Course Content
Crop Production (Unit 6)
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ASRB NET / SRF / Ph.D. Agronomy
Soil Fertility & Fertilizer Use; Essentiality of Plant Nutrients
  1. History of Soil Fertility
  • Ancient Period
    • Early farmers relied on natural fertility (alluvial soils, river plains).
    • Use of farmyard manure (FYM), compost, and green manures practiced in India, China, and Egypt.
    • Kautilya’s Arthashastra (300 B.C.) mentioned use of oil cakes and animal manures.
    • Romans and Greeks used marl, gypsum, ashes as soil amendments.

 

  • Medieval Period
    • Recognition of crop rotation (legumes in sequence for soil fertility).
    • Use of organic amendments continued.
    • In India, texts like Krishi-Parashara highlighted manuring and fallowing.

 

  • Modern Period
    • 17th Century: J.B. van Helmont (1648) – conducted experiments on willow tree growth, wrongly concluded that plant mass comes only from water.
    • 18th Century: Jethro Tull emphasized tillage to release soil nutrients.
    • 19th Century: Major breakthrough with chemistry of plant nutrition.
      • Justus von Liebig (1840): Law of Minimum – yield is proportional to the most limiting nutrient.
      • Development of chemical fertilizers began (superphosphate, ammonium salts, potassium salts).
    • 20th Century: Expansion of fertilizer industry, NPK fertilizers, micronutrient fertilizers.
    • 21st Century: Integrated Nutrient Management (INM), biofertilizers, nano-fertilizers, customized fertilizers.

 

  1. Fertilizer Use – Historical Milestones
  • 1842: Lawes & Gilbert patented superphosphate of lime → first commercial fertilizer.
  • 1861: First NPK fertilizer developed in Germany.
  • 1890–1900: Potash fertilizers from Stassfurt mines, Germany.
  • Early 1900s: Haber-Bosch process developed for synthetic ammonia (basis of nitrogen fertilizers).
  • India:
    • 1906: First fertilizer trial (NPK trial at Coimbatore).
    • 1951: Sindri plant – first ammonium sulfate plant.
    • 1965 onwards: Green Revolution → exponential increase in fertilizer use.
    • Present: India = 2nd largest consumer of fertilizers (after China).

 

  1. Concept of Essentiality of Plant Nutrients
  • Introduction
    • Plants require certain mineral elements for growth, reproduction, and yield.
    • Arnon and Stout (1939) gave the criteria of essentiality.

Criteria of Essentiality (Arnon & Stout, 1939)

  • Indispensability: The element is necessary for normal growth & reproduction; deficiency prevents plant from completing life cycle.
  • Specificity: The element is irreplaceable by another element.
  • Direct involvement: The element must have a direct role in plant metabolism (not just correcting toxic effect).

 

  1. Classification of Plant Nutrients
  • Based on quantity required:
    • Macronutrients (Primary): N, P, K
    • Secondary nutrients: Ca, Mg, S
    • Micronutrients (Trace elements): Fe, Mn, Zn, Cu, B, Mo, Cl, Ni

 

  • Based on function:
    • Constituents of biomolecules: C, H, O, N, S, P
    • Energy transfer: P
    • Enzyme activators/regulators: K, Mg, Mn, Zn, Cu, Cl
    • Structural role: Ca, Si, B
    • Redox reactions: Fe, Cu, Mo

 

  1. Law of Minimum & Law of Restitution
  • Law of Minimum (Liebig, 1840): Plant growth is limited by the most deficient nutrient, even if others are adequate.
  • Law of Restitution: Nutrients removed by crops must be replenished through manures/fertilizers to maintain soil fertility.

 

  1. Current Fertilizer Use Scenario
  • India’s consumption (2023–24): ~ 61 million tonnes (urea largest share).
  • Issues: Imbalanced fertilization (N>P>K = 8:3:1 vs recommended 4:2:1), declining soil fertility, micronutrient deficiencies, low fertilizer use efficiency (30–40% for N).
  • Approach: INM, site-specific nutrient management (SSNM), biofertilizers, slow-release and nano-fertilizers.

 

Important Points: 

  • Remember Arnon & Stout (1939) – criteria of essentiality.
  • Liebig (1840) – Law of Minimum.
  • Lawes & Gilbert (1842) – Superphosphate.
  • First NPK trial in India – 1906 at Coimbatore.
  • Green Revolution (1965) – sharp rise in fertilizer use.
  • Important Facts
  • Kautilya’s Arthashastra (300 B.C.) → mentioned manures and oil cakes.
  • Krishi-Parashara (1000 A.D.) → described crop rotation, manuring.
  • Van Helmont (1648): Mistakenly thought plants’ mass came only from water.
  • Jethro Tull (1731): Emphasized tillage → nutrient release.
  • Justus von Liebig (1840): Law of Minimum.
  • Lawes & Gilbert (1842): Patented Superphosphate of lime → first commercial fertilizer.
  • Haber-Bosch process (1908): Industrial production of synthetic ammonia (basis for N fertilizers).
  • First fertilizer trial in India (1906): NPK trial at Coimbatore.
  • First fertilizer plant in India (1951): Sindri (ammonium sulfate).
  • India today: 2nd largest consumer of fertilizers (after China).
  • Arnon & Stout (1939): Proposed criteria of essentiality.
  • Plant Nutrients (17 Essential Elements)
  • From air & water (non-mineral): C, H, O.
  • Macronutrients: Primary: N, P, K, Secondary: Ca, Mg, S
  • Micronutrients: Fe, Mn, Zn, Cu, B, Mo, Cl, Ni
  • Law of Minimum (Liebig, 1840): Yield is limited by most deficient nutrient.
  • Law of Restitution: Nutrients removed by crops must be replenished.
  • Law of Diminishing Returns: Each additional unit of fertilizer gives less yield increase beyond optimum.
  • Current Issues in Fertilizer Use
  • Imbalanced fertilization (N:P:K = 8:3:1 instead of 4:2:1).
  • Low Fertilizer Use Efficiency (N: 30–40%, P: 15–20%, K: 50–60%).
  • Micronutrient deficiencies (Zn, B, Fe widespread in India).
  • Shift towards Integrated Nutrient Management (INM), biofertilizers, nano-fertilizers.
  • Law of Minimum – Liebig (1840)
  • Criteria of Essentiality – Arnon & Stout (1939)
  • First fertilizer trial in India – Coimbatore (1906)
  • First fertilizer plant in India – Sindri (1951)
  • First commercial fertilizer – Superphosphate (1842)

 

 

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