Fertilizer fundamentals — Which statement about ammonium sulfate [(NH4)2SO4] fertilizer is most accurate for agronomic use?

Introduction:
Ammonium sulfate [(NH4)2SO4] is a widely used nitrogenous fertilizer supplying both nitrogen and sulfur. Understanding its agronomic niche versus alternatives like urea or ammonium nitrate helps in crop-specific recommendations, especially for flooded rice (paddy) systems.

Given Data / Assumptions:

• Comparison of form, analysis, and soil reaction among common N fertilizers.
• Paddy fields are typically flooded and slightly reduced (low-oxygen) environments.
• Sulfur nutrition can be limiting in some soils; sulfate provides readily available S.

Concept / Approach:

Ammonium sulfate is an ammoniacal fertilizer that acidifies soils over time due to nitrification of NH4+ to NO3− releasing H+. In flooded paddy, the ammonium form is retained better (less leaching) and is plant-preferred under reduced conditions. It also supplies sulfate-sulfur, which benefits many cereals including rice. Although urea has a higher N concentration (46% N), ammonium sulfate’s agronomic behavior often makes it a recommended choice for paddy where S is needed and volatilization losses can be managed.

Step-by-Step Solution:

Verification / Alternative check:

Agronomy guides often list ammonium sulfate as suitable for rice, especially where sulfur deficiency is present. By contrast, urea is the highest concentration N source, not ammonium sulfate.

Why Other Options Are Wrong:

A: Incorrect; urea (46% N) is higher concentration. C/D: It is acid-forming, not basic or neutral. E: It is not urea-based and is not primarily a slow-release product.

Common Pitfalls:

Assuming highest N concentration automatically means best agronomic fit—crop and soil conditions determine suitability.

Final Answer:

the best fertiliser for paddy