Although liquid anhydrous ammonia contains about 82% nitrogen, it is generally not applied directly as fertiliser in tropical regions (such as India). What is the primary practical reason?

Introduction / Context:
Liquid anhydrous ammonia is a concentrated nitrogen source widely used in temperate agriculture with specialized injection equipment. Climatic and logistical factors influence whether direct ammonia application is practical or safe, especially in warmer regions.

Given Data / Assumptions:

• Boiling point of NH3 ≈ −33 °C at 1 atm.
• Tropical ambient temperatures are far above this value.
• Field application requires high-pressure tanks, injectors, and soil sealing.

Concept / Approach:
Because ammonia boils at very low temperature, it flashes to gas at normal tropical ambient conditions. Without dedicated injection and immediate soil sealing, large losses occur and safety issues arise, making routine direct application uncommon compared to solids (urea) or solutions (UAN) in these contexts.

Step-by-Step Solution:

Verification / Alternative check:
Adoption patterns correlate with infrastructure: regions with widespread anhydrous ammonia application use specialised equipment and practices to prevent volatilisation; tropical smallholder systems favour urea granules.

Why Other Options Are Wrong:

• Pungent smell: true but not the decisive technical barrier.
• Toxic/corrosive: ammonia hazards are managed; volatility is the main practical hurdle.
• Short supply/banned: not universally true; depends on market and regulation.

Common Pitfalls:
Confusing hazard characteristics with the primary physical limitation of high vapour pressure at ambient temperatures.

Final Answer:
vaporises at normal temperature