Background. The pesticide burial site in the Jizzakh region of the Republic of Uzbekistan, covering an area of 12.7 hectares, has been exerting long-term anthropogenic pressure on the soil, leading to significant disruptions in its microbiological and agrochemical structure. Soil microorganisms and enzymes are highly sensitive to such contamination, and thus their abundance and activity serve as reliable bioindicators of the ecological condition of soil resources. Experimental findings have demonstrated a sharp decline in microbial populations, enzymatic activity, and soil fertility in contaminated areas, underscoring the urgent need for biological remediation and agrochemical correction to restore soil biocenosis and enhance the resilience of the ecosystem as a whole.

Studying the mycobiota of soils contaminated with pesticides allows us to evaluate and assess the impact of these chemicals on the composition and functions of soil microorganisms, which is critical for maintaining the health of the soil and the ecosystem as a whole.

Such studies are conducted using microbiological and molecular methods, which allow us to identify qualitative and quantitative indicators of the metabolic activity of bacteria, fungi, and other soil organisms, as well as to assess their role in the decomposition of pesticides and their impact on soil fertility

Purpose. To assess the microbiological, enzymatic, and agrochemical status of soils from various sections of the pesticide burial site in order to determine the extent of anthropogenic impact and the necessity for implementing biological remediation measures.

Materials and methods. In this study, five soil samples were analyzed, collected from various sections of the pesticide burial site and adjacent territories. For microbiological analysis, aqueous suspensions were prepared from the samples (10 g per 100 mL) and incubated at 30 °C for 24 hours. Microorganisms–including bacteria, fungi, and actinomycetes–were cultivated on selective nutrient media (nutrient agar (NA), Sabouraud agar (HiMedia), and Czapek medium) using serial dilutions of the soil suspension ranging from 10¹ to 107. Colony growth for each microbial group was recorded every 12 hours, with quantification and morphological assessment.

The physical properties of the soils (friability, sedimentation, homogeneity, and color) were evaluated visually. The control sample was collected from the dendropark zone of the Institute of Microbiology of the Academy of Sciences of the Republic of Uzbekistan (Tashkent).

Enzymatic activity in soil samples (catalase, peroxidase, polyphenol oxidase, and invertase) was determined using gasometric and colorimetric methods according to standard protocols (Galstyan, Khaziev et al.).

Agrochemical parameters–including pH, humus content, available forms of phosphorus and potassium, exchangeable cations, and degree of salinization–were determined according to GOST standards and methodological guidelines (Tashkent, 2005), using potentiometry, colorimetry, photometry, and gravimetric analysis.

Results. Microbiological analysis revealed a significant decrease in the total number of bacteria, fungi, and actinomycetes in soils from the pesticide burial site compared to the control sample (4,905 × 105 CFU/g). The lowest values were recorded in the central part of the site (25 × 105 CFU/g), which is attributed to unfavorable physicochemical soil conditions. The eastern section exhibited the highest microbial counts among contaminated areas (118 × 105 CFU/g), including bacteria–113 × 105, fungi–2 × 105, and actinomycetes–3 × 105 CFU/g. However, the physical structure of this soil showed signs of degradation. Soils from the western and northern parts had lower bacterial counts (36 × 105 and 43 × 105 CFU/g, respectively). Even at a distance of 2 km from the site, bacterial counts were 40 × 105 CFU/g, actinomycetes were present in minimal numbers (1 × 105 CFU/g), and fungi were entirely absent, indicating prolonged contamination effects beyond the site’s boundaries.

Enzymatic activity (catalase, polyphenol oxidase, peroxidase, and invertase) was also significantly reduced across all contaminated areas, reflecting disrupted metabolic processes in the soil microbial community. Peroxidase activity was relatively higher in the central and northern parts, while polyphenol oxidase activity was consistently suppressed–ranging from 2.4 to 4.3 mg benzoquinone/20 g·4 h–compared to the control value of 6.8 mg benzoquinone/20 g·4 h. Particularly low values were recorded in the center (2.4 mg/20 g·4 h) and northern areas (3.0 mg/20 g·4 h), suggesting impaired metabolism of phenolic aromatic compounds by the soil microbiota. Invertase activity was also notably reduced in the northern section, indicating a sharp decline in carbohydrate metabolism, likely due to a deficiency of active saprotrophs. A sample collected 2 km from the site showed increased enzymatic activity, indicating partial recovery.

Agrochemical analysis revealed that soils in the southern and western sections had higher levels of humus and carbon but suffered from potassium deficiency. In contrast, the eastern and northern sections were depleted in all major indicators: nitrate nitrogen (N-NO3) ranged from 22.9 to 69.7 mg/kg, available phosphorus (P2O5) from 18.0 to 34.0 mg/kg, and potassium (K2O) from 252.8 to 409.4 mg/kg. The best agrochemical parameters were observed in the southern section, while the poorest were found in the eastern and northern parts of the site.

Conclusion. The conducted study revealed pronounced anthropogenic suppression of the microbiological, enzymatic activity, and agrochemical structure of soils within the pesticide burial site. The northern, eastern, and central zones were found to be the most degraded. Although the southern and western areas retained partial biological potential, they still require corrective interventions. The obtained data underscore the urgent need for biological remediation and agrochemical restoration of contaminated soils.

It was established that the abundance of soil microorganisms and enzyme activity can serve as sensitive bioindicators of the ecological condition of soils at the toxic waste burial site in the Forish district of the Jizzakh region. The observed changes indicate a significant anthropogenic disruption of the enzymatic system of the microbial community within the site. These findings highlight the relevance of implementing biological remediation measures aimed at restoring both microbial populations and enzymatic potential–key indicators of the sustainability of soil ecosystems.