Heavy metal content of alfalfa irrigated with waste and tubewell water

A field experiment was conducted to study the effect of wastewater on yield and heavy metal uptake of alfalfa along with a tubewell irrigated crop as control at the Agricultural University Peshawar during 2009. The experiment was conducted in small plots (2 x 1 m) replicated thrice with fertilizer additions. The crop was either irrigated with Hayatabad Industrial Estate (HIE) wastewater or tubewell water. The yield data revealed that shoot dry weight was significantly affected by the irrigation water supplies and higher yield was recorded in wastewater irrigated plots and the increase was consistent with time (different cutting). By comparing the total dry biomass of the two treatments, it was observed that there was about 37% increase in yield over control with application of wastewater. The shoot dry weight increased by a factor of about two to three times from first cutting to third cutting in both the treatment plots and the magnitude of increase in yield was higher in wastewater irrigated plots. The heavy metal uptake by the crop was much higher in wastewater irrigated plots compared to tubewell water. The order of metal uptake was Fe greater than Mn greater than Zn greater than Cu greater than Pb greater than Ni greater than Cr greater than Cd. Shoot analysis showed no metal toxicity because the concentration of the metal was less than phytotoxic level and all the metals were within the permissible limits.