STUDY OF THE POSSIBLE INDIRECT EFFECT OF DIFENOCONAZOLE ON SOIL MICROORGANISMS

Application of fungicides in agriculture can have harmful effects on non-target organisms, including soil microorganisms. Pesticides usually have negative impact on soil quality in general. Enzyme activities constitute the bases of nutrient cycling and can function as bioindicators assessing the impact of xenobiotics on communities of microorganisms in the soil. Difenoconazole (3-clor-4-[(2RS, 4RS, 2RS, 4SR)-4-metil-2-(1H-1,2,4-triazol-1-il-metil)-1,3-dioxolan-2-il] fenil4-clorfenil eter) is a broad-spectrum fungicide frequently used in crops to destroy pathogen fungi. The aim of this study was to determine the possible effects of different applied doses of difenoconazole on soil based on enzymatic activities (dehydrogenase and urease) in laboratory condition. The soil was treated with three different concentrations of difenoconazole as follows: half dose (HD) - 0.037 mg DFC/g soil, normal dose (ND) - 0.075 mg DFC/g soil, and double dose (DD) - 0.150 mg DFC/g soil. Following the treatment, the soil was incubated under laboratory conditions, at two different temperatures: 19 degrees C (variant A) and 28 degrees C (variant B). Variant C was untreated soil. Biochemical parameters were dehydrogenase and urease activities, and they were determined using spectrophotometric methods in all experimental variants. This study was performed during a period of 21 days after the fungicide treatment. Dehydrogenase activity registered values between 0.352 +/- 0.059 and 0.497 +/- 0.107 mg triphenyl-formazan g-1 soil for variant A, respectively between 0.439 +/- 0128 and 0.541 +/- 0.130 mg triphenyl-formazan g-1 soil for variant B. The values of urease activity in experimental samples varied between 2.388 +/- 0.169 and 2.720 +/- 0.291 mg HN4 g-1 soil for variant A, respectively 2.169 +/- 0.171 and 3.092 +/- 0.279 mg HN4 g-1 soil for variant B. Statistical tests revealed a significant decrease of the dehydrogenase and urease activities for the treated soil compared to untreated soil. As expected, there is also a significant increase of both enzymes activities for higher temperature. Difenoconazole inhibits the dehydrogenase and urease activities in treated soil samples regardless of incubation conditions. The metabolism of the communities of microorganisms in soil treated by difenoconazole was affected.