Controlled irrigation and drainage of a rice paddy field reduced global warming potential of its gas emissions

Abstract

The effect of controlled drainage on methane (CH₄) and nitrous oxide (N₂O) emissions from a paddy field under controlled irrigation (CI) was investigated by controlling the sub-surface drainage percolation rate with a lysimeter. CI technology is one of the major water-saving irrigation methods for rice growing in China. Water percolation rates were adjusted to three values (2, 5, and 8 mm d⁻¹) in the study. On the one hand, the CH₄ emission flux and total CH₄ emission from paddy fields under CI decreased with the increase of percolation rates. Total CH₄ emissions during the growth stage of rice were 1.83, 1.16, and 1.05 g m⁻² in the 2, 5, and 8 mm d⁻¹ plots, respectively. On the other hand, the N₂O emission flux and total N₂O emissions from paddy fields under CI increased with the increase of percolation rates. Total N₂O emissions during the growth stage of rice were 0.304, 0.367, and 0.480 g m⁻² in the 2, 5, and 8 mm d⁻¹ plots, respectively. The seasonal carbon dioxide (CO₂) equivalent of CH₄ and N₂O emissions from paddy fields under CI was lowest in the 2 mm d⁻¹ plot (1364 kg CO₂ ha⁻¹). This value was 1.4% and 19.4% lower compared with that in the 5 and 8 mm d⁻¹ plots, respectively. The joint application of CI and controlled drainage may be an effective mitigation strategy for reducing the carbon dioxide equivalents of CH₄ and N₂O emissions from paddy fields.

Keywords:

• methane
• nitrous oxide
• paddy field
• percolation rate
• water-saving irrigation

Acknowledgments

The research was financially supported by the National Natural Science Foundation of China (No. 50839002).