Ammonium sulphate (AS) is one of those “old but getting hot again” fertilizers. It’s been around for more than a century, but agronomy and market dynamics have quietly pushed it back into the spotlight.

What is ammonium sulphate?

Ammonium sulphate is an inorganic fertilizer containing:

• 21% nitrogen (N) in ammonium form

• 24% sulphur (S) as sulphate

Chemically, it’s $(NH₄)₂SO₄$. It’s produced mainly as a by-product of industrial processes (caprolactam, coke oven gas, flue gas desulphurization), and also via synthetic routes.

Why is it important in agriculture?

Because it delivers two essential nutrients at once, in forms crops can actually use.

1. Nitrogen efficiency

• Nitrogen is in ammonium form, not nitrate.

• Less prone to leaching than nitrate fertilizers.

• Works well in warm, high-rainfall regions where nitrate losses are a big issue.

2. Sulphur has become a limiting nutrient

• Sulphur is critical for protein formation, oil synthesis, and enzyme activity.

• Many modern soils are now sulphur-deficient due to:

  • Cleaner fuels (less atmospheric sulphur deposition)

  • Higher crop yields removing more S

  • Heavy use of high-analysis fertilizers (urea, DAP, MAP) that contain no sulphur

3. Soil and crop benefits

• Slightly acidifying effect, very useful in alkaline or calcareous soils

• Improves uptake of nitrogen and micronutrients

• Particularly suitable for oilseeds, cereals, sugar crops, pasture, coffee, tea, and rice

Why has demand for ammonium sulphate grown?

This is where agronomy meets market reality.

1. Rising sulphur deficiency worldwide
Sulphur is no longer “free” from the air. Farmers now have to apply it deliberately, and AS is the cheapest and most direct sulphur source.

2. Limits of urea-only nutrition
Urea provides nitrogen only. In many regions:

• Crops respond poorly to N if S is missing

• Farmers are seeing better yield response when AS replaces or complements urea
  This is especially obvious in Brazil, India, Southeast Asia, and Africa.

3. Better fit for tropical agriculture

• Lower nitrogen loss compared to urea in high rainfall

• No volatilization issues like surface-applied urea

• Strong performance in pasture and perennial crops

4. Structural supply advantages

• Large volumes are produced as industrial by-products

• AS availability has increased as caprolactam and environmental desulphurization capacity expanded

• Often priced below urea on a nutrient-adjusted basis, especially when sulphur is valued

5. Changing fertilizer strategies

• More balanced fertilization (N + S, not N alone)

• More granular AS use for blending and direct application

• Increasing use in bulk and containerized international trade

In simple terms

Ammonium sulphate matters because:

• Crops need sulphur again

• Nitrogen efficiency matters more than ever

• Farmers want predictable, stable performance

• Markets are moving away from “nitrogen only” thinking

That’s why an “old” fertilizer like ammonium sulphate is quietly becoming a core nutrient, not just a secondary one.