Response mechanisms of agricultural soil biochemical properties and CO₂ emissions to field application of modified biochar

Besides fuel combustion, coal processing, etc., agricultural soils are also a major source of greenhouse gas CO₂. How to reduce agricultural greenhouse gas (GHG) emissions through anthropogenic regulatory factors has received widespread attention. A high-quality soil amendment to improve soil habitat, biochar, has emerged.

In this study, a novel and efficient functional biochar was prepared by potassium hydroxide (KOH) modification. Virgin biochar (450BC) and modified biochar (450KBC) were grown in two ratios (w/w) for 61 days for soil improvement, and a total of five treatments were set up: CK (0%), 2%450BC (20 g 450BC·kg⁻¹ soil⁻¹), 2%450KBC (20 g 450KBC·kg⁻¹ soil⁻¹), 4%450BC (40 g 450BC·kg⁻¹ soil⁻¹), 4%450KBC (40 g 450KBC·kg⁻¹ soil⁻¹).

The biochar caused an increase in soil pH, CEC, SOM content, and the concentration of soil NH₄⁺-N and a decrease of the concentration of NO₃⁻-N. Bivariate correlation analysis revealed that CO₂ emissions are negatively correlated with SOC, pH, and MBN and positively with CEC and MBC. The biochar inhibited the β-glucosidase activity and kept the SOM degradation under control. The activity of β-glucosidase was not significantly related to the amount of biochar applied, but the effect of the modified biochar was significantly multiplied compared with the virgin biochar, and the most significant reduction in β-glucosidase activity was observed with 4%450 KBC (30%). The order of total CO₂ emissions for 61 days of indoor incubation was 4%450KBC < 2%450KBC < 4%450BC < 2%450BC < CK.

The application of 450KBC is an appropriate agricultural management strategy that improves the soil biochemical environment while helping to suppress soil CO₂ emissions.