Maximum Allowable Depletion (MAD) by affecting on number of irrigation in growing season and   irrigation use reduction can be used as a managerial tool to save water. The purpose of this study was to investigate the effect of MAD in irrigation interval, applied irrigation water, top and root growth of grass under subsurface drip irrigation system. Three irrigation treatments which were MAD equal to 40%(W1), 60%(W2), and 80%(W3) arranged in a randomized complete blocks statistical design with three replications in 2012 and 2013 in Isfahan University of Technology. The soil moisture was measured daily using Moisture Meter GMK-770S in the root zone depth of grass to manage irrigation. The apparent parameters and root parameters of grass were collected periodically. These parameters were analyzed by Duncan's multiple range test and the results showed that the irrigation treatments had no significant effect on the root growth parameters and top weight. In the depth of 0-13 cm the maximum root volumetric density and fresh and dry root weighted density were occurred in W1, W2 and W3 treatments, respectively. On the average, 80.14% of the mentioned parameters were in of 0-5 cm depth and 19.86% of them were in of 5-13 cm depth. The maximum (3.93g/day) and minimum (3.21/day) dry biomass were observed in W1 and W3 treatments, respectively. Overall, the results indicated that although the increment of MAD to 80% in a clay-loam soil slightly decreased the shoot and root growth of mix sport grass under a subsurface drip irrigation system, it is a reasonable management solution with the aim of conserving water in the water shortage condition which had the least negative effect on apparent parameters of grass.