Use of the open-path TDL analyzer to monitor ammonia emissions from winter wheat in the North China Plain

The backward Lagrangian stochastic (BLS) model and open-path tunable diode laser (OPTDL) analyzer were used to monitor ammonia (NH₃) emissions from urea applied to winter wheat in the North China Plain. The high-temporal resolution measurements of ammonia concentrations provided an opportunity for estimating the diel patterns of ammonia emissions, as well as valuable information about the factors that influence NH₃ emissions. The results showed both large diel variability and daily variability in NH₃ volatilization, with NH₃ emissions highest during the daytime. The diel pattern of ammonia volatilization depended mainly on the diel variation of wind speed and soil temperature, while the overall pattern of NH₃ loss was strongly affected by soil moisture content, soil NH₄ ⁺-N concentration, wind speed and soil temperature. At the end of the measurement period, the cumulative NH₃ loss was 12.21–16.43 kg N ha^?1, calculated based on different time scale average Q _BLS. Due to sensitivity of the OPTDL analyzer, the estimated total ammonia loss was still doubtful in this study.