Nutrient Management in Agriculture

Why Nutrient Management Matters

Plants, like humans, require a balanced diet.
Out of all substances available in soil, air, and water, only 17 elements are essential plant nutrients—meaning the plant cannot complete its life cycle without them.

These nutrients are divided into:

• Macronutrients (9) → required in large quantities
• Micronutrients (8) → required in trace amounts (less than 1% of plant dry weight)

Poor nutrient management leads to:

• Low yields
• Soil degradation
• Environmental pollution
• Economic inefficiency

Hence, nutrient management is a core pillar of sustainable agriculture.

Macronutrients: The Primary Nutrient Requirements

List of Macronutrients (9)

• Carbon (C), Hydrogen (H), Oxygen (O)
• Nitrogen (N), Phosphorus (P), Potassium (K) → Primary nutrients
• Calcium (Ca), Magnesium (Mg), Sulfur (S) → Secondary nutrients

Source of Macronutrients

• C, H, O → obtained mainly from CO₂ and water
• Remaining nutrients → absorbed from the soil as mineral nutrition

Among all, NPK (Nitrogen–Phosphorus–Potassium) are the most critical for crop productivity.

Role of Major Macronutrients

Carbon (C), Hydrogen (H) and Oxygen (O)

• Form the structural backbone of proteins, carbohydrates, starch, and cellulose
• Photosynthesis converts CO₂ into carbohydrates
• Hydrogen from water is essential in photosynthesis
• Oxygen is required for cellular respiration, especially at night

Nitrogen (N): The Growth Driver

Nitrogen has received maximum attention because:

• It is easily converted into soluble forms (nitrates, nitrites)
• It shows immediate yield response

Functions

• Fundamental component of: Proteins, Amino acids, Hormones, Chlorophyll
• Promotes rapid vegetative growth and healthy green colour

Sources

• Soil organic matter
• Absorbed by plants as NH₄⁺ (ammonium) and NO₃⁻ (nitrate)
• Legumes fix atmospheric nitrogen biologically

Fertiliser Source: Urea

• Urea (CO(NH₂)₂) has the highest nitrogen content among solid fertilisers
• Low transportation cost per unit nitrogen
• Breaks down in soil to form ammonium

Nitrogen Deficiency

• Slow growth
• Pale leaves (chlorosis)
• Reduced chlorophyll
• Occurs when soil microbes consume nitrogen to decompose high-carbon material

Phosphorus (P): The Energy Manager

Functions

• Essential for ATP formation (energy currency of plants)
• Stimulates:
  • Early root development
  • Nitrogen fixation in legumes
  • Flowering and maturity
• Improves grain and fruit quality
• Strengthens stalk and stem

Deficiency

• Stunted growth
• Weak plants

Source

• Superphosphate (from rock phosphate + sulfuric acid)
• Present in all organic manures

Potassium (K): The Stress Protector

Functions

• Increases resistance to: Diseases, Pests, Drought and temperature stress
• Regulates:
  • Stomatal opening and closing
  • Water uptake and osmosis
• Prevents lodging in cereals
• Improves fruit quality and carbohydrate transport

Deficiency

• Plants lodge or bend near the ground
• Poor grain filling

Source

• Potassium chloride (KCl)
• Potassium sulphate (K₂SO₄)

Secondary Macronutrients

Calcium (Ca)

• Cell division and root growth
• Pollen growth and prevention of leaf fall
• Sources: Lime, gypsum, dolomite, superphosphate

Magnesium (Mg)

• Core component of chlorophyll
• Enzyme activation in respiration and photosynthesis
• Phosphate transport within plants
• Sources: Dolomite, magnesite, Epsom salt

Sulfur (S)

• Component of amino acids and vitamins
• Root growth and seed formation
• Responsible for odour compounds in plants
• Sources: Gypsum, elemental sulfur, ammonium sulfate, organic matter

Micronutrients: Small Quantity, Big Impact

Micronutrients (8)

• Iron (Fe), Copper (Cu), Zinc (Zn), Manganese (Mn)
• Boron (B), Molybdenum (Mo), Nickel (Ni), Chlorine (Cl)

Key Functions

• Iron → Chlorophyll formation, protein synthesis
• Manganese → Photosynthesis and growth
• Copper → Respiratory enzymes
• Zinc → Hormones for stem and leaf expansion
• Boron → Cell wall formation and calcium use
• Molybdenum → Nitrate reductase; nitrogen fixation in legumes
• Nickel → Prevents toxic urea accumulation
• Chlorine → Osmotic balance, stomatal regulation, disease resistance

Micronutrient deficiency is now widespread due to fertiliser imbalance.

Fertiliser Subsidy Regime in India: Read Here.