Nitrogen cycle sequence: Organic nitrogen formation → Ammonia formation → Nitrate formation → Soil organic nitrogen formation. Correct answer: (B), (A), (D), (C) – Option 3.

Nitrogen Cycle Sequence Logic

Standard nitrogen cycle: Nitrogen fixation (N₂ → organic N compounds in plants) → Ammonification (organic N → NH₃) → Nitrification (NH₃ → NO₃⁻) → Assimilation/decomposition (NO₃⁻ back to soil organic N).

Option Analysis

• (A) A,B,C,D: Ammonia first (wrong—needs organic source).

• (B) A,B,D,C: Organic N → Ammonia → Nitrate → Soil organic (correct cycle).

• (C) B,A,D,C: Ammonia before organic N (reversed).

• (D) B,C,A,D: Soil organic before ammonia (disordered).

Nitrogen Cycle Processes Order: Ammonia Organic Nitrate Soil Sequence

Arrange the given processes involved in nitrogen cycle: Organic nitrogen formation (B) → Ammonia formation (A) → Nitrate formation (D) → Soil organic nitrogen formation (C) follows biological nitrogen flow. This nitrogen cycle processes guide clarifies ammonia nitrate organic nitrogen sequencing for competitive exams.

Step-by-Step Cycle

1. Organic nitrogen formation (B): N₂ fixation → amino acids/proteins in plants

2. Ammonia formation (A): Plant/animal decay → NH₃/NH₄⁺ (ammonification)

3. Nitrate formation (D): NH₃ → NO₂⁻ → NO₃⁻ (nitrification: Nitrosomonas → Nitrobacter)

4. Soil organic nitrogen (C): NO₃⁻ uptake → new organic N compounds

Why Option 3 (B,A,D,C)?

Matches textbook sequence: Fixation → Ammonification → Nitrification → Assimilation. Other options violate biological logic (no free ammonia without organic precursors).

Exam Mnemonic

“Organic Animals Nitrate Soil”** (B-A-D-C). Remember bacteria: Ammonification (A), Nitrification (Nitrosomonas/Nitrobacter).