Metal accumulation in soil and forage crops irrigated with treated wastewater

الملخص

Use of treated wastewater (TWW) in agriculture could potentially be an important alternative source of irrigation water to mitigate water scarcity. Field experiments were conducted to study the influence of TWW for irrigation on the growth, quality and bioaccumulation of select nutrients and heavy metals in alfalfa (Medicago sativa L.), sorghum (Sorghum bicolor) and pearl millet (Pennisetum americanum) harvested at two times. The concentrations of heavy metals in waste water were in acceptable range. Frequent use of polluted water for irrigation resulted in accumulation of Cu, Cd, Zn and Fe in the soil which was 9.4, 3.5, 4.6 and 6.1 fold more than unpolluted site, respectively. Yield of all three species were higher when irrigated with TWW than fresh water regardless of harvesting time. Fodders grown in contaminated soil accumulated much higher metals than unpolluted site but did not follow a specific trend in accumulating various metals. Except for Cd+2, the metal content in aerial tissues of all three fodders lied below the critical threshold. Protein content of the three fodders grown in polluted sites was significantly higher in both cuttings. Other fodder quality indices including NDF, ADF, TDN, DMD, and NEl remained unaffected when plant species were irrigated with TWW. Results indicated that treated effluent can be cautiously used for irrigation in areas with limited water resources.