Effects of Biochar Addition on Organic Carbon in Aggregates of Soil under Phyllostachys edulis Forest

Objective The aims were to explore the effects of different application rates of biochar on organic carbon content in aggregates of soil uner Phyllostachys edulis forest, which would provide a reference for the sustainable development of soil carbon sequestration.

Method Four biochar addition treatments (control: CK, 0 t ha⁻²; low biochar: LB, 5 t hm⁻²; medium biochar: MB, 10 t hm⁻²; high biochar: HB, 20 t hm⁻²) were set with the determination of soil physicochemical properties and the organic carbon content in different size of aggregates.

Result Compared with the control, biochar addition significantly increased 10 − 20 cm soil bulk density by 17.4% − 22.1%, capillary porosity by 21.3% − 22.8%, non-capillary porosity by 20.5% − 42.2% and maximum water holding capacity by 20.1% − 24.5% (P < 0.05). LB and HB significantly reduced the total phosphorus contents of 0 − 10 cm and 10 − 20 cm soils by 13.6%, 10.8%, and 16.1%, 10.5% (P < 0.05), respectively. In the 0 − 10 cm soil layer, MB increased the organic carbon content of >2000 µm aggregates by 21.5% compared with the control. In the 10 ~ 20 cm soil layer, HB increased the organic carbon content of 53 − 250 µm and 250 − 2000 µm aggregates by 24.1% and 43.0%, compared with MB, respectively. With different doses of biochar addition, soil aggregate particle size and different soil depths had significant effects on the organic carbon content of soil aggregates. Only the interaction between biomass charcoal and soil horizons was significant (P < 0.05). The redundancy analysis showed that the application of biochar enhanced the positive correlation among >2000 µm aggregates and soil organic carbon, soil microbial biomass nitrogen, and total soil nitrogen. LB and MB caused a negative correlation between soil aggregate structure and soil bulk density.

Conclusion The relative higher biochar application rates (10 − 20 t hm⁻²) could increase the organic carbon content and stability of soil aggregates, and improve the soil carbon sequestration potential of Phyllostachys edulis forest.