Question

For the crop available water held between

• A. Field capacity and wilting point
• B. Field capacity and depletion point
• C. Saturation and wilting point
• D. Field capacity and hygroscopic coefficient

Hint:

Available Water = Field Capacity (FC) $-$ Permanent Wilting Point (PWP). Clay soils have high water storage capacity, but loamy soils provide the highest volume of plant-available water.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Soil water is classified into different categories based on how tightly it is bound to soil particles, which determines its availability to plants.
- Gravitational Water: Free water that drains out of the root zone due to gravity.
- Hygroscopic Water: Water held tightly as a thin film around soil particles, which cannot be extracted by plant roots.
- Capillary Water: Water held in soil micropores against gravity, which is accessible to plants.

Step 2: Detailed Explanation:
The volume of soil water available for crop uptake is defined by two physical limits:
1. Field Capacity (FC): The upper limit of available water. It represents the moisture remaining in the soil after excess gravitational water has drained away (usually occurring 2 to 3 days after a heavy rain or irrigation). The suction tension is about $-0.1$ to $-0.33$ bar.
2. Permanent Wilting Point (PWP): The lower limit of available water. This is the soil moisture level at which plants can no longer exert enough suction to extract water from soil pores. The plant wilts and cannot recover even when placed in a humid environment. The suction tension is about $-15$ bars.
The moisture held between these two limits is termed the Available Water Capacity.
Thus, Option (A) correctly identifies this range.

Step 3: Final Answer:
The correct option is (A).