Rice nitrogen use efficiency does not link to ammonia volatilization in paddy fields.

Ammonia (NH3) volatilization is a major pathway of nitrogen (N) losses from paddy fields, and could be potentially mitigated by cultivation of high nitrogen use efficiency (high-NUE) rice cultivars. However, the relationship between NUE and NH3 volatilization has not been validated under field conditions. A field experiment was conducted to evaluate the impact of four rice cultivars with different NUE [Wuyunjing 23 (W23), Zhendao 11 (Z11), Wuyujing 3 (W3), and Aoyusi 386 (A386)] on NH3 volatilization, as well as the related mechanisms. Two high-NUE rice cultivars W23 and Z11 was not more effective in reducing total NH3 volatilization from the paddy field compared to cultivar A386 with the lowest NUE. Cultivar A386 had 12.7-17.8% and 35.7-54.1% lower NH3 volatilization than other three rice cultivars at tillering fertilization stage (TFS) and panicle fertilization stage (PFS), respectively, mainly due to its greater shoot N accumulation, root biomass and volume at TFS and its greater shoot biomass, leaf area index and shoot N accumulation at PFS. There was no significant difference in NH3 volatilization among W23, Z11 and W3 at TFS. However, premature senescence phenomenon at later growth stages of A386 eventually led to its lowest NUE among the four rice cultivars. Our results suggest that NUE of rice does not link to NH3 volatilization from paddy fields. In order to make high-NUE rice cultivars also effective in mitigating NH3 volatilization, future breeding works should aim to improve N uptake capability and canopy structure at early tillering and panicle development stages while prevent premature senescence of rice plants to maintain high yields.