Metal accumulation and shoot yield of Miscanthus × giganteus growing in contaminated agricultural soils: Insights into agronomic practices

Abstract

The choice of agronomic practices for phytomanagement of metal-contaminated soils is of crucial importance to optimize plant biomass yields and to mitigate both environmental and health risks due to metal exposure. The present study aimed to assess the effects of agronomic practices on shoot yield and on metal (Cd, Pb, and Zn) accumulation in the organs of the energy crop miscanthus (Miscanthus×giganteus) during the first three years since the plantation on metal-contaminated agricultural soils. Three miscanthus cultivars, hereafter named Mis-A, Mis-B and Mis-I, were planted at low and high density. An inoculum of arbuscular mycorrhizal fungi-AMF (Glomus LPA Val 1) was added during plantation, and nitrogen fertilization was applied during the third growing season. Metal accumulation in miscanthus organs was determined during the second growing season, whereas shoot yields and their metal concentrations were determined during both the second and the third growing seasons. Based on metal concentrations and bioconcentration factors, the three cultivars mainly accumulated metals in their roots. The shoot yields increased from 3.7 to 10.3tDWha−1 in the second growing season to 15.8–23.3tDWha−1 in third growing season. There were no or very few significant differences in metal concentrations and shoot yields within treatments comprising the same cultivar. The addition of AMF inoculum increased metal (mainly Cd and Zn) accumulation in miscanthus organs and in the shoot yields and this was more observed in both Mis-B and Mis-I which presented a higher root mycorrhization level than in Mis-A. Shoot yields in treatments comprising different cultivars depended not on fertilization but on the interactions between cultivar and planting density, and between cultivar, planting density and AMF inoculum. Whatever the treatment and the sampling period, Pb concentrations did not significantly differ in shoot yields. The interaction between cultivar and planting density resulted in higher Cd concentrations in the yields of Mis-B planted at low density during the third growing season. Zn concentrations increased with fertilization in all treatments, and with the addition of the AMF inoculum in Mis-B and in Mis-I. Overall, the results demonstrated that the three cultivars could be potential candidates for coupling phytostabilization and biomass production on metal-contaminated soils.