Changes Of Enzyme Activities And Abundance Of Nitrifying Microorganism Of Three Diffrent Type Soils Under Long-term Fertilization

In order to investigate the response of enzyme activity and nitrifying microorganism abundance of different types of soil to fertilizer application,we selected three long-term typical zonal soil,including black soil,aquic brown soil and red soil.We collected no fertilizer?CK?,single chemical N fertilizer?N?,NPK fertilizer?NPK?,fertilization of organic manure?M?and NPK fertilizer+organic fertilizer?MNPK?5 kinds of soil samples,using microplate fluorimetric assay method to detect 9 kinds of soil enzyme activities including enzymes involved in carbon cycle:?-1,4-Glucosidase??G?and?-1,4-Glucosidase??G?,?-1,4-Xylosidase??X?,Cellobiohydrolase?CBH?,involved in nitrogen cycle:Leucine amino peptidase?LAP?,?-1,4-N-Acetyl-glucosaminidase?NAG?and enzyme involved in the phosphorus cycle enzymes:Acid phosphatase?AP?and oxide enzymes:Phenol oxidase?POX?and Peroxidase?PER?.Quantitative PCR was used to detect the abundance of nitrifying microorganisms,including ammonia-oxidizing bacteria?AOB?,ammonia-oxidizing archaea?AOA?,complete ammonia oxidation bacteria?Comammox?,and three nitrite oxidizing bacteria?Nitrobacter-nxrA,Nitrospira-nxrB and Nitrospira-16S rRNA?,in order to clarify the changes of various indexes under the influence of soil type and fertilization.The main results are as follows:?1?The enzyme with the largest change in black soil was?G,increasing by-30%?99%.LAP was the most variable enzyme in both aquic brown soil and red soil,with increases of-89%?38%and-82%?1118%,respectively.?2?The enzyme activity of black soil and aquic brown soil was significant decreased by fertilizer.In the black soil decreased by 5.2%?82%,and by 1.8%?89%in the aquic brown soil.The two soil enzymes with the largest changes were LAP,which decreased 82%and 89%,respectively,the enzyme activity was 3.86 nmol·g^-1·h^-1 and 3.88 nmol·g^-1·h^-1.Organic fertilizers can significantly increase the enzyme activity,with the increase rate of 6%?99%in black soil,and?G had the greatest response to the black soil,with the enzyme activity of 26.74 nmol·g^-1·h^-1,the increase rate of M treatment in aquic brown soil was 1%?109%,and the largest response of it was POX which activitiy achieved to 930nmol·g^-1·h^-1.Red soil was the soil with the greatest response of enzyme activity to fertilization,and both chemical fertilizers and organic fertilizers can increase the enzyme activity,with a change of-90%?510%in chemical fertilizers and a change of 4%?1118%in organic fertilizers.Among them,?G had the greatest response to chemical fertilizers,with an enzyme activity achieved to 41.69 nmol·g^-1·h^-1,and LAP had the largest response to organic fertilizers,which can achieve to 126.5 nmol·g^-1·h^-1.?3?Black soil,aquic brown soil and red soil had the greatest influence on AOB,increasing by-32%?1403%,18%?1157%,and-86%?6542%,respectively.The maximum values were 2.04×10⁹copies·g^-1,5.30×10⁸ copies·g^-1 and 5.38×10⁸ copies·g^-1 in NPK,MNPK of surface soil and MNPK of subsurface soil,which were 10.5,10.5 and 460 times of the lowest abundance treatment.?4?Black soil chemical fertilizer and MNPK treatment had significantly influence on nitrifying microorganisms,changed from-68%to 1406%,significantly affected the surface layer of aquic brown soil nitrifying microorganisms abundance,changed from 68%to 1157%.Red soil nitrifying microorganisms increased significantly in the organic fertilizer,decreased in the chemical fertilizer,changed from 86%to 6542%.Three kinds of soil AOB response to fertilization was the largest.?5?AOA abundance of three type soils was higher than that of Comammox,and it was more suitable for the growth of AOB after applying fertilizer.The surface abundances of AOB,Nitrobacter-nxrA and Nitrospira-nxrB in black soil and aquic brown soil were higher than those in20?40 cm soil layer,while those in red soil were opposite.?6?The main factors affecting the abundance of nitrifying microorganisms in black and aquic brown soil were ammonium nitrogen and nitrate nitrogen,microbial biomass carbon and nitrogen in red soil.Overall,long-term fertilization can significantly change the soil enzyme activity and nitrifying microorganisms abundance,the biggest change in black soil enzymes was?G,LAP in aquic brown soil and red soil.Soil type and fertilization had the biggest influence on AOB.According to the results,we recommend that black soil and aquic brown soil should apply organic fertilizer combined with chemical fertilizer,red soil should apply organic fertilizer or with chemical fertilizer,but problem should be paid attention such as nutrient leaching.