Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: The total available water for plant growth (TAW) is the water between field capacity and ultimate wilting point. Reason R: The maximum allowable deficit (MAD) is a part of total available water (TAW) and is usually considered as \(50%\) of TAW. In the light of the above statements, choose the most appropriate answer from the options given below:
• Both A and R are correct and R is the correct explanation of A
• Both A and R are correct but R is NOT the correct explanation of A
• A is correct but R is not correct
• A is not correct but R is correct

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is NOT the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Important irrigation relation: \[ \boxed{ TAW = FC - PWP } \] where:
• \(FC\) = Field Capacity
• \(PWP\) = Permanent Wilting Point Also remember: \[ MAD \approx 50% \text{ of TAW} \] Memory Trick: \[ \boxed{\text{“Plants use water between FC and wilting”}} \]

Answer 1

The Correct Option is B

Concept: In irrigation engineering and agricultural water management, understanding soil moisture availability is extremely important for proper irrigation scheduling and crop growth. Plants can only use a certain portion of water stored in soil. The important moisture concepts are:
• Field Capacity (FC)
• Permanent Wilting Point (PWP)
• Total Available Water (TAW)
• Maximum Allowable Deficit (MAD) These parameters help determine:
• When irrigation should be applied
• How much water should be supplied
• How much moisture is available to plants Field Capacity (FC): Field capacity is the moisture content remaining in soil after excess gravitational water has drained away. At this stage:
• Soil holds maximum useful water
• Drainage becomes very slow Permanent Wilting Point (PWP): Permanent wilting point is the moisture level below which plants cannot extract water and permanently wilt. Total Available Water (TAW): The water available for plant uptake is: \[ \boxed{ TAW = FC - PWP } \] Thus TAW is the water stored between field capacity and wilting point. Maximum Allowable Deficit (MAD): MAD represents the fraction of available water that may be depleted before irrigation is required. Usually: \[ MAD \approx 50% \text{ of TAW} \] for many crops under normal conditions.

Step 1: Analyzing Assertion A carefully. Assertion A states: \[ \text{“TAW is the water between field capacity and ultimate wilting point.”} \] This statement is correct. Mathematically: \[ TAW = FC - PWP \] Thus total available water is exactly the moisture available between these two soil moisture limits. Hence: \[ \boxed{\text{Assertion A is correct}} \]

Step 2: Analyzing Reason R carefully. Reason R states: \[ \text{“MAD is a part of TAW and is usually considered as 50% of TAW.”} \] This statement is also correct. Explanation:
• Plants are usually not allowed to consume entire TAW before irrigation.
• Irrigation is applied when a certain allowable depletion occurs.
• This allowable depletion is MAD. For many practical irrigation systems: \[ MAD \approx 0.5 \times TAW \] Hence: \[ \boxed{\text{Reason R is correct}} \]

Step 3: Checking whether Reason R explains Assertion A. Now evaluate whether R correctly explains A. Assertion A defines: \[ What TAW is \] Reason R discusses: \[ How much of TAW may be depleted \] Although Reason R is correct, it does not explain why TAW is defined as water between field capacity and wilting point. The reason merely provides additional information regarding irrigation management. Therefore: \[ \boxed{\text{Reason R is NOT the correct explanation of Assertion A}} \]

Step 4: Selecting the correct option. Thus:
• Assertion A is correct
• Reason R is correct
• But R is not the correct explanation of A Hence the correct answer is: \[ \boxed{(B)\ \text{Both A and R are correct but R is NOT the correct explanation of A}} \] Final Conclusion: Both statements are individually true, but the reason does not explain the assertion. Therefore: \[ \boxed{(B)} \]