Acid-modified biochar-based bacterial fertilizer and increase soil available phosphorus

The various biochars were modified by phosphoric acid to load phosphorus-solubilizing microorganisms to prepare biochar-based fertilizers (BFs) in this study. The purpose is to provide a new way to develop and utilize BFs to improve available phosphorus and reduce fertilizer consumption.

We conducted a 2-hour pyrolysis of apple wood and cotton straw using a muffle furnace at different temperatures to obtain apple wood biochar and cotton straw biochar, respectively. The prepared biochar was modified using sulfuric acid, hydrochloric acid, and nitric acid. Enterobacter hormaechei. Wu-15 and biochar (10:1) were put into the conical flask. The conical flask was shaken for 1 h to yield BFs, which were subsequently applied in soil at mass ratio of 1:20, 1:10 and 3:20 over a period of 15 days. The experiment was conducted under soil conditions of different pH (5–7) and temperature (20–30 ℃).

Enhancing hydrophobicity promotes the adhesion of microorganisms to biochar. The enhanced presence of functional groups and the honeycomb structure significantly improved the adsorption performance of biochar, resulting in an adsorption capacity for microorganisms that reached 2.23 × 10⁹/g. The application of acid-modified biochar-based bacterial fertilizers (ABFs) in soil resulted in maximum total phosphorus and soluble phosphorus concentrations reaching 37.21% and 16.65%, respectively, due to the synergistic interaction between biochar and phosphorus-solubilizing bacteria.

Phosphoric acid-modified biochar exhibits an enhanced pore structure and superhydrophobicity properties, facilitating the adhesion between biochar and microorganisms. This modification can augment the effective phosphorus content in soil, thereby contributing to agricultural productivity.