They are a major component of modern agriculture, enabling higher yields per unit area by providing readily available nutrients to plants.

Fertilizers differ from manures in that they are manufactured or mineral-based, have higher nutrient content, and are readily available to crops.

2. Definition

• Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to the soil to supply one or more essential nutrients required for plant growth.
• FAO Definition: “Fertilizers are natural or manufactured materials containing one or more essential plant nutrients that are used for their growth and productivity.”

3. Importance of Fertilizers

• Increase crop yield and productivity.
• Correct soil nutrient deficiencies.
• Promote balanced plant nutrition.
• Improve the quality of agricultural produce (e.g., protein in cereals, oil in oilseeds).
• Essential for intensive cropping systems.
• Support food security through enhanced agricultural output.

4. Difference Between Manures and Fertilizers

5. Classification of Fertilizers

Fertilizers can be classified based on several criteria:

• Based on Nutrient Composition
• Straight Fertilizers: Supply only one primary nutrient. Examples: Urea (N), Single Super Phosphate – SSP (P), Muriate of Potash – MOP (K)
• Complex Fertilizers: Contain two or more primary nutrients chemically combined. Examples:  Diammonium Phosphate (DAP) – N & P, Nitro-Phosphate – N & P, Ammonium Phosphate Sulphate – N & P
• Mixed Fertilizers: Physical mixtures of two or more straight fertilizers. Example: NPK mixtures (e.g., 15:15:15 or 20:20:0)

• Based on Nutrients Supplied

Based on Manufacturing Origin

• Inorganic (Chemical) Fertilizers – Manufactured industrially (e.g., urea, SSP).
• Organic Fertilizers – Derived from natural sources (e.g., bone meal, compost).
• Biofertilizers – Contain living microorganisms (e.g., Rhizobium, Azotobacter).

• 6. Major Types of Fertilizers

Nitrogenous Fertilizers

These fertilizers supply nitrogen (N), essential for vegetative growth and chlorophyll formation.

Notes:

• Nitrogen promotes leaf and stem growth.
• Nitrogen deficiency causes yellowing (chlorosis) of leaves.

• Phosphatic Fertilizers

Supply phosphorus (P), important for root development, energy transfer (ATP), and seed formation.

Notes:

• P deficiency causes stunted growth and purpling of leaves.
• SSP also supplies sulfur, beneficial for oilseed crops.

• Potassic Fertilizers

Supply potassium (K), which regulates water balance, enzyme activation, and disease resistance.

Notes:

• K deficiency causes scorching of leaf margins (“leaf burn”).
• Essential for fruit and seed quality.

• Secondary Nutrient Fertilizers

• Micronutrient Fertilizers

Fertilizer Control Order (FCO) – 1985

• Regulates the quality, manufacture, sale, and distribution of fertilizers in India.
• Specifies standards for nutrient content and labeling.
• Ensures quality control through authorized laboratories.

Summary Table of Common Fertilizers