Soil moisture characteristic curve represents the relationship between

Correct option is D

The correct answer is (D) Soil moisture tension and soil moisture content

Explanation:
• The Soil Moisture Characteristic Curve (also known as the water retention curve) shows the relationship between soil water potential (or tension/suction) and the volumetric water content.
• As the soil dries, the remaining water is held more tightly in smaller pores, and the tension increases.
• This curve is unique for every soil textural class. For example, a clay soil will have a much higher water content at a given tension than a sandy soil.
• It is used to determine important soil hydraulic parameters like Field Capacity and Wilting Point.

Information Booster:
• The curve shows "hysteresis," meaning the relationship between moisture and tension is different depending on whether the soil is being wetted or dried.
• pF value is the common logarithm of the soil moisture tension expressed in centimeters of water head.
• Field Capacity corresponds to pF 2.5, and PWP corresponds to pF 4.2.

Additional Knowledge:
• Soil texture (Option A): Influences the shape of the curve but is not the variable plotted on the axes.
• Soil structure (Option B): Affects water retention mainly at low tensions (near saturation) by influencing macropore space.
• Available moisture (Option C): Is a value derived from the curve (the difference in content between two tension points), not the relationship plotted by the curve itself.