Effects Of Pesticide Residues On Soil Enzyme Activities In Orchards

Pesticides are the main source of pollution in orchards.Unreasonable use of pesticides will lead to excessive pesticide residues in soil,decreased fruit quality and serious environmental problems in the producing area.This study conducted two years of field research on the four major apple producing areas in China(Loess Plateau producing area,Bohai Bay producing area,southwest cold producing area and Xinjiang characteristic producing area),and obtained a large number of questionnaires.Through indoor soil culture experiments,the effects of pesticides(imidacloprid)on soil microbial enzyme activities in Yanyuan County,Sichuan Province(southwest cold producing area),Luochuan County,Shaanxi Province(Loess Plateau producing area),Aksu Prefecture,Xinjiang Uygur Autonomous Region(Xinjiang characteristic producing area)and Yantai City,Shandong Province(Bohai Bay producing area)were analyzed.Combined with in situ zymography technology,the influence of imidacloprid on the four major regions was analyzed to provide guidance for the rational use of pesticides and the healthy development of the environment.The main conclusions are as follows:Through the investigation of the main apple producing areas in China,it is found that the apple varieties are rich in the Loess Plateau,mainly late-maturing varieties.The Bohai Bay region has the least varieties and faces the current situation of single variety and urgent need to introduce new varieties.In terms of pests and diseases,the cold production areas in southwest China are mainly diseases,while the characteristic production areas in Xinjiang are mainly pests.The use of pesticides is mainly based on fungicides and insecticides in the Loess Plateau producing area,the Bohai Bay producing area and the southwest cold producing area,among which the southwest cold producing area accounts for the largest proportion.For the characteristic producing areas in Xinjiang,the types of pesticides are mainly insecticides and acaricides.In terms of pesticide use,fungicides decreased from south to north,and insecticides and acaricides increased from southeast to northwest inland.Pesticide residues showed a decreasing trend from the Loess Plateau to the surrounding areas.Through in situ enzyme spectrum technology,it was found that imidacloprid had different effects on soil in different producing areas.On the third day,imidacloprid had a slight stimulation on soil enzyme activity in salt source area.The spatial distribution of soil enzyme activity in Luochuan,Aksu and Yantai was brighter from the center to the periphery,which indicated that imidacloprid had obvious inhibition on soil in the three regions.Compared with CK treatment,the hot spot area of alkaline phosphatase(AKP)activity in Luochuan,Aksu and Yantai decreased by 15.16 %,14.16 % and 9.98 %,respectively.β-1,4-glucosidase(BG),Luochuan,Aksu and Yantai NY treatment decreased by 6.26 %,2.86 % and 7.09 %,respectively;β-D-cellobiosidase(CBH),NY treatment in Luochuan,Aksu and Yantai decreased by 1.35 %,21.48 % and 3.89 %,respectively;l-leucine aminopeptidase(LAP)decreased by 6.22 %,1.85 % and 9.67 % in Luochuan,Aksu and Yantai,respectively.Compared with CK treatment,β-1,4-N-acetylglucosaminidase(NAG),NY treatment in Aksu area increased by 13.21 %,and NY treatment in Luochuan and Yantai decreased by 9.15 %and 12.38 %,respectively.With the passage of time,the brightness of soil enzyme activity decreased.In terms of soil phosphorus cycle-related enzymes,imidacloprid stimulated the soil AKP enzyme activity in the Yanyuan area in the early stage and inhibited it in the later stage,while the Aksu area was the opposite,and the Luochuan and Yantai areas were completely inhibited.In terms of soil nitrogen cycle-related enzymes,imidacloprid stimulated the LAP enzyme activity in the salt source and Aksu area in the early stage,inhibited the enzyme activity in the Luochuan and Yantai areas,and the LAP enzyme activity was stimulated in the later stage.NAG enzyme activity was stimulated in the early stage of Yanyuan,Luochuan and Aksu,and inhibited in the later stage of Luochuan and Yantai.In terms of carbon cycle-related enzyme activities,imidacloprid stimulated soil BG enzyme activities in the salt source area and inhibited soil enzyme activities in Luochuan,Aksu and Yantai.The CBH enzyme was activated in the whole process except the salt source.Luochuan and Yantai were activated first and then inhibited,while Aksu was the opposite.The activity of soil microorganisms in apple orchards in four regions is limited by phosphorus,but there are differences between regions.The addition of imidacloprid alleviated the soil phosphorus limitation in Yanyuan area,but increased the soil carbon limitation.For Luochuan,Aksu and Yantai,the soil carbon limitation and phosphorus limitation in Yantai area were alleviated.Combined with the hot spot area of enzyme and microbial enzyme activity,it was found that the hot spot area of AKP enzyme activity in Yantai area was slightly lower than that of CK on the 30 th day of culture,and the remaining enzymes were larger than CK treatment,and significantly increased by 29.46 %,11.75 % and 19.02 % in CBH,LAP and NAG;in terms of enzyme activity,except that the LAP enzyme showed that NY treatment was greater than CK,the other enzyme activities were reduced,among which AKP,BG and CBH were significantly reduced by 47.71 %,38.92 % and 33.37,which can be seen that Yantai area is more susceptible to imidacloprid.In summary,this study found that imidacloprid had different effects on the four major producing areas,and Yantai area was more susceptible to imidacloprid.Therefore,imidacloprid should be used reasonably,and scientific guidance and publicity of pesticides should be strengthened to ensure the safety of apple producing areas and the healthy development of apple industry in Yantai area.