Effects of irrigation management on arid soils enzyme activities

Unconventional water resources such as treated wastewater (TWW) are being increasingly used for irrigation in regions with limited freshwater availability. Likewise, subsurface drip irrigation (SSDI) has been proposed for improving water use efficiency in arid lands. The combined effects of both factors (SSDI/TWW) on soil health have received little attention. This study assessed the mid-term (6 years) impact of irrigation with TWW apply by SSDI and surface drip irrigation (SDI) on soil chemical properties and enzyme activities under arid climate. The calculation of a numerical index (integrated biological response version 2; IBRv2) for enzymatic activities showed a significant deviation in soils irrigated with TWW with regard to control soils (irrigated with desalinated brackish water-DBW), particularly after SSDI. That combination TWW/SSDI inhibited most of assessed enzyme activities, save for catalase, with respect to the reference treatment (for example in a clay-loamy soil, decrease varied between 69% for esterase and 12% for dehydrogenase). Increased soil salinity (up to EC similar to 15 dS m(-1)) due to SSDI/TWW appears as one of the potential factors involved. These results suggest that current irrigation strategies in arid lands might accelerate soil degradation processes in regions where desertification is of particular concern.