Field experiments were concerned with studying the performance of a subsurface drip irrigation system in maize in heavy clay soil. Moisture and salinity distribution should be well understood for developing optimum management strategies. The main objective of this study was to determine the optimum depth of the lateral irrigation line beneath the soil surface of the subsurface drip irrigation system for row crops. Three levels of water application rate were considered, which were 60 -70 and 80 % of reference evapotranspiration (ETp). The study also aimed to determine the water use efficiency (WUE) of maize (High tech 2031) in the case of applying subsurface drip irrigation (SSDI). The contour maps of soil moisture content distribution showed that it reached about 90.4 % of its filed capacity at 25 cm of lateral line depth with polymer addition (PAM) case at 80 % ETp. The higher values of electrical conductivity (Ec) were 3.3 ds/m and 3.7 ds/m recorded at 15 cm of lateral line depth in case of without polymer addition (N.PAM) and irrigation with polymer addition (PAM), respectively at 60 % ETp. The higher value of total root weight was 6.3 g per plant, occurred at 80 % ETp and increased by about 4.9 %, at 25 cm of lateral line depth with polymer addition. The higher value of water use efficiency (WUE) was 2.1 kg/m3 and observed at a lateral depth of 25 cm in the case of polymer addition (PAM) with 80% ETp of water application rate.