Organic fertilizer substitution for chemical fertilizers is an important strategy for sustainable agriculture. This study aimed to investigate the effects of different organic nitrogen substitution ratios for a chemical nitrogen fertilizer on the soil microbial community structure in cotton fields. A three-year field experiment was conducted in Changji, Xinjiang, China, with six treatments: no fertilization (CK), a single application of chemical fertilizer (CF), and organic nitrogen substituting for 25% (T1), 50% (T2), 75% (T3), and 100% (T4) of a chemical nitrogen fertilizer. High-throughput sequencing was used to analyze the bacterial and fungal community structures. Results showed that organic substitution treatments significantly increased the bacterial Simpson and Shannon diversity indices compared to CK. At the phylum level, organic substitution treatments increased the relative abundance of Proteobacteria (1.27–22.44%), Gemmatimonadota (3.50–9.33%), and Actinobacteriota (17.25–38.57%) compared to CK. For fungi, organic substitution treatments improved the Simpson and Shannon indices, with the T2, T3, and T4 treatments showing significant increases. Organic substitution treatments increased the relative abundance of Ascomycota (2.05–14.75%), Basidiomycota (0.41–178.44%), and Glomeromycota (6.15–502.88%) compared to CK, while Rozellomycota was exclusively present in organic substitution treatments. Cotton yield data showed that the T1 treatment produced the highest seed cotton yield over the three-year study period, with significant increases of 6.19% compared to the CF treatment in the third year. These findings suggest that organic fertilizer substitution can effectively improve the soil microbial community structure and diversity, with moderate to high substitution ratios showing the most beneficial effects for maintaining soil health in cotton fields.

Purpose: Gibberellins (GAs) are key phytohormones that regulate plant growth, development, and responses to environmental stress, and their metabolism is mediated by 2-oxoglutarate-dependent dioxygenases (2OGDs). Cotton (Gossypium spp.) is a polyploid crop with a complex genome; however, the evolutionary characteristics and stress-responsive regulation of GA-related 2OGDs remain poorly understood. This study aimed to systematically investigate the evolution, expression patterns, and stress-associated regulation of the cotton 2OGD multigene family, with particular emphasis on GA-related members. Methods: 2OGD genes were identified genome-wide in four Gossypium species and Arabidopsis thaliana. Phylogenetic relationships, gene structures, conserved motifs, cis-acting regulatory elements, and synteny were analyzed. Transcriptomic data from multiple tissues and developmental stages, together with time-course RNA-seq under salt stress, were examined. Transcriptome–metabolome association analysis, endogenous GA quantification, and predicted protein–protein interaction analysis were conducted. Results: A total of 583 2OGD genes were identified and classified into three major classes, including a Class C group comprising GA2ox, GA3ox, and GA20ox genes. Polyploidization-associated duplication contributed to the expansion of the 2OGD family, and most duplicated gene pairs exhibited signatures of purifying selection. GA-related 2OGDs displayed conserved motif compositions with variation in cis-acting elements. Promoter analysis identified abundant hormone-responsive, stress-responsive, and growth-related cis-elements, suggesting complex regulatory control of GA-related 2OGDs in cotton. Under salt stress, GhGA2OX1 and GhGA20OX2 were upregulated, whereas GhGA3OX1 was downregulated, accompanied by reduced endogenous GA levels. Conclusions: GA-related 2OGDs in cotton are transcriptionally responsive to salt stress and are associated with changes in GA metabolism, providing a basis for future functional studies.

Soil salinization and alkalization severely constrain crop production worldwide, yet the combined effects of mixed saline-alkaline stress on minor cereal germination have received limited investigation. This study sought to elucidate the effects of mixed saline-alkaline stress on seed germination and seedling growth of proso millet (Panicum miliaceum L.) under controlled laboratory conditions, and to comparatively assess the relative contributions of osmotic stress, ionic toxicity, and high-pH damage through analysis of different neutral-to-alkaline salt ratios at equivalent Na⁺ concentrations. Seeds were subjected to nine treatment combinations comprising three salinity levels (80, 160, and 240 mM Na⁺) and three neutral-to-alkaline salt ratios (3:1, 1:1, and 1:3), employing NaCl, Na₂SO₄, NaHCO₃, and Na₂CO₃. Germination characteristics, seedling morphology, and key physiological parameters were assessed over seven days. Mixed saline-alkaline stress markedly suppressed germination in a concentration-dependent manner, with germination percentage decreasing from 94.5% (control) to 23.8% at 240 mM Na⁺ under high-alkali conditions (P < 0.05). At equivalent Na⁺ concentrations, high-alkali treatments (pH > 9.5) diminished germination index by 35.6-52.3% relative to low-alkali treatments. The IC₅₀ values were 187.3 mM Na⁺ (95% CI: 171.2-205.8 mM; R² = 0.982), 142.6 mM Na⁺ (95% CI: 131.4-155.1 mM; R² = 0.976), and 98.4 mM Na⁺ (95% CI: 89.7-108.3 mM; R² = 0.991) for low-, medium-, and high-alkali ratios, respectively. High-alkali stress was associated with 67.4% greater electrolyte leakage and 2.3-fold higher MDA accumulation than neutral salt treatments at equivalent Na⁺ concentrations, indicating greater membrane disruption under high-pH conditions. Two-way ANOVA revealed significant main effects of both Na⁺ concentration and alkaline proportion, as well as a significant salinity × alkalinity interaction (P < 0.001; Supplementary Table S1). These results demonstrate that alkaline stress exerts stronger inhibitory effects on proso millet germination compared to neutral salt stress, with the magnitude of salinity effects being dependent on the pH level. While complete mechanistic separation of osmotic, ionic, and pH components was not achieved due to experimental design limitations (absence of iso-osmotic non-ionic controls and direct ion measurements), comparative analysis across salt ratio treatments suggests that high pH is associated with additional inhibitory effects beyond those observed in neutral salt treatments. These controlled-condition findings establish preliminary germination -stage thresholds that may inform screening protocols for saline-alkaline tolerance breeding in proso millet, pending validation under field conditions.