Effects Of Pyraclostrobin And Fluoxystrobin On Microbial And Soil Enzyme Activities In Fluvo-aquic Soil

Pyraclostrobin and fluoxystrobin are methoxy acrylate fungicides with good protection,treatment,osmotic effect,low toxicity,broad spectrum,safety,high efficiency and good environmental compatibility.Pesticide sprayed into soil has a certain effect on soil microorganism and soil enzyme.The effect of pesticide on soil microbial and enzyme activity can reflect the ecological and environmental safety of the pesticide to some extent.The mechanism of the decrease of enzyme activity caused by pollutants may be the combination of enzyme and pollutants,or the inhibition of microbial proliferation,which indirectly affects the enzyme activity.This compound,which does not cause protein denaturation,is called enzyme inhibitor.Enzyme inhibitors can be divided into two types: reversible inhibition and irreversible inhibition.The effects of two fungicides including pyraclostrobin and fluoxystrobin on soil microorganism and soil enzyme activity in fluvo-aquic soil were studied.The study on the number changing caused by the two fungicides of bacteria,fungi and actinomycetes by plate counting was carried out.meanwhile,the activities changing caused by the two fungicides of urease,dehydrogenase and ?-glucosidase were determined.The concentration of the two pesticides was 0.1 mg/kg?1.0 mg/kg?2.5 mg/kg respectively.In the experiment,solvent acetone was used as control.Soil samples were cultured in a incubator with a flowerpot after exposure.The soil moisture content was maintained at 60% of the maximum water holding capacity in the field by regular water supplementation.The soil samples were sampled at 7?14?21?28?48 d.The results are as follows:Pyraclostrobin inhibited number of both bacteria and actinomycetes during the experiment.The effect of pyraclostrobin on the number of fungi was activated at the beginning and then decreased with the increase of concentration.The effect of fluoxystrobin on the number of bacteria was basically inhibitory,but it was activated at the 14 th day and became stronger and stronger with the increase of the concentration.The effect of fluoxystrobin on the number of fungi was inhibited.The inhibitory effect was the strongest in the initial stage and strengthened with the increase of the concentration,but the inhibition gradually weakened later.The inhibition of fluoxystrobin on the number of actinomycetes was observed at the beginning of the experiment,and increased with the increase of concentration.However,the treatment group of 0.1 mg/kg showed activation later.Pyraclostrobin and fluoxystrobin mainly prevent and cure fungal diseases.The inhibitory effect of flupyridamole on the number of fungi is more rapid,and the effect on the number of bacteria and actinomycetes is small,which can reflect the high efficiency and environmental friendliness.Initial activation of urease by pyraclostrobin working appeared,especially for 0.1 mg/kg,contrary to the dehydrogenase basically inhibited,and as for the ?-glucosidase,decreased first and then increased.The effects of fluoxystrobin and pyrazolyl ester on urease were compared.In the experiment of the effect of fluoxystole on urease,the treatment group of 0.1 mg/kg was different from that of pyraclostrobin in that it was inhibited first and then activated,and that in other treatment groups it was inhibited.The effect of fluoxystrobin on dehydrogenase was similar to that of pyraclostrobin,and was activated in the treatment group with only 0.1 mg/kg,and the effect of fluoxystrobin on ?-glucosidase was mainly inhibited.Only 0.1 mg/kg showed activation at 21 d,and the inhibitory effect of fluoxystrobin was more obvious than that of pyraclostrobin.