Effects of long-term biochar and biochar-based fertilizer application on brown earth soil bacterial communities

The objective of this study was to investigate the effects of 6 years of continuous biochar and biochar-based fertilizer (BBF) application on the soil bacterial community of brown earth soil (Cambisol) growing peanuts. There were five treatments: no fertilizer, low biochar (LB, 250 kg ha−1), high biochar (HB, 750 kg ha−1), chemical nitrogen (N)–phosphorus (P)–potassium (K) fertilizer (NPK, 83 kg ha−1 N, 36 kg ha−1 P, and 41 kg ha−1 K), and BBF (750 kg ha−1). The community richness (ACE) and community diversity (Shannon) indices were highest in the HB treatment, and the ACE of the HB treatment was higher than in the LB treatment (15.4 %). Proteobacteria was the dominant phylum (more than 38.5 % in all treatments). Compared to the CK and NPK treatments, Acidobacteria increased, and Actinobacteria decreased with biochar addition, but there were no significant differences in the microbial community structures of the biochar treatments (LB, HB, and BBF). The soil pH, total nitrogen, and available phosphorus were significantly associated with the bacterial community composition (phyla level). Cell wall/membrane/envelope biogenesis, signal transduction mechanisms, amino acid transport and metabolism, and energy production and conversion were the main gene types. The genes related to energy production and conversion, amino acid transport, metabolism, nucleotide transport and metabolism, carbohydrate transport and metabolism, and other functional roles were significantly more abundant in the biochar treatments (LB, HB, BBF) than in the CK and NPK treatments.