Soil Fertility and Nutrient Management Point Wise Notes for Competitive exam

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Soil Fertility

AB Stewart laid the foundations of soil fertility research in India.

Lawes was the first person to manufacture a fertilizer, he manufactured SSP.

• First fertilizer factory setup in India at Ranipur in the year 1906.

• Quantity of plant nutrients depleted annually from Indian soils is 8-10 MT of N+P2O5+K2O.(Soil Fertility)

• In recent soil sample analysis in India 43% deficient in Zinc, 33% deficient in B, 15% deficient in Iron, 6% deficient in Manganese, 4% deficient in Copper.

• Nutrient deficiencies are found to be in the order N = P > Zn = S > B > K = Fe > Mn > Cu.

Mineral nutrient refers to inorganic ion obtained from the soil and required for plant growth.

• The process of absorption, translocation and assimilation of nutrients by the plants is known as mineral nutrition.

• Plants need 16 elements for their growth and completion of life cycle.

Ni is the nutrient considered essential for plant growth in addition to 16 nutrients.(Soil Fertility)

• In addition, four elements viz., sodium, cobalt, vanadium and silicon are absorbed by some plants for special purposes.

• All these essential elements are not required for all plants, but all have been found essential for one plant or the other.

• All carbon atoms and most of the oxygen atoms are derived from carbon dioxide which is assimilated principally in photosynthesis.

• Approximately one-third of oxygen atoms in organic material in higher plants are derived from soil water and two-thirds from carbon dioxide of the atmosphere.

C, H, O are not minerals.(Soil Fertility)

• Rest of the elements are absorbed from the soil and these are are called mineral elements since they are derived from minerals.

Arnon and stout (1939) proposed criteria of essentiality which was refined by Arnon (1954).

• Criteria of essentiality of an element are

1. Plants cannot complete vegetative or reproductive stage of life cycle due to its deficiency.

2. When this deficiency can be corrected or prevented only by supplying this element.

3. When the element is directly involved in the metabolism of the plant.(Soil Fertility)

• According to criteria of essentiality, sodium is considered as nonessential.

• However, sodium increases yield of several crops like sugar beets, turnips and celery.

Nicholas (1961) proposed the term functional nutrient for any mineral element that functions in plant metabolism whether or not its action is specific.

Sodium, cobalt, vanadium and silicon are also considered as functional nutrients in addition to 16 essential elements.

C, H and O which constitute 96 per cent of total dry matter of plants are considered as basic nutrients.

• C and O constitute 45 per cent each of the total dry matter.

• Nutrients required in large quantities are known as macronutrients (N, P, K, Ca, Mg and S).

• N, P and K are called primary nutrients.

• Ca, Mg and S are known as secondary nutrients.

• Secondary nutrients are inadvertently applied to the soils through N, P and K fertilizers which contain these nutrients.(Soil Fertility)

• Nutrients which are required in small quantities are known as micronutrients or trace elements (Fe, Zn, Cu, B, Mo and Cl).

Micronutrients are very efficient and minute quantities produce optimum effects.

• N, P, S, B, Mo and Cl are non-metals.

FUNCTIONS OF NUTRIENTS

• C, H and O are the elements that provide basic structure to the plant.

• N, S and P are useful in energy storage, transfer and bonding.

• N, S and P are accessory structural elements which are more active and vital for living tissues.(Soil Fertility)

• K, Ca and Mg are necessary for charge balance. They act as regulators and carriers.

• Fe, Mn, Zn, Cu, B, Mo and Cl are involved in enzyme activation and electron transport. They act as catalysers and activators.

• Basic nutrients C, H and O are constituents of carbohydrates and several biochemical compounds.

Nitrogen is a constituent of proteins, enzymes, hormones, vitamins, alkaloids, chlorophyll etc.

Phosphorus is a constituent of sugar phosphates, nucleotides, nucleic acids, coenzymes and phospholipids.

• Process of anabolism and catabolism of carbohydrates proceed when organic compounds are esterised with phosphoric acid.

Potassium is not a constituent of any organic compound.

• Potassium is required as a cofactor for 40 or more enzymes.

• Potassium controls movement of stomata and maintains electroneutrality of plant cells.(Soil Fertility)

Sulphur is a constituent of several amino-acids and fatty acids.

Calcium is a constituent of cell wall as calcium pectate.

• Calcium is required as a cofactor in hydrolysis of ATP and phospholipids.

Magnesium is a constituent of chlorophyll.

• Magnesium is required in several enzymes involved in phosphate transfer.

• Iron is a constituent of various enzymes like cytochrome, catalase and plays the part of a vital catalyst in the plant.

• Iron is a key element in various redox reactions of respiration, photosynthesis and reduction of nitrates and sulphates.

Manganese is a constituent of several cation activated enzymes like decarboxylases, kinases, oxidases etc.

• Manganese is essential for the formation of chlorophyll, reduction of nitrates and for respiration.

• Copper and Zinc are involved in cation activated enzymes.

Boron helps in carbohydrate transport.(Soil Fertility)

Boron is necessary for the germination of pollen, formation of flowers and fruits and for the absorption of cations.

Molybdenum is required for the assimilation of nitrates as well as for the fixation of atmospheric nitrogen.

Chlorine is involved in reaction relating to oxygen evolution.

• Co, Se are the elements that need to be applied to forage crops from the viewpoint of animal nutrition.

Cobalt is essential for the synthesis of vitamin B12.

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