The fast pace of cropland loss in China is causing alarm over food security and China’s ability to remain self-reliant in crop production. Mudflats after organic amendment can be an important alternative cropland in China. Land application of sewage sludge has become a popular organic amendment to croplands in many countries. Nevertheless, the land application of sludge to mudflats has received little attention. Therefore, the objective of the present work was to investigate the impact of sewage sludge amendment (SSA) at 0, 30, 75, 150 and 300 t ha⁻¹ rates on soil physicochemical properties, perennial ryegrass (Lolium perenne L.) growth and heavy metal accumulation in mudflat soil. The results showed that the application of sewage sludge increased organic matter (OM) content by 3.5-fold while reducing salinity by 76.3% at the 300 t ha⁻¹ rate as compared to unamended soil. The SSA reduced pH, electric conductivity (EC) and bulk density in mudflat soil, increased porosity, cation exchange capacity (CEC) and contents of nitrogen (N), phosphorus (P), exchangeable potassium ions (K⁺), sodium ions (Na⁺), calcium ions (Ca²⁺) and magnesium ions (Mg²⁺) in comparison to unamended soil. There were 98.0, 146.6, 291.4 and 429.2% increases in fresh weight and 92.5, 132.4, 258.6 and 418.9% increases in dry weight of perennial ryegrass at 30, 75, 150, and 300 t ha⁻¹, respectively, relative to unamended soil. The SSA increased metal concentrations of aboveground and root parts of perennial ryegrass (p < 0.05). The metal concentrations in perennial ryegrass were Zn > Cr > Mn > Cu > Cd > Ni, and the metal concentrations in roots were significantly higher than aboveground parts. The metal accumulation in perennial ryegrass correlated positively with sludge application rates and available metal concentrations in mudflat soil. Land application of sewage sludge was proved to be an effective soil amendment that improved soil fertility and promoted perennial ryegrass growth in mudflat soil. However, heavy metal accumulation in plants may cause food safety concern.

China is facing a shortage of arable land resources, and the mudflat salt-affected soil along the east coast of China is an important reserve arable land resource. In this study, we conducted a randomized field trial to investigate the effects of vermicompost application rate (0, 25, 50, 125, and 250 t ha⁻¹) on barley growth and heavy metal accumulation in mudflat salt-affected soil. We found that vermicompost application decreased bulk density, electrical conductivity (EC), and pH of mudflat salt-affected soil while increasing its organic carbon, nitrogen, and phosphorus contents. With the increase in vermicompost application rate, the yield of grain and total biomass of barley plants increased. The yield of grain in the vermicompost application treatments of 25, 50, 125, and 250 t ha⁻¹ increased by 66.0%, 226.0%, 340.0%, and 512.0%, respectively, relative to the control. In addition, the concentrations of heavy metals (Cd, Cr, Cu, and Zn) in mudflat salt-affected soil and barley plant increased as the vermicompost application rate increased.