Humic acid, as a novel organic fertilizer, has the potential to improve soil fertility and the agronomic performance of crops. However, the efficacy of humic acid varied in previous studies and the mechanisms by which climatic conditions, soil properties, and fertilization regimes regulate it remain unclear. To test this, a comprehensive meta-analysis was conducted to evaluate the effects of humic acid across various environmental and agricultural conditions. The results showed that the humic acid amendment significantly increased the crop yield by 12%, nitrogen use efficiency by 27%, and nitrogen uptake by 17%, on average. Optimal effects were observed in regions with an annual precipitation > 300 mm and mean annual temperatures > 10 °C, and in soils with a moderate pH (6 < pH ≤ 8) or low total nitrogen. Its efficacy was attenuated in alkaline soils and high total nitrogen (≤1.5 g kg⁻¹) or low soil organic carbon (<10 g kg⁻¹) conditions. Cash crops and upland cereals showed a superior response compared to paddy rice, with optimal nitrogen application rates of 100–200 kg ha⁻¹. This study quantifies humic acid’s positive impacts on crop productivity and nitrogen utilization across various conditions, providing empirical evidence for optimizing its application in sustainable agricultural systems, potentially reducing excessive fertilizer use and its associated environmental pollution.

Rice (Oryza) is a genus in the Gramineae family, which has grown widely all over the world and is a staple food source for people’s survival. The genetic information of rice has garnered significant attention in recent years, prompting numerous researchers to conduct extensive investigations in this field. But rice mitochondrial codon usage patterns have received little attention. The present study systematically analyzed the codon usage patterns and sources of variance in the mitochondrial genome sequences of five rice species by the CodonW and R software programs. Our results revealed that the GC content of codons in rice mitochondrial genome genes was determined to be 43.60%. Notably, the individual codon positions exhibited distinct GC contents: 48.00% for position 1, 42.65% for position 2, and 40.16% for position 3. These findings suggest the preference of the rice mitochondrial genome for codons ending in A or U. A weak codon bias was observed, with the effective number of codons (ENC) varying between 40.02 and 61.00, with an average value of 54.34. Subsequently, we identified 25 identical high-frequency codons in five rice mitochondrial genomes, with 11 codons ending in A and 12 codons ending in U. The regression lines in the neutrality plot exhibited slopes of less than 0.5 in five rice species, indicating a predominant role of natural selection, while mutation pressure remained relatively insignificant. In the PR2-plot analysis, most of the genes were located in the right half of the plot, indicating that the third base of the synonymous codon was preferred to end in G than C. Additionally, the ENC plot and ENC ratio analysis unveiled that codon preferences in the rice mitochondrial genome were predominantly influenced by natural selection rather than mutational pressure. The analysis of correspondence revealed distinct variations in the codon usage pattern across five rice mitochondrial genomes. Based on the RSCU values of species, a cluster tree was inconsistent with the mitochondrial genetic data, indicating that RSCU data could not be used as a basis for classification at the species level in the Oryza genus. These results will help decide the specific types of natural selection pressures influencing codon usage and improve the expression of exogenous genes in rice mitochondrial genomes by optimizing their codons.

Saline–alkali soils in southern Xinjiang present significant challenges for sustainable jujube cultivation, necessitating innovative fertilization strategies to improve soil health and enhance fruit quality. This study investigated the synergistic effects of biochar–nitrogen (N) co-application on soil amelioration and the improvement of jujube quality in saline–alkali jujube orchards. A field experiment was conducted using different biochar application rates (0, BC1, BC2) combined with various N fertilizer types (conventional nitrogen N1, N2, UI-N (urease inhibitor), and NI-N (nitrification inhibitor)), which systematically analyzed soil physicochemical properties, nutrient dynamics, enzyme activities, microbial community structure, and jujube fruit yield and quality parameters. The BC1 biochar application rate emerged as the optimal threshold for soil carbon and N sequestration, with BC1 + N2 treatment achieving the highest total carbon and total nitrogen concentrations, representing increases of 12.4% and 21.42%, respectively, compared to controls. Biochar–N co-application significantly enhanced soil available nutrients, with BC1 + UI-N treatment producing the greatest soil organic matter increase within the BC1 group (9.20–14.51% enhancement). Notably, the treatments modulated soil microelement profiles, suppressing potentially toxic Cu and Mn while enhancing the availability of beneficial Mg and Fe. Soil enzyme activities responded differently, with urease and sucrase activities reaching maximum levels under BC2 + N1 and BC1 + UI-N treatments, respectively. Microbial community analysis revealed that biochar–N combinations significantly restructured both bacterial and fungal communities, with BC1 + NI-N treatment demonstrating superior bacterial α-diversity across all indices. Soil enzyme activities exhibited distinct response patterns, with urease and sucrase activities reaching their peak under the BC2 + N1 and BC1 + UI-N treatments, respectively. Moreover, the co-application of biochar (BC1) with N fertilizer significantly improved fruit performance, increasing per-tree yield by 24.23% and fruit vitamin C content by 16.47%, compared to the control. This study demonstrates that moderate biochar application (BC1) combined with urease inhibitor- enhanced N fertilizer (UI-N) represents an optimal fertilization strategy for saline–alkali jujube orchards, achieving simultaneous soil amelioration and fruit quality enhancement through coordinated regulation of soil–microbe–plant interactions. The established quantitative relationships provide a scientific foundation for the implementation of precision agriculture in arid saline–alkali regions, offering significant implications for sustainable specialty fruit production and soil health restoration in environmentally challenged agricultural systems.

Jujube (Ziziphus jujuba Mill.) cultivation in arid regions of China faces severe soil constraints, including high alkalinity, low organic matter content, and poor water retention. Although soil amendments have demonstrated potential for improving soil quality, their combined effects on soil–plant–microbe interactions in desert agroecosystems remain poorly understood. This study conducted a three-year field experiment in a desert jujube orchard in southern Xinjiang, China, to evaluate six nitrogen fertilizer management strategies: urea alone (CK) or combined with biochar (NB), bentonite (NP), graphene (NS), biochar plus bentonite (NBP), or microbial inoculants (NW). Soil physicochemical properties, enzyme activities, bacterial community structure, and jujube yield were analyzed. Structural equation modeling (SEM) was employed to elucidate the pathways linking soil amendments to crop productivity. Results showed that NBP was the most effective in improving soil physical structure, significantly reducing bulk density and enhancing water retention capacity compared to the control. The NBP treatment also enhanced soil organic matter (30% increase), available phosphorus (119% increase), and urease activity (44% increase), resulting in the highest jujube yield (7.14 kg per tree). Bacterial community analysis revealed that NBP significantly increased Shannon diversity and enriched Actinobacteriota and Proteobacteria. SEM analysis indicated that urease activity served as a significant mechanistic pathway linking soil organic matter improvements to enhanced crop productivity. These findings demonstrate that combined application of biochar and bentonite with nitrogen fertilizer represents an effective strategy for improving soil quality, enhancing microbial functionality, and increasing crop yield in desert jujube orchards, providing a practical and synergistic amendment combination for sustainable soil management and productivity enhancement in arid agroecosystems.

Understanding the regulatory mechanisms of water–nitrogen coupling effects on soil–plant–microbe systems in arid regions is crucial for sustainable agricultural development. This study systematically investigated the interactive effects of field capacity (75% vs. 45%) and nitrogen application rates (100 vs. 300 kg ha⁻¹) combined with different enhanced-efficiency nitrogen fertilizers (EENFs) on rhizosphere soil fertility and microbial community structure of Jujube (Ziziphus jujuba Mill.) seedlings through a two-year pot experiment. Two-year-old jujube seedlings were employed with five treatments: NS (urea), NM (urease inhibitor), XH (nitrification inhibitor), W (microbial fertilizer), and CK (control), to analyze soil physicochemical properties and microbial community responses. Soil available N accumulated under high-N/adequate moisture but declined under drought. NM curbed NH₃ volatilization by 32.38–43.22%, while XH increased NH₄⁺-N by 35.76%. Drought raised microbial α-diversity (bacteria + 33.88–37.5%, fungi + 43.62–68.75%). NM demonstrated optimal performance in ammonia volatilization (32.38–43.22% reduction), while XH showed notable efficacy in ammonium-N regulation (35.76% enhancement). Microbial α-diversity exhibited enhanced responses under drought stress, with bacterial and fungal community improvements reaching 33.88–37.5% and 43.62–68.75%. Redundancy analysis showed environmental factors explained more community variance under water stress (bacteria: 79.19→88.76%; fungi: 64.64→92.52%). These findings provide theoretical support for jujube cultivation in arid zones, demonstrate the potential of targeted EENFs, and offer new insights for precision water–fertilizer and microbial management.