Field application in the tropics: Why is liquid anhydrous ammonia generally not applied directly as a fertilizer in hot tropical countries such as India?

Introduction / Context:
Anhydrous ammonia (NH3) is widely used as a high-analysis nitrogen fertilizer in temperate regions by injecting it into soil. However, its direct application is uncommon in hot tropical climates due to handling and loss concerns tied to its physical properties.

Given Data / Assumptions:

• High ambient temperatures typical of tropical regions.
• Surface or shallow application (spraying) under field conditions.
• No specialized injection equipment ensuring deep soil sealing.

Concept / Approach:
Ammonia boils at around −33 °C at 1 atm. In hot climates, any unsealed application leads to immediate volatilization, causing large nitrogen losses and safety hazards. Effective use requires pressurized tanks and deep injection with soil sealing—logistically complex for many smallholder systems.

Step-by-Step Solution:
Recall NH3 volatility at ambient tropical temperatures.Understand need for sub-surface injection and sealing to prevent loss.Recognize practical limitations in tropical agriculture; thus rapid evaporation is the key reason.Select option (c).

Verification / Alternative check:
Extension guidelines recommend alternatives like urea or ammonium sulphate for broadcast or top-dress in hot regions, reserving NH3 for mechanized systems with injection rigs.

Why Other Options Are Wrong:
NH3 has very high nitrogen content (~82% N), so (a) is false.

Cost and availability vary, but evaporation loss is the primary technical barrier in this context.

Common Pitfalls:

• Applying NH3 without proper sealing, leading to crop injury and N loss.
• Confusing aqua ammonia solutions with anhydrous ammonia practices.

Final Answer:
It rapidly evaporates upon application/spraying under hot conditions.