Profile soil samples up to 90 cm depth were collected from fields irrigated with industrial waste water (IWW) for 2 and 5 years as well as from fields irrigated with underground tubewell water (TW). Soils irrigated with IWW had lower pH but higher organic carbon as compared to those which received TW as a source of irrigation (DTPA extractable Zn, Cu, Mn and Fe largely accumulated in the upper 15 cm soil depth and the extent of their accumulation depended on the period of use of IWW. In the 0–5 cm soil layer, the respective values of DTPA available Zn, Cu, Mn and Fe were 0.9, 1.6, 3.2 and 28.5 mg kg−1 soil where TW was used for irrigation and the use of IWW for five consecutive years increased these valuesby 52, 16, 4 and 3 times, respectively. The effect was almost similar in two subsequent 5 cm soil layers. The bioavailability of these elements to wheat depend not only on their content in soils but also on the levels of interacting metal ions. Despite more than adequate levels of Mn in soils, severe Mn deficiency symptoms were observed in fields where large amount of Zn and Fe accumulated as a result of the application of IWW for 5 years.
Industrial waste water, polluted soil, bioavailability of micronutrient elements
