| Acetochlor·metribuzin·butylate is a new type of compound herbicide used in black soil in Northeast China in recent years.It can enlarge the killing spectrum and reduce crop damage caused by broadleaf weeds and gramineous families in bean fields.At present,the research of acetochlor·metribuzin·butylate mostly concentrated on the amount of field application and the mechanism of weed control,however,there were few studies on the effects of acetochlor·metribuzin·butylate application on soil environment.Therefore,taking black soil as the object,changes of microbial biomass and enzyme activities of soil carbon cycle and nitrogen cycle and phosphorus cycle in different concentrations on different days and the changes of soil bacterial community structure and bacterial species by the DGGE molecular technology were studied in order to reveal the trend of microorganism and enzyme activity in black soil after acetochlor·metribuzin·butylate application and to provide theoretical reference for the rational application of acetochlor·metribuzin·butylate in black soil farmland in Northeast china.Through the experiment,the following conclusions were obtained:1.Soil respiration showed the effect of number of days.It increased gradually with the increase of days.Cellulose decomposing bacteria showed the effect of concentration and the number gradually increased with the increase of concentration(P < 0.05).The activity of invertase was affected by both days and concentration of treatment,and gradually increased with the increase of concentration and number of days(P < 0.05).Cellulase and amylase activity did not change after acetochlor·metribuzin·butylate application.Above results showed that soil carbon cycle was affected by acetochlor·metribuzin·butylate application,and could promoted the carbon decomposition process of soil to some extent.2.The number of soil nitrogen fixing bacteria ammonifying bacteria,nitrifying bacteria and urease activity and nitrate reductase activity showed the time effect and the amount of nitrifying bacteria decreased with the increase of number of days(P < 0.05).Nitrite reductase activity,nitrogen fixation bacteria,ammonifying bacteria and urease activity increased with the increase of number of days(P < 0.05).Protease activity showed the concentration effect,and protease activity decreased at different concentrations(P < 0.05).The number of denitrifying bacteria was affected by the number of days and concentration of treatment,and gradually increased with the increase of concentration and number of days(P < 0.05).There was no change in the activity of nitrate reductase after acetochlor·metribuzin·butylate application.Above results showed that soil nitrogen cycle was affected by acetochlor·metribuzin·butylate application.Acetochlor·metribuzin·butylate could promoted the activity of nitrogen decomposing bacteria to a certain extent and accelerated the speed of mutual transformation between ammonium nitrogen and nitrate nitrogen,at the same time,it also promoted the transformation of nitrate nitrogen to gaseous nitrogen,the nitrogen lossed and was not conducive to the accumulation of nitrogen.3.Acid phosphatase activity,nuclease activity and soil available phosphorus content showed the time effect.The content of available phosphorus and nuclease activity gradually increased with the increase of days(P < 0.05).Acid phosphatase activity showed the increase-decrease-increase rule with the increase of days(P < 0.05).There was no change in organic phosphorus.Above results showed that the activity of soil phosphorus decomposing was increased,and the phosphorus transformation was promoted to some extent after acetochlor·metribuzin·butylate application.4.Based on 16 S rRNA PCR-DGGE technology,the diversity of soil microorganisms of black soil after acetochlor·metribuzin·butylate application were studied.The results showed that there were soil bacteria Bacillus sp.(Bacillus),Nocardia sp.(Nocardioides),proteus sp.(Proteus),acid(Acidobacteriaceae)and so on.The diversity of soil microorganisms decreased firstly and then increased at 45 d,these bacteria were related to the organic carbohydrate synthesis and decomposition of cellulose,starch,protein,urea,and organic phosphorus.Above results showed that microorganisms of soil carbon,nitrogen and phosphorus cycling had a gradual recovery trend after acetochlor·metribuzin·butylate application.5.There were correlations among soil carbon,nitrogen and phosphorus cycle,the correlation between carbon cycle and nitrogen cycle was higher after acetochlor·metribuzin·butylate application of different concentrations in different days.Among the soil microbial and enzyme activities,nitrogen fixing bacteria,ammonification bacteria,nitrite reductase and acid phosphatase were the main indexes and they could indicate the soil nutrient change. |
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