华北山前平原农田氨挥发速率与调控研究

Ammonia volatilization and control mechanisms in the piedmont of North China Plain

本文依托中国科学院栾城农业生态系统试验站小麦-玉米轮作长期田间试验,利用双层海绵氨吸收装置,分析了不同施肥处理下氨挥发速率和损失量的变化规律;并采用室内培养试验方法,分析了浇水和秸秆还田等不同措施下氨挥发变化特征。结果表明,肥料施用时间、土壤温度和灌水等因素显著影响土壤氨挥发速率;氨挥发损失量在0.66-35.00 kg.hm-2.d-1之间,占施肥量的0.09%-14.90%,且大部分氨挥发发生在夏玉米时期。施肥后及时浇水能有效减少氨挥发,特别是在低初始水分条件下最为明显;而在高土壤水分含量条件下,浇水时间对氨挥发量的影响减弱。与单施化肥相比,小麦或玉米秸秆混合配施化肥增加了石灰性土壤的尿素水解速率,缩短了尿素的氨挥发时间,并可显著减少氨挥发损失。单施尿素的累积氨挥发损失量占尿素施用量的7.2%-9.7%,而小麦或玉米秸秆配施尿素的累积氨挥发损失量分别占尿素施用量的1.1%-2.1%和2.2%-7.2%。因此,为了减少农田氨挥发损失,在施用尿素时应充分考虑土壤水分状况和秸秆类型对氨挥发的影响。

As an important mode of nitrogen（N） loss,ammonia volatilization in farmlands causes air pollution and water eutrophi-cation.Increased N application dose should be accompanied with reduced ammonia volatilization to improve N fertilizer efficiency.This could lay a strong theoretical basis for optimal fertilizer use.To that end,a double-layer-sponge-trapping method was used to measure ammonia volatilization following the application of different N fertilizers in the growing season of wheat-maize double cropping system and in an incubation experiment with different soil moistures or amended with wheat or corn straw.The experiments were conducted at the Luancheng Agro-Ecosystem Experimental Station（LAES） of Chinese Academy of Sciences from October 2002 through June 2004.Urea N fertilizer was applied at the rates of 200,400 and 600 kg（N）-hm-2-a-1,respectively,and with no N fertilizer as the control.The study showed that ammonia volatilization was significantly affected by the fertilization dose and time,soil moisture and irrigation mode.For winter wheat,ammonia volatilization occurred immediately after N fertilizer application.It gradually increased,apparently reaching the maximum in the first 1-5 days after fertilization.Ammonia volatilization was high dur-ing summer maize growing season,increased sharply after（N fertilizer） dressing,and hit the highest rate on the 1st day after fertili-zation.N loss via accumulated ammonia volatilization was 0.66-35.00 kg（N）-hm-2-d-1,accounting for 0.09%-14.90% of the applied fertilizer.Ammonia volatilization largely occurred in summer maize season,accounting for 80% of N loss in the double cropping system.The high ammonia volatilization in the summer maize season was due mainly to the high temperature and overland broadcast mode of fertilization.Irrigation reduced ammonia volatilization.The earlier the irrigation after fertilization was conducted,the less was ammonia volatilization.Ammonia volatilization also increased with lower initial water content.Amendment with wheat or maize straw increased the rate of urea hydrolysis in loam soils,triggering peak NH3 loss to occur one day earlier and much lower than non-amended urea.With urea alone,cumulative NH3 loss was 7.2%-9.7% of applied urea.When urea was amended with wheat or maize straw,cumulative NH3 loss was only 1.1%-2.1% or 2.2%-7.2% of applied urea,respectively.Thus the characteristics of am-monia loss were dependent on the modes of application of urea and soil moisture conditions.