Potential ammonia emission from flag leaves of paddy rice (Oryza sativa L. cv. Koshihikari)

The present study aimed to investigate the potential ammonia (NH3) emission from flag leaves of paddy rice (Oryza sativa L. cv. Koshihikari). The study was conducted at a paddy field in central Japan that was designed as a free-air CO2 enrichment (FACE) facility for paddy rice. A dynamic chamber method was used to measure the potential NH3 emissions. The air concentrations of NH3 at two heights (2 and 6 m from the ground surface) were measured using a filter-pack method, and the exchange fluxes of NH3 of the whole paddy field were calculated using a gradient method. The flag leaves showed potential NH3 emissions of 25–38 ng N cm−2 h−1 in the daytime from the heading to the maturity stages, and they showed potentials of approximately 22 ng N cm−2 h−1, even in the nighttime, at the heading and mid-ripening stages. The exchange fluxes of NH3 of the whole paddy field in the daytime were net emissions of 0.9–3.9 g N ha−1 h−1 whereas the exchange fluxes of NH3 in the nighttime were approximately zero.

► Flag leaf of paddy rice has a potential of ammonia emission.
► Potentials were significant in the daytime.
► Potentials were found even at night.
► Potentials in the daytime were different among growth stages.
► The paddy field acted as a net source of atmospheric ammonia.