| Maize is the largest food crop in China with the top ranking in planting area and total output among major food crops.As the largest corn production region,Jilin province reported planting 3.696 million hectares of corn in 2014,accounting for 65%of the province’s crop planting area.In recent years,Jilin has actively promoted the adjustment of the corn industry in order to drastically reduce the corn planting area through the crop replacement or rotation with soybeans,wheat and potatoes.Atrazine is a triazine herbicide which has a long history in the application of corn field weed control.However,due to the stable chemical structure,Atrazine’s persistence in the environment with a long residual period in soil causes phytotoxicity to the succeeding crops in the corn field and impacts its growth negatively.Therefore,studying the residues of atrazine in the soil of Jilin’s major corn production areas and evaluating its safety level on the succeeding crops provides an effective scientific basis for the conversion of the corn field for other crops.Furthermore,this technical support also facilitates the implementation of the adjustment of the corn industry in Jilin province.In this study,soil samples of maize fields were collected from 28 counties of 6 prefecture-level cities in Changchun,Siping,Jilin,Baicheng,Songyuan and Liaoyuan.Atrazine residues in soil samples were determined by gas chromatography.The residues of atrazine in soil of main maize-growing areas in Jilin Province were determined by pot experiment.The effects of detoxification on symptoms and growth and development of maize crop after cropping in wheat,soybean and sorghum fields were studied.The threshold of detoxification of soil residual atrazine on succeeding crops was determined.Herbicide varieties and application methods suitable for succeeding crops were screened and studied.The main results are as follows:1.A gas chromatographic method for the determination of atrazine residues in soils in our laboratory was established.The residue of atrazine in soil was determined by gas chromatography.The Agilent 6890N gas chromatograph was used.DB-17,30 m*0.25 m m*0.25 um capillary column was selected as the chromatographic column.The detector was micropool electron capture mu-ECD type.The column temperature was 180 C,carrier gas velocity was 1.0 m L/min,injection volume was 1 mu L,and atrazine was detected at a minimum of 0.2*10-10g.It has high sensitivity and is suitable for the detection and analysis of large quantities of soil samples from the same experiment in our laboratory.2.The soil residues of atrazine in main maize producing areas in Jilin Province were mastered.Among 145 soil samples,the detection rate of atrazine was 31.69%,the maximum residue was 2.478 mg/kg,and the average residue was 0.187 mg/kg.The order of residues from high to low is Changchun City>Siping City>Jilin City>Songyuan City>Baicheng City>Shuangliao City.The average residues of atrazine in soil from high to low were Siping City>Changchun City>Jilin City>Songyuan City>Baicheng City>Shuangliao City.This indicates that atrazine residues in soil in the central region are higher than those in the eastern mountain areas and the western semi-arid areas.The average residues of soil samples collected in April and July were 0.141 mg/kg and 0.163 mg/kg,which generally accorded with the rule that the upper soil layer was higher than the lower soil layer.3.The effects of atrazine residue in soil on sorghum,peanut and wheat were determined.Sorghum showed a high tolerance to atrazine.When the residue of atrazine in soil ranged from 0.1 mg/kg to 1.0 mg/kg,there was no significant effect on Sorghum growth.When atrazine residue reached 0.1 mg/kg,it caused drug damage to wheat,cucumber,peanut and soybean,which manifested as leaf discoloration and withering,and plant stopped growing until death with the increase of atrazine residue.Suitable crops for crop rotation or alternative planting should be selected according to the residue of atrazine in Maize field.4.Herbicides suitable for wheat,peanut,sorghum and other maize crops were screened.50%metolachlor atrazine was used for pre-seedling weeding in Sorghum field.When the treatment dose was 300 ml/mu,the control effect reached 98.9%,and 10%quinolone SC + 38%atrazine SC was used for Post-Seedling weeding.When the treatment dose was 120 ml/mu and 130 ml/mu,the control effect reached 89.8%.78%promethazine acetochlor isoxazolone suspension was used for pre-seedling weeding in peanut field.When the treatment dose was 250 ml/mu,the control effect was 91.2%.After seedling weeding,4%methoxy tobacco SL + 24%enoxanone EC was used as herbicide.When the treatment dose was 80 ml/mu and 40 ml/mu,the control effect was 93.5%.Herbicides used in wheat field were 2.4-drops of isooctyl ester EC + 5%zolinolate EC.When the treatment dose was 40 ml/mu and 60 ml/mu,the control effect reached 70.3%. |
