Atrazine causes serious contamination of agricultural soils and groundwater. This study investigated the influence mechanism of sterilized soil (CKs), unsterilized soil (CKn), sterilized soil amended with 45 (SsV1), 60 (SsV2), 75 (SsV3) days of vermicompost (the maturity days of vermicompost), and unsterilized soil amended with 45 (SnV1), 60 (SnV2), 75 (SnV3) days of vermicompost on atrazine catabolism. The atrazine degradation experiment lasted for 40 days. The results showed that the atrazine degradation rates for CKs, CKn, SsV1, SsV2, SsV3, SnV1, SnV2, and SnV3 were 24%, 56.9%, 62.8%, 66.1%, 65.9%, 87.5%, 92.9%, and 92.3%, respectively. Indigenous microorganisms capable of degrading atrazine were present in unsterilized soil, and the addition of vermicompost enhanced atrazine degradation. The humic acid content of SnV2 was the highest, at 4.11 g/kg, which was 71.97% higher than that of CKn. The addition of the vermicompost enhanced the production of hydroxyatrazine, deethylatrazine, and deisopropylatrazine. Vermicompost increased the abundance of atrazine-degrading bacteria (Mycobacterium, Devosia, etc.), and introduced new atrazine-degrading bacteria (Mesorhizobium, Demequina). The above results showed that the best degradation of atrazine was achieved with 60 days of vermicompost addition. This study provides a new, efficient, economical, and environmentally friendly strategy for the remediation of atrazine-contaminated soil.

High pH, ${\mathrm{Na}}^{+}$, and $({\mathrm{CO}}_3^{2-}+{\mathrm{HCO}}_3^{-}$) are the primary characteristics of soda saline–alkali soil. Current strategies for ameliorating soda saline–alkali soil often involve the combined use of cow manure and maize straw, the addition of biochar (BC), and the inoculation of Bacillus subtilis (BS). In this study, B. subtilis-loaded biochar (BSC) was prepared using an adsorption technique. An incubation experiment was conducted. The treatments were as follows: soda saline–alkali soil amended with maize straw and cow manure (T₁), which was used as a control; T₁ supplemented with earthworms (T₂); and T₂ supplemented with BS (T₃), BC (T₄), or BSC (T₅). After a 60-day incubation, T₅ showed the most significant reduction in pH, ESP, and (${\mathrm{H}\mathrm{C}\mathrm{O}}_3^{-}$ + ${\mathrm{C}\mathrm{O}}_3^{2-}$) concentrations, with reductions of 0.24 units, 3.26%, and 120 mg kg⁻¹, respectively, compared to the T₁ treatment. The content of soil humic acid, available potassium, and available nitrogen and the activities of β-glucosidase and urease were highest in T₅, increasing by 33.5%, 70.1%, 26.1%, 19.0%, and 17.9%, respectively. Microbial sequencing analysis revealed that the Bacillus abundance in T₃ was highest during the first 45 days (2.51–3.65%), while the Bacillus abundance in T₅ peaked at 3.22% after the 60-day incubation. The soil that was cultivated for 60 days in the experiments was then used for planting alfalfa. T₅ showed the highest alfalfa aboveground biomass and peroxidase, increasing by 30.1% and 73.1%, respectively, compared with T₁. This study demonstrated that loading onto biochar is beneficial for the survival of B. subtilis in soda saline–alkali soil. When traditional organic materials are used, the combination of earthworms and B. subtilis-loaded biochar significantly alleviates the constraints of soda saline–alkali soil.