Study On The Effect Of Environmental Sludge On Improved Tidal Soil And Its Environmental Effects

Sewage sludge, complied with Chinese agricultural standard, can be used to amend mudflat soils. The arable land in China has been shrinking sharply for recent years, and the costal mudflat might be considered to be the most accessible arable land resource. However, mudflat soil can be converted to crop land only by addition of a lot of organic matter. The goal of this study is to assess application effects and its mechanisms in a mudflat amended by sewage sludge amendment (SSA) at0,30,75,150, and300t ha-1ratesThe results showed that the application of sewage sludge improved physicochemical properties of mudflat soil. The SSA reduced salinity, pH, electric conductivity (EC) and bulk density in mudflat soil, increased porosity, cation exchange capacity (CEC), contents of nitrogen (N), phosphorus (P), exchangeable K+, Na+, Ca2+and Mg2+in comparison to unamended soil.The SSA increased the biomass of ryegrass, sesbania, ryegrass and corn in mudflat soil. The highest yield of ryegrass and corn at reproductive stage was at75t ha-1SSA rate, while the yield dropped at150t ha-1SSA rate. The yield was not significantly change in sesbania. ryegrass and corn at various SSA rates.The SSA increased total Zn and Cu concentrations at150and300t ha-1rates, whereas there were either no changes in total Mn, Cr, Ni, and Cd concentrations in the sludge amended soils compared to unamended soil. The available metal concentrations for Zn, Cu, Ni and Cd increased with SSA, whereas the available Mn and Cr showed only minor increases with increasing SSA rates.The SSA increased heavy metal concentration and accumulation in ryegrass. The metal concentrations in roots of ryegrass were higher than that of aboveground parts in all SSA rates. The correlation analysis showed that heavy metal accumulation in ryegrass grown in sewage sludge-amended soils were positively correlated with SSA rates, available metal and ryegrass biomass.The optimum sewage sludge amendment rate is75t ha-1with maximum plant yield yet permissible metal accumulation.