Effects of rice and corn straw biochar combined with microbial inoculant on soil health in protected vegetable production

The biochar and microbial inoculant are commonly used amendments in soil improvement, but their effectiveness in protective agriculture is currently unclear. Based on this, this study takes the pepper vegetable greenhouse located in Zhuxi Town, Chongqing as the research object, and selects biochar prepared from corn straw and rice straw, as well as microbial inoculant, as the improvement materials. Five treatments were established, including corn straw biochar alone (CB), rice straw biochar alone (RB), microbial inoculant alone (CKM), combined corn straw biochar and microbial inoculant application (CBM), and combined rice biochar and microbial inoculant application (RBM), conventional fertilization was used as a control. This study explores the changes in soil physicochemical properties of protected vegetable production under different treatments at distinct time points (first, third, and fifth months after returning field) and soil depth (0-10 cm and 10-20 cm). The results demonstrated that the overall soil bulk density increased With the increase of returning time. There was no significant difference in the soil capillary porosity or mineral-associated organic carbon content (P > 0.05), whereas the other soil properties decreased with increasing return field time. In contrast, the soil bulk density (BD) increased with increasing soil depth. Except the capillary porosity, which exhibited no significant differences at different depths (P > 0.05), all the other soil properties demonstrated downward trends with increasing depth. After 5 months of transplantation, the soil carbon pool management index of RBM treatment was higher than that of CBM treatment, with a 4.35% increase. The soil health index was 14.51% lower than that of CBM. However, the differences in soil carbon pool management index and soil health index between the two treatments did not reach a significant level. Overall, the RBM and CBM showed better improvement effects on soil carbon pool management index and soil health status, making them the better ratios for vegetable greenhouse farmland soil improvement in this study.