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

Area of Science:

• Agricultural Science
• Agronomy
• Soil Science

Background:

• Ammonia (NH3) volatilization represents a significant nitrogen loss pathway in paddy fields.
• Cultivating high nitrogen use efficiency (NUE) rice cultivars is a potential strategy to mitigate NH3 volatilization.
• The direct relationship between rice NUE and NH3 volatilization under field conditions requires validation.

Purpose of the Study:

• To evaluate the impact of four rice cultivars with varying NUE on NH3 volatilization in paddy fields.
• To investigate the underlying mechanisms influencing NH3 volatilization in relation to rice NUE.
• To determine if high-NUE rice cultivars effectively reduce nitrogen losses through NH3 volatilization.

Main Methods:

• A field experiment was conducted using four rice cultivars with distinct NUE levels.
• Measurements of NH3 volatilization were taken at key growth stages (tillering and panicle fertilization).
• Agronomic traits such as N accumulation, biomass, root characteristics, and leaf area index were assessed.

Main Results:

• The rice cultivar with the lowest NUE (A386) exhibited significantly lower NH3 volatilization (12.7-54.1%) compared to other cultivars.
• Lower NH3 volatilization in A386 was attributed to greater shoot N accumulation, root biomass/volume at tillering, and shoot biomass/LAI at panicle stages.
• High-NUE cultivars (W23, Z11) did not show reduced NH3 volatilization compared to the lowest NUE cultivar; A386 showed premature senescence, lowering its overall NUE.

Conclusions:

• Rice NUE is not directly correlated with NH3 volatilization from paddy fields.
• Future breeding for high-NUE rice should incorporate traits that enhance N uptake and canopy structure early in development.
• Preventing premature senescence is crucial for high-NUE cultivars to ensure sustained high yields and potentially mitigate N losses.