Atrazine has been extensively used in China’s agricultural production for a long time and the potential risks to the environment have received widespread attention. The purpose of this study was to examine the effect of the continuous application of atrazine on soil herbicide residues, soil enzyme activity, and microbial community structure, as well as to provide a theoretical reference for the appropriate application of atrazine and the improvement of soil. Previous studies have focused on the effects of atrazine on soil microorganisms, but the experiments used higher doses than recommended. To reveal the actual effects of atrazine on soil microorganisms, the recommended dose of atrazine was used for 0, 1, and 2 years. We studied atrazine residues and enzyme activity in the soil, and phospholipid fatty acids (PLFA) were measured to study the structure of the soil microbiome. The results show that the rate of atrazine degradation occurred rapidly after the initial administration, and with the increase in continuous administration, its half-life decreased from 24.6 d in the first year to 14.1 d in the second year. The application of atrazine significantly affected soil urease activity and cellulase activity, but it had no significant effect on saccharase activity. The continuous application of atrazine had a significant effect on the biomass of cultured bacteria in soil, but not on the biomass of culturable fungi and actinomycetes in the soil. Furthermore, the results of PLFA analysis show that the application of atrazine had a significant effect on the microbial structure of the soil. These results indicate that the significant increase in the degradation rate of atrazine during continuous application is related to the high adaptability of the soil microbiome.

Late blight of potato is caused by the pathogen Phytophthora infestans, which has been considered to be the most destructive disease affecting potato crops worldwide. In recent years, the use of antagonistic microorganisms to control potato late blight has become a green and environmentally friendly means of disease control, greatly reducing the use of chemical pesticides. To obtain antagonistic bacteria with a high biocontrol effect against potato late blight, a total of 16 antagonistic bacterial strains with an inhibition rate of more than 50% against P. infestans were screened from potato rhizosphere soil by double-culture method, among which the bacterial isolate (X3-2) had the strongest inhibitory activity against P. infestans, with an inhibition rate of 81.97 ± 4.81%, respectively, and a broad-spectrum inhibitory activity. The bacterial isolate (X3-2) was identified as Bacillus velezensis based on its 16S rDNA gene sequence and morphological as well as biochemical properties. The results of our in vitro experiments demonstrated that X3-2 was a potent inducer of resistance in potato tubers and leaflets against late blight. In greenhouse experiments, it was confirmed that the biological preparation X3-2 exhibits an anti-oomycete effect, demonstrating a significant control efficacy on potato late blight. Further analyses showed that the antagonistic substances of X3-2 were distributed both intracellularly and extracellularly. In addition, screening for plant-growth-promoting (PGP) traits showed that X3-2 has the ability to produce siderophores and secrete indole acetic acid (IAA). The findings from this research suggest that B. velezensis X3-2 exhibits promise as a biocontrol agent for managing late blight. In the future, the composition and mechanism of the action of its antimicrobial substances can be studied in depth, and field trials can be carried out to assess its actual prevention and control effects.

Atrazine is a long residual herbicide commonly used in maize fields. Although atrazine can effectively control weeds and improve crop yield, long-term application leads to continuous pollution in the agricultural ecological environment, especially in the soil ecosystem, and its impact on soil microorganisms is still not clear. Four methods were used in the experiment to clarify the effect of atrazine on the bacterial populations of cultivated soil layers of chernozem in a cold region in different periods: high-performance liquid chromatography (HPLC), colorimetry, microplate, and high-throughput sequencing. The level of residual atrazine in cold chernozem decreased from 4.645 to 0.077 mg/kg soil over time, and the residue gradually leached into deep soil and then decreased after accumulating to a maximum value. Atrazine significantly affected the activities of urease and polyphenol oxidase activity in the soil layers at different periods but had no significant effect on sucrase and phosphatase activity. Atrazine significantly reduced the diversity of microbial carbon source utilization and total activity in soil layers of 0–10 and 20–30 cm but only reduced the diversity of microbial carbon source utilization in the 10–20 cm layer. Atrazine had no significant effect on bacterial populations (10–12 phyla, 29–34 genera), but had a slight effect on the relative abundance of various groups. Atrazine significantly reduced the diversity of bacterial populations in cultivated soil layers of chernozem in a cold region, and the diversity of bacterial populations decreased with decreased residue. This lays a foundation for guiding the safe use of herbicides on farmland in Northeast China.

Understanding the influence of fertilizer on soil quality is vital to agricultural management, yet there are few studies, particularly in black soil. In this study, soils under various treatments, namely no fertilizer, bio-organic + humic acid, bio-organic + chemical, and chemical fertilizer, were sampled to identify their major physiochemical properties, and to investigate the fungal community structure using environmental sequencing techniques. Physiochemical properties and fungal community structure were examined at four important stages of the maize life cycle: seedling, jointing, heading period, and maturity. We found that chemical fertilizer in the mature stage increased the soil available phosphorous (AP) content. Organic matter content was greatly affected by bio-organic + chemical fertilizer during the mature stage. Bio-organic + humic acid significantly increased soil phosphatase activity in maturing maize, whilst chemical fertilizers reduced invertase activity. Taken together, our results clearly illustrated that bio-organic + humic and chemical fertilization indirectly alter fungal community structure via changing soil properties (especially AP). Chemical fertilizer markedly heightened the AP content, thereby decreasing specific fungal taxa, particularly Guehomyces. OM was of positive connection with bio-organic + humic acid and Mortierella abundance, respectively, through RDA analysis, which are in agreement with our result that bio-organic + humic acid fertilization to some extent increased Mortierella abundance. Additionally, bio-organic + humic acid decreased the abundance of Fusarium and Humicola, suggesting that bio-organic + humic acid possibly could help control crop disease. These results help to inform our fundamental understanding of the interactions between fertilizers, soil properties, and fungal communities.

The main purpose of this study was to explore the effects of the recommended usage level and twice the recommended usage level of the long-acting herbicide fomesafen on the soil enzymes and microbial community structure in chernozems of soybean fields. Culturable microbial biomass and phospholipid fatty acids (PLFA) were used as the main references for this evaluation. The digestion curve of fomesafen in soil conforms to the law of a single exponential function. The activities of four soil enzymes decreased significantly when exposed to twice the recommended amount, and then returned to the control level. The inhibition of the fungal and bacterial biomass section of culturable microorganisms in soil at twice the recommended usage level was greater than that under the recommended usage level, and this dosage also stimulated the rapid recovery of the initial level of fungal biomass before the application of fomesafen. The PLFA analysis showed that the ratio of GN/GP decreased significantly, and soil pressure increased significantly. Compared with the recommended usage level, the effect of twice the recommended usage level of fomesafen on soil microbial community structures was more significant. This provides a reference for environmental location recommendations, environmental safety assessments, and the rational use of herbicides.

In this study, the effect of Metarhizium spp. M. marquandii on the seed germination of cabbage, a cruciferous crop, was investigated. The effects of this strain on the seed germination vigor, bud growth and physiological characteristics of Chinese cabbage were analyzed by a seed coating method. The results showed the following: (1) The coating agent M. marquandii SGSF043 could significantly improve the germination activity of Chinese cabbage seeds. (2) The strain concentration in the seed coating agent had different degrees of regulation on the antioxidase system of the buds, indicating that it could activate the antioxidant system and improve the antioxidant ability of the buds. (3) When the concentration of M. marquandii SGSF043 was 5.6 × 10⁶ CFU/mL (average per grain), the effect of M. marquandii SGSF043 on the leaf hormones Indole Acetic Acid (IAA), Gibberellic Acid (GA) and Abscisic Acid (ABA) of Chinese cabbage seedlings was significantly higher than that of other treatment groups, indicating that the strain could optimize the level of plant hormones. (4) M. marquandii SGSF043 could induce the expression of stress-resistance-related genes in different tissue parts of Chinese cabbage and improve the growth-promoting stress resistance of buds. This study showed that M. marquandii SGSF043 could not only improve the germination vitality of Chinese cabbage seeds but also enhance the immunity of young buds. The results provide a theoretical basis for the application potential of Metarhizium marquandii in agricultural production.