| Twenty years practice showed that problems in terms of resources and ecological security have been new restrictive factors to China's continuous food high yield. The loss of farmland ammonia volatilization is not only introducing reduction of nitrogen fertilizer use efficiency, waste of resources, but also causing a lot of eco-environmental problems. But related studies revealed that the measuring methods and means were backward on ammonia volatilization, from farmland ecosystem in our country, the new technologic research and new method application were not in-time. The data accumulation of farmland ammonia volatilization from continuous and automatic monitoring system was deficient. All of these were affected our scientific research level of agro-ecosystem in some extents. So the study was carried out on the application of tunable diode laser absorption spectroscopy technique, which was high time resolution and high sensitivity.Fengqiu State Experiment Station for Agro-ecosystem in Henan Province in the Huang-Huai-Hai Plain was selected as the research area in this study. This study was emphatically carried out about the mew methods of ammonia volatilization monitoring, ammonia volatilization loss and its affecting factors. The open path tunable diode laser absorption spectroscopic (TDLAS) technology was an online and continuous measurement from a field, which combined with micro-meteorological method of backward Lagrangian Stochastic (bLS) dispersion technique. From comparing with venting method, the main results were as follows:(1) Ammonia volatilization from topsoil occured mainly within one week after fertilization. Ammonia volatilization rate, total ammonia (N) loss and its proportion in total amount of applied N fertilizer were increased with the increase of applied fertilizer under different application ways. Ammonia volatilization was considerably influenced by the applied fertilizer in soil depth. Under furrow fertilization of base fertilizer, the accumulated amount of ammonia volatilization was obviously higher than that of traditional fertilization, except the situation under N fertilizer application amount of 150 kg/hm2,while the situation was opposite for top dressing.The proportions of ammonia volatilization loss from winter wheat field varied in ranges of 4.78%～6.72% and 4.31%～11.24% of the total applied amount of N fertilizer under the traditional fertilization and furrow fertilization respectively. Moreover, the ammonia volatilization loss was less than 10% under both the traditional fertilization and furrow fertilization. The ammonia volatilization loss was in an order of F3B(D)> F2B(D)> F3A(C)> CK> F1A(C)> F1B(D). There was a positive correlation between the ammonia volatilization rate and the NH4+-N concentration in topsoil. But a negative correlation was found between the ammonia volatilization rate and pH value. Climatic conditions, such as temperature and rainfall, affected ammonia volatilization in a certain degree, lower temperature and rainfall restricted ammonia volatilization.(2) Tunable diode laser absorption spectroscopic (TDLAS) technology can measure continuous and dynamic ammonia volatilization concentration variation. This system could be realized on the online and continuous measurement of ammonia volatilization. The total ammonia (N) loss from winter wheat was 27.51 kg N hm-2. The proportion of total amount of applied N fertilizer was 24.3% during top dressing period detected by TDLAS-bLS method, significantly greater than venting method determining (5.11 kg N hm-2 and 4.52%). As wind direction controlled was not strict, TDLAS-bLS method may overestimate the actual volatile situation. There were significant positive correlations between the ammonia volatilization estimated by TDLAS-bLS method and atmospheric temperature, wind velocity, temperature in soil layers of 0～5 cm and 5～10 cm respectively.(3) NH3 emission rate from summer maize field was 7.57 kg N hm-2, and with 5.41% of total N fertilizer detected by TDLAS-bLS method. Simultaneously, venting method was 0.82 kg N hm-2 and 0.59%. The both were quite similar. Ammonia volatilization estimated by TDLAS-bLS had a significant positive correlation with atmospheric temperature, wind velocity, wind direction and topsoil temperature respectively. |
