Effects of Ammonia Volatilization Mitigation Options On Greenhouse Gas Emissions From a Paddy Field Fertilized with Anaerobically Digested Cattle Slurry.

We reported that NH₃ volatilization from a paddy field planted with a whole crop rice variety and fertilized with anaerobically digested cattle slurry (ADCS) was suppressed by adding wood vinegar or by managing the floodwater level high.  To evaluate the effects of the NH₃ mitigation options on emissions of CH₄ and N₂O, a lysimeter experiment (1 m square with 0.5 m depth) was done in this study, since these are generally considered to enhance CH₄ emission. Four treatments and each three replicated lysimeters were prepared: 1) chemical fertilizer (CF), 2) ADCS, 3) ADCS + wood vinegar (WV) and 4) ADCS + deeper floodwater (ca. 10 cm, 3-4 cm in the other treatments) (DFW) just before application. Fertilization rate was 30 g NH₄⁺-N m^-2 (basal and two times top-dressing) and NH₃, CH₄ and N₂O emissions were monitored. The results revealed that NH₃ volatilization loss in the ADCS treatment throughout a growing season was 2.7 g NH₃-N m^-2 which was significantly reduced by 79% and 55% in the ADCS + WV and ADCS + DFW treatments, respectively. A total amount of CH₄ emitted in the ADCS treatments in a growing period was not significantly enhanced by the NH₃ volatilization mitigation options (146 ± 80, 147 ± 12 and 153 ± 52 g CH₄ m^-2 in the ADCS, ADCS + WV and ADCS + DFW, respectively), although these values were ca. 2.5 times higher than that in the CF treatment. Net negative N₂O emissions in a growing period were observed in all the treatments. Results revealed that NH₃ ammonia mitigation options reduced NH₃ volatilization while not having a negative impact in greenhouse gases, CH₄ and N₂O emissions.