菜地土壤CO2与N2O排放特征及其规律

为了解不同集约化类型菜地土壤CO2和N2O排放特征及影响因子,选取京郊20年露地老菜地(OV20)、3年菜地种植历史的露地新菜地(OV3)、3年大棚菜地(GV3),以及相邻的当地典型粮田玉米地(Maize)4个类型地块,研究了春黄瓜生育期间土壤CO2和N2O排放特征及影响因子。结果表明:1)春黄瓜生育期间的土壤CO2排放通量主要受土壤5 cm处温度(指数关系)和土壤水分(对数关系或二次抛物线关系)影响;期间玉米地土壤CO2平均排放通量为(346.8±56.5)mg.m-2.h-1,20年露地菜地、3年露地菜地有机肥处理、3年露地菜地配施处理、3年大棚菜地的土壤CO2平均排放通量分别是玉米地的1.38、1.21、1.39和1.56倍。2)土壤N2O排放通量与施肥活动密切相关,排放高峰都出现在氮肥施用后,并受土壤温度和水分的影响。基肥后土壤温度低(15～20℃),排放峰出现在第5 d,排放峰持续时间(长达20 d)与施肥量相关;追肥后土壤温度高(>20℃),排放高峰发生早(追肥后第3 d),但因追肥用量低,因此持续时间短(仅一周)。3)黄瓜生长期内玉米地N2O累积排放量为N(1.95±0.10)kg.hm-2,20年老菜地、3年大棚菜地和3年新菜地N2O累积排放量分别是同期大田玉米地的1.67、1.95和1.99倍。4)本实验中春黄瓜生长季菜地土壤化肥氮N2O排放系数在1.86%～4.71%之间,显著高于IPCC旱地排放缺省值1%。其中,新菜地排放系数高于老菜地,设施菜地排放系数高于露地菜地;但有机肥氮的N2O排放系数则远远低于化肥氮的排放系数,仅为0.11%。

Study on the characteristics of CO2 and N2O emission from different vegetable soils

To identify the characteristics and influence factors of CO2 and N2O emission from the different intensified vegetable soils,we selected four typical fields to do the experiment which include the typical open-ground vegetable field which had over 20 years history of planting vegetable crops(OV20),new developed open-ground vegetable field which had 3 years planting history of vegetable crops converted from maize(OV3),the new developed greenhouse vegetable field which was converted from a typical maize field 3 years early(GV3),and the typical local maize field(maize).The results showed that:i)The emission flux of soil CO2 was affected mainly by soil temperature described by the exponential function and soil moisture described by the logarithmic or second-degree parabola function.The average soil CO2 emission flux from maize field was(346.8±56.5) mg· m-2·h-1 through March to July during the spring cucumber growth period,while the CO2 emission flux from OV20,OV3-M,OV3,and GV3 fields were 1.38,1.21,1.39,and 1.56 times of that from maize field respectively.ii)Soil N2O emission flux was mainly controlled by fertilization activities and also influenced by the soil temperature and soil water content.The emission peak occurred five days since basal application happened when soil temperature was at 15~20℃ and the emission peak lasted 20 days.The emission peak occurred 3 days later just after topdressing and lasted one week when soil temperature was higher than 20℃.iii)The accumulated soil N2O emission flux from maize field was N(1.95±0.10) kg·hm-2 through March to July during the spring cucumber growth period,while the N2O-N emitted from OV20,GV3,and OV3 fields were about 1.67,1.95,and 1.99 times of that from maize field respectively.iv)The N2O emission factor of chemical nitrogen was at the range of 1.86%~4.71% for the different vegetable fields during the spring cucumber growth period(through March to early-August),which were higher than the IPCC default value(1%)for the cropland soil.The emission factors of different vegetable soils were OV3>OV20,and it was also higher for the greenhouse vegetable soil than that for open-ground vegetable soil.The emission factor of organic nitrogen was lower as to 0.11%.