The Influence Of Sludge And Vermicompost On Important Physical And Chemical Properties Of Tidal Flat Soil And Its Fertilization Effect

Mudflat reclamation is an important approach to relieve the pressure from the arable land reduction.Although the east coast of China has large areas of mudflat,coastal mudflat are usually characterized by high salinity,inferior structure and low fertility and its amendment needs the inout of large amount of organic matters from the outside.Rich in organic matters and other nutrients,sewage sludge vermicompost(SSV)is a potential resource which is available for amending coastal mudflat.However,the reports pertaining to the effect of SSV application on mudflat soil properties and fertility development have yet been scarce.Using sorghum and barley as indicator plants,a field experiment with different application rates(0,25,50,125,250 t ha-1)of sewage sludge vermicompost(SSV)was conducted in a newly reclaimed mudflat in 2016 and 2017,to investigate the effect of SSV addition on physi-chemical properties of mudflat soil,growth and N,P uptake of sorghum and barley,and accumulation of heavy metals in soil and plants.Results showed as followings:(1)SSV application significantly improved mudflat soil physio-chemical properties.With the increase of SSV,pH and EC in mudflat decreased.Compared with the treatment with no SSV applied,soil bulk density was declined.SSV improved soil organic matters and increased water-stable aggregates in 0-20 cm soil layers.(2)Regression analysis indicated that the bulky density of mudflat soil was negatively correlated with soil organic matter content.There was a negative correlation between EC and aggregate,and EC had a higher impact on>0.25 mm aggregate than on 0.106-0.25 mm aggregate.There existed a negative correlation between aggregate an bulky density,but 0.106?0.25 mm aggregate had more influence on bulky density than>0.25 aggregate.(3)Total N,alkaline N,total P and available P were elevated by SSV application.The increments of available N and P under SSV application was wider than those of total N and P.(4)With the increase of SSV rate,the biomass of sorghum and barley were significantly increased.The plant height and yield of barley were significantly elevated.The increment of total N ranged 13.8%?53.3%,in sorghum compared with 25 t ha-1,and 32.6%?128.3%in barley compared with CK(with no SSV applied);the increment of total P anged by 25.2%?160.4%in sorghum compared with 25 t ha-1,and 43.9%-90.2%in barley compared with CK.(5)With the increase of SSV rate,total heavy metal concentrations(Cu,Zn,Cr,Cd,Pb,Mn)in mudflat soil showed a trend of accumulation,with an exception of available Cr.The heavy metal concentrations,with the exception of Cd,were below the control standards for agricultural field in China.However,the behaviors and environmental risk control of heavy metals derived from SSV application in mudflat soil need further investigation.