Salinization is a global agricultural problem with many negative effects on crops, including delaying germination, inhibiting growth, and reducing crop yield and quality. This study compared the salt tolerance of 20 soybean varieties at the germination stage to identify soybean germplasm with a high salt tolerance. Germination tests were conducted in Petri dishes containing 0, 50, 100, 150, and 200 mmol L⁻¹ NaCl. Each Petri dish contained 20 soybean seeds, and each treatment was repeated five times. The indicators of germination potential, germination rate, hypocotyl length, and radicle length were measured. The salt tolerance of 20 soybean varieties was graded, and the theoretical identification concentration was determined by cluster analysis, the membership function method, one-way analysis of variance, and quadratic equation analysis. The relative germination rate, relative germination potential, relative root length, and relative bud length of the 20 soybean germplasms decreased when the salt concentration was >50 mmol L⁻¹, compared with that of the Ctrl. The half-lethal salt concentration of soybean was 164.50 mmol L⁻¹, and the coefficient of variation was 18.90%. Twenty soybean varieties were divided into three salt tolerance levels following cluster analysis: Dongnong 254, Heike 123, Heike 58, Heihe 49, and Heike 68 were salt-tolerant varieties, and Xihai 2, Suinong 94, Kenfeng 16, and Heinong 84 were salt-sensitive varieties, respectively. This study identified suitable soybean varieties for planting in areas severely affected by salt and provided materials for screening and extracting parents or genes to breed salt-tolerant varieties in areas where direct planting is impossible. It assists crop breeding at the molecular level to cope with increasingly serious salt stress.

Soybean is an important food crop in the world. Drought can seriously affect the yield and quality of soybean; however, studies on extreme drought—weak and strong—are absent. In this study, drought-tolerant soybean Heinong 44 (HN44) and sensitive soybean Heinong 65 (HN65) were used as the test varieties, and the effects of strong and weak droughts on the physiological stability of soybean were explored through the drought treatment of soybean at the early flowering stage. The results showed that the contents of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and superoxide anions (${\mathrm{O}}_2^{·-}$) increased with the increase in the degree of drought. The plant height and relative water content decreased, and photosynthesis was inhibited. The activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the total antioxidant capacity (T-AOC) showed a trend of first increasing and then decreasing. Through contribution analysis, CAT changed the most, and the role of SOD gradually increased with the aggravation of drought. With the aggravation of drought, the contents of soluble sugar (SSC) and proline (Pro) increased gradually, and the content of soluble protein (SP) increased initially and then decreased. According to contribution analysis, SSC had the highest contribution to osmotic adjustment. SSC and Pro showed an upward trend with the aggravation of drought, indicating that their role in drought was gradually enhanced.

Soybeans are the main sources of oil and protein for most of the global population. As the population grows, so does the demand for soybeans. However, drought is a major factor that limits soybean production. Regulating soybean response to drought stress using mepiquat chloride (MC) is a feasible method; however, its mechanism is still unclear. This study used PEG-6000 to simulate drought stress and quantitative proteomic techniques to reveal changes in Heinong44 (HN44) and Heinong65 (HN65) subjected to drought following the application of 100 mg/L of MC. The results showed that SOD in HN44 did not change significantly but decreased by 22.61% in HN65 after MC pretreatment, and MDA content decreased by 22.75% and 21.54% in HN44 and HN65, respectively. Furthermore, MC improved the GSH–ASA cycle and simultaneously promoted the Calvin cycle process to enable the plant to maintain a certain carbon assimilation rate under osmotic stress. In addition, MC upregulated some proteins during gluconeogenesis and starch metabolism and increased soluble sugar content by 8.41% in HN44. MC also reduced ribosomal protein abundance, affecting translation and amino acid metabolism. In summary, MC improved GSH–ASA cycle and Calvin cycle under stress to alleviate oxidative damage and maintain crop growth. Our study is the first to report the mechanism of MC regulation in soybean under osmotic stress, providing new insights for the rational application of MC in soybean.

Nitric oxide (NO) plays a significant role in plant drought resistance. However, the effects of the exogenous application of NO to crops under drought stress vary within and among species. In this study, we explored the influence of exogenous sodium nitroprusside (SNP) on the drought resistance of soybean leaves in the full flowering stage using two varieties: drought-tolerant HN44 and non-drought-tolerant HN65. Spraying SNP on soybean leaves at the full flowering period under drought stress improved the NO content in soybean leaves. The activities of nitrite reductase (NiR) and nitrate reductase (NR) in leaves were affected by NO inhibition. The activity of antioxidant enzymes in leaves increased with the extension of SNP application time. Contents of osmomodulatory substances, including proline (Pro), soluble sugar (SS), and soluble protein (SP) increased gradually with the extension of SNP application time. The malondialdehyde (MDA) content decreased as the NO content increased, thus reducing membrane system damage. Overall, spraying SNP reduced damage and improved the ability of soybean to cope with drought. This study explored the physiological changes of SNP soybean under drought stress and provided theoretical basis for improving drought-resistant cultivation of soybean.

Background: Drought is the main restricted agent for growth and development of soybean and the physiological characteristics of different parts of soybean leaves changed significantly. Methods: To explore the impacts of drought stress on the physiological characteristics of leaves in different parts of soybean, in this study, Williams 82 was used as the experimental material and drought stress was simulated by a watering nutrient solution containing 10% PEG-6000. Under different treatment time conditions, the superoxide dismutase (SOD) activity and proline (Pro) content in different parts of soybean leaves were determined. Result: The results indicate that the SOD activity and Pro content in the upper and bottom leaves of soybean increased significantly under drought stress conditions and with the increase in drought stress time, the SOD activity in the upper and bottom leaves of soybean increased first and then declined and the content of Pro increased gradually. In general, soybean relief drought damage by increasing SOD activity and Pro content under drought stress. This study offered the theoretical foundation for exploring the mechanism of soybean drought resistance.

In Northeast China, increasing agricultural activities has led to severe soil compaction, reducing soil aeration and water infiltration capacity. Conservation tillage, through multiple approaches, alleviates this compaction while simultaneously enhancing crop yields and promoting sustainable agricultural production. In light of domestic and international developments, this paper provides a detailed elaboration on conservation tillage (CT) as a sustainable agricultural practice system. It examines its core technical measures, global adoption status, and impacts on soil physicochemical properties. Furthermore, by analyzing the causes and detrimental effects of soil compaction, it proposes approaches and elucidates the significance of using CT to alleviate compaction in black soils. Integrating considerations of its influence on climate change, economic benefits, future development, challenges, and trends, the paper offers a forward-looking perspective.