Which of the following represents the abiological mode of adding nitrogen to the soil

Options

A. Ammonification
B. Nitrification
C. Lightning
D. Nodule formation

Answer

To determine which of the following represents the abiological mode of adding nitrogen to the soil, we need to analyze the options provided and understand the processes involved in nitrogen addition.

### Step-by-Step Solution:

1. **Understand the Concept of Abiological Nitrogen Addition**:
- Abiological processes refer to those that do not involve living organisms. In this context, we are looking for a process that adds nitrogen to the soil without the direct involvement of biological organisms.

2. **Identify the Options**:
- The options typically include processes like ammonification, nitrification, lightning, and nodule formation. We need to evaluate each of these to see which one fits the criteria.

3. **Evaluate Ammonification**:
- Ammonification is the process where organic nitrogen (from dead plants and animals) is converted into ammonia by decomposers. This process, while involving bacteria, is primarily a breakdown of organic matter and can be considered a biological process rather than an abiological one.

4. **Evaluate Nitrification**:
- Nitrification is the conversion of ammonia into nitrate by nitrifying bacteria. This process also involves living organisms and is therefore not abiological.

5. **Evaluate Lightning**:
- Lightning can convert atmospheric nitrogen (N2) into nitrates through a high-energy reaction. This process does not involve any biological organisms and is considered an abiological method of adding nitrogen to the soil.

6. **Evaluate Nodule Formation**:
- Nodule formation occurs in legumes where nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia. This process is biological and thus not what we are looking for.

7. **Conclusion**:
- Based on the evaluations, the correct answer to the question is **lightning**, as it represents an abiological mode of adding nitrogen to the soil.

### Final Answer:
**Lightning** is the abiological mode of adding nitrogen to the soil.