NDA Chemistry · Industrial and Applied Chemistry
Fertilizers
The chemicals that supply the three plant nutrients — nitrogen (N), phosphorus (P) and potassium (K) — to soil, which nutrient each fertilizer carries, and how the common ones are manufactured.
Why this matters
Five PYQs, all recall. The bank's favourite move is 'which is NOT a fertilizer' or 'which nutrient does urea supply?' — both answered by knowing the nutrient each fertilizer carries. Two reliable traps: urea is a NITROGEN fertilizer (not phosphorus), and ammonium sulphide is not a fertilizer at all.
Concept 1 of 2: Which nutrient each fertilizer supplies
Definition
The nutrient each common fertilizer supplies:
- Nitrogen (N) fertilizers: urea (CO(NH₂)₂), ammonium nitrate, ammonium sulphate, ammonium phosphate (also P), calcium ammonium nitrate.
- Phosphorus (P) fertilizers: superphosphate of lime, ammonium phosphate (also N).
- Potassium (K) fertilizers: potassium chloride (muriate of potash), potassium sulphate.
- Ammonium sulphide ((NH₄)₂S) is NOT a fertilizer — it is a laboratory reagent.
- Urea is the richest common nitrogen fertilizer (≈ 46% N), and supplies NO phosphorus.
| Fertilizer | Nutrient supplied | Note |
|---|---|---|
| Urea | Nitrogen (N) | ≈ 46% N — highest-N solid fertilizer Urea is a NITROGEN fertilizer, not a phosphorus one. |
| Ammonium nitrate | Nitrogen (N) | Common N fertilizer |
| Ammonium sulphate | Nitrogen (N) | Common N fertilizer |
| Superphosphate of lime | Phosphorus (P) | Made from rock phosphate + H₂SO₄ |
| Muriate of potash (KCl) | Potassium (K) | Main K source |
| Ammonium sulphide ((NH₄)₂S) | None — not a fertilizer | A lab reagent Ammonium SULPHIDE is the odd one out — it is NOT used as a fertilizer (sulphate, nitrate and phosphate of ammonium all are). |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Industrial and Applied Chemistry · Fertilizers
Urea = nitrogen, never phosphorus
Ammonium sulphide is not a fertilizer
Concept 2 of 2: How superphosphate and nitrolim are made
Definition
The manufacturing facts the bank tests:
- Superphosphate of lime is made by treating calcium phosphate (rock phosphate) with sulphuric acid — this converts insoluble phosphate into a soluble (plant-available) form.
- Nitrolim (calcium cyanamide) is made by heating calcium carbide (CaC₂) with nitrogen: CaC₂ + N₂ → CaCN₂ + C. In soil it slowly decomposes to release ammonia.
- Nitrolim supplies nitrogen only — it is inorganic and is NOT an NPK fertilizer.
| Fertilizer | Made from | Key fact |
|---|---|---|
| Superphosphate of lime | Calcium phosphate + sulphuric acid | Makes phosphate soluble Superphosphate = rock phosphate (calcium phosphate) treated with H₂SO₄. |
| Nitrolim (calcium cyanamide) | Calcium carbide (CaC₂) + nitrogen | Decomposes to ammonia in soil Nitrolim supplies nitrogen only, is inorganic, and is NOT an NPK fertilizer. |
Practice this concept4 quick reps
The same idea in a real exam question:
Example 2 · Industrial and Applied Chemistry · Fertilizers
Nitrolim is N-only and inorganic
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Which nutrient each fertilizer supplies6 rows
| Fertilizer | Nutrient supplied | Note |
|---|---|---|
| Urea | Nitrogen (N) | ≈ 46% N — highest-N solid fertilizer Urea is a NITROGEN fertilizer, not a phosphorus one. |
| Ammonium nitrate | Nitrogen (N) | Common N fertilizer |
| Ammonium sulphate | Nitrogen (N) | Common N fertilizer |
| Superphosphate of lime | Phosphorus (P) | Made from rock phosphate + H₂SO₄ |
| Muriate of potash (KCl) | Potassium (K) | Main K source |
| Ammonium sulphide ((NH₄)₂S) | None — not a fertilizer | A lab reagent Ammonium SULPHIDE is the odd one out — it is NOT used as a fertilizer (sulphate, nitrate and phosphate of ammonium all are). |
How superphosphate and nitrolim are made2 rows
| Fertilizer | Made from | Key fact |
|---|---|---|
| Superphosphate of lime | Calcium phosphate + sulphuric acid | Makes phosphate soluble Superphosphate = rock phosphate (calcium phosphate) treated with H₂SO₄. |
| Nitrolim (calcium cyanamide) | Calcium carbide (CaC₂) + nitrogen | Decomposes to ammonia in soil Nitrolim supplies nitrogen only, is inorganic, and is NOT an NPK fertilizer. |
Watch out for (3)
- Urea = nitrogen, never phosphorus→ Which nutrient each fertilizer supplies
- Ammonium sulphide is not a fertilizer→ Which nutrient each fertilizer supplies
- Nitrolim is N-only and inorganic→ How superphosphate and nitrolim are made
Test yourself on Industrial and Applied Chemistry
10 past NDA questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.