Define biofertilizers.

Explanation

### Step-by-Step Text Solution

1. **Definition of Biofertilizers**: Biofertilizers are defined as living organisms that enhance the nutrient quality of the soil.

2. **Components of Biofertilizers**: The main sources of biofertilizers include various types of microorganisms such as bacteria, fungi, and cyanobacteria.

3. **Function of Biofertilizers**: These organisms work by increasing the availability of essential nutrients in the soil, thereby improving soil fertility.

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