Explanation:

- Black Soil (Option 4) is famously known as ‘self-mulching soil’ due to its ability to form a natural mulch on the surface, which helps in conserving moisture and maintaining soil structure.

- Grey Soil (Option 1) is typically found in areas with poor drainage and is not known for self-mulching characteristics.

- Red Soil (Option 2) is usually acidic and found in tropical and subtropical areas, and does not exhibit self-mulching properties.

- Brown Soil (Option 3) is generally fertile but lacks the specific properties of self-mulching seen in black soils.

Your answer is:

- Black soil is indeed known as ‘self-mulching soil’.

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