Although numerous studies have investigated the individual effects of salinity, irrigation and fertilization on soil microbial communities, relatively less attention has been paid to their combined influences, especially using molecular techniques. Based on the field of orthogonal designed test and deoxyribonucleic acid sequencing technology, the effects of saline water irrigation amount, salinity level of irrigation water and nitrogen (N) fertilizer rate on soil bacterial community structure were investigated. The results showed that the irrigation amount was the most dominant factor in determining the bacterial richness and diversity, followed by the irrigation water salinity and N fertilizer rate. The values of Chao1 estimator, abundance-based coverage estimator and Shannon indices decreased with an increase in irrigation amount while increased and then decreased with an increase in irrigation water salinity and N fertilizer rate. The highest soil bacterial richness and diversity were obtained under the least irrigation amount (25 mm), medium irrigation water salinity (4.75 dS/m) and medium N fertilizer rate (350 kg/ha). However, different bacterial phyla were found to respond distinctively to these three factors: irrigation amount significantly affected the relative abundances of Proteobacteria and Chloroflexi; irrigation water salinity mostly affected the members of Actinobacteria, Gemmatimonadetes and Acidobacteria; and N fertilizer rate mainly influenced the Bacteroidetes' abundance. The results presented here revealed that the assessment of soil microbial processes under combined irrigation and fertilization treatments needed to be more careful as more variable consequences would be established by comparing with the influences based on an individual factor, such as irrigation amount or N fertilizer rate.

中文翻译：

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咸水灌溉施肥对土壤细菌群落结构的综合影响

尽管许多研究已经调查了盐分、灌溉和施肥对土壤微生物群落的个体影响，但对它们的综合影响的关注相对较少，尤其是使用分子技术。基于正交设计试验场和脱氧核糖核酸测序技术，研究了盐水灌溉量、灌溉水盐度水平和氮肥施用量对土壤细菌群落结构的影响。结果表明，灌溉量是决定细菌丰富度和多样性的最主要因素，其次是灌溉水盐度和氮肥施用量。Chao1 估计器的值，基于丰度的覆盖度估计值和香农指数随着灌溉量的增加而减小，而随着灌溉水盐度和氮肥施用量的增加先增加后减小。在最少灌溉量（25 mm）、中等灌溉水盐度（4.75 dS/m）和中等氮肥施用量（350 kg/ha）下，土壤细菌丰富度和多样性最高。然而，发现不同的细菌门对这三个因素有独特的反应：灌溉量显着影响变形杆菌和绿曲菌的相对丰度；灌溉水盐度主要影响放线菌、宝石单胞菌和酸杆菌；和氮肥施用量主要影响拟杆菌的丰度。