| Nitrous oxide(N2O)is an important greenhouse gas,and agricultural soils contributed about 75%of global N2O emissions.Greenhouse vegetable field is considered as the hot spot of soil N2O emission because of its high nitrogen fertilizer input and other reasons.Compared with chemical fertilizers,organic fertilizers can alleviate soil acidification,improve soil structure and stimulate soil microbial activities.However,the effects of organic fertilizer on N2O emissions for greenhouse vegetable plots had shown inconsistent results.Besides,only a few researches focused on the functional microbes related to nitrogen cycle and how they affect the soil N2O emission.This study focused on organic fertilizer and greenhouse vegetable fields,which consists of two parts.On the first part,the windrow composting system(test Ⅰ)were conducted to study the N2O emission from the preparation process of organic fertilizers using vented chamber technique.The second part was the in-situ observation test(test Ⅱ)on the influence of organic fertilizer application on the N2O emission of vegetable fields.The N2O fluxes of vegetable field(cucumber)were measured by gas chromatography.Meanwhile,the abundance of functional genes(AOA,AOB,nirS,nirK and nosZ)involved in soil N2O emissions was determined by q-PCR,and the relationship between functional genes and N2O emission was further analyzed.The research results were showed as follows:Test Ⅰ:1)During the process of organic fertilizer preparation,the early stage of the N2O emission is low;and then the N2O emissions dramatically increased with the declined temperature.,The N2O flux varied within the range of 6.88-164.46 mg·m-2·d-1,and the cumulative N2O emission was 2.35g·m-2 from the whole measurement period.2)The pile temperature stably raised in the early stage of compost,and then declined,and the pile temperature changes between 44-71℃.The water content of piles decreased rapidly with the composting process,ranging from 12.35%to 62.46%.The pile pH varies from 6.72-7.4.The NH4+-N concentration ranged from 1.96 g·kg-1-3.00 g·kg-1,and the NO3--N concentration ranged from 0.21 g·kg-1-0.77 g·kg-1.3)The q-PCR results showed the variation ranges of gene abundance of AOA,AOB,nirS,nirK and nosZ were 4.35-5.96 log copy numbers g-1,5.12-6.40 log copy numbers g-1,5.91-8.61 log copy numbers g-1,5.23-7.79 log copy numbers g-1 and 6.25-6.95 log copy numbers g-1,respectively.The Pearson correlation analysis between N2O fluxes and functional genes abundance showed that the N2O fluxes positively correlated to AOB and nirK gene abundance(P<0.05).In addition,the NH4+-N concentration was positively correlated to water content,nirK and nosZ gene abundance(P<0.01).The NO3--N concentration was significantly positively correlated with the abundance of AOA,AOB,nirS and nirK gene(P<0.01).There was a significant positive correlation between pile temperature and nosZ gene abundance(P<0.05).Test Ⅱ:1)During the cucumber growth period,the average N2O flux of control(CK),chemical fertilizers(CF)and organic fertilizer(OF)treatment was 46.2,117.8,and 74.1μg·m-2·h-1,and the cumulative N2O emissions were 0.74,1.89,and 1.19 kg N2O-N ha-1,respectively.The N2O flux of CK treatment varied within the range of 8.7-149.5 μg·m-2·h-1.The N2O fluxes treated by CF and OF varied within the range of 12.6-362.6 μg·m-2·h·-1 and 6.4-258.4 μg·m-2·h-1,respectively.Compared with CK treatment,the seasonal N2O emissions under CF and OF treatment increased by 1.55 and 0.61 times respectively.The cumulative N2O emissions were significantly increased under fertilization treatments(P<0.05).In addition,compared with CF treatment,OF treatment significantly reduced soil N2O emission by 37%(P<0.05).2)The vegetable yields were depended on the fertilizer application.Compared with CK treatment,CF and OF treatment increased the cucumber yield by 9.6%and 14.4%,respectively.3)During the whole cucumber growing season,soil temperature ranged from 21℃ to 25.7℃.WFPS changes within the range of 37.9-92.9%,and no significant difference was observed from all the treatments(P>0.05).The NH4+-N concentration for CF treatment,within the range of 12.5-103 mg·kg-1,was significantly higher than that in other treatments(P<0.05).In addition,there was no significant difference for NO3--N concentration between all treatments(P>0.05).Correlation analysis results showed that WFPS,NH4+-N and NO3--N concentration were significantly positively correlated with N2O emission(P<0.05).4)According to q-PCR results,the application of fertilizer(inorganic and organic fertilizer)significantly increased the AOB gene abundance(P<0.05).The amendment of organic fertilizer significantly increased the nirK gene abundance(P<0.05).No difference for nirS gene abundance was observed from all treatments(P>0.05).The highest value of(nirK+nirS)/nosZ was observed in OF treatment.The soil N2O flux was significantly positively correlated with AOA,AOB and nirK gene abundance(P<0.05). |
PDF Full Text Request