HYGIENIC ASSESSMENT OF THE PESTICIDES EFFECT OF TRICETONES AND CARBOXAMIDES CLASSES ON LEACHED CHERNOZEM NITRIFYING ACTIVITY

Abstract

The analysis of the current ecological situation shows the intensification of soil degradation processes and the slowing down of soil self- purification processes due to pollution by heavy metals, radionuclides, pesticides, pathogenic microorganisms. Aim research: regularities establishment of tricetone herbicide bicyclopyrone influence and carboxamide fungicide pydiflumetofen on self-purification of chernozem leached from nitrogen-containing substances. Materials and methods. The effect of the studied pesticides on the processes of nitrification in leached chernozem was studied in a laboratory hygienic experiment. Bicyclopyrone was added in concentrations of 0.05; 0.25 and 1.0 mg/kg, corresponding to 1; 5 and 20 maximum application rates (0.15 kg/ha), pydiflumetofen – in initial concentrations of 0.12; 0.6 and 1.8 mg/kg, corresponding to 2; 10 and 30 maximum application rates (0.18 kg/ha). Determination of nitrogen compounds (ammonium ions, nitrite anions and nitrate nitrogen) was carried out in the soil extract by photometric method on the 1st, 3rd, 5th, 7th, 10th, 15th, 20th and 30th days from the beginning of the experiment. Results. It was found that the average and maximum concentrations were of bicyclopyrone (0.25 and 1.0 mg/kg) and pydiflumetofen (0.6 and 1.8 mg/kg) in soil were effective because they caused unidirectional changes in the content of ammonium ions and nitrite anions more than 25 % compared to control, for more than 7 days. According to the effect on the dynamics of nitrogen nitrates, all studied concentrations of bicyclopyrone in soil were ineffective, because the differences with the control at all observation times were insignificant and did not exceed 25%. The high concentration of pydiflumetofen inhibited formation of nitrates was effective, the average was recognized as a threshold, the minimum (0.12 mg/kg) was ineffective. In general, the threshold concentration of bicyclopyrone by the effect on the nitrifying activity of soil is 0.05 mg/kg; the threshold concentration of pydiflumetofen is higher than 0.12 mg/kg and lower than 0.6 mg/kg. Conclusions. Bicyclopyrone and pydiflumetofen in the average and maximum investigated concentrations inhibit of self-purification process of chernozem leached from nitrogen-containing compounds, causing a more pronounced effect on ammonification and the 1st phase of nitrification. The use of pesticides based on them in agriculture will not worsen the course of nitrification processes in real soil-climatic conditions of Ukraine.

Keywords

• : pesticides
• soil
• self-purification
• nitrifying activity.