垄作覆膜条件下田间氨挥发及影响因素

Factors Influencing Ammonia Volatilization in a Winter Wheat Field with Plastic Film Mulched Ridges and Unmulched Furrows

通过大田试验,采用密闭法研究了垄沟覆膜栽培条件下冬小麦生育期内土壤氨挥发动态过程及相关土壤理化性质.结果表明,生育期内垄沟覆膜处理氨挥发累积量(以N计)为(1.66±0.3)～(3.28±0.51)kg.hm-2,常规栽培为(4.68±0.35)kg.hm-2,垄作栽培比常规栽培减少了29.8%～63.8%,氮肥损失率从常规栽培的1.9%下降到了0.3%～0.8%.小麦生育期内土壤氨挥发速率先升后降,冬前高、冬后低.常规栽培土壤氨挥发主要发生在越冬前,其挥发量占总挥发量的82%;而垄作栽培的越冬前挥发量只占挥发总量的49%～61%.越冬前常规栽培土壤氨挥发速率受土壤铵态氮浓度和土壤含水量的共同影响;而垄作条件下土壤氨挥发主要受土壤铵态氮浓度影响,地表温度和土壤含水量通过土壤铵态氮间接影响氨挥发.返青后2种栽培模式下的氨挥发主要受土壤铵态氮浓度的影响.常规栽培和垄沟覆膜高施氮量条件下土壤氨挥发累积量动态过程符合对数函数;而不施肥和垄沟覆膜低施氮量条件下的动态过程可以用线性函数表示.垄沟覆膜栽培在一定程度上改变了土壤氨挥发机制和过程,显著降低土壤氨挥发和氮肥损失.

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 NH+4-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 NH+4-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 NH+4-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.