What is the benefit of thunder and lightning to farmers?

Analyze the question: It asks how thunder and lightning specifically help farmers. Think about what lightning does chemically to the air.

Explain the concept: This is part of the nitrogen cycle, specifically atmospheric nitrogen fixation.

• About 78% of the air is nitrogen gas (N₂), but plants cannot use it directly.
• Lightning produces very high temperature and electrical energy. This makes nitrogen and oxygen in the air combine.

Step-by-step solution:

1. Lightning energy makes nitrogen react with oxygen: N₂ + O₂ → 2NO (nitrogen monoxide)
2. Nitrogen monoxide is oxidised further in the air: 2NO + O₂ → 2NO₂ (nitrogen dioxide)
3. Nitrogen dioxide dissolves in rain water to form nitrous and nitric acids: 4NO₂ + 2H₂O + O₂ → 4HNO₃
4. The rain carries this into the soil, where the acids react with minerals to form nitrates.
5. Plants absorb the nitrates through their roots and use them to make proteins.

Checking the options:

• A. Addition of nitrates to the soil: Correct. This is the direct benefit of lightning.
• B. Aeration of the soil: Aeration comes from earthworms, ploughing and tilling, not lightning.
• C. Removal of harmful bacteria: Lightning does not do this.
• D. Addition of rain water: Rain comes with thunderstorms, but it is not the benefit specific to thunder and lightning. Rain falls without lightning too.

Exam tip: Remember "Lightning = Nitrates". When you see lightning in a question, think of the nitrogen cycle and nitrogen fixation. The three ways nitrogen is fixed are lightning, nitrogen-fixing bacteria (such as Rhizobium in legume root nodules), and industrial fertiliser production.