Given below are two statements
Statement I: A soil with good tilth is quite porous and has free drainage up to water table
Statement II: The capillary and non-capillary pores should be in a ratio of 1:4 so that sufficient amount of water is retained in the soil as well as free air
In light of the above statements, choose the correct answer from the options given below:
Show Hint
An ideal soil composition by volume is:
- \( 45\% \) Mineral matter
- \( 5\% \) Organic matter
- \( 25\% \) Water (stored in capillary/micro pores)
- \( 25\% \) Air (contained in non-capillary/macro pores)
This yields a balanced \( 1:1 \) pore ratio.
Step 1: Understanding the Concept:
Soil tilth refers to the physical condition of soil in relation to its suitability for planting or crop growth.
Good tilth is characterized by a stable, loose, granulated structure with an optimal balance of pore spaces.
These pore spaces are divided into capillary (micro) pores, which retain water against gravity, and non-capillary (macro) pores, which allow for air exchange and drainage. Step 2: Detailed Explanation:
Let us evaluate both statements:
- Statement I: A soil with good tilth has a well-developed crumb or granular structure.
This structure provides high total porosity, allowing water to infiltrate easily and drain freely through the soil profile down to the water table.
This prevents waterlogging and ensures that roots have access to oxygen.
Therefore, Statement I is true.
- Statement II: For optimal plant growth, an agricultural soil should have approximately equal proportions of capillary (micro) and non-capillary (macro) pores.
This balance means the ratio of capillary to non-capillary pores should be approximately \( 1:1 \) (representing a \( 50:50 \) distribution within the pore space).
This equal distribution ensures the soil can store sufficient available water for plant use while maintaining adequate aeration for root respiration.
A ratio of \( 1:4 \) represents a severe imbalance with too few capillary pores, which would cause the soil to have very low water-holding capacity and dry out too quickly.
Therefore, Statement II is false.
Since Statement I is true and Statement II is false, option (C) is the correct choice. Step 3: Final Answer:
Statement I is true but Statement II is false.
