Long-term Effects of Biochar Application on Rhizobacteria Community and Winter Wheat Growth on the Loess Plateau in China

The use of biochar as a soil amendment has obvious impacts on soil biota and crop productivity. However, the relationship between the rhizosphere bacterial community and crop growth under biochar application is unclear, especially long-term analysis under repeated application of biochar. Thus, we evaluated changes in soil envi-ronmental factors, rhizosphere bacterial community structure, and growth traits of winter wheat following the application of different amounts of biochar. Biochar was applied twice in October 2011 and October 2016. The medium or high amount of biochar (10 t ha-1 or 20 t ha-1) application increased the soil moisture, nutrient contents, and urease and catalase activities. The beta-diversity of the rhizosphere bacterial community was significantly affected by biochar and its interaction with different growth stages. Biomarkers enriched under biochar addition belonged to phyla comprising Cyanobacteria, Gemmatimonadetes, Nitrospirae, and Chloroflexi. Biochar addition significantly (P < 0.05) improved crop biomass, carbon and nitrogen uptake, and increased the relative crop nitrogen and carbon uptake rates (RNU and RCU) in all growth stages, with the highest dose in a medium amount of biochar (10 t ha-1). Biomarkers enriched under biochar treatments had positive correlations with RNU and RCU, such as Chloroflexales, Thermobioceraceae, and Parviterribacter. Our study furthers the understanding of the association of rhizobacteria community and crop growth under long-term application of biochar.