effect of different amounts of municipal wastewater on yield of cotton under drip irrigation

due to limitation of conventional water resources, the use of unconventional water for agriculture is unavoidable. therefore, in order to investigate the effect of using different amounts of municipal wastewater on yield, yield components and water use efficiency of cotton in drip irrigation systems, a field experiment was carried out during 2010 and 2011 growing season at experimental farm of jopar agriculture and natural resources research center in kerman province. the treatments were laid out in split plot with a randomized complete block design (rcbd) with three replications. the treatments were comprised of three levels of irrigation including 100% (control), 80%, and 60 percent of  crop water requirement in the main plot, and two water qualities (groundwater and wastewater) as sub plot, under surface drip irrigation system. the results showed reduction of ph and increment of soil salinity due to the high concentration of elements such as na and k in the wastewater. also, comparison of 100 percent with 80 percent of water requirement using wastewater showed a water saving of 1800 m3 ha-1, while water use efficiency was increased 18 percent. however, the same treatment caused a decrease of 1.5%, 2.1%, 2.9%, 15.2%, and 11.6 percent in yield, number of boll, boll weight, plant height, and leaf area index, respectively. considering the results obtained in this study, to cope with the water shortage in the country and increase water use efficiency, make use of wastewater, and conserve water, applying 20 percent less water than the full crop water requirement of cotton is recommendable in kerman,.