Laboratory tests were performed on sandy loamy soil to establish the relations between bacterial diversity, soil enzyme activity and degradation of Amistar 250 SC, Falcon 460 EC and Gwarant 500 SC fungicides. Apart from carrying out microbiological and biochemical analyses, the residues of active substances from the tested fungicides were determined. Structural diversity of was determined based on the next-generation sequencing (NGS) method, and fungicide residues the liquid chromatography tandem-mass spectrometry (LC-MS/MS). It was found that changes in bacterial diversity occurred in the soil subject to fungicide treatment, particularly at the family and genus level. Proteobacteria, Firmicutes and Actinobacteria were prevailing in all soil samples. Bacillus occurred both in the control soil and in the soil treated with fungicides, while Pseudonocardia occurred only in the fungicide-treated soil. Of all the fungicides tested, the biggest changes in bacterial diversity were caused by Gwarant 500 SC. The preparations tested not only affected the composition of soil microbiota, but also contributed to changes in the biochemical properties of soil by inhibiting the activity of almost all tested enzymes, with the exception of alkaline phosphatase and β-glucosidase. Chlorothalinil was the fastest degraded in the soil and spiroxamine at the slowest.
The aim of this study was to determine the effect of carfentrazone-ethyl (CE) doses of 0.265, 5.280, 10.560, 21.180, 42.240 μg kg-1 soil DM on fungi, Acnomycetes, organotrophic bacteria, total oligotrophic bacteria and spore-forming oligotrophic bacteria, and on the activity of dehydrogenases, catalase, urease, alkaline phosphatase, acid phosphatase, arylsulfatase and β-glucosidase. Carfentrazone-ethyl had a stimulating effect on total oligotrophic bacteria and organotrophic bacteria, but it inhibited the growth of Azotobacter, fungi, spore-forming oligotrophic bacteria and Actinomycetes. The analyzed substance modified the structure of soil microbial communities, and it induced the most profound changes in fungi. The highest values of the colony development (CD) index and the eco-physiological (EP) index were observed in organotrophic bacteria. The optimal dose of carfentrazone-ethyl stimulated the activity of dehydrogenases, catalase, urease, alkaline phosphatase, acid phosphatase and β-glucosidase, but it had no effect on arylsulfatase. The highest doses of the analyzed substance inhibited the activity of dehydrogenases (reduction from 11.835 to 11.381 μmol TPF), urease (reduction from 0.545 to 0.500 mmol N-NH4) and arylosulfatase (reduction from 0.210 to 0.168 mmol PNP). Dehydrogenases were most resistant to CE, whereas acid phosphatase and arylsulfatase were least resistant to the analyzed compound
A laboratory experiment was completed to determine the effect of the herbicides Alister Grande 190 OD, Fuego 500 SC and Lumax 537.5 SE on counts of actinomycetes as well as the activity of enzymes and their resistance to herbicides. Sandy loam was mixed with appropriate doses of the herbicides, such as: 0 - the control, 1 - technological dose and doses 20-, 40-, 80- and 160-fold higher than recommended. On day 20, 40, 80 and 160, counts of actinomycetes and activity of urease, acid phosphatase and alkaline phosphatase were determined. For 160 days, soil was incubated at 25°C and its moisture content was maintained on a constant level equal 50% of water capillary capacity. On days 20 and 80 of the experiment, the ecophysiological (EP) and colony development (CD) indices were computed. Additionally, the resistance (RS) of enzymes to the herbicides was assessed on day 20 and their resilience index (RL) was determined on day 160. It has been found out that soil contamination with herbicides contributed to elevated counts of actinomycetes. The highest number of these microorganisms was observed in soil with Lumax 537.5 SE, and the lowest one appeared in soil with Alister Grande 190 OD. The CD for actinomycetes was the highest in treatments with Fuego 500 SC and the highest EP was determined in soil with Alister Grande 190 OD. Application of the herbicides in doses from 20- to 160-fold higher than recommended by the manufacturer significantly increased the activity of acid and alkaline phosphatases. With respect to the activity of urease, the herbicides produced variable effects. The strongest inhibitory effect on the activity of urease was produced by Fuego 500 SC, which reduced the activity of this enzyme by 13.39% when added to soil in a dose exceeding by 160-fold the recommended rate. The RS of the enzymes to the herbicides ranged from 0.461 to 0.955. Urease was the most tolerant to soil contamination with the herbicides.