Seasonal and depth variation of soil physical parameters irrigated with treated wastewater in the case of light textured soil

In places with scarce water supplies, treated wastewater (TWW) can be used for irrigation. This is the case in many places on the Mediterranean coast. In order to examine changes in soil physical proprieties irrigated with secondary-treated wastewater for >38 years, a study was conducted under real agricultural conditions and three different sampling seasons (Summer, autumn and winter). Five soil depth distribution (0-20, 20-40, 40-60, 60-80 and 80-100 cm was also investigated. The soil parameters studied were: salinity (EC), permeablity (K) and  structural stability (IS). The results demonstrate that K and IS depended significantly on the season and varied throught the soil profile. However, only the depth had an impact on the EC. The maximum EC and K were observed in summer at 0-60 and 0-20 cm, respectively. The highest IS, although, was detected during the winter at 40–60 cm depth layer. More interstingly, to take into consideration the interactions of both factors, a positive correlations were shown between K and EC, and IS (r =0.56***, r = 0.62***, respectively) and between EC and IS (r = 0.44**) in summer. In contrast, only K and EC showed a negative correlation (r = -0.35*) in the autumn, but no correlation was detected between all parameters in winter. The results indicate that treated wastewater is a suitable alternative during hot seasons, especially in sandy soils. Further research is required to investigate the effect of this wastwater on crops responses.