effects of treated wastewater on soil microbial and chemical contamination and wheat

nowadays, application of unconventional water such as wastewater is one of the strategies for preventing water deficit. this study was conducted to evaluate effect(s) of treated wastewater application on microbial and chemical contamination of soil and wheat (chamran v.). five treatments included t1 (irrigation with 100% fresh water), t2 (75% fresh water + 25% wastewater), t3 (50% fresh water + 50% wastewater), t4 (25% fresh water + 75% wastewater), and t5 (100% wastewater) that were conducted with three replications, in a randomized complete blocks design in the research station of ahvaz agricultural research center. the irrigations were done based on soil moisture monitoring. the volumes and the time of irrigation were determined based on the 70% soil field capacity. the soil (0-30 cm) and plant (seed) samples were taken during wheat growth periods and were analyzed for some parameters such as soil microbial population as well as cadmium (cd) concentration and micronutrients in soil and plant. the results showed that the total soil cd concentration in 95% of the samples was less than 1.6 mg.kg-1. however, soil dtpa-cd concentrations in all the treatments decreased compared to initial cd soil content. the results revealed that wastewater treatments had no significant (p<0.05) effect on seed microelements, except fe. the average soil dtpa-cd in each wheat growth stage did not increase compared to its initial concentration. the soil microbial population at different growth stages was not significantly different (p<0.05) in t3 and t5 treatments, possibly due to growth limitations as a result of nutrient accessibility limitation. it may be concluded that the application of wastewater (along with fresh water) had no adverse effect on soil and wheat quality in short term. however, long term application of unconventional waters may cause contamination in soil and agricultural products.