Which of the following statements are correct?
(i) Cochineal insect is used to eliminate Opuntia.
(ii)Water logging decreases the amount of salts in the soil that increases soil fertility
(iii) Fertilisers are not readily soluble in water, so they are absorbed by the plants slowly.
(iv) Rust of wheat is a fungal disease.
(v) The practice of growing two or more dissimilar crops in the same field one after the other is called mixed cropping.

Options

A. (i), (ii), (iii) and (v) only
B. (i) and (iv) only
C. (ii) and (iv) only
D. (iii), (iv) and (v) only

Explanation

To determine which statements are correct, let's analyze each one step by step:

1. **Statement (i): Cochineal insect is used to eliminate Opuntia.**
- The cochineal insect is indeed used as a biological control agent to manage the growth of Opuntia, which are cactus plants. The insect produces carminic acid that helps in controlling the cactus population.
- **Conclusion:** This statement is **correct**.

2. **Statement (ii): Water logging decreases the amount of salts in the soil that increases soil fertility.**
- Water logging typically leads to an increase in soil salinity because excess water can cause salts to accumulate in the soil. This condition can harm plant growth and decrease soil fertility.
- **Conclusion:** This statement is **incorrect**.

3. **Statement (iii): Fertilisers are not readily soluble in water, so they are absorbed by the plants slowly.**
- Most fertilizers, particularly those containing nitrogen, phosphorus, and potassium, are designed to be soluble in water. This solubility allows plants to absorb them quickly.
- **Conclusion:** This statement is **incorrect**.

4. **Statement (iv): Rust of wheat is a fungal disease.**
- Rust of wheat is indeed caused by a fungus known as Puccinia triticina. It is a well-known disease that affects wheat crops.
- **Conclusion:** This statement is **correct**.

5. **Statement (v): The practice of growing two or more dissimilar crops in the same field one after the other is called mixed cropping.**
- The practice described here is actually known as crop rotation, where different crops are planted in succession to maintain soil fertility. Mixed cropping refers to growing two or more crops simultaneously in the same field.
- **Conclusion:** This statement is **incorrect**.

### Summary of Correct Statements:
- Correct statements: (i) and (iv).
- Incorrect statements: (ii), (iii), and (v).

### Final Answer:
The correct statements are (i) and (iv).

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