Nitrogen fertilizers comparison: Why is urea generally considered a better nitrogen fertilizer than ammonium sulfate for many field applications?

Introduction / Context:
Farmers often compare common nitrogen (N) fertilizers such as urea and ammonium sulfate to choose the most economical source of plant-available nitrogen. The key differentiator in many agronomic and economic calculations is the percentage of nitrogen by mass, because it governs transport, storage, application rates, and cost per kilogram of nutrient supplied.

Given Data / Assumptions:

• Typical urea analysis ≈ 46% N (by mass).
• Typical ammonium sulfate analysis ≈ 21% N and ≈ 24% S (as sulfate).
• Decision is about “better as a nitrogen fertilizer,” not sulfur nutrition or soil chemistry side benefits.

Concept / Approach:
When the goal is to supply nitrogen alone, a material with higher N concentration usually reduces logistical costs per unit N. Urea's 46% N allows lower application mass for the same amount of N compared with ammonium sulfate at 21% N. This affects freight, storage volume, and spreading time. While ammonium sulfate adds valuable sulfur where needed, for pure N supplementation the higher analysis of urea is the primary advantage and is why urea is widely used globally.

Step-by-Step Solution:

Verification / Alternative check:
Cost-per-kg-N calculations routinely favor urea in regions where sulfur is not limiting and volatilization losses are managed with timing, incorporation, or inhibitors.

Why Other Options Are Wrong:

• Cheaper in every market: prices fluctuate; not always true.
• “Not poisonous”: both require safe handling; this is not the core reason.
• “Easier to manufacture”: process complexity does not define field “better.”
• “Contains N and P”: urea contains no phosphorus.

Common Pitfalls:
Ignoring sulfur needs; in S-deficient soils, ammonium sulfate may be preferable despite lower %N. Also, manage urea to minimize ammonia volatilization.

Final Answer:
Nitrogen content is higher.