寿光设施菜地土壤N_2O排放规律及其影响因素

N_2O emission from the greenhouse soils in Shouguang City,northern China

设施栽培是我国蔬菜生产的重要方式之一.设施菜地土壤高温、高湿、持续且大量施肥等特点,可能改变土壤氮素周转及N_2O排放.寿光是我国重要的蔬菜生产基地之一.然而,鲜有研究关注寿光市设施菜地土壤N_2O排放规律及其影响因素.本文以寿光市农田、种植6、12年设施菜地及荒废设施菜地为例,研究农田转变为设施菜地后土壤N_2O排放规律,并探讨其影响机理.结果表明,设施菜地土壤N_2O年排放量明显高于农田及荒废设施菜地,且种植6年设施菜地土壤N_2O年排放量显著大于种植12年设施菜地(P<0.05).其原因可以归结为:(1)设施菜地种植过程中施加大量有机肥及化肥,会促进土壤氮素周转.(2)设施菜地土壤温度、含水率及硝态氮含量均高于农田,且均与土壤N_2O排放通量呈显著正相关关系(P<0.05),表明设施菜地土壤高温、高湿的环境特点会促进土壤硝化过程,加速土壤N_2O排放.(3)设施菜地具有较高的土壤脲酶活性,且与土壤硝态氮含量、含水率呈显著正相关关系(P<0.05),表明农田变为设施菜地增加了土壤脲酶活性,促进土壤硝化过程及硝态氮累积,这可能间接加速土壤N_2O排放.

Nitrous oxide （N2 O） is an important greenhouse gas. Greenhouse is a vital method of vegetable production in China. Due to high soil temperature, moisture and continuous and large quantities of fertilizer application, these factors may change the nitrogen cycling and N2 O emissions. Shouguang city is one of the largest bases for vegetable production in China where many farmland （FL） were changed into greenhouse for the vegetable production. However, little attention has been paid to the N2 O emissions from the greenhouse soils in Shouguang city. In the present study, farmland（ FL）, greenhouse soils that were cultivated for 6 （6GH） and 12 （12GH） years and greenhouse abandoned for 12 years （AG） were taken as samples to investigate the variation of soil N2 O emissions along the changes from FL to greenhouse and AG. The results showed that FL had similar annual N2 O emissions with AG. Greenhouse had higher annual N2 O emissions compared with FL, while the annual N2 O emission in 6GH was larger than that in 12GH. It may be attributed to the following reasons. （1） More organic fertilizer were applied in the greenhouse soils compared with FL, which may supply more available substrates for the soil microbes. （2） Greenhouse had higher soil temperature, moisture and nitrate concentration compared with FL. These factors also had positive relationships with N2 O emissions, which indicate that the increased soil temperature and moisture in greenhouse soils may promote the nitrification and then the N2 O emissions. （ 3） Alteration from FL to Greenhouse enhanced urease activity. The urease activity had positive relationships with soil nitrate and moisture, respectively. These indicate that the increased urease activity may enhance the accumulation of soil nitrate and indirectly accelerate the N2 O emissions through affecting the nitrification. When the greenhouse was cultivated over ten years, the application of fertilizer reduced. This may decrease the supply of available substrates and thus N2 O emission.