Nutritional Status in Grapevine–Alfalfa Intercropping System on Agricultural and Heavy Metal‐Contaminated Soils

Wild grapevine was cultivated either alone or in association with Medicago sativa– rhizobia symbiosis on two soil types: an agricultural soil and a contaminated one. In the present work, we observed that in the agricultural soil, grapevine intercropped with the alfalfa–rhizobium combination exhibited a significant increase in whole plant biomass compared to plants grown in monoculture, reaching values from 26 to 38 g/plant, respectively. However, in the contaminated soil, intercropping had no significant effect on plant biomass (approximately 26 g/plant). In the agricultural soil, intercropped grapevines showed no significant difference in shoot Zn, Mg, Ca, and Fe concentrations compared with those grown in monoculture. Nevertheless, root Zn, Ca, and Fe concentrations (0.5, 80, and 10 g/kg·DW, respectively) were significantly lower than in grapevines cultivated alone. This suggests that grapevine competes with alfalfa for mineral uptake. In the contaminated soil, a significant reduction in root Fe and Ca concentrations was also observed in intercropped plants compared with monocultured grapevines—approximately 35% and 64% lower, respectively. It is likely that intercropping improves nutrient use efficiency while decreasing trace metal accumulation in intercropped grapevines. In fact, compared with monoculture, intercropping with alfalfa and rhizobia did not enhance mineral nutrient levels in grapevines.