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.

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.

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.