Given below are two statements:
Statement (I): Tilth indicates two properties of soil viz. the size distribution of aggregates and mellowness or friability of soil.
Statement (II): A higher per cent of larger aggregates (> 5 mm in diameter) is necessary for irrigated agriculture.
In light of the above statements, choose the most appropriate answer from the options given below.
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Optimum soil aggregate size for seedbed preparation: \(1\text{ to }5\text{ mm}\) in diameter.
Aggregates larger than \(5\text{ mm}\) reduce seed-to-soil contact and dry out too quickly, while aggregates smaller than \(0.5\text{ mm}\) can seal the surface and cause waterlogging.
Both Statement (I) and Statement (II) are correct.
Both Statement (I) and Statement (II) are incorrect.
Statement (I) is correct but Statement (II) is incorrect.
Statement (I) is incorrect but Statement (II) is correct.
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The Correct Option isC
Solution and Explanation
Step 1: Understanding the Concept:
Soil tilth is a physical term that describes the suitability of a soil's structure for plant growth and root penetration.
A good soil tilth depends on the size, stability, and distribution of soil aggregates, as well as the balance of pore space for water and air movement. Step 2: Detailed Explanation:
Let us evaluate both statements:
- Statement (I): Tilth refers to the physical condition of soil in relation to plant growth, which is determined by two main properties:
1. The size distribution of soil aggregates (ideally containing a mix of crumbly, granular aggregates that create a balanced pore system).
2. Mellowness or friability, which is the ease with which soil aggregates can be crumbled or fractured by tillage tools or plant roots.
Therefore, Statement (I) is correct.
- Statement (II): In irrigated agriculture, soil aggregates must maintain a stable structure that prevents surface crusting while retaining sufficient moisture.
If soil aggregates are too large (greater than 5 mm in diameter), the soil becomes extremely coarse, leading to excessive aeration, rapid water drainage, and poor seed-to-soil contact, which reduces seed germination rates.
Conversely, if aggregates are too small (less than 0.5 mm), they can cause surface crusting, pore clogging, and poor soil aeration.
The optimum aggregate size range for most irrigated field crops is between 1 mm and 5 mm (ideally 1 to 3 mm), which provides a balanced ratio of water-holding micropores and aerating macropores.
Therefore, a higher percentage of aggregates larger than 5 mm is not desirable, making Statement (II) incorrect.
Since Statement (I) is correct and Statement (II) is incorrect, option (C) is the correct choice. Step 2: Final Answer:
Statement (I) is correct but Statement (II) is incorrect.
