Why are earthworms called as farmer's friends?

Explanation

**Step-by-Step Solution:**

1. **Introduction to Earthworms**: Earthworms are organisms that primarily live in the soil, especially in the upper layer known as the O-horizon.

2. **Role in Soil**: Earthworms play a crucial role in soil health and fertility. They are known for their ability to produce humus, which is an essential component of healthy soil.

3. **Process of Humus Production**: Earthworms have enzymes that help them break down complex organic materials, such as dead plants and decaying matter found on the soil surface.

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