This study was carried out to evaluate the effects of the combined application of water-retaining agents and nitrogen fertilizers on soil physicochemical properties, bacterial communities, and root growth under winter wheat planting mode in the Guanzhong area of Shaanxi Province. Based on the positioning experiment of dry farming in the loessal soil area of Shaanxi Province, four treatments were set up by using the tillage method of subsoiling + rotary tillage and straw returning: only fertilization (U), only water retention agent sodium polyacrylate (C₃H₃NaO₂)n (S), combined use of water-retaining agent sodium polyacrylate (C₃H₃NaO₂)n and fertilizer (US), and control group CK (no treatment). The ultra-high-throughput sequencing of 16S rRNA genes of soil bacteria was performed by the Illumina Hiseq platform, and the effects of different tillage measures on soil bacterial diversity and community structure were analyzed. In addition, the effects of these tillage measures on soil physicochemical properties and winter wheat root length density at booting and flowering stages were evaluated. The results indicated that the combination of the water-retaining agent and fertilizer markedly enhanced the contents of ammonium nitrogen, available phosphorus, and available potassium in the 0~20 cm soil layer, significantly increased the soil moisture content, and promoted the deep growth of roots. The root length density was 4.70 times higher than that of the control group at the booting stage. In addition, the combined application alleviated the decrease in soil microbial diversity caused by individual fertilization, especially significantly increasing the abundance of Gemmatimonadetes, Acidobacteria, and Planctomycetes in the 0~10 cm soil layer. This study reveals the potential of the combined use of water retention agents and fertilizers to optimize the soil environment and enhance winter wheat yield, which provides a scientific basis for improving local agricultural practices.

Mixing saline and fresh water can help to increase the agricultural water utilization rate and solve the water shortage situation, but its role on rhizosphere microbes is unknown. This study revealed the effects of mixed saline and freshwater sprinkler irrigation at different proportions on the rhizosphere soil microbial community of summer maize. Compared to freshwater sprinkler irrigation, sprinkler irrigation with 2 g·L⁻¹ of mixed saline and fresh water significantly increased the bacterial α-diversity and significantly affected the structure and composition of bacterial communities, increasing the number of OTUs, the ACE index, and the Shannon index in the rhizosphere soils, whereas sprinkler irrigation with 3 g·L⁻¹ did not lead to significant changes. In addition, there was a significant difference in β-diversity between the mixed saline and freshwater sprinkler irrigation and the freshwater sprinkler irrigation. Principal coordinate analysis revealed that the 2 g·L⁻¹ and 3 g·L⁻¹ sprinkler irrigation treatments were closer to each other, but both were at a greater distance from the freshwater sprinkler irrigation, indicating that mixed saline and freshwater irrigation significantly affected the structure of rhizosphere soil bacterial communities. Ammonium nitrogen, alkaline dissolved nitrogen, and total nitrogen all affected the soil bacterial community structure by more than 10%, with ammonium nitrogen being the most influential environmental factor. The relative abundance of most microbes in the mixed saline and freshwater sprinkler treatments was positively correlated with ammonium nitrogen, especially in the 2 g·L⁻¹ treatment, while that of most microbes in the freshwater sprinkler treatment was negatively correlated with ammonium nitrogen. In conclusion, selecting a sprinkler irrigation model with a mineralization level of mixed saline and freshwater not exceeding 2 g·L⁻¹ could enhance the rhizosphere soil microbial community while conserving water resources.

Balancing soil nitrogen leaching with production benefits remains a critical challenge in sustainable greenhouse tomato cultivation. This study evaluated the effects of reduced water-soluble nitrogen fertilizer (N) application rates on soil environmental parameters and production outcomes to optimize nitrogen management strategies. Four treatments were implemented across two growing seasons: control (CK), high-N (H), medium-N (M), and low-N (L) nitrogen fertilizer applications in soil solution (SS) and autumn–winter (AW) systems. Results demonstrated that reduced nitrogen inputs significantly decreased soil electrical conductivity and soil nitrogen retention by 88% and 83% in SS and AW, respectively, while reducing soil residual nitrate nitrogen. The tomato yield decreased by 14–26% under low fertilizer treatment, while fruit quality was substantially enhanced, with soluble solid content increasing by 56% in SS and 217% in AW for the L treatment compared to the CK. Nitrogen-use efficiency improved by 54.7% and 34.78% in SS and AW, respectively, demonstrating superior resource utilization under reduced fertilizer applications. Principal component analysis revealed that fruit quality was primarily influenced by soluble solid content, organic acid, total soluble solids, and sugar–acid ratio. Gray relational analysis identified the L treatment (361.62 kg ha⁻¹ in SS and 182.6 kg ha⁻¹ in AW) as optimal for comprehensive performance evaluation. The findings demonstrate that strategic nitrogen reduction effectively balances production benefits with environmental sustainability, providing a practical framework for sustainable nitrogen management in controlled environment agriculture.

Drip irrigation burial depth is a critical management factor for saline-alkali agriculture, yet its mechanisms of influencing crop productivity through soil–microbe–plant interactions remain poorly understood. To explore the regulatory effects of drip irrigation burial depth on the growth and rhizosphere microenvironment of dryland wheat in saline-alkali soil, three treatments (no irrigation control, CK; 5 cm shallow-buried drip irrigation, T5; 25 cm deep-buried drip irrigation, T25) were set up, with soil physicochemical properties, microbial community characteristics, and crop yield analyzed. The results showed that drip irrigation significantly improved soil environment and yield, and T25 exhibited superior comprehensive benefits: soil electrical conductivity was reduced by 63%, organic matter content increased by 44%, and water-salt status was significantly optimized; meanwhile, microbial community structure was altered and root nutrient uptake capacity was enhanced, ultimately achieving a yield of 5347.1 kg ha⁻¹, 55.0% higher than CK. In conclusion, 25 cm deep-buried drip irrigation may provide advantages for wheat cultivation primarily through improved water distribution, desalination, and soil structure enhancement.

Plant cell wall-derived oligosaccharides, such as xylo-oligosaccharides (XOS), serve as key signaling molecules regulating plant growth and immunity. The bioactivity of XOS is closely tied to their degree of polymerization (DP), yet the molecular mechanisms underlying DP-specific effects remain poorly understood. Here, we investigated the transcriptional and phenotypic responses of lettuce (Lactuca sativa) to foliar application of four high-purity XOS variants: xylobiose (XOSY, DP2), xylotriose (XOSB, DP3), xylotetraose (XOSD, DP4), and xylopentose (XOSW, DP5). Phenotypic analyses revealed that high-DP XOS (XOSD and XOSW) significantly enhanced aboveground biomass and root system development, with XOSD showing the most pronounced effects, including a 31.74% increase in leaf area and a 20.71% increase in aboveground biomass. Transcriptomic profiling identified extensive transcriptional reprogramming across treatments, with XOSD eliciting the highest number of differentially expressed genes (DEGs). Functional enrichment analyses indicated that XOSD and XOSW upregulated genes involved in plant hormone signaling, starch and sucrose metabolism, and cell wall biosynthesis, while downregulating photosynthesis-related genes. Notably, MapMan and KEGG pathway analyses revealed that XOSD significantly activated biotic stress-related pathways, including MAPK signaling, β-1,3-glucanase activity, and PR protein pathways. In contrast, XOSY treatment primarily upregulated genes linked to basal immunity, highlighting distinct mechanisms employed by low- and high-DP XOS. These findings demonstrate that XOS with varying DP differentially modulate growth- and immunity-related processes in lettuce. High-DP XOS, particularly XOSD, not only promote plant biomass accumulation but also enhance immune responses, highlighting their potential as biostimulants for sustainable agriculture. This study provides a molecular framework for understanding the DP-specific bioactivity of XOS and their dual role in optimizing plant growth and defense.

To explore the directional regulatory effects of drip irrigation burial depths on the growth and rhizosphere microenvironment of dry alkali wheat in saline-alkali soil, three treatments were set up in this study: control (CK, no irrigation), shallow-buried drip irrigation (T5, 5 cm), and deep-buried drip irrigation (T25, 25 cm). The differences in soil physicochemical properties, microbial community structure and functions, as well as crop yield were systematically analyzed. The results showed that drip irrigation treatments significantly improved the soil environment and production performance of saline-alkali soil. The T5 treatment reduced the electrical conductivity (EC) of the 0–60 cm soil layer (15.4% lower than CK), increased microbial species richness (OTU number, ACE index, etc., were significantly higher than those of other groups), and achieved a yield of 4830.96 kg/hm² (40.0% higher than CK), but it had the disadvantages of large water evaporation and low water-fertilizer use efficiency. The T25 treatment exhibited more prominent comprehensive advantages: its desalination effect was significantly better than that of T5 (EC of 0–60 cm soil layer was 61.5% lower than CK), soil organic matter content was 53.8% higher than CK, and total nitrogen and total potassium contents were slightly lower than those of T5. However, T25 could directionally enrich functional groups such as Acidobacteria and Sphingomonas, enhance nitrogen cycling functions including nitrite_respiration, and improve nutrient availability. Meanwhile, it directly delivered water and fertilizer to the root dense zone, reducing losses and promoting absorption. The final yield reached 5347.1 kg/hm² (55.0% higher than CK and 10.7% higher than T5), and the drip irrigation tapes had a longer service life and were suitable for large-scale cultivation. In conclusion, drip irrigation burial depths improved dry alkali wheat yield through a chain mechanism of "soil microenvironment improvement—microbial community optimization—crop growth promotion". Among them, the 25 cm deep-buried drip irrigation synergistically optimized soil water-salt status, nutrient availability and microbial functions, which balanced ecological and production benefits, and provided theoretical basis and technical support for efficient water and fertilizer management in dry alkali wheat drip irrigation cultivation in saline-alkali soil.