Changes in soil microbial community structure and enzyme activity with amendment of biochar-manure compost and pyroligneous solution in a saline soil from Central China

• Amendment of biochar-manure plus pyroligneous solution increased microbial biomass.
• Enzyme activities significantly enhanced in bulk soil but no change in rhizosphere.
• Change over years in bacterial gene abundance differed from in fungi.
• Diversity increased for bacteria in bulk soil but reduced in rhizosphere for fungi.
• Amendment altered bacterial community composition altered with new bands emerged.

Salt stress has been increasingly constraining crop productivity in arid and semiarid lands of the world. In a previous study, salt stress was alleviated and maize productivity improved remarkably with soil amendment with biochar poultry-manure compost (BPC) in conjunction with pyroligneous solution (PS) in a saline soil from Central China Plain. In 2010, before maize sowing, BPC was incorporated into topsoil at 12 t ha−1 following surface spray of diluted PS solution at 0.15 t ha−1 one week in advance (BPC-PS2). Such an experiment was repeated in adjacent fields in 2011 (BPC-PS1). Both bulk and rhizosphere samples of these experiment plots were collected at the vegetative growth stage of maize in 2012. Microbial biomass carbon (Cmic) and nitrogen (Nmic), and soil enzyme activity were measured. Based on 16S rRNA and 18S rRNA gene, bacterial and fungal community structure and abundance were respectively characterized using denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR (qPCR). With the amendment, Cmic and Nmic, and bacterial gene abundance were significantly and greatly increased in both bulk and rhizosphere samples, being greater under BPC-PS2 than under BPC-PS1. On contrast, smaller increase in fungal gene abundance was observed, along with a significant reduction in fungal diversity under BPC-PS2. In addition, two single bands belonging respectively to Alphaproteobacteria and Deltaproteobacteria emerged in the amended soil. Meanwhile, activities of urease, invertase and phosphatase in both bulk soils and rhizosphere soils were increased by 19–44% with the amendment except of urease in rhizosphere soils. Therefore, with the great enhancement of microbial growth and enzyme activities, combined use of biochar and poultry manure with pyroligneous solution could be a practical option to alleviate salt stresses on plant and soil microbial community in order to improve crop production in saline soils.