[Effects of Wheat Straw-derived Biochar Application on Soil Carbon Content Under Different Tillage Practices]

This study intended to examine the influence of biochar application on soil carbon content under different tillage conditions. For this, an indoor incubation experiment was performed with treatments included wheat straw-derived biochar application (0, 5, and 20 g·kg^-1) and soil with different tillage measures (ploughing and no-tillage). The effects of biochar addition on soil organic carbon (SOC), dissolved organic carbon (DOC), soil microbial biomass carbon (MBC), readily oxidized organic carbon (ROC), soil inorganic carbon (SIC), pH, water soluble calcium and magnesium, and soil CO₂ emissions were analyzed. The results showed that:① Compared with the control, the contents of SOC, ROC, DOC, and water soluble Ca and Mg increased by 20.3%-105.6%, 0.5%-36.0%, 0.8%-30.5%, 3.5%-42.3%, and 2.4%-75.2% in the no-tillage treatments, respectively; and the contents of SOC, ROC, DOC, water-soluble Ca and Mg increased by 29.2%-145.1%, 1.3%-63.9%, 2.4%-55.6%, 18.2%-89.8%, and 10.1%-150.5% in the ploughing treatment, respectively, under different dosage biochar amendments, and was enhanced with an increase in the biochar application amount. Cumulative CO₂ emissions were highest with biochar amendment at 5 g·kg^-1 under the no-tillage soil condition; however, this increased with an increase in the biochar amount in the ploughing treatment. At the end of incubation experiment, the soil MBC content increased by 35.5%-45.7% compared with the control treatment; however, there was no significant effect on soil pH and SIC between the treatments. ② Compared with the ploughing treatment, the cumulative CO₂ emissions, SOC, ROC, DOC, MBC, and water-soluble Ca and Mg contents of the no tillage treatment increased by 34.2%-79.0%, 8.9%-45.5%, 28.2%-73.9%, 40.4%-78.4%, 0.2%-131.7%, 8.7%-39.8%, and 0.3%-61.0%, respectively, while soil pH and SIC decreased by 0.08-0.17 unit and 2.4%-13.9%, respectively, under the same biochar amendment treatments. Overall, the addition of biochar significantly increased soil organic carbon, active organic carbon, soil water soluble calcium and magnesium content, and soil cumulative CO₂ emissions, but no significant effect was observed on soil inorganic carbon content.