Soil Fertility & Fertilizer Use; Essentiality of Plant Nutrients
- 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.
- 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).
- 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).
- 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
- 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.
- 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)