Changes Of Soil Microbial Biomass And Enzyme Activities In Facilities(Vegetables) And Their Relationship With Soil Fertility In Wuqing District,Tianjin

Taking the soil of facilities in Wuqing District of Tianjin as an example,the fertility,contents of soil microbial and enzyme of the soil in the facility were analyzed.The physicochemical properties,soil microbial biomass and enzyme activities of tillage layer(0-30cm)were analyzed under the different planting years.The relationship between the soil fertility,soil microbial biomass and soil enzyme activity was investigated by calculating the path coefficient.The main findings are as follows;(1)The contents of soil organic matter,total phosphorus and available phosphorus were higher,indicating that the soil fertility of the facility is better and the phosphorus is rich.The low levels of total nitrogen,alkali nitrogen and available potassium indicate that soil nitrogen and potassium nutrient elements are lacking in the study area,which may be one of the important reasons affecting the yield and quality of facilities(vegetables).Therefore,greenhouse managers should increase the application of nitrogen and potassium fertilizers in an appropriate amount to optimize soil structure and ensure the normal growth and development of crops.(2)The average values of soil microbial biomass carbon,nitrogen and phosphorus in greenhouse cultivation were 387.05mg·kg-1,71-08mg·kg-1 and 30.08mg·kg-1,respectively,which were significantly higher than the corresponding open soil.With the extension of the planting years(0-16a),the soil microbial biomass carbon and nitrogen content increased year by year.The microbial biomass carbon content is less variable between 10-16a planting.The soil microbial biomass nitrogen content varies greatly from 3-16a.The content of soil microbial biomass phosphorus showed a trend of decreasing first and then increasing after 3-16a.(3)Soil urease and alkaline phosphatase activities were enhanced with the increase of planting years,and reached the highest activity at 16a.The activities of invertase and catalase increased and decreased with increasing planting years.The soil neutral phosphatase activity was less affected by the planting years,and it did not change significantly with the increase of planting years.(4)There was a significant positive correlation between soil microbial biomass carbon and total nitrogen and available potassium.Path analysis shows that total nitrogen has a direct impact on soil microbial biomass carbon and is a positive effect.Soil microbial biomass nitrogen was significantly positively correlated with soil total nitrogen,alkali nitrogen and available potassium,and was significantly negatively correlated with pH.Soil total nitrogen,alkali nitrogen and available potassium are the main direct influencing factors of soil microbial biomass nitrogen.Soil microbial phosphorus is significantly positively correlated with soil available phosphorus and is also manifested by direct effects.(5)Soil urease was significantly correlated with soil total nitrogen,alkali nitrogen,available potassium and pH.The direct effect of soil total nitrogen is stronger,while alkali nitrogen,available potassium and pH all play an indirect role.Soil invertase was significantly correlated with soil organic matter,total phosphorus,available phosphorus and pH.The correlation between soil catalase and neutral phosphatase and soil fertility was not significant.Soil alkaline phosphatase was significantly correlated with soil total nitrogen,total phosphorus,alkali nitrogen and available potassium.