Evaluation of Nitrogen Loss from Leaves of Different Varieties of Rice Using 15N-Labelling Technique

Losses of nitrogen from an agricultural system into the atmosphere may cause global warming through the contribution of N2O, NO, and CH4. Therefore, it is important to identify and quantify the source and amount of nitrogen loss in the soil-plant systems. The release of nitrogen from rice leaves throughout the growth period was studied by using a 15N-labelling technique. Indica and Japonica rice crops were evaluated throughout the experiment. Indica plants produced more biomass both shoot and root compared to those of Japonica. However, Indica produced a lower weight of panicle compared to that of Japonica. The effect of rice varieties and nitrogen form became more evident with the growth stage. When labelled-N was applied at tiller stage, 16.2-38.7% of absorbed-N can be lost from rice leaves. When labelled-N was applied at panicle stage, the loss rate of absorbed-N ranged from 18.9% (Japonica, 15NH4+-N) to 62.1% (Indica, 15NO3–-N), and when it was applied at heading stage, the loss percentage of absorbed-N was 14.1% (Japonica, 15NH4+-N), 19.0% (Indica, 15NH4+-N), 59.1% (Japonica, 15NO3–-N), 60.8% (Indica, 15NO3–-N), respectively, at harvest, indicating that nitrogen loss was higher when rice was applied with 15NO3–-N than 15NH4+-N either in Indica or Japonica, and for variety, Indica had much more nitrogen loss from leaves than that of Japonica. Accordingly, it may be concluded that 15N-labelled technique showed a high amount of nitrogen loss from leaves of rice.