Which of the following statements will not hold true if a plant is grown in only sand (S), only clay (C) and only humus (H)?

Options

A. water availability to the roots will be more in (C) and (H) as compared to (S)
B. Ability of roots to penetrate (S) and (H) will be low as compared to (C).
C. Nutrient availability to roots will be less in (S) as compared to (C) and (H).
D. Oxygen availability to roots will be low in (C) as compared to (S) and (H).

Answer

To solve the question regarding which statement will not hold true when a plant is grown in only sand (S), only clay (C), and only humus (H), we will analyze each statement provided.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "Water availability to the roots will be more in clay and humus as compared to sand."
- **Analysis**: This statement is true. Clay retains more water than sand due to its fine particles, and humus also retains moisture well. Therefore, this statement holds true.

2. **Statement 2**: "Availability of roots to penetrate soil and humus will be low as compared to clay."
- **Analysis**: This statement is false. Clay is compact and dense, making it difficult for roots to penetrate. In contrast, humus and sandy soils allow for easier root penetration. Thus, this statement does not hold true.

3. **Statement 3**: "Nutrient availability to roots will be less in sand as compared to clay and humus."
- **Analysis**: This statement is true. Clay and humus have higher nutrient-holding capacities than sand, which tends to drain nutrients quickly. Therefore, this statement holds true.

4. **Statement 4**: "Oxygen availability to roots will be low in clay as compared to sand and humus."
- **Analysis**: This statement is true. Clay's compact structure limits air spaces, reducing oxygen availability for roots. In contrast, sand and humus provide better aeration. Therefore, this statement holds true.

### Conclusion:
Based on the analysis, the statement that does not hold true is **Statement 2**: "Availability of roots to penetrate soil and humus will be low as compared to clay."