Increases in temperature response to CO₂ emissions in biochar-amended vegetable field soil

To explore the effects of biochar application on CO₂ and CH₄ emissions as well as the temperature response of CO₂ emissions, a 1-year experiment was conducted with three treatments (control; CF, chemical fertilizer only; BCF, biochar combined with chemical fertilizer) in a vegetable field. The results showed that (1) compared with CF, short-term application of biochar significantly enhanced the cumulative CO₂ emissions by 27.5% from a soil-plant system by increasing the soil microbial biomass (e.g., MBC) and C substrates (e.g., SOC); (2) lowest emissions of CH₄ were observed in the BCF treatment, and an increase in CH₄ consumption and reduced competition with NH₄⁺ may be responsible for the significant reduction in CH₄ source strength in biochar-amended soil; and (3) activation energy (E_a) was identified as an important factor influencing the temperature sensitivity (Q₁₀) of CO₂ emissions. Fertilization (CF and BCF) reduced the average Q₁₀ and E_a values of CO₂ emissions by 9.0-26.7% and 23.5-10.1%, respectively, relative to the control. In addition, the average E_a value in the BCF treatment (51.9 kJ mol^-1) was significantly higher than those in the control and CF treatments. The increase in Q₁₀ and E_a values following biochar application possibly contributed to the supplementation of limited labile C and nutrients but highly resistant C following biochar application. Soil pH and crop cultivation may play key roles in influencing the change in E_a. Our study concludes that biochar amendment increased CO₂ emissions and temperature response of CO₂ emission from the soil-plant system while reducing CH₄ emissions.