加气灌溉水氮互作对温室芹菜地N2O排放的影响

为揭示加气条件下不同灌溉和施氮量对设施菜地N2O排放的影响,提出有效的N2O减排措施,该研究以温室芹菜为例,设置充分灌溉(1.0 Ep,I1;Ep为2次灌水间隔内φ20 cm标准蒸发皿的累计蒸发量)和亏缺灌溉(0.75 Ep,I2)2个灌溉水平和0 (N0)、150 (N150)、200 (N200)、250 kg/hm2 (N250)4个施氮水平,采用静态箱-气相色谱法对各处理土壤N2O的排放进行监测,并分析不同灌溉和氮肥水平下土壤温度、湿度、矿质氮(NH4+-N和NO3--N)、硝化细菌和反硝化细菌的变化,以及对土壤N2O排放的影响.结果表明:充分灌水温室芹菜地N2O排放显著(P＜0.05)高于亏缺灌溉;施氮显著(P＜0.05)增加了土壤N2O排放,N150、N200和N250处理的N2O累积排放量分别是N0处理的2.30、4.14和7.15倍.设施芹菜地N2O排放与土壤温度、湿度和硝态氮含量呈指数相关关系(P＜0.01),与硝化细菌和反硝化细菌数量呈线性相关关系(P＜0.01),而与土壤铵态氮没有显著相关关系.灌水和施氮提高芹菜产量的同时,显著增强了土壤N2O排放.综合考虑产量和温室效应,施氮量150 kg/hm2、亏缺灌溉为较佳的管理模式.该研究为设施菜地N2O减排及确定合理的水氮投入量提供参考.

Effects of water and nitrogen coupling on soil N2O emission characteristics of greenhouse celery field under aerated irrigation

The global warming potential of nitrous oxide (N2O) is 298 times that of carbon dioxide (CO2),and N2O degrades stratospheric ozone.Agriculture N2O emission accounts for 59％ of anthropogenic N2O emission.Microbial nitrification and denitrification are the major pathways of N2O production in soils.Synthetic fertilizers application in China is still the main way in agricultural production,so the increase of N2O emissions might be inevitable.The annual synthetic nitrogen (N) fertilizer consumption in China increased from 9.34× 106t in 1980 to 22.97× 106t in 2009,and it accounted for more than one fifth of the total world consumption in 2007.The harvest area of vegetable crops rose from 9.5 × 106 hm2 in 1995 to 18.4× 106 hm2 in 2010 in China and is still increasing.The fertilization rate for vegetable crops in China was 628.05 kg/hm2,nearly 2 times that for cereal crops (314.4 kg/hm2) in 2006,of which N fertilizer occupied the largest share.The rough estimation showed that N2O emissions from vegetable fields accounted for 20％ of the total direct N2O emission and N emission accounted for 17％ of total N consumption nationally.Besides,agricultural practices such as irrigation and aeration potentially affect N2O emission from soils through influencing soil physical and chemical characteristics to constrain soil microbial processes.However,the microbial pathways of N2O production after N application and irrigation input in aerated condition are not well known.In order to reveal the effects of water and nitrogen coupling on soil N2O emission characteristics under aerated irrigation,and further put forward effective reduction measures,a field experiment with celery was conducted in greenhouse in Yangling District of Shaanxi Province.The experiment adopted 2 irrigation levels (I1:full irrigation,1.0 Ep;I2:deficit irrigation,0.75 Ep.Ep is the cumulative evaporation from a 20 cm diameter pan between 2 irrigations) and 4 N levels (N0:0 kg/hm2;N150:150 kg/hm2;N200:200 kg/hrn2;N250:250 kg/hm2),and 8 treatments in total.In the present study,the effects of irrigation levels,nitrogen application amount,soil temperature and moisture,quantities of nitrifying bacteria and denitrifying bacteria on soil N2O emission were also analyzed.The results showed that the N2O emission from the full irrigation treatment was significantly higher than the deficit irrigation treatment.Nitrogen increased the cumulative N2O emission significantly under the same irrigation level.The cumulative N2O emissions of N150,N200 and N250 treatments were 2.30,4.14 and 7.15 times that of N0 treatment in the whole growing season of celery,respectively.The correlation analysis showed that the significant exponential relationships existed between soil N2O emission and soil temperature,water filled pore space (WFPS％),and nitrate content.And the significant positive relationship was observed between soil N2O emission and nitrifier and denitrifier.There was no relationship between soil N2O emission and soil ammonium content.Irrigation and fertilization were contributed to the improvement of crop yield,but the soil N2O emission was also significantly increased.Therefore,the combination of N application amount of 150 kg/hm2 and deficit irrigation was the best coupled mode of water and nitrogen to increase celery yield and reduce N2O emission among the 4 treatments.It should be heavily emphasized in future in the Northwest China.The results can provide valuable information for the selection of water-saving and nitrogen-saving method in Northwestern region.