Abstract
Soil microbes provide important ecosystem services. Though the effects of changes in nutrient availability due to fertilization on the soil microbial communities in the topsoil (tilled layer, 0–20 cm) have been extensively explored, the effects on communities and their associations with soil nutrients in the subsoil (below 20 cm) which is rarely impacted by tillage are still unclear. 16S rRNA gene amplicon sequencing was used to investigate bacterial and archaeal communities in a Pup-Calric-Entisol soil treated for 32 years with chemical fertilizer (CF) and CF combined with farmyard manure (CFM), and to reveal links between soil properties and specific bacterial and archaeal taxa in both the top- and subsoil. The results showed that both CF and CFM treatments increased soil organic carbon (SOC), soil moisture (MO) and total nitrogen (TN) while decreased the nitrate_N content through the profile. Fertilizer applications also increased Olsen phosphorus (OP) content in most soil layers. Microbial communities in the topsoil were significantly different from those in subsoil. Compared to the CF treatment, taxa such as Nitrososphaera, Nitrospira, and several members of Acidobacteria in topsoil and Subdivision 3 genera incertae sedis, Leptolinea, and Bellilinea in subsoil were substantially more abundant in CFM. A co-occurrence based network analysis demonstrated that SOC and OP were the most important soil parameters that positively correlated with specific bacterial and archaeal taxa in topsoil and subsoil, respectively. Hydrogenophaga was identified as the keystone genus in the topsoil, while genera Phenylobacterium and Steroidobacter were identified as the keystone taxa in subsoil. The taxa identified above are involved in the decomposition of complex organic compounds and soil carbon, nitrogen, and phosphorus transformations. This study revealed that the spatial variability of soil properties due to long-term fertilization strongly shapes the bacterial and archaeal community composition and their interactions at both high and low taxonomic levels across the whole soil profile.
Highlights
Soil microbes play key roles in the functions of ecosystems by cycling nutrients, degrading organic material and pollutants as well as in maintaining the quality of groundwater (Madsen, 1995; Fierer et al, 2003a; King, 2014)
The soil pH in both the chemical fertilizer (CF) and combined with farmyard manure (CFM) treatments was higher in the subsoil (20–90 cm) (Figure 1A), while soil moisture, soil organic carbon (SOC), and total nitrogen (TN) were lower in both CF and CFM treatments at the subsoil (Figures 1B–D)
Soil AK in the topsoil was significantly higher in the CFM (P = 0.05), while they were low in both CF and CFM treatments in the subsoil (Figure 1F)
Summary
Soil microbes play key roles in the functions of ecosystems by cycling nutrients, degrading organic material and pollutants as well as in maintaining the quality of groundwater (Madsen, 1995; Fierer et al, 2003a; King, 2014). In the topsoil (0–20 cm, tilled layer) both the microbial biomass and diversity are the greatest, yet in the subsoil (below 20 cm) microbes are diverse and abundant due to the large volume of soil on a depthweighted basis (Will et al, 2010; Li et al, 2014). The combined use of inorganic and organic fertilizer likely increase the microbial diversity, biomass and activity, and helps to maintain even increase the soil nutrients (Birkhofer et al, 2008; Kumar et al, 2017). Nutrients added to the soil by fertilizer may directly alter the abundance and composition of microbial community in topsoil; in subsoil soluble nutrients leaked from topsoil change these microbial parameters indirectly (Stowe et al, 2010; Eilers et al, 2012). Little is known about the characterization and spatial variability of microbial communities with depth in fertilized paddy soils (Bao et al, 2015; Yu et al, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
