Biochar with N-Fertilizer Effects on Soil CO ₂ Emissions and Soil Physical Properties

Abstract Biochar has gained attention as a soil amendment due to its potential to mitigate climate change by improving soil properties and reducing greenhouse gas emissions. This study investigates the effects of biochar application and reapplication, in combination with different nitrogen (N) fertilization levels, on soil CO 2 emissions and soil physical properties. The field experiment was conducted in a temperate climate zone over a five-year period, with biochar applied at doses of 0, 10, and 20 t.ha −1 , and N-fertilizer applied at 0, 108, and 162 kg.N.ha −1 . Soil temperature, soil water content (SWC), and CO 2 fluxes were monitored biweekly during the 2019 growing season (April–October). Results showed that biochar reapplication significantly reduced cumulative CO 2 emissions, particularly at higher application rates and in fertilized treatments. In contrast, a single biochar application led to increased CO 2 emissions in some cases. A strong correlation was found between CO 2 emissions and soil temperature ( p <0.001), while the relationship between CO 2 emissions and SWC was not significant ( p >0.05) except in one fertilized treatment. These findings suggest that biochar application, particularly when reapplied, can play a role in reducing soil CO 2 emissions while influencing soil physical properties. However, further research is needed to assess its long-term effects across various soil types and climatic conditions.