Nutritional status and its interaction with soil properties and trace elements in six Mediterranean shrub species grown in reclaimed pyritic tailings

- Growth of shrubs in amended tailings to assess improvement in nutritional status.
- Soil organic matter, N, P and K related to increases in plant biomass, P and K.
- Addition of CaCO3 increased N, Ca, Mg and Fe uptake, and pig manure N uptake.
- Low pH increased metal bioaccumulation with lower nutrients uptake except for B.
- L. dentata and C. albidus were more sensitive to improve nutrition with amendments.

For phytostabilization to successfully reclaim mine tailings, an adequate soil nutrient level should be provided to promote the growth of healthy plants and plant succession. In this study, six Mediterranean shrub species (Lavandula dentata, Rosmarinus officinalis, Thymus vulgaris, Nerium oleander, Cistus albidus and Pistacia lentiscus) were grown in mine tailings, unamended and amended with calcium carbonate and pig manure, and in a reference unpolluted substrate as positive control. We aimed to assess if amendments enhanced plant growth and nutritional status and to study the relationships between soil properties, soil metal(loid) contents and nutrients and plant growth and nutritional status. These data are necessary to infer how soil characteristics influence plant health in tailings for proper management. The experiment was conducted in pots for 120 d. The results showed that at the end of the experiment the addition of amendments had increased soil pH from ∼4.5 to ∼7.7, exchangeable Ca, K and P and had decreased exchangeable Mn and Fe, with no effect on N and Mg. In general, unamended tailings supported plants with high accumulation of Cd, Zn, Mn and B in their tissues, related to high availability of metals and low pH. Amended tailings supported plants with better root development and higher levels of N, K, Ca, Mg, Fe and Cu in all parts, with regard to unamended tailings. Thus, the reclamation strategy improved the nutritional status of plants and root development, mainly related to increases in soil CaCO3 and pH. However, reclamation led to enhanced accumulation of As and Pb (below toxicity limits), related to increases in pH and soluble organic compounds, respectively. Amendment addition did not favor P accumulation by the plants, despite its increase in the soil. Among species, L. dentata and C. albidus were the species with the highest improvement in nutrient content with the addition of the amendments, while T. vulgaris was the species least affected by soil conditions.