Microbial mechanisms responsible for the effects of bamboo biochar and biochar-coated compound fertilizer on soil phosphorus availability in a Moso bamboo forest soil

Objectives From the perspective of soil properties and microbial diversity, the effect of bamboo-biochar-coated compound fertilizer and bamboo-biochar on availability of soil phosphorus in Moso bamboo forest was studied, to guide the choice of suitable method for bamboo-biochar application.

Methods A field experiment was conducted in the red-yellow soil in Hangzhou, Zhejiang Province. The three treatments included compound fertilizer alone (CK), biochar-coated compound fertilizer (BF), and applying biochar and compound fertilizer at the same time (SC). The soil pH, bulk density, total C, total N, total P, and available P were measured at 30 and 100 days after fertilizer application, respectively. In addition, Miseq and metagenomic sequencing were performed to investigate the phoD microbial community structure and quantify the abundance of phosphorus-cycling functional genes.

Results Compared with CK, SC treatment significantly increased soil pH and available P content, decreased soil bulk density (P<0.05). Both SC and BF treatments altered the phoD microbial community structure. RDA analysis showed that soil pH was an important driving factor influencing soil phoD functional bacteria in Moso bamboo forest. Metagenomic analysis revealed that SC treatment markedly increased the relative abundance of glycerol-3-phosphate transporter subunit (ugpAEC), C-P lyase subunit (phnGHIJL), phosphonate transporter subunit (phnCD), phosphate transport system (pstCAB) and alkaline phosphatase (phoA and phoD) genes. However, BF treatment only increased the relative abundance of ugpE, pstA and phoD genes.

Conclusions Bamboo charcoal amendment improved the availability of soil phosphorus, led to a shift in the phoD microbial community, and increased the abundance of soil phosphorus cycling functional genes, while bamboo charcoal lost these effects when used as coating material of slowly released fertilizer. The beneficial effect of P availability and the increased expression of phoD gene were driven by soil pH, and these were especially enhanced by bamboo charcoal.