Biochar Effects on Bacterial Community and Metabolic Pathways in Continuously Cotton-Cropped Soil

This study was purposely designed to understand the role of biochar in soil bacterial community structure and diversity over continuous cotton-cropping years. The research questions addressed were what was the bacterial taxonomic status, the microbial community diversity and the cluster distribution and prediction of microbial metabolic functions across the continuous cotton-cropping years (5, 10, 20, and 40 years) under different biochar treatment rates (0 t ha-1, 20 t ha−1, and 40 t ha−1)? High-throughput sequencing of the 16S and integrated bioinformatic analysis techniques was used. The result showed that biochar of 20 t ha−1 and 40 t ha−1 application rate of up to 20 years of continuously cotton-cropped soils significantly increased bacterial diversity. However, higher application rates of up to 40 years on continuously cropped soils did not significantly change bacterial diversity and richness as compared to the 20 years of continuously cropped soil. The study also established the optimum bacterial diversity to be at 20 years of continuous cotton cropping, and the value were highest at 20 t ha−1 and 40 t ha−1 of biochar application rates. In contrast to the 20 years of continuous biochar application in cropped soils, higher application rates of up to 40 years on continuously cropped soils did not significantly change bacterial diversity and richness. In conclusion, controlled biochar application positively influences soil bacterial community and metabolic pathways in continuously cropped cotton soils. This indicates the significance of biochar application under different years of continuous cotton cropping on soil bacterial community structure, diversity, cluster distribution, and metabolic functions.