Saline–alkali land is widely distributed worldwide, and poses significant challenges to agricultural productivity and ecological restoration, particularly in the Qaidam Basin. This study investigates the effects of intercropping and mixed sowing systems of oats (Avena sativa L.) and forage peas (Pisum sativum L.) on hay yield and soil chemical fertility in mildly saline–alkali soils of the Qaidam Basin. Through a comprehensive analysis of hay yield, soil chemical properties, and enzyme activities under different sowing methods (mixed sowing, intercropping, and monoculture) and row spacings (30, 25, 20 and 15 cm), an optimal planting pattern was identified. The 25 cm intercropping treatment produced the highest amount of fresh biomass (2242 kg hm⁻¹), with an increase ranging from 3.17% to 70.44% compared to other treatments. Additionally, this treatment led to significant reductions in soil pH and electrical conductivity (by 3.87–8.31% and 5.13–6.05%, respectively), while enhancing organic matter content and enzyme activities. The intercropping system also demonstrated higher ammonium nitrogen and available phosphorus contents compared to the mixed sowing system. Structural equation modeling revealed that row spacing indirectly influenced both hay yield and enzyme activities, with the 25 cm row spacing proving to be the most effective. A comprehensive evaluation using the TOPSIS model further affirmed that the 25 cm intercropping system significantly enhanced hay yield, soil chemical properties, and enzyme activities, making it the most suitable planting pattern for sustainable land management in the study area. Therefore, the 25 cm intercropping model not only optimizes hay yield, but also improves soil quality and ecological functions in saline–alkali land, offering valuable insights and practical recommendations for the sustainable use of saline–alkali land in the Qaidam Basin.

Introduction: This study aimed to investigate the seed germination characteristics and metabolic response mechanisms of Medicago ruthenica under saline-alkali stress, with the goal of elucidating its physiological and molecular mechanisms of salt-alkali tolerance.Methods: It was systematically analyzed the germination characteristics of four M. ruthenica germplasm resources (YSZ, XHZ, Shoulu, and Longzhong 1) from different origins with various concentrations of individual salts (NaCl, Na₂SO₄, NaHCO₃) and compound saline-alkali stress treatments. Additionally, the metabolite changes in the domesticated species under saline-alkali stress were examined using metabolomics technology.Results: The results indicated that low concentrations of NaCl stress did not significantly inhibit the germination of M. ruthenica seeds; rather, it promoted germination to some extent. In contrast, high concentrations of NaHCO₃ and compound saline-alkali stress significantly inhibited both seed germination and seedling growth. The germination characteristics of M. ruthenica germplasm resources from different sources exhibit variability under saline-alkali stress. Domesticated species demonstrated strong tolerance to salt-alkali conditions. Metabolomic analyses indicated that saline-alkali stress significantly impacts key metabolic pathways, including amino acid metabolism, sugar metabolism, and lipid metabolism in M. ruthenica sprouts, with a notable increase in the accumulation of amino acids and their derivatives. Correlation analyses revealed that amino acids such as L-arginine, histidine, and glutamine are significantly positively correlated with germination rate and root length, suggesting that these amino acids play a crucial role in M. ruthenica’s response to saline-alkali stress.Discussion: This study provided a new theoretical foundation for understanding the salt-alkali tolerance mechanisms of M. ruthenica and serves as an important reference for breeding salt-alkali tolerant forage varieties and for the ecological restoration of saline-alkali land.

Soil salinization severely limits global agricultural sustainability, particularly across the saline–alkaline landscapes of the Qinghai–Tibet Plateau. We examined how potassium fulvate (PF) modulates oat (Avena sativa L.) performance, soil chemistry, and rhizospheric microbiota in the saline–alkaline soils of the Qaidam Basin. PF markedly boosted shoot and root biomass, with the greatest response observed at 150 kg hm⁻². At the same time, it enhanced soil fertility by increasing organic matter, nitrate-N, ammonium-N, and available potassium, and improved ionic balance by lowering Na⁺ concentrations and the sodium adsorption ratio (SAR), while increasing Ca²⁺ levels and soil moisture content. Under the high-dose treatment (F2), endogenous fungal contributions declined sharply, exogenous replacements increased, and fungal α-diversity fell; multivariate ordinations confirmed that PF reshaped both bacterial and fungal communities, with fungi exhibiting the stronger response. We integrated three machine learning algorithms—least absolute shrinkage and selection operator (LASSO), Random Forest (RF), and eXtreme Gradient Boosting (XGBoost)—to minimize the bias inherent in any single method. We identified microbial β-diversity, organic matter, and Na⁺ and Ca²⁺ concentrations as the most robust predictors of the Soil Salinization and Alkalization Index (SSAI). Structural equation modeling further showed that PF mitigates salinity chiefly by improving soil physicochemical properties (path coefficient = −0.77; p < 0.001), with microbial assemblages acting as key intermediaries. These findings provide compelling theoretical and empirical support for deploying PF to rehabilitate saline–alkaline soils in alpine environments and offer practical guidance for sustainable land management in the Qaidam Basin.

White-flowered alfalfa (Medicago sativa L.) persisting in Qinghai–Tibet Plateau’s saline–alkali habitats provides a unique model to explore floral color polymorphism-linked ecological adaptation. We systematically compared phenotypic, physiological, transcriptomic, and metabolomic profiles of white-flowered (WF) and purple-flowered (PF) alfalfa under high-altitude cold/saline–alkali field conditions (three biological replicates; Student’s t-test). WF showed a significant growth-defense trade-off: flower size and chlorophyll a content decreased by 18.9% and 46.0%, with reduced gibberellin levels, while jasmonic acid (36.3%), proline (51.5%), antioxidant enzyme activities, total flavonoids (17.7%), and condensed tannins (18.2%) were significantly increased (p < 0.001). Multi-omics analysis revealed phenylpropanoid pathway reprogramming (suppressed anthocyanin biosynthesis, precursor accumulation) and coordinated hormone signaling (jasmonic acid activation, salicylic acid inhibition). Our findings confirm the white-flower trait is not an isolated mutation. It is a key component of a coordinated adaptive syndrome, mediated by metabolic reprogramming and hormonal crosstalk. These results provide theoretical and technical support for breeding stress-resistant alfalfa varieties suitable for marginal land cultivation.

Soil salinization and alkalization severely limit agricultural sustainability in alpine regions. The integrated responses of oats to complex saline–alkali stress, covering phenotypic, physiological, and metabolomic alterations, remain poorly elucidated. This study aimed to clarify the synergistic adaptive mechanisms of oats with differential saline–alkali tolerance. Three oat varieties with distinct tolerance levels, including the tolerant cultivar Meida, the moderately tolerant cultivar Qingtian No. 2, and the sensitive cultivar Qinghai Sweet Oat, were treated with a 150 mmol·L⁻¹ mixed saline–alkali solution (Na₂SO₄:NaCl:NaHCO₃ = 2:1:1, pH 8.65) to simulate the natural alpine soil environment of Qinghai Province. Compound saline–alkali stress markedly inhibited oat growth and aggravated cellular oxidative damage. The tolerant cultivar effectively alleviated stress injury by improving antioxidant enzyme activities and accumulating osmoprotectants. A total of 396 core differential metabolites were screened in this study, and flavonoid biosynthesis was identified as a conserved core pathway for oat stress resistance. Tolerant oat varieties simultaneously activated defense responses and energy metabolism to adapt to stress conditions. In contrast, sensitive varieties only depended on basal metabolic adjustments to cope with stress. These findings clarify the differential adaptive strategies of oats under saline–alkali stress. They provide key metabolic marker resources and a solid theoretical basis for the breeding and cultivation of salt–alkali-tolerant oats in alpine saline–alkali land.

Background: Soil salinization and alkalization are major constraints to global crop production. Fenugreek ( Trigonella foenum-graecum L.) is considered a potential salt-alkali-tolerant crop; however, the molecular mechanisms underlying its tolerance remain poorly understood. Methods: Four fenugreek provenances were evaluated under saline-alkali stress at the seedling stage. Growth and physiological traits were measured to assess stress tolerance. Based on these results, the most tolerant provenance was selected for transcriptome analysis. Saline-alkali treatments of 0 (control), 100 mmol/L (moderate stress), and 200 mmol/L (severe stress) were applied according to preliminary physiological experiments to induce measurable but non-lethal stress responses suitable for transcriptomic investigation. Results: The tolerance of the four provenances followed the order: Qinghai > Anhui > Yunnan > Gansu, with the Qinghai provenance showing the strongest tolerance. Transcriptome sequencing generated 47,757 unigenes, of which 27,300 were successfully annotated. A total of 2,041 differentially expressed genes (DEGs) were identified among treatments. Functional enrichment analysis indicated that these DEGs were mainly involved in metabolic processes, stress responses, and key pathways such as flavonoid biosynthesis, plant hormone signal transduction, and starch and sucrose metabolism. In addition, 24 transcription factors associated with abiotic stress were identified, primarily belonging to the AP2/ERF, bHLH, MYB, and NAC families. The reliability of the RNA-Seq results was confirmed by qRT-PCR analysis of nine selected DEGs using β-actin as the reference gene. Conclusions: These findings provide new insights into the molecular mechanisms underlying saline-alkali tolerance in fenugreek and offer valuable genetic resources for the breeding of stress-tolerant cultivars.