The Influence of Irrigation with Raw and Treated Municipal Wastewater on Wheat Yield and Microbial Characteristics of Soil and Plant

In this study, the influence of Irrigation with raw (RWI) and treated (TWI) wastewater on the quantitative and microbial properties of wheat in comparison with using safe water for Irrigation (SWI) was investigated under a completely randomized block design. Irrigation water quality was analyzed every two weeks during the growing season. At the end of the growing season, the yield and yield components were determined. Also, the Escherichia coli and Parasitic Nematode were determined in soil samples, taken from 0-30 cm depth, and plant samples. Results showed that despite favorable water quality of SWI, the values of EC, pH, BOD5, COD, total coliform and fecal coliform in raw and treated wastewater exceeded the available standard values. Using raw wastewater caused significant increase in the number of grain per spike, spike length, fertile spike number, total grain number, grain yield, biological yield and harvest index, in the ranges of 0.86-30 and 4.4-88.1 percentages compared with those for SWI and TWI treatments, respectively. However, insufficiency of nutrients in TWI as well as the degradation of soil physicochemical properties under unmanaged usage of treated wastewater led to a significant reduction of 827.3 Kg ha-1 in grain yield. Nevertheless, the soil and plant microbial conditions were favorable under TWI treatment. The existence of E. coli and Parasitic Nematode beyond the standard values in soil and plant under RWI treatment indicated the necessity for stopping irrigation with this water resource in the study area. The favorable conditions of soil and plant regarding the microbial contaminants, showed the possibility of substituting the fresh water with the treated wastewater through suitable application management.