地膜的水热效应与麦田土壤N2O排放

通过两个小麦生长期田间试验,研究了地膜覆盖对耕层土壤N_2O排放的影响.结果表明,无论是否耕种小麦,地膜覆盖均能明显提高耕层土壤含水量,且对休耕地的保水作用高于小麦田.小麦田覆膜后增温幅度小于休耕地,但在孕穗期前和成熟期后增温效果大,而小麦生长中期小;尤其能显著提高0～5 cm耕层土壤温度,甚至10 cm深土壤温度.地膜覆盖后小麦田耕层土壤中NO_3~--N平均含量增加5.34 mg·kg~(-1),且小麦生长旺盛期增加量明显.覆膜使大多数小麦生育期土壤N_2O排放通量高于常规耕作,其增排效应与土壤水分、温度、NO_3~--N含量、有机质增加量存在较好的线性关系;小麦田土壤N_2O增排的最大影响因子是耕层5 cm处土壤温度的变化,其次与土壤养分有效性增加密切相关;而休耕地土壤N_2O的增排作用主要受控于覆膜对水热条件及微生物能量供给的改善.

Effects of Film Mulching on Soil Water and Temperature and N_2O Emissions in Wheat Fields

Global warming affects the soil greenhouse gas emission in croplands. The effect of film mulching on soil water and temperature and N_2O emissions was explored in two trials conducted on winter wheat. The results showed that film mulching could significantly improve soil water contents at the cultivated layer, and such effects on soil moisture in the fallow lands was better than that in wheat fields. Film mulching also increased soil temperature at 0～5 cm depth significantly, even at 5～10 cm layer. The warming effect in wheat fields was less than that in fallow lands, and mainly occurred before crop booting and after entering the mature stage. After being mulched, soil NO~-_3-N con-tent in the cultivated layer of wheat field increased by 5.34 mg·kg~(-1) on average, remarkably in the quick-growing stage of wheat. In most wheat growing period, film mulching increased soil N_2O flux when compared with the conventional tillage. Linear correlations were found be-tween soil N_2O flux and soil moisture, temperature, NO~-_3-N and organic matter. In wheat fields, the increasing effect of film on soil N_2O emis-sion was mainly influenced by the temperature changes in the topsoil of 5 cm, followed by the increased soil nutrient availability. In the fallow lands, however, such effect was mainly by the improvements of the film mulching on soil hydro-thermal conditions and micro-organisms en-ergy supply.