Question

One atmosphere soil moisture tension is equal to

• A. 936 cm of water column
• B. 1036 cm of water column
• C. 1136 cm of water column
• D. 1236 cm of water column

Hint:

Pressure equivalences:
$1\text{ atm} = 1.013\text{ bar} = 760\text{ mm Hg} = 10.33\text{ m of } \text{H}_2\text{O} \approx 1036\text{ cm of } \text{H}_2\text{O}$.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Soil moisture tension is the tenacity with which water is held in the soil pores by capillary and adsorptive forces, standardly expressed in equivalent bars or hydrostatic head of water.
Key Formula or Approach:
\[ P = \rho g h \implies h = \frac{P}{\rho g} \]
\[ 1\text{ atm} = 1.01325 \times 10^5\text{ Pa} = 1.013\text{ bar} \approx 1033.6\text{ cm of } \text{H}_2\text{O} \approx 1036\text{ cm} \]

Step 2: Detailed Explanation:
Standard atmospheric pressure is:
\[ 1\text{ atm} = 101,325\text{ N/m}^2 \]
Calculating the equivalent column height of pure water (\(\rho = 1000\text{ kg/m}^3\), \(g = 9.81\text{ m/s}^2\)):
\[ h = \frac{101325}{1000 \times 9.81} = 10.3287\text{ m} = 1032.87\text{ cm of water} \approx 1036\text{ cm of water column} \]
- In pF notation, \(\text{pF} = \log_{10}(h \text{ in cm}) = \log_{10}(1036) \approx 3.01\).

Step 3: Final Answer:
Therefore, one atmosphere soil moisture tension is equal to 1036 cm of water column, corresponding to option (B).