Continuously Monocropped Jerusalem Artichoke Changed Soil Bacterial Community Composition and Ammonia-Oxidizing and Denitrifying Bacteria Abundances.

Xingang Zhou,Zhilin Wang,Li Li,Huiting Jia,Fengzhi Wu

doi:10.3389/fmicb.2018.00705

Abstract

Soil microbial communities have profound effects on the growth, nutrition and health of plants in agroecosystems. Understanding soil microbial dynamics in cropping systems can assist in determining how agricultural practices influence soil processes mediated by microorganisms. In this study, soil bacterial communities were monitored in a continuously monocropped Jerusalem artichoke (JA) system, in which JA was successively monocropped for 3 years in a wheat field. Soil bacterial community compositions were estimated by amplicon sequencing of the 16S rRNA gene. Abundances of ammonia-oxidizing and denitrifying bacteria were estimated by quantitative PCR analysis of the amoA, nirS, and nirK genes. Results showed that 1–2 years of monocropping of JA did not significantly impact the microbial alpha diversity, and the third cropping of JA decreased the microbial alpha diversity (P < 0.05). Principal coordinates analysis and permutational multivariate analysis of variance analyses revealed that continuous monocropping of JA changed soil bacterial community structure and function profile (P < 0.001). At the phylum level, the wheat field was characterized with higher relative abundances of Latescibacteria, Planctomycetes, and Cyanobacteria, the first cropping of JA with Actinobacteria, the second cropping of JA with Acidobacteria, Armatimonadetes, Gemmatimonadetes, and Proteobacteria. At the genus level, the first cropping of JA was enriched with bacterial species with pathogen-antagonistic and/or plant growth promoting potentials, while members of genera that included potential denitrifiers increased in the second and third cropping of JA. The first cropping of JA had higher relative abundances of KO terms related to lignocellulose degradation and phosphorus cycling, the second cropping of JA had higher relative abundances of KO terms nitrous-oxide reductase and nitric-oxide reductase, and the third cropping of JA had higher relative abundances of KO terms nitrate reductase and nitrite reductase. The abundances of amoA genes decreased while nirK increased in the third cropping of JA, nirS continuously increased in the second and third cropping of JA (P < 0.05). Redundancy analysis and Mantel test found that soil organic carbon and Olsen phosphorus contents played important roles in shaping soil bacterial communities. Overall, our results revealed that continuous monocropping of JA changed soil bacterial community composition and its functional potentials.

Highlights

The rapidly increasing global food demand poses a huge challenge for the sustainability of agricultural production (Tilman et al, 2011)
After filtering reads by basal quality control and removing singletons, Illumina Miseq sequencing of bacterial 16S rRNA gene fragments generated 322,976 quality bacterial sequences with an average read length of 397 bp, and 22,503–30,340 sequences were obtained per sample
Our results demonstrated that continuous monocropping of Jerusalem artichoke (JA) changed soil bacterial community composition and function profile, and soil bacterial community diversity was lower the third cropping of JA

Summary

Introduction

The rapidly increasing global food demand poses a huge challenge for the sustainability of agricultural production (Tilman et al, 2011). The continuous monocropping system, in which the same crop is repeatedly monocropped on the same land, is not long-term sustainable, because it usually results in reduction of crop yield and quality, a phenomenon which has been described as ‘soil sickness’ (Cook, 2006; van der Putten et al, 2013). Changes in soil biological properties have been proposed to account for the yield decline in continuous monocropping systems (Nayyar et al, 2009; Huang et al, 2013; Zhou et al, 2017a)

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Results

Discussion

Conclusion