Match List-I with List-II
List-I (Theory proposed)

Correct option is A

[a]-(II), [b]-(IV), [c]-(I), [d]-(III)
Correct matching: Option (a)
Explanation of correct pairs:
· (a) Contact exchange → Jenny and Overstreet (II)
· Explains ion exchange occurring when plant roots come in direct contact with soil colloids.
· Important in understanding nutrient uptake at the root–soil interface.
· (b) Air capacity of soil → Khonke (IV)
· Khonke emphasized soil physical properties related to aeration, including air capacity.
· Air capacity affects root respiration and microbial activity.
· (c) Mobility of nutrients → Bray (I)
· Bray classified nutrients based on their mobility in soil (mobile, moderately mobile, immobile).
· Helps guide fertilizer placement and management.
· (d) Growth factor and yield → Mitscherlich (III)
· Mitscherlich’s law relates crop yield to the availability of growth factors (nutrients).
· Yield increases diminish as the limiting factor approaches sufficiency.
❌ Why other options are incorrect
· Option (b): Misassigns contact exchange and growth–yield relationships.
· Option (c): Incorrectly links mobility of nutrients and growth factor theories.
· Option (d): Swaps key author–theory pairs (e.g., Mitscherlich).
�� Key Points to Remember
· Jenny & Overstreet → Contact exchange
· Khonke → Air capacity of soil
· Bray → Nutrient mobility
· Mitscherlich → Growth factor and yield