मृदा उर्वरता एवं उर्वरक प्रौद्योगिकी

Copper deficiency causes the growing tips of young leaves to turn bleached and white, known as 'white tip' or 'reclamation disease'.

• Iron - Mottled yellow green leaves with yellowish vein: Iron deficiency produces interveinal chlorosis where veins remain distinctly green.
• Potassium - Chlorosis starting from leaf tip: Potassium deficiency causes marginal necrosis and scorching starting from margins of older leaves.
• Sulphur - Mottled yellow green leaves with green veins: Sulphur deficiency produces uniform pale yellowing of young leaves without distinct green reticulation.
• Copper - Youngest leaves have white tip: Copper deficiency results in chlorosis, rolling, and terminal bleaching of young leaves, causing characteristic white tips in cereals.

The term 'Functional Nutrient' was coined by D. J. D. Nicholas in 1961.

• Arnon and Stout (1939): Proposed the classic 'Criteria of Essentiality' of plant nutrients.
• Finck (1982): German soil scientist noted for textbook contributions on plant nutrition and fertilizer classification.
• Bray (1948): Proposed the nutrient mobility concept and formulated Bray-1 and Bray-2 extractants for soil phosphorus.
• Nicholas (1961): D. J. D. Nicholas (1961) proposed the concept of functional nutrients to include mineral elements that perform a metabolic role, expanding beyond essential nutrients to include beneficial elements like Co, Na, Si, and V.

An N:S ratio of 16:1 is the universally accepted critical threshold for differentiating sulfur-deficient from sulfur-sufficient plants.

• 10:1: Indicates luxury sulfur consumption relative to nitrogen.
• 20:1: Indicates severe sulfur deficiency limiting protein synthesis.
• 16:1: Critical boundary ratio; plant tissues with N:S > 16:1 are diagnosed as sulfur-deficient, while values <= 16:1 indicate adequacy.
• 12:1: Standard tissue ratio typical of high-sulfur requiring cruciferous crops.

• Calcium deficiency causes hypocalcemia (milk fever or parturient paresis) in dairy cattle.
• Magnesium deficiency causes hypomagnesemia (grass tetany / grass staggers).
• Hypokalemia is an electrolyte disturbance in animals caused by deficiency or subnormal blood serum concentrations of Potassium (K+), leading to muscle weakness, recumbency, and cardiac dysfunction.
• Copper deficiency causes swayback / enzootic ataxia in sheep.