1552 Advances in Environmental Biology, 6(4): 1552-1557, 2012 ISSN 1995-0756 RTICLE A RIGINAL O nally screened and reviewed This is a refereed journal and all articles are professio Corresponding Author Mina Omidbakhsh, Department of Soil Science, Science and Research Branch, Islamic Azad University, Khouzestan, Iran E-mail: omidbakhsh_mina@yahoo.com Study of Effect of Refined Waste Water Application on Trend of Changes in Certain Soil Chemical Properties in Khouzestan, Iran 1 Mina Omidbakhsh, 2 Alireza Jafarnejadi, 3 Ali Gholami, 2 Seyed Mohammadhadi Mosavifazl 1, 3 Department of Soil Science, Science and Research Branch, Islamic Azad University, Khouzestan, Iran 2 Soil and Water Research Department of Agricultural and Natural Resources Research Center of Khouzestan, Iran Mina Omidbakhsh, Alireza Jafarnejadi, Ali Gholami, Seyed Mohammadhadi Mosavifazl; Study of Effect of Refined Waste Water Application on Trend of Changes in Certain Soil Chemical Properties in Khouzestan, Iran ABSTRACT Today, water scarcity and declining water quality lead to use of unconventional water in farming including wastewater and urban sewage. In order to examine how wastewater irrigation possibly affect trend of changes in calcareous soil chemical properties, a field experiment has been carried out at Ahvaz Experimental Station (AES) during 2010-2011. The experiment was laid out under RCBD with five treatments and three replications. Composite soil samples were collected according to growth stages of wheat at 0-30cm depth interval of topsoil. The experimental treatments were %100 ordinary water (T1), %75 ordinary water+ %25 wastewater (T2), %50 ordinary water+%50 wastewater (T3), %25 ordinary water+ %75 wastewater (T4), and %100 wastewater (T5). Chemical analysis of wastewater revealed that electrical conductivity exceeded allowable range; however, wastewater pH remained in the permissible range. The concentration of chloride ion and trace elements in studied wastewater significantly exceeded permissible ranges recommended by FAO for irrigation practice. It was also indicated that use of refined urban sewage increased soil salinity (%40), organic carbon (%1.5), absorbable phosphorus (%41), zinc (%1.7), manganese (%7) considerably compared to initial parameters, whereas it did not affect on pH variation and copper concentration. In general, the results approved use of refined wastewater as a fair alternative for ordinary water. Key words: Irrigation, Soil chemical properties, Urban sewage, Wheat, Khuzestan (Iran). Introduction Increasing urban population, development of industrial and agricultural food-producing activities and successive severe droughts have driven fresh water over-consumption during recent years. Moreover, unstoppable production of undesirable material such as wastewater and urban solid waste grows unprecedentedly. The urban wastewater, itself, causes irreparable damages to environment if it would not be appropriately refined and disposed. Wastewater reuse needs to be considered an irrigation source more than ever before as the country faces extreme scarcity of fresh water and use of low quality or unconventional water as an alternative source for irrigation is inevitable [1]. Numerous efforts were made to study qualitative outcomes of irrigation using refined wastewater for soil over a long period. Qian and Mecham [23] and Rusan et al. each reported increased soil salinity and Na accumulation associated with longer periods of irrigation using refined urban sewage led to decreased aggregate stability and soil hydraulic conductivity [23]. However, the presence of Ca and Mg in calcareous soils can mitigate this deleterious effect [16].Wastewater contains a large amount of nourishing ingredients which can feed the crops. In addition to enrich nourishing ingredients of soil, several studies revealed that organic compounds in wastewater would be decomposed by microorganisms as soon as they would integrate into soil; hence, increasing humus, and finally improving the physicochemical properties as well as soil fertility [30,7]. Wastewater is also an important source of nutrients for crop production particularly for poorly fertile soils [15]. Irrigation using raw wastewater probably increases soil organic matter, nitrogen and concentrations of major cations [5]. However, it has been associated with negative impacts on health [11,24]. Long-term irrigation using raw wastewater possibly drives accumulation of heavy metal, and consequent quality loss of soil depending on the wastewater origin [17,19]; hence, wastewater refinement is routinely recommended