地膜覆盖对菜地生态系统N_2O排放的影响

Effects of Plastic Film Mulching on Nitrous Oxide Emissions from a Vegetable Field

为了探讨地膜覆盖对菜地N_2O的排放通量、土壤剖面N_2O浓度以及土壤温度和湿度的影响,选取西南地区常见菜地(辣椒-萝卜轮作)为研究对象,采用静态暗箱/气相色谱法,进行了为期1 a的野外观测实验.结果表明,在辣椒季,常规处理(不覆膜)N_2O的平均排放通量为1000.0μg·(m^2·h)^(-1),覆膜处理为400.6μg·(m^2·h)^(-1),覆膜显著低于常规处理(P<0.05);而在萝卜季,N_2O的平均排放通量则表现为覆膜处理[128.1μg·(m^2·h)^(-1)]高于常规处理[107.8μg·(m^2·h)^(-1)],但两者差异未达到显著水平(P>0.05).覆膜和常规菜地土壤中N_2O含量均基本随土层深度的增加而增加,表现为:30 cm>20cm>10 cm,相同处理各层次土壤N_2O含量间均呈显著相关,不同处理相同深度处的土壤N_2O含量间也存在显著的正相关关系.对不同土层中的N_2O含量与地表N_2O排放通量的相关性分析可得出,常规处理各土层处的N_2O含量与地表N_2O排放通量呈显著正相关关系.覆膜处理的N_2O排放通量仅与30 cm深土壤中的N_2O含量存在显著正相关关系.通过对土壤湿度和温度的观测可以得出,地膜覆盖对土壤的增温效应在夏季更加明显,对土壤的保水作用在秋冬季更加突出.相关性分析和主成分分析结果表明,土壤中氮素形态是决定农田N_2O排放最重要的因素,其中常规菜地N_2O排放主要受土壤中总氮含量的影响,而覆膜菜地N_2O的排放对土壤中无机态氮含量的变化更加敏感.

Considering the common cropping system（ chili-radish rotation） in Southwest China,the objective of this study is to explore the effect of plastic film mulching on N2O flux,N2O concentrations in the soil profile,soil temperature,and humidity from a vegetable field. The method of the static opaque chamber was used and the experimental period lasted for one year. The results showed that the average flux of N2O was 1000. 0 μg·（m^2·h）^-1in the conventional treatment and 400. 6 μg·（m^2·h）^-1in the film mulching treatment during the chili growing period. The N2O flux of the film mulching treatment was significantly lower than that of conventional treatment（ P〈 0. 05）. However,in the radish growing season,the N2O flux of the film mulching treatment was higher than that of conventional treatment,but the difference between the two treatments was not significant（ P〉0. 05）. N2O concentrations in the soil profile of the two treatments both increased with the increase in soil depth. The N2O concentrations showed significant correlations among the different soil profiles of each treatment; meanwhile,there was also a significant correlation between soil N2O concentrations at the same soil depth in different treatments. There was a significant positive correlation between the N2O concentration in different profiles and N2O fluxes in surface soils in the conventional treatment,but the N2O flux under the plastic mulching film treatment was only positively correlated with the N2O concentrations of 30 cm deep soil. The soil moisture and temperature observations showed that the effect of plastic film mulching on soil temperature was more significant in summer and the soil moisture was more prominent in autumn and winter. However,the results of the correlation analysis and principal component analysis showed that N2O emissions were mainly determined by the distribution of nitrogen in the soil and were affected by the change in soil total nitrogen content in the conventional treatment but N2O emissions were more sensitive to the variation in soil inorganic nitrogen in the film mulching treatment.