Investigation of the effects of some pesticides used in agricultural activities in Bitlis on soil nematodes and microorganisms

This study was conducted to determine the effects of Pyridaben (%20, acaricide), Pendimethalin (330 g/l, herbicide), Penconazole (100 g/l, fungicide) and Chlorpyrifos-methyl (227 g/l, insecticide) pesticides, which are widely used in agricultural fields of Bitlis, on non-target soil nematodes, aerobic mezophilic bacteria, microfungi communities and pH. The study was repeated (six times) according to variance analysis method (under in-vitro conditions). Selected pesticides were treated to soil samples (one kg per pots) using a sprayer at a recommended dose with the injector. According to the variance analysis, the Period×Treatment interactions are important for pH, plant-parasitic and fungivore nematodes respectively (P=0.007; P=0.008; P=0.000), for omnivore-predatore, bacterivore and total nematodes, on the other hand, (P=0.000; P=0.000; P=0.000) both period and the main effect of the treatments were statistically significant (P=0.046; P=0.017; P=0.009). Based on the profile analysis; pH increased especially in Pyridaben treatment, although the number of aerobic mesophilic bacteria increased in the control treatment, it decreased in all pesticide treatments; the number of microfungi increased in Penconazole treatment but decreased in other treatments; plant-parasitic, fungivore and total nematode count decreased in all pesticide treatments; omnivore-predatore and bacterivore nematodes were found to be partially affected. As a result, it has been determined that the used pesticides have positive or negative effects at different degree on the non-target studied soil parameters, depending on the type of pesticide and the parameters considered. In addition, it is recommended that pesticide toxicity tests should be carried out as widely as possible, and the pesticides used by the farmers should be applied carefully since they may affect non-target organisms and factors.