Effect of application of wastewater treatment on soil chemical and physical properties under millet cultivation

Treated wastewater is valuable water source to supply water and compensation of drought, especially in arid and semiarid regions. However, it should be noted that soil pollution and environmental protection should be considered during its application. The objects of this study were the evaluation of the effects of treated wastewater on the availability of soil nutrients, physical properties, and soil pollution. For this purpose, treated wastewater was used for irrigation in two ways. In the first method, only the treated wastewater was used during the growing season and in the second, the treated wastewater was used periodically with well water for irrigation throughout the growing season. After the end of the growing season, a chosen number of plats were randomly selected for sampling. The results showed that the application of treated wastewater improved the physic-chemical properties of soil in both application methods. The percentage of nutrients in both methods was increasing. Geoaccumulation index and contamination factor indicated that in the first method, cadmium and iron had high and medium pollutions, respectively. The results indicated that treated wastewater increased soil organic matter content to 0.52% as a soil modifier, which resulted in a decrease in bulk density (from 1.44 to 1.31) and stability of soil structure (from 10.81 to 7.59). Therefore, depending on the type and quality of treated wastewater used in irrigation water supply, it can be used as a soil modifier as well as a fertilizer source.