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EFFECTS OF UN-TREATED SEWAGE SLUDGE ON WHEAT YIELD, METAL UPTAKE BY GRAIN AND ACCUMULATION IN THE SOIL

MUHAMMAD ALI KHAN^1*, T.G. KAZI², R. ANSARI³, S.M. MUJTABA, B. KHANZADA, M.A. KHAN, M.U. SHIRAZI AND S. MUMTAZ

Abstract: The high nutrients and organic matter contents of sewage sludge make it an excellent fertilizer to enhance soil fertility and crop production. However, presence of metals is a major problem for such a utilization of sludge. In Pakistan, there are only two-sewage treatment plant, one in Islamabad and the other in Karachi. Due to not having sewage treatment facility, in the country on wide scale, usually sludge is directly mixed with agricultural soil. As the sewage sludge, produced in municipal station, is highly toxic, therefore, there is a danger for the uptake of toxic metals by plant and accumulation in the soil. The present study describes the effects of un-treated sewage sludge on wheat yield and uptake of metals by grain as well as addition of metals to the soil. The treatment consisted of sewage sludge @ 10, 20, 40 & 80 Mg ha^-1, keeping 120:60:60 NPK as a standard application rate (control). The results indicated that the sewage sludge @ 80 Mg ha^-1 yielded significantly (p£0.05) higher when compared with control. Sewage sludge increased the levels of Zinc (Zn) and Cadmium (Cd), within the permissible limits, in wheat grain; whereas no significant increase was observed in Copper (Cu) and Lead (Pb). Analysis of soil showed significant increases in AB-DTPA-extractable Zinc and Copper and non-significant increases in 0.1N HCl-extactable Lead and Cadmium. It may be concluded that application of sewage sludge was good for improving crop yield but it was also a source of metals. Therefore monitoring of metals, in soils as well as in plant parts, should always be carried out in case of continuous use of sewage sludge.

¹Nuclear Institute of Agriculture (NIA), Tandojam,

²National Centre of Excellence, University of Sindh, Jamshoro,

³Department of Botany, University of Karachi, Karachi, Pakistan.