Crop Management

Ammonia volatilisation from rice field: Does it cause atmospheric pollution?

In low land rice, under submergence condition, the applied nitrogenous fertiliser undergoes reduction and lost as ammonia (NH3) through volatilisation. Excess NH3 in atmosphere can have harmful effects on ecosystem.

In a submerged field, NH3 volatilization is comparatively less during night. During day time, CO2 is used by algae (those are present in rice field under waterlogged situation) during photosynthesis. In night time, algae also do respiration in which CO2 is released. These CO2 will form carbonic acid which will reduce the pH of soil. Volatilization loss is less in low pH.

In a recent study by Shen et al (2020), it was found that 80% of the volatilised NH3 got dry deposited in downwind sides of the rice field upto 100 m distance (Fig). Whereas, only 20% of the volatilised NH3 was actually lost to the atmosphere.

(Source: YI, Y., SHEN, J., YANG, C., WANG, J., LI, Y., & WU, J. (2020). Dry deposition of ammonia around paddy fields in the subtropical hilly area in southern China. Atmospheric and Oceanic Science Letters, 13(3), 216-223)

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