Liquid nitrogen and plough: what they have in common

1. Step 1. Liquid nitrogen — is made of — Nitrogen. Nitrogen.
2. Step 2. Nitrogen — is material for — Ammonia. Nitrogen from the air.
3. Step 3. Ammonia — is material for — Mineral fertilizer. Nitrogen fertilizers.
4. Step 4. Mineral fertilizer — evolved from — Crop rotation. Fertilizers solved the problem of fertility that crop rotation used to solve.
5. Step 5. Crop rotation — uses — Plough. The three-field system with a heavy plough.

Open Evothings