The supplementation of soil amendments may not only improve the soil physical and chemical properties but also lead to the accumulation of heavy metals in soil. This experiment included six treatments:control (CK), organic manure (OM), polyacrylamide+organic manure (PAM+OM), straw mulching+organic manure (SM+OM), buried straw+organic manure (BS+OM), and bio-organic manure+organic manure (BM+OM) to explore the effects of different soil amendments on heavy metals and soil enzyme activities in coastal saline land and the relationship between them. The results revealed that compared with that in the CK treatment, the contents of soil Cr, Cu, Ni, and Pb exhibited an upward trend after the supplementation of soil amendments, among which the SM+OM and PAM+OM treatments had the most significant effects on the contents of soil Cr and Cu, respectively, whereas the BM+OM treatment had the most significant effects on the contents of soil Ni and Pb. Compared with those in the CK treatment, the activities of soil invertase and urease increased significantly following supplementation of soil amendments, and the BM+OM treatment had the best effect. The alkaline phosphatase activity exhibited a slightly upward trend after the supplementation of soil amendments, whereas the catalase activity did not change significantly. The redundancy analysis revealed that the first two axes cumulatively accounted for 70.3% of the variability in enzyme activities, and the importance of single soil heavy metals on soil enzyme activity was as follows:Ni>Cu>Cr>Pb.
Keywords: coastal saline land; redundancy analysis; soil amendments; soil enzyme activity; soil heavy metals.