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| Effects of long-term saline water drip irrigation on the abundance and community structure of ammonia oxidizers |
| Received:May 30, 2019 |
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| KeyWord:saline water drip irrigation;ammonia-oxidizing archaea;ammonia-oxidizing bacteria;nitrification rate;community structure |
| Author Name | Affiliation | E-mail | | MA Li-juan | Department of Resources and Environmental Sciences, Shihezi University, Shihezi 832000, China | | | ZHANG Hui-min | Department of Resources and Environmental Sciences, Shihezi University, Shihezi 832000, China | | | HOU Zhen-an | Department of Resources and Environmental Sciences, Shihezi University, Shihezi 832000, China | | | MIN Wei | Department of Resources and Environmental Sciences, Shihezi University, Shihezi 832000, China | minwei555@126.com |
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| Abstract: |
| Ammonia-oxidizing microorganisms are the main drivers of soil nitrification. However, little is known about the effects of saline water irrigation on the ammonia-oxidizing archaea(AOA)and ammonia-oxidizing bacteria(AOB)communities and their relative contribution to soil nitrification. Toward this end, a 10-year field experiment was conducted to evaluate the effects of long-term saline water irrigation on AOA and AOB in alluvial gray desert soil. The experimental design comprised three irrigation water salinity levels established at 0.35, 4.61, and 8.04 dS·m-1, representing freshwater, brackish water, and saline water, respectively. Irrigation with brackish water and saline water reduced the soil NO3--N content and potential nitrification rate(PNR), while the soil salinity and NH4+-N content increased markedly. The amoA gene copy numbers of AOA and AOB were in the range of 2.2×106~3.6×106 and 1.9×105~3.2×105 copies·g-1dry soil, respectively. Irrigation with brackish and saline water decreased the amoA gene copy numbers of AOA and AOB. The AOA/AOB ratios were 11.3 and 11.2 in the freshwater and saline water treatments, respectively, indicating that more brackish water irrigation decreased the AOA/AOB ratios. Moreover, the PNR was positively correlated with AOA and AOB abundance(P<0.001). The number of operational taxonomic units (OTUs)of AOA based on the amoA gene was larger than that of AOB under different irrigation water salinity treatments. Irrigation with brackish and saline water significantly decreased the OTUs of AOB. Compared with freshwater irrigation, irrigation with brackish and saline water significantly increased the Shannon diversity index of AOA, while saline water treatment significantly reduced the Shannon index of AOB. The dominant groups of the AOA and AOB communities were Candidatus Nitrosocaldus and Nitrosospira, respectively. Irrigation with saline and brackish water inhibited the growth of Betaproteobacteria in the AOA community, while the abundance of Candidatus Nitrosocaldus in irrigation with saline water was significantly higher than that under irrigation with freshwater and brackish water. The relative abundance of Nitrosomonas in the AOB community decreased significantly with increasing salinity of the irrigation water. Lefse analysis revealed only one differential species in AOA under irrigation with saline water, while five differential species were detected in AOB under irrigation with brackish water. Redundancy analysis showed that the variations in AOA community structure were closely associated with the changes in soil NO3--N, pH, and salinity, whereas the AOB community structure was only significantly correlated with NO3--N and pH. In conclusion, salinity was the dominant factor affecting the growth of ammonia-oxidizing microorganisms and community structure. AOB may be the dominant microbial population of nitrification with freshwater and brackish water irrigation, while AOA may be the dominant microbial population with saline water irrigation. These results can provide a scientific basis for further exploring the response mechanism of ammonia-oxidizing microorganisms and their roles in nitrogen transformation in the agricultural soils of arid areas. |
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