Depression of Groundwater Table and Reduced Nitrogen Application Jointly Regulate the Bacterial Composition of nirS-Type and nirK-Type Genes in Agricultural Soil

Abstract

Despite the known influence of nitrogen fertilization and groundwater conditions on soil microbial communities, the effects of their interactions on bacterial composition of denitrifier communities have been rarely quantified. Therefore, a large lysimeter experiment was conducted to examine how and to what extent groundwater table changes and reduced nitrogen application would influence the bacterial composition of nirK-type and nirS-type genes. The bacterial composition of nirK-type and nirS-type genes were compared at two levels of N input and three groundwater table levels. Our results demonstrated that depression of groundwater table, reduced nitrogen application and their interactions would lead to drastic shifts in the bacterial composition of nirS-type and nirK-type genes. Structural equation models (SEMs) indicated that depression of groundwater table and reduced nitrogen application not only directly altered the species composition of denitrifier bacterial communities, but also indirectly influenced them through regulating soil nutrient and salinity. Furthermore, the variation in soil NO3−–N and electrical conductivity caused by depression of groundwater table and reduced nitrogen application played the most important role in altering the community composition of denitrifier bacterial communities. Together, our findings provide first-hand evidence that depression of groundwater table and reduced nitrogen application jointly regulate the species composition of denitrifier bacterial communities in agricultural soil. We highlight that local environmental conditions such as groundwater table and soil attributes should be taken into account to enrich our knowledge of the impact of nitrogen fertilization on soil denitrifier bacterial communities, or even biogeochemical cycles.

Different responses of abundant and rare bacterial composition to groundwater depth and reduced nitrogen application in summer maize field

“…Nitrogen is one of the most important limiting factors for the growth of soil microbes ( Sun et al, 2015 ; Hou et al, 2018 ; Zhang et al, 2022 ). Nitrogen fertilizers can not only directly affect soil microbial communities but also indirectly affect soil microbial communities by regulating soil fertility, soil salt content and groundwater salt content ( She et al, 2018 ; Bai et al, 2020 ; Wu et al, 2020 ; Bai et al, 2023 ). However, over-application of nitrogen fertilizers may result in a series of severe environmental problems, including soil salinization, nitrate contamination and groundwater pollution ( Zhang et al, 2013 ; Lasagna et al, 2016 ).…”

“…In the past decades, its groundwater consumption increased sharply because of population growth, urbanization and development of industry and agriculture ( Changming et al, 2001 ; Chen et al, 2020 ; Jing et al, 2023 ; Xiao et al, 2023 ), causing various environmental geologic problems, including groundwater table fall, water quality worsening and surface subsidence ( Changming et al, 2001 ; Shi et al, 2020 ; Gan et al, 2022 ). Notably, groundwater table can regulate soil microbial species richness and composition ( Bai et al, 2020 ; Wu et al, 2020 ; Zhang et al, 2020 ). Besides, groundwater depth change can indirectly influence soil microbial communities by altering soil attributes such as salinity, pH and nutrients ( Bai et al, 2020 ; Zhang et al, 2020 ).…”

“…Notably, groundwater table can regulate soil microbial species richness and composition ( Bai et al, 2020 ; Wu et al, 2020 ; Zhang et al, 2020 ). Besides, groundwater depth change can indirectly influence soil microbial communities by altering soil attributes such as salinity, pH and nutrients ( Bai et al, 2020 ; Zhang et al, 2020 ). The interactions between reduced nitrogen application and groundwater depth have a significant influence on soil microbial communities ( Bai et al, 2020 ).…”

“…Besides, groundwater depth change can indirectly influence soil microbial communities by altering soil attributes such as salinity, pH and nutrients ( Bai et al, 2020 ; Zhang et al, 2020 ). The interactions between reduced nitrogen application and groundwater depth have a significant influence on soil microbial communities ( Bai et al, 2020 ). Furthermore, over-nitrogen form release may lead to severe groundwater contamination ( Matzeu et al, 2017 ; Paladino et al, 2020 ; Abbasi and Sepaskhah, 2023 ).…”

“…Soil microbial communities may be determined by a wide range of soil attributes such as soil pH, salinity and nutrients ( Bai et al, 2020 ; Wan et al, 2020 ; Jiao and Lu, 2020b ; Wang et al, 2021b ). In addition, the effects of different soil factors vary significantly between abundant and rare sub-communities ( Jiao and Lu, 2020b ; Wang et al, 2021b ).…”