The present study focuses on the inhibitory effect of volatile metabolites released by Bacillus velezensis CT32 on Verticillium dahliae and Fusarium oxysporum, the causal agents of strawberry vascular wilt. The CT32 strain was isolated from maize straw compost tea and identified as B. velezensis based on 16S rRNA gene sequence analysis. Bioassays conducted in sealed plates revealed that the volatile organic compounds (VOCs) produced by the strain CT32 possessed broad-spectrum antifungal activity against eight phytopathogenic fungi. The volatile profile of strain CT32 was obtained by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 30 volatile compounds were identified, six of which have not previously been detected in bacteria or fungi: (Z)-5-undecene, decyl formate, 2,4-dimethyl-6-tert-butylphenol, dodecanenitrile, 2-methylpentadecane and 2,2’,5,5’-tetramethyl-1,1’-biphenyl. Pure compounds were tested in vitro for their inhibitory effect on the mycelial growth of V. dahliae and F. oxysporum. Decanal, benzothiazole, 3-undecanone, 2-undecanone, 2-undecanol, undecanal and 2,4-dimethyl-6-tert-butylphenol showed high antifungal activity, with benzothiazole and 2,4-dimethyl-6-tert-butylphenol being the most potent compounds. These results indicate that the VOCs produced by B. velezensis CT32 have the potential to be used as a biofumigant for management of vascular wilt pathogens.

Ammonium inhibition is a key limiting factor for anaerobic digestion when using chicken manure as the main substrate, especially in a digestion system with biogas slurry reflux. Air stripping is usually used as a recycled biogas slurry treatment. In this study, we carried out the anaerobic co-digestion of chicken manure and corn straw. The fermentation performance was investigated with and without air stripping at different biogas slurry reflux ratios and with an increasing organic loading rate. The results show that air stripping enhanced biogas production, system stability, and volatile solid removal efficiency via the mitigation control of ammonium inhibition. The total ammonium nitrogen in the digesters with air stripping was 20.24–46.40% lower than in those without air stripping. The highest specific biogas production and volatile solid removal efficiency values were obtained in the digesters at an organic loading rate of 3.3 g volatile solid (VS)/(L·d) and a reflux ratio of 75% with air stripping, reaching 480.43 mL/gVS_add and 63.36%, respectively. Moreover, air stripping also improved the organic loading rate and reflux ratio. Stable operation was achieved at an organic loading rate of 5.3 gVS/(L·d) and a reflux ratio of 75%, with specific biogas production of 392.35 mL/gVS_add and a volatile solid removal efficiency of 50.33%. The fermentation performance deteriorated when the organic loading rate was increased to 8.0 gVS/(L·d) at a reflux ratio of 75%, even when air stripping was conducted, indicating that a slighter lower reflux ratio (50%) could be more feasible at a higher organic loading rate (8.0 gVS/(L·d). Additionally, the methanogen community structure varied according to the use of air stripping, with a shift in the methanogenic pathway from hydrogenotrophic to acetoclastic methanogens. Overall, our findings support the adoption of air stripping for ammonium mitigation in anaerobic digestion with biogas slurry reflux.

In this study, we examined the impact of various physical and chemical properties of growth media on strawberry growth, yield, quality, and economic returns. Six treatments were established: T1 (biogas residue/peat/perlite/vinegar residue = 1:5:1:4), T2 (biogas residue/peat/perlite/vinegar residue = 2:3:1:5), T3 (biogas residue/peat/perlite/vinegar residue = 2:3:1:4), T4 (biogas residue/peat/perlite/vinegar residue = 2:4:1:3), T5 (biogas residue/peat/perlite/vinegar residue = 3:4:1:5), and CK (peat/perlite = 4:1). The results showed that compared with CK treatment, the total nitrogen level increased by 3.26- to 3.95-fold and the organic matter content increased by 14.13–25.70%. In particular, T3 (biogas residue/peat/perlite/vinegar residue = 2:3:1:4) exhibited significant growth advantages, with stem diameter, root volume, and fresh weight increasing by 18.89%, 36.41%, and 35.26%, respectively, compared to CK. The yield per plant saw a 14.54% increase, soluble solids rose by 29.34%, and the solid acid ratio was 1.68 times higher than that of CK. Furthermore, the net income was 2.37 times greater than that of CK. A comprehensive assessment revealed that the T3 treatment demonstrated superior performance in both growth parameters and economic returns, suggesting its suitability as an optimal formulation for further experimentation.

The development of plant-growth-promoting bacteria (PGPB) is one of the important research topics in agricultural microbiology. Four bacterial isolates that exhibited nitrogen fixation, phosphate and potassium solubilization, as well as indole-3-acetic acid (IAA) and siderophore production abilities, were selected from biogas residue, namely BR-1, BR-16, BR-17, and BR-44. According to morphological and molecular biological identification, BR-1, BR-16, BR-17, and BR-44 belonged to Bacillus subtilis, Bacillus cereus, Bacillus megaterium, and Bacillus subtilis, respectively. The four functional strains were combined into a composite microbial community. The optimal media were peptone (15 g/L), sucrose (10 g/L), and KCl (2 g/L); the optimal incubation conditions were an initial pH of 7.0, a volume of 47 mL/250 mL, an inoculum size of 6% v/v, an incubation temperature of 31 °C, a shaking speed of 205 r/min, and an incubation period of 20 h, as determined through a single factor test and the response surface methodology (RSM). In the optimized process, a liquid bacterial inoculant with an OD₆₀₀ of 1.866 was obtained, with an effective viable count of 8.955 × 10⁹ CFU/mL. A solid bacterial inoculant was prepared by using bran as a substrate, and its effective viable count was 1.11 × 10⁹ CFU/g. The application of the bacterial inoculants promoted the growth of watermelon, increased the photosynthetic efficiency and yield, and improved fruit quality. This study provides a theoretical basis and technical support for the development and application of microbial inoculants.

To address soil degradation from long-term monoculture, rotary tillage, and excessive chemical fertilization in semi-arid regions of China, we conducted a three-year field experiment. We assessed the synergy of integrated management practices combined with both continuous and rotational tillage methods (including ploughing, rotary, moldboard ploughing) at varying tillage depths (10–15, 15–25, 25–35 cm) with different fertilization regimes (chemical vs. organic–inorganic). Among all treatments, the rotational tillage practice that integrates moldboard ploughing at 25–35 cm depth with organic–inorganic fertilization [1200 kg ha⁻¹ mature compost + 375 kg ha⁻¹ compound fertilizer (N:P₂O₅:K₂O = 15:15:15)] significantly reduces bulk density by 11.8% and increases total porosity by 17.9% in the 15–25 cm soil layer. This practice optimizes nutrient stratification, elevating available nitrogen and potassium in the shallow layer (10–15 cm) to 126.13 and 372.45 mg kg⁻¹, respectively, while boosting available phosphorus in the subsoil (25–35 cm) by 247.8%. Furthermore, it significantly enhances soil microbial activity, increasing populations of bacteria, actinomycetes, and fungi by 3.42 × 10⁵, 0.65 × 10⁵, and 2.40 × 10³ CFU g⁻¹, respectively, alongside a 49.4% rise in soil respiration. These synergistic improvements collectively promote stable maize yields (increasing by 1731.4 kg ha⁻¹) and high economic returns (net income increasing by 3301.6 CNY ha⁻¹). These findings support the promotion of integrated tillage–fertilization strategies to enhance maize productivity and soil ecological function in semi-arid regions.

To investigate the adaptability and efficacy of biogas residue soil conditioner in conjunction with other commercially available soil conditioners in arid conditions, a study was conducted using dryland maize as the experimental crop. Five treatments were implemented based on the “dry sowing and wet emergence” method for Xinjiang cotton: T1 with traditional fertilization, T2 with biogas residue soil conditioner, T3 with biogas residue soil conditioner and endophytic arbuscular mycorrhizal bacteria, T4 with commercial Fuli Bang soil conditioner, and T5 with commercial Tianji soil conditioner. Results indicated that the combined use of biogas residue particulate soil conditioner and arbuscular mycorrhizal fungi (T3) had the most positive effects. T3 treatment reduced soil bulk density, increased soil organic matter content, and enhanced rhizosphere microbial diversity. Compared to T1, T3 led to a decrease in soil bulk density by 8.89%, higher microbial diversity indices, and significant increases in plant height, stem diameter, and yield by 6.25%, 15.48%, and 37.43%, respectively. Moreover, T3 showed elevated antioxidant enzyme activities (SOD and POD) and lower malondialdehyde content, indicating enhanced stress resilience and root activity. T3 showed ideal balance in yield, aboveground growth, and root stress resilience. It also improved soil organic matter levels and structure, highlighting the significant potential of combining biogas residue soil conditioner and endophytic arbuscular mycorrhizal fungi to alleviate spring drought stress.