Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): NBPT (N-(n-butyl) thiophosphoric triamide) (commercial name Agrotain\textregistered) is a widely used urease inhibitor.
Reason (R): It competes for active sites on the urease enzyme and ties up activity for about 25 days.
In light of the above statements, choose the correct answer from the options given below:
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Urease inhibitors like NBPT are highly beneficial in conservation tillage and no-till systems where urea cannot be incorporated into the soil immediately after application.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
(A) is true but (R) is false.
(A) is false but (R) is true.
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The Correct Option isA
Solution and Explanation
Step 1: Understanding the Concept:
When urea is applied to the soil, it is rapidly hydrolyzed into ammonia and carbon dioxide by the soil enzyme urease.
This rapid hydrolysis can lead to significant nitrogen losses through ammonia volatilization, especially when urea is broadcast on the soil surface.
Urease inhibitors are compounds added to urea to temporarily slow down this enzymatic hydrolysis. Step 2: Detailed Explanation:
Let us evaluate Assertion (A):
NBPT (N-(n-butyl) thiophosphoric triamide), commercially sold under the trade name Agrotain\textregistered, is the most widely used and successful chemical urease inhibitor in agriculture.
It is coated onto urea granules to slow down the action of the urease enzyme.
Thus, Assertion (A) is true.
Let us evaluate Reason (R):
NBPT is a structural analog of urea.
It binds to the active site of the urease enzyme, acting as a competitive inhibitor.
By blocking the active site, it temporarily disables the enzyme, delaying urea hydrolysis for up to 14 to 25 days.
This delay allows rainfall or irrigation to wash the urea deeper into the soil profile, reducing ammonia volatilization losses by up to 50% to 90%.
Thus, Reason (R) is true and physically explains how NBPT functions as a urease inhibitor. Step 2: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A).
