水肥气耦合滴灌番茄地土壤N2O排放特征及影响因素分析

Characteristics and influencing factors of N2O emission from greenhouse tomato field soil under water-fertilizer-air coupling drip irrigation

为了解水肥气耦合滴灌下不同水肥气调控措施对土壤N2O排放的影响,该研究设置施氮量(低氮和常氮)、掺气量(不掺气和循环曝气处理)和灌水量(低湿度和高湿度处理)3因素2水平完全随机试验,通过静态箱-气相色谱法、q PCR技术和结构方程模型,系统研究了不同水肥气组合方案下温室番茄地土壤N2O排放特征及其与相关影响因素之间的关系。结果表明,水肥气耦合滴灌下N2O排放峰值出现在施氮后2 d内,其余时期N2O排放通量较低且变幅较小。施氮量、掺气量和灌水量的增加可增加土壤N2O排放通量和排放总量。其中,高湿度条件下N2O排放总量较低湿度平均增加了30.14%,曝气条件下N2O排放总量较对照平均增加了35.16%,常氮条件下N2O排放总量较低氮平均增加了33.83%。施氮量、掺气量和灌水量的增加可提高温室番茄的产量和氮肥偏生产力。土壤NH4+-N和NO3--N含量对N2O排放的总效应为0.60和0.79,是影响水肥气耦合滴灌下土壤N2O排放的主导因子。综合考虑作物产量、N2O排放总量和氮肥偏生产力,常氮曝气低湿度处理是适宜的水肥气耦合滴灌方案。

Water-fertilizer-air coupling drip irrigation is a new type of drip irrigation technology,which covers both the advantages of drip fertilization and aerated irrigation.Water-fertilizer-air coupling drip irrigation can effectively improve the root zone hypoxia stress caused by irrigation,harmonize the water and fertilizer conditions needed for crop production,and unlock the gate of high yield potential of crops.We focus on the effects of different combinations of water,fertilizer and air application on soil nitrous oxide(N2O)emission,and thus to provide scientific supports for N2O emission reduction from greenhouse vegetable filed soil and the increase of crop yield as well as nitrogen use efficiency.A total of 3 factors,2 levels of completely randomized experiment were set up with the three factors and two levels as nitrogen application rate(low and normal nitrogen),aeration rate(non-aeration and continuous aeration)and irrigation amount(low and high soil moisture,82.37 and 123.71 mm),respectively.Through the coupled use of static box gas chromatography,qPCR technology and structural equation model,the relationship between N2O emission from tomato filed soil and its related physical and chemical factors were studied systematically.Results show that water-fertilizer-air coupling irrigation changes soil moisture and soil aeration,and also influences soil N2O emissions.Under low soil moisture treatments,the average ODR(oxygen diffusion rate)of continuously aerated irrigation increases by 7.70%compared with the non-aerated irrigation.While in the high moisture treatments,the average ODR of continuously aerated irrigation increases by 29.23%compared with the non-aerated irrigation treatments.Compared to the low level of irrigation treatment without aeration,the average WFPS(water filled pore space)of the high level of irrigation treatment increases by 12.63%;While under the aeration condition,the average WFPS value of the high level of irrigation treatments increases by 6.12%compared with the low irrigation treatment.The peak N2O emission under water-fertilizer-air coupling irrigation occurs within 2 days after nitrogen application,and the N2O emission flux becomes low and the amplitude is small during the rest of the period.The increases of nitrogen application rate,aeration amount and irrigation amount increase the N2O emission flux and total N2O emission amount from soil.The average N2O emission in the high soil moisture treatment increases by 30.14%compared to the low soil moisture condition.The total N2O emission under aeration treatment increases by 35.16%compared to non-aeration treatment.While the total amount of N2O emissions under normal nitrogen applications increases by 33.83%comparison to the low nitrogen applications.The increase of nitrogen application rate,aeration amount and irrigation amount can increase the yield of greenhouse tomato and the partial productivity of nitrogen fertilizer.The total effects of NH4+-N and NO3--N content on N2O emissions were 0.60 and 0.79,suggesting as the dominant factors affecting soil N2O emissions under water-fertilizer-air coupling irrigation.The yield under the combination of normal nitrogen application level,aeration and high level of irrigation amount is the largest(39.47 t/hm^2).The yield-scaled N2O emission under the combination of normal nitrogen application and low irrigation is the lowest(20.06 mg/kg).Considering crop yield,total N2O emission and nitrogen fertilizer partial productivity,the combination of normal nitrogen application,continuous aeration and low soil moisture treatment is an optimal scheme for water-fertilizer-air coupling irrigation.