The concentrations of Mn and Zn in both plant species and in all treatments (except in B. vulgaris with manure treatment) were in excess of the threshold micronutrient concentration in animal feeds (>70 and 100 mg kg−1 Mn and Zn, respectively; Georgievskii et al., 1982). The concentration of Cu in B. maritima in all treatments did not exceed the threshold for animal feed ( 2.16 > 1.53 mg kg−1 in olive husk, control and manure, respectively; B. maritima: 5.05 > 3.88 > 2.35 mg kg−1 in control, olive husk and manure, respectively).