The black soil layer has undergone substantial degradation in Northeast China, and it is crucial to adopt reasonable tillage measures to prevent black soil degradation. Organic amendment strategies provide an effective solution for mitigating nutrient loss in black soil; meanwhile, there is still a lack of systematic investigation into their impact on soil microbial communities. Thus, we carried out a five-year field experiment from 2020 to 2025 in Jilin Province. Four organic amendment strategies were set up: conventional tillage (CT); straw returning (SR); straw returning + inorganic fertilizer (SRI); and straw returning + inorganic fertilizer + organic fertilizer (SRIO). Furthermore, we investigated the effects of organic materials on soil properties and microbial communities during the maize seedling stage. The results showed that SR significantly increased the relative abundance of Bradyrhizobium, Tausonia and Coprinopsis, while SRI led to a 140.3% increase in Nocardioides. In SRIO treatment, Gaiella and Fusarium were significantly enriched by 103.9% and 142.5%, respectively. Moreover, SR treatment significantly decreased the fungal Shannon and Simpson index by 18.8% and 4.2%, respectively. Organic matter, alkali nitrogen, and available potassium were the primary environmental factors shaping both bacterial and fungal community structures. Additionally, the co-occurrence network suggested that straw returning promoted more diverse interactions among soil bacterial and fungal communities. Our study highlights the potential of organic amendment strategies in enhancing black soil nutrients, as well as their important role in maintaining soil microbial function and stability.

Soybean is the most crucial oilseed and plant-protein crop worldwide, yet its yield is frequently threatened by salinity and drought stress. In this study, the chitinase gene AcCHI was cloned from the highly stress-tolerant plant Atriplex canescens and heterologously overexpressed in soybean to generate stable T₃ homozygous transgenic lines. Wild-type and transgenic plants were subjected to water-withholding drought treatment, 20% PEG6000-induced osmotic stress, and 150 mM NaCl salt stress. After drought treatment, the survival rate of transgenic lines reached 2.66–2.69 times relative to wild-type plants. Under osmotic and salt stress conditions, AcCHI-overexpressing lines exhibited better-maintained photosynthetic performance, higher proline accumulation, and lower malondialdehyde (MDA) levels compared with wild-type controls. Enhanced antioxidant enzyme activities and weakened histochemical ROS staining were also observed in transgenic leaves. Stress-responsive genes associated with DREB, RD22, and SOS pathways showed stronger stress-inducible expression in transgenic plants. Our results show that heterologous AcCHI expression is associated with improved osmotic- and salt-stress tolerance in soybean seedlings under laboratory conditions. This study provides new observational insights into chitinase-linked abiotic-stress responses and offers candidate genetic resources for breeding stress-tolerant soybean varieties.