Effect Of Quinclorac On Soil Microbial Community Structure And Enzyme Activity

Quinclorac belongs to the quinoline carboxylic acid hormone type selective herbicide, it can effectively promote ethylene biosynthesis, resulted in the accumulation of abscisic acid, so that the pores shrink, reducing water evaporation, absorption of carbon dioxide to reduce, plant growth slowed (Cheng Hongfang 2006),that is one of the main herbicide in paddy field in china. In recent years, paddy to dryland Tanaka herbicide residue increased year by year, quinclorac potential environmental risk has received extensive attention. In this paper, we had the Guangdong Academy of Agricultural Baiyun base for many years planting rice farmland soil as the materials, combined modern bio-analytical technology and soil enzymatic research methods, used the indoor cultivation and statistical analysis, carried out the research that the relationship between soil enzyme activities and soil microbial community after quinclorac pollution. It means a lot to reveal soil enzyme activities of the quinclorac pollution response mechanisms and the biological abatement, and to evaluate the environmental quality of quinclorac contaminated soil.The main conclusions obtained in this research as follows:(1) This research through the aqueous acetone solution by adding 10% in paddy soils, using the method of soil phospholipid fatty acid assay and enzyme activity detection,10% effect of acetone on soil microbial structure and enzyme activity detection. In the upland field, the addition of acetone can reduce the total PLFA of soil microorganisms, soil fungi/bacteria had significant fluctuations; in paddy field, the addition of acetone made the soil microbial PLFA changing at different stages, overall it had less disturbed on soil stability.In the paddy field, acetone can stimulate urease activity, this activation was time-related, with the extension of time, urease activity of paddy field soil is growth slower. And there is no such law in the upland field. Acetone inhibited catalase activity significantly, in upland field, this inhibition was slow down as time goes on. Acetone affected on dehydrogenase activity depended on the state of the soil, in the upland field, 10% acetone added to the soil making dehydrogenase activity increased, but the regularity in the paddy field is not strong. Acetone can significantly stimulate cellulase activity in both fields, the regularity was similarity to urease.(2) In this paper with 83.3μg/kg and 166.6μg/kg quinclorac processing of paddy soil, simulation environment of paddy field and dry farmland, in experiment period sampling, detection of micro-organisms in the soil by using PLFA method, observation of different quinclorac treatment, changed the soil microbial community. Research shows that, during the 60d of experimental treatments, the soil of fry field, after being treated with 83.3μg/kg quinclorac, had inhibiting effects on the total biomass of soil microbial, bacterial biomass and fungi biomass, and after the treatments with 166.6μg/kg quinclorac, the various indicators of various biomass were all obviously elevated, but the treatments of these two kinds of concentrations both made the fungi/bacteria ratio decrease, indicating the treatments of quinclorac will make the soil microbial stability of dry fields drop; under the treatment of 83.3μg/kg quinclorac, the paddy field soil had enhanced functions on the soil microbial total biomass and fungi biomass, and had certain inhibiting functions on bacterial biomass, and the treatments of 166.6μg/kg quinclorac all had enhanced functions on the total biomass of the soil microbial, bacteria and fungus biomass, and seen from the fungi/bacteria ratio, treatments of different concentrations had no significant variations with the controls, indicating quinclorac had no obvious interference in paddy field biological stability. The analysis of the PLFA principal components analysis indicated that the two kinds of soil microbial communities of different concentrations had the microbial containing 14:0,15:0,16:0 and 18:2n6c as the dominant populations.The study found that, quinclorac effect on soil enzyme activities due to the type of soil enzymes,83.3μg/kg dry soil and 166.6μg/kg dry soil with two quinclorac concentration treatments, the catalase of both fields were activated; dehydrogenase within 14 days after spraying was no significant difference with the control, and had significantly inhibited after 14 days; 166.6μg/kg dry soil treatments in both fields, urease had a stimulating effect, while 83.3μg/kg in the upland field promotion urease activity, and in paddy field it inhibited the urease activity; the two concentrations Quinclorac in the paddy field, cellulose enzymes were inhibited, and the inhibition increased with increasing of concentration.(3) The use of SPSS software, to analyze the correlation of soil microbial PLFAs and soil urease, catalase, dehydrogenase, cellulase, found the different soil PLFAs had different effects on soil enzymes, the behalf of the bacterial fatty acids on two soils impacted the four soil enzyme activities mostly. In upland field, catalase, dehydrogenase, cellulase and urease regulated by different soil microorganisms. In paddy field, the fatty acid 22:2 had significantly related to four enzymes activity, and it regulated them in different direction.