Question

E value was given by _______

• A. Larsen
• B. Russel
• C. Fried and Dean
• D. Beer and Lambert

Hint:

To remember the isotopic values: 1. "L-value" $\to$ Larsen (measures exchangeable P with plants). 2. "A-value" $\to$ Fried & Dean (measures P availability using fertilizers). 3. "E-value" $\to$ Russel (measures exchangeable P in laboratory suspensions without plants).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Radioisotopes are used in soil chemistry to measure the quantity of nutrients that can be exchanged between the soil solid phase and the soil solution.
Various index values, such as the L-value, A-value, and E-value, represent different pools of available phosphorus.

Step 2: Detailed Explanation:
Let us differentiate the isotopic exchange concepts:
L value: Proposed by Larsen in 1952.
It represents the quantity of soil phosphorus that is exchangeable with added radioactive phosphorus ($^{32}\text{P}$) in a soil-plant system during plant growth.
A value: Proposed by Fried and Dean in 1952.
It measures the plant-available nutrient pool based on the assumption that a plant will absorb nutrients from the soil and added fertilizer in proportion to their availability.
E value: Proposed by Russel (Russel et al., 1954).
It represents the quantity of isotopically exchangeable phosphorus measured in-vitro (in laboratory suspension, without plants) by equilibrating the soil with a carrier-free $^{32}\text{P}$ solution.
Beer and Lambert (D): Proposed the law relating light absorption to the concentration of absorbing species in spectrophotometry.
Therefore, the E-value was proposed by Russel.

Step 3: Final Answer:
The E-value was proposed by Russel, which corresponds to option (B).