Wastewater contains essential elements for plant growth as well as heavy metals which may be toxic for plant and human. In the northern regions of the Nile Delta, mixed water (wastewater mixed with fresh water) is used in land irrigation long time ago. The present study was conducted to assess the impact of long-term irrigation with mixed water (MW); compared to Nile fresh water (FW), on “Navel” orange [Citrus sinensis (L.) Osbeck] orchards (aged 10 to 12 years). Some soil properties, yield, fruit quality and heavy metals contamination were evaluated in three orchards irrigated with mixed water and compared with another three orchards irrigated with Nile water. The Results indicated that long term application of MW induced significant (p<0.05) increase of soil pH and Ec, particularly in the surface layer. In comparison with FW irrigated soil, mixed water resulted in accumulation of K, Fe, Mn, Cu, Zn, Ni and Na in the soil. On the other hand, MW irrigation increased yield parameters (fruit weight and yield/tree), soluble solids content and Brix/acid ratio. Fruit is still looking apparently healthy despite increasing of K, Fe, Mn, Zn, Ni and Na in its peel and pulp. It can be concluded that MW irrigation may be useful in the reduction of fertilizers applied to orchards. Whereas, there is a potential risks associated with crops consumption that irrigated for a long-term with mixed water. Therefore, we have to be careful about mixed water irrigation and use it under controlled conditions to protect soil properties and minimize hazards from heavy metal accumulation in agricultural products and the food chain.

mixed water, irrigation, heavy metals, soil, peel, pulp, orange