| The nitrification is widespread in the soil, and acid soils occupy large areas in China. Early studies showed that:Nitrification is widely existed in alkaline soil and its activity is very strong, and nitrification is almost non-existent in acidic soil. But as researchers continue to explore a lot of evidence that the acidic soil also exists nitrification.And in some certain acid soils, the nitrification is even very strong. For these reasons, acidic soil nitrification is attracted by more and moreresearchers. Many scholars at home and abroad are beginning to do a detailed stud on acidic soil of nitrification influence factors and mechanism.Since the surface of soil particles with a large amount of negative charge,which form a "continuous" distribution of a strong electric field, it impact.s on the activity of H+, NH4+, and soil microorganisms, and therefore on the nitrification process. In previous studies, few people consider the role of electric field of the surface of soil particles.This article from the point of view on soil particle electric field intensity to study soil nitrification and soil microorganisms, quantity, activity and the community structure changes.This experiment used the soil in Jinyun Mountain pine (Acid Yellow pH 5.2), A gradient of surface electrochemical parameters was obtained by amendment of a subtropical acid pine soil (Oxisol) with 0%(control),3%,5%,8%,10% and 12% pure Ca-Montmorillonite by weight, air-dried, crushed through lmm sieve to be used.Regulate the samples moisture content to 60% of the field moisture content, constant temperature incubator at 28℃in the first month of pre-culture.One month after pre-incubation, we added the equivalent weight of 100mg/kg dry soil NH4+-N. After NH4+-N added, taking samples, and then soil samples were placed in the 28℃constant temperature incubator to continue to cultivate.Samples were cultured for 4 weeks, and take samples once a weeks during the month. The H+ and NH4+ activities, the time-dependent kinetics of net nitrification were investigated. The abundance and composition of soil ammoniaoxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities were investigated using real-time polymerase chain reaction and denaturing gradient gel electrophoresis (DGGE). The results are as follows:Soil particle surface specific area of ranged from 52.9-102.4m2/g and increased with increasing montmorillonite addition. Similar to specific area, surface charge quantity, surface charge density, electric field strength and surface potential increased after montmorillonite amendment. H+ and NH4+ activities decreased linearly after montmorillonite amendment.The largest net nitrification (103mg/kg) was observed in the 10% montmorillonite amendment and the least in unamended soil (62 mg/kg). While montmorillonite did not change the kinetic patterns of net nitrification, the highest nitrification potential (275 mg/kg) for the 10% of montmorillonite treatment was more than 3 times higher than unamended soil from simulation of time-dependent kinetics. Nitrification was significantly stimulated after montmorillonite amendment in acid soil mainly due to an increase in the quantity and activity of AOB and AOA.AOB amoA gene copy number was 1.82×105 copies g-1 for unamended soil, and the highest AOB amoA gene copy numbers were found in the 10% of montmorillonite amendment (3.11×107g-1 soil), which was more than 170 times higher than unamended soil. AOA amoA gene copy numbers were 9.19×103 copies g-1 dry unamended soil, and the highest AOA amoA gene copy numbers were found in the 8% montmorillonite amendment (1.22×105g-1 soil). The largest net nitrification (103 mg N/kg) was observed in the 10% montmorillonite amendment and the least in unamended soil (62 mg N/kg). While montmorillonite did not change the kinetic patterns of net nitrification, the highest nitrification potential (275 mg/kg) for the 10% of montmorillonite treatment was more than 3 times higher than unamended soil from simulation of time-dependent kinetics. Nitrification was significantly stimulated after montmorillonite amendment in acid soil mainly due to an increase in the quantity and activity of AOB and AOA.Through clustering analysis of DGGE map we know that:the highest similarity of Community composition esxts in soil treatment of 8% and 10%,and it is above 0.7.Then they again clustered with treatment 12%.These three treatments community composition are most similar, first clustering; Then again clustered with treatment 0%, their value of similarity is above 0.5.The community composition similarity of treatment 5% and 3% is the lowest, slightly more than 0.4, finally clustering.We concluded that, the of quantity AOB and AOA are significant increased after adding montmorillonite in acid soil, and they reaches maximum in the content of montmorillonite to 10% and 8%, respectively;Adding montmorillonite significantly boosts nitrification in the acid soil, except different initial pH, mainly due to an increase in the quantity and activity of AOB and AOA; After adding montmorillonite, in the soil, the composition of AOB community structure changed obviously.
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