Cold Black Of Atrazine Residue On The Soil Microbial Community Dynamics And Influence

Frigid black soil is a scarce land resource in our country. The long-time effectiveherbicide, atrazine, has brought huge economic benefits to our black soil area, andnevertheless, it has become a main agricultural pollutant. The herbicide with large quantityand repeat use for a long time not only poison the after-reap crops, but also change the soilstructure, damaging the soil ecological system and the sustainable utilization of resources.Soil microorganisms are very sensitive to pollutants even with very low concentration, andcan be used to predict soil fertility and soil health with earlier. Taking soil microorganismsas the research object, this study combine traditional method with molecular biologytechnique to investigate the residual dynamic of atrazine and the impacts of this residual onsoil microbial community from aspects of microbial biomass, enzyme activities and thelevel of phospholipid fatty acids (PLFA) in soil, expecting to provide scientific reference forreasonable, effective and safely using of atrazine, so as to reduce environmental pollutionbrought by atrazine and improve life quality. The main results were as follows:1) The residues and change dynamic of atrazine in the soil were detected using HPLC.The results showed that atrazine residual reached the maximal value at the spraying dayduring the two-year period implementation, and displayed decline trend with prolonging thespraying time.And the half-life of atrazine is37days and38days in2012and2013,respectively.2) In addition, the influence of atrazine on the activities of the major soil enzymes wasdetermined. The results showed that atrazine had no obvious effect on soil sucrase, butshowed a high-concentration inhibition on cellulase,and this inhibitory effect exhibited adecline trend with the decrease in atrazine concentration, and showed no significantdifference compared with control when the remaining amount of atrazinewas0.15mg/kg.Atrazine residual could significantly influenced the activity of urease,which showed inhibitory trend during theentire detection period, and ureaseactivity in treatmentgroup decreased by up to38%compared with controlgroup.3) The changes in the amount of soil culturable microbes were determined during thetwo years’spraying of atrazine. With the decrease in atrazine residual, the amount ofmicrobes was impacted with varying degrees with respect to bacteria, fungiandactinomycetes.When atrazine residual was above2.3mg/kg, bacterial amount increased by11.3～15.8%in treatment group than in control, while decreased by16.9～25%whenatrazine residual was below1.38mg/kg. On the other hand, fungi level in treatment groupincreased by15～30%when atrazine residual was above1.72mg/kg, however, decreased by15～17.9%when atrazine residual was below1.38mg/kg comparing to control. It suggestedatrazine had a high-concentration promoting and low-concentration inhibitory effect onbacterial and fungi. Different from bacterial and fungi, the influence of atrazine onactinomycetes showed inhibitory on the whole, and with the decrease in atrazine residual,this inhibitory effect showed more striking, when atrazine residual was between0.092and0.21mg/kg, the amount of actinomycetes decreased by27～41.9%.4) GC-MS was used to determine the PLFAs profile of soil microorganisms, the impactof atrazine on soil fungi/bacteria ratio, GN/GP, pressure index and total PLFAs level wasmeasured. Fungi/bacteria ratio displayed high-level atrazine promoting and low-levelatrazine inhibition, and increased by25～30%when atrazine concentration was2.3～4.9mg/kg, while decreased by11～15%whenatrazinelevel was2.3～1.41mg/kg. GN/GPshowing the same trend with fungi/bacteria ratio also displayed high-level atrazinepromoting and low-level atrazine inhibition, when atrazine concentration was4.13～5.71mg/kg, GN/GP increased9.1～11%while decreased9.1～11%when the concentrationwas2.16～1.74mg/kg. On the contrary, pressure indexdisplayed high-level atrazineinhibiting and low-level atrazine promoting. When the concentration of atrazine was3.14～4.03mg/kg, compared with control pressure index decreased13～15.1%, and increased by12～18.9%when the concentration was2.1～1.1mg/kg. When the amount of atrazine residual decreased to1.38mg/kg, total PLFAs showed increase trend, and increased by20～25%when atrazine content was in rang of2.1～0.35mg/kg.