The response of wild olive to the addition of a fulvic acid-rich amendment to soils polluted by trace elements (SW Spain)

We studied the response of wild olive (Olea europaea L. var. Sylvestris Brot.), a representative species of the Mediterranean forests, to a fulvic acid-rich amendment added to soils polluted by trace elements under semi-arid conditions. Fulvic acids are known to increase the availability of minor elements; however, phytotoxic effects might arise if the mobilization of potentially toxic trace elements was excessive. The amendment caused some mobilization of As under laboratory conditions. However, 'in situ', phytotoxic concentrations of As in the plants were never registered. The concentrations of Cd, Cu, Pb, Tl and Zn were not phytotoxic either and were generally within the ranges considered normal for plants. The positive effects on plant growth and on the nitrogen and chlorophyll content derived from the amendment application seem to corroborate the absence of phytotoxicity.