Factors Influencing Ammonia Volatilization in a Winter Wheat Field with Plastic Film Mulched Ridges and Unmulched Furrows
垄作覆膜条件下田间氨挥发及影响因素

The objective of this experiment was to quantify ammonia volatilization from a winter wheat field with plastic film mulched-ridges and unmulched-furrows (PMRF). The trial was conducted during the 2010-2011 winter wheat growing season at Yangling, Shaanxi Province. Ammonia volatilization from the soil was measured using the closed-chamber method. The results indicated that NH3 emission losses ranged between (1.66±0.3) and (3.28±0.51) kg·hm-2 in the PMRF treatment. In comparison, the NH3 emission loss was (4.68±0.35) kg·ha-1 in the conventional tillage treatment (i.e., smooth soil surface). The PMRF treatment reduced NH3 emissions by 29.8 to 63.8% compared with the conventional treatment. The NH3 emission losses were equivalent to 1.9% of the applied N in the conventional practice treatment. In contrast, the losses were equivalent to only 0.3% to 0.8% of the applied N in the PMRF treatment. Ammonia emissions were greatest during the first two weeks after sowing. Emissions before winter accounted for 82% of total NH3 emission in the conventional practice treatment, but only 49% to 61% of the total NH3 emission in the PMRF treatment. The soil NH4+-N content and the soil moisture content had direct effects on NH3 emission before winter in the conventional treatment. In the PMRF treatment, the soil NH4+-N content had a direct effect on NH3 emission before winter, whereas soil surface temperature and soil moisture had indirect effects. Ammonia emissions after the greening stage were mainly influenced by the soil NH4+-N content. Simulation results indicated that logarithmic functions best described cumulative NH3 emission in the PMRF+high N rate treatment and the conventional treatment. A linear function best described cumulative NH3 emission in the PMRF+low N rate treatment and the unfertilized treatment. In conclusion, the PMRF treatment can significantly reduce N losses from winter wheat fields by changing the spatial-temporal dynamics of soil NH3 volatilization.