Effect of biochar amendment and subsurface drainage on microbial communities in saline coastal soils

【Background】 Soil microorganisms underpin soil functions, and its community is influenced by a multitude of abiotic and biotic factors. The objective of this paper is to study the combined effect of biochar amendment and subsurface drainage on microbial communities in salinized soil in coastal ecosystems. 【Method】 The experiment was conducted in a field at the Yellow River delta, with the subsurface drains spaced by10 m (S10), 20 m (S20), and 30 m (S30), respectively. For each drain spacing, there was a biochar amendment treatment and non-biochar treatment. During the experiment, we measured the changes in soil physicochemical properties and microbial community structure. And the main driving factors for the changes in microbial community structure under synergistic effect of biochar and subsurface drainage were elucidated. 【Result】 Biochar amendment and subsurface drainage altered soil physicochemical properties. Biochar amendment and drain spacing were interactive having a significant impact on salinity, nitrate nitrogen, organic matter and total phosphorus in the soil. The sequencing of AccuITSTM and Accu16STM showed that drain spacing working separately or in combination with biochar amendment had a significant effect on Agaricomycetes and Acidobacteria_Gp4, albeit the underlying mechanisms are elusive. Redundancy analysis and Pearson correlation analysis showed that the absolute abundance of Agaricomycetes and Mortierellomycetes, beneficial for crop growth, were negatively correlated with soil salinity and sodium ions while positively correlated with organic matter and nitrate nitrogen, both at significant levels. Sodium ion content was the key factor affecting soil bacteria and fungi in all treatments we compared. 【Conclusion】 Amending the salinized soil by biochar coupled with subsurface drainage with the drains spaced 10 m apart worked best for improving soil nutrient and soil microbial community structure. It can be used as an improved technique for soil reclamation and agriculture production in salinized soils in coastal regions.