Effects of sewage sludge and other wastes application on the growth and element uptake of Jatropha curcas in abandoned rare-earth mine soil.

Abstract

The wastes such as sewage sludge (SS) can be used to amend soil of abandoned rare-earth mine land (ARL). The energy plant Jatropha curcas could be used as a pioneer tree species in the ARL. In a pot experiment to address the responses of growth and element uptake of J. curcas, three treatments were established: adding SS to the soil of ARL (T1), adding SS and bagasse to the soil of ARL (T2), adding SS, bagasse and passivator to the soil of ARL (T3), with the untreated soil of the ARL as the control (CK). The results showed that compared with CK, T1 only significantly increased the plant height of J. curcas, T2 and T3 significantly increased the plant height, ground diameter and dry biomass of J. curcas, of which the total dry biomass increased by more than 184.7%. All the three treatments significantly increased the contents of N, P, K and Cu in J. curcas. T1 and T2 significantly increased the proportion of exchangeable Zn, Cd and Ni in the substrates, while T3 showed the opposite effects. T3 significantly decreased the migration factor (M) and mobility factor (MF) of Zn, Cd, Ni in the substrates, and significantly reduced the contents of Zn, Pb, Cd, Ni in J. curcas, with an inhibition rate of over 36.1%. The comprehensive evaluation of the membership function showed that the order of growth promotion effects on J. curcas was T2>T3>T1>CK, while the order of capacity of inhibiting J. curcas to accumulate Cu, Zn, Pb, Cd, Ni was T3>CK>T2>T1. The combined application of SS and bagasse significantly promoted the growth and element accumulation of J. curcas, and the addition of passivator significantly reduced heavy metals uptake without affecting the growth of J. curcas.