Pre-cultivation with herbaceous plants assists in the revegetation process of iron mining tailings with enterolobium contortisiliquum

In the process of recovering degraded areas, the establishment of succession of arboreal plants after the planting of herbs is an efficient strategy for diversifying vegetation cover and improving soil quality. In this sense, the objective of this research was to evaluate, in microcosm, the effect of herbaceous pre-cultivation on the initial development of Enterolobium contortisiliquum and on the rehabilitation of the physical, chemical, and biological characteristics of the iron mining tailings from the Fundão dam, Mariana, Brazil. Five different herbaceous pre-cultivation systems were applied: control without pre-cultivation (T/E); Urochloa ruziziensis (U/E); U. ruziziensis + Crotalaria spectabilis (U + C/E); U. ruziziensis + Guizotia abyssinica (U + G/E); and U. ruziziensis + C. spectabilis + G. abyssinica (U + C + G/E). After 120 days of cultivation, we evaluated the tree development and the physical, chemical, and biological attributes of the tailings. The dry mass of the total shoot and the stem of E. contortisiliquum did not differ between the pre-cultures, whereas the dry mass of the leaf was lower in U + C/E. In general, the biological attributes of the tailings were the most sensitive to the changes that occurred due to the different herbaceous pre-cultivation arrangements. In the treatments U/E, U + C/E, and U + G/E, greater efficiency was observed in the production of microbial biomass carbon and in the total enzymatic activity of the soil. E. contortisiliquum proved to be efficient in the absorption of sodium (Na), copper (Cu), zinc (Zn), chromium (Cr), and nickel (Ni), demonstrating that this tree species has the potential to be used in the revegetation of tailings. The use of fast-growing plants activates the soil microbiota and favors the arboreal being an efficient strategy for the tailings rehabilitation process.