Wastewater irrigation in Jordan: A mismatch in macro nutrient provision

Abstract

By using sewage nutrients in irrigation, both the costs for nutrient removal and costs for fertilisers at the farm can be distinctly reduced. The present study describes the wastewater use scheme in the Seil Al-Zarqa and Middle Jordan Valley regions, Jordan. Through field studies, information on water and nutrient flows were gathered on 13 fields using semi-quantitative methods and processed in a simplified nutrient mass balance model. Outcomes show a complete mismatch between nutrient demand and nutrient supply. While the N-supply is up to a factor of 7-8 in excess, data nearby the sewage treatment plant show a P excess up to a factor 30! Elevated nutrient concentrations were measured up to 70 km downstream the sewage treatment plant. However, farmers dose chemical fertilisers as if they are dealing with clean fresh water. The nutrients and particularly the N over-dosages have considerable negative impacts on crops and environment. Treatment facilities should better adjust their effluent quality to the subsequent needs, while farmers should be better informed on the effluent quality and be trained how to adjust their irrigation and additional fertilization to this reality.