Pig manure biochar enhances soil organic carbon, aggregate stability, and microbial biomass in the clay soil of Bangladesh

Biochar is a widely used soil amendment that can improve soil physical properties like aggregation. However, little information is available regarding how pig manure biochar improves soil structure formation and organic carbon content in clay soil. This short-term field experiment (120 days) investigated the impacts of biochar on soil organic carbon (SOC) and aggregate stability (MWD) coupling with microbial biomass carbon (MBC) in clay soil under Pumpkin (Cucurbita maxima L.). The experiment consisted of five treatments as follows: (i) Control as no biochar (T0), (ii) inorganic fertilization (triple super phosphate) at 2 t ha-1 (T1), (iii) biochar at 4 t ha-1 (T2), (iv) biochar at 8 t ha-1 (T3) and (v) biochar at 16 t ha-1 (T4). Results showed that large macroaggregates were increased by 1.9, 2.2 and 2.7 times higher, while MWD was increased by 53, 75 and 103 % in the T2, T3 and T4 treatments, respectively, upon biochar incorporation as compared to T0 (P < 0.01). The SOC was increased significantly with all treatments compared to T0 (P < 0.001). Moreover, MBC and GRSP were enhanced by 4.5 and 1.25-fold, respectively, with only T4 biochar treatment (P < 0.001), while T2 treatment had no impact on MBC and GRSP (P > 0.05). SOC, MBC and GRSP were significantly correlated with MWD (P < 0.05), while iron oxides had no impacts on MWD (P > 0.05). The study indicates that biochar, particularly at 16 t ha-1, can potentially enhance MWD, boosting microbial activity and SOC in clay texture soils of southeast Bangladesh.