【Objective】 There is a long history, more than 400 years, of fertilization at booting stage of single cropping rice (Oryza sativa L.) in the Taihu Lake region. Historical records show it started in the late Ming Dynasty. Fertilization at the booting stage of rice can effectively improve yield and quality of rice. However, ammonia volatilization is liable to occur when top-dressing fertilizer is broadcasted onto paddy fields. Ammonia emitted from agricultural fields brings about adverse effects on the air and water environment, such as smog and eutrophication. How ammonia emits from paddy ecosystems after fertilization at the booting stage of rice is still not clear. 【Method】Field measurement of ammonia emissions from paddy fields at the booting stage of single cropping rice was conducted in the rice season of 2017 in the Taihu Lake region, using simultaneously three different techniques different in monitoring principle, including micrometeorological mass-balance integrated horizontal flux (IHF), dynamic chamber technique and static chamber technique. For the IHF technique, five layers of passive flux ammonia samplers were placed at a set interval around a mast in the center of circular plots (20-m radius) above the soil-water surface, and this apparatus did not need simultaneous measurement of ammonia concentration and wind speed. For the dynamic technique, air exchange rate of 17 times per minute was adopted, and NH₄⁺-N concentration and pH in the floodwater on the surface of the paddy field was measured after surface application of urea. 【Result】Results show that dynamics of the daily ammonia emissions monitored with the three different techniques were similar in feature. Ammonia emission peaked on the second day after surface application of urea and continued till the 5th day when it stopped. The dynamics of the NH₄⁺-N concentration in the surface floodwater and ammonia emission varied similarly. Monitoring with the IHF technique showed that cumulative ammonia (NH₃-N) emission above the rice canopy was 5.45 kg·hm^-2, accounting for 6.73% of the applied nitrogen. Monitoring with the dynamic chamber technique showed that ammonia emission from soil-water surface was 17.4 kg·hm^-2, accounting for 21.5% of the applied nitrogen, and that ammonia emission from the soil-water surface and ammonia emission flux were linearly related with air temperature. And monitoring with the dynamic chamber technique showed that the optimal timing for air sampling was 8:00~9:00 and 16:00~17:00. What it monitored was ammonia emission potentials from the soil-water surface after surface application of urea, without taking into account the volatilized ammonia captured by the rice canopy. Consequently, the dynamic chamber technique tended to overestimate ammonia emissions from paddy fields at the booting stage of rice after urea application. In using this technique to monitor ammonia emission in different treatments and their replicates, it is essential to have uniform air chamber specifications and air flow rates. Like the dynamic chamber technique, the static chamber technique monitored ammonia emission from the soil-water surface. However, the former was much higher than the latter in air exchange rate in the chamber, because the air exchange was somewhat hindered in the chamber of the latter. So the ammonia flux monitored with the static chamber technique was much lower than that monitored with the dynamic chamber technique. 【Conclusion】The assessment of ammonia emission from paddy fields after fertilization at the booting stage of rice should be based on what is obtained with the micrometeorological IHF method because it monitors ammonia emission above the canopy of the crop. As when topdressing urea is applied to rice at its booting stage, the crop has already formed its canopy, which covers almost the whole soil-water surface of the paddy field and recaptures and absorbs the ammonia emitted from soil-water surface. Hence as a matter of fact, the ammonia emission in the rice ecosystem is not serious. The dynamic chamber technique is only suitable for monitoring ammonia emissions from soil-water surface when the rice plant is still at its growth stages after transplanting.