Digestate improved birch (Betula pendula) growth and reduced leaf trace element contents at a red gypsum landfill

Revegetation of industrial landfills and mine tailing may restore key soil functions and reduce the environmental impacts of contaminants. These marginal sites are often characterized by phytotoxic levels of trace elements (TE) (Cu, Fe, Mn, and Zn) and low nutrient status (N, P, and K). The aim of this study was to test the effect of digestate and bacterial inoculation on soil physicochemical properties (pH, CaCl(2 )extractable Mn, and microbial enzyme activities) and birch (Betula pendula) growth and physiology on a red gypsum substrate in a lab-to-field exper-imental approach. The biomass of birches amended with digestate (D0.05% N) was on average 2-and 6-fold greater than that of control birch in the laboratory and field experiments, respectively. A higher concentration of digestate (0.1% N) had an inhibitory effect on plant growth, and reduced the survival rates of amended plants by 40% as compared with controls. The digestate (D0.05% N) treatment significantly increased leaf P and K contents while decreasing leaf Ca, Fe and Mn contents. Digestate also increased some key soil enzyme activities of C, N, P and S metabolism by > 10-fold compared with the control soil. In a phytomanagement scenario, digestate would be a preferred amendment resource for the production of clean birch leaf biomass on contam-inated red gypsum landfill, as birch trees amended with digestate had lower leaf TE and higher leaf nutrient contents than control birches.

Automated summary

The addition of digestate to red gypsum substrate significantly improved soil properties and promoted the growth and physiology of birch trees. Appropriate concentration of digestate increased plant biomass, enhanced leaf nutrient content, and reduced the accumulation of contaminants.