Soil chemical changes in ancient irrigated fields of Udhruh, southern Jordan

Since ancient times, irrigation has been fundamental for achieving large agricultural yields, especially in the more arid areas of the world. An example of this practice is represented by the vast water infrastructures found near Udhruh (southern Jordan). These engineering works were constructed, maintained and restored from the Nabataean to early Islamic periods (first century BCE to eighth century CE). It still remains unknown why the ancient agricultural landscape of the region shifted towards an unproductive desert. In this study, we analysed the soil chemical and physical properties of an ancient irrigated field to assess whether ancient agricultural practices have altered soil properties that are still noticeable today, and might have contributed to the abandonment of the area. Soil samples were taken randomly from within an ancient qanat-irrigated agricultural field and from adjacent surfaces believed never to have been irrigated. Our results indicate that the effects of irrigation are still detectable today; electrical conductivity and total Na, B, Li and Sr in the soil of the ancient fields were significantly lower than those in the undisturbed control soils, which suggests leaching of soluble elements due to irrigation. Our results provide evidence of the mastery of ancient civilizations in their agricultural practices. Engineers and farmers apparently managed to conduct irrigation in the area of Udhruh for long periods of time without causing soil degradation.