This study aimed to investigate the effect of deficit irrigation based on the cut-off time of the inflow into the furrow on the yield and water productivity of forage maize in the research field of the University of Tehran in Karaj with clay loam soil texture. The experiment was conducted in a randomized complete block design with five treatments of the cut-off time based on the arrival of the wetting front to a specific soil depth at different distances from the furrow inlet and in three replications. TDR moisture sensors were placed at distances of 100 (L2), 90 (L3), 60 (L4) and 0 (L5) meters from the furrow inlet. In the control treatment (L1), the cut-off was after providing the required water depth of the plant at the end of the furrow. Four depths of 18, 20, 22 and 24 cm were determined for the sensors and during the growing season, before each irrigation, the sensor depth was selected according to the required irrigation water depth. The irrigation water depth in treatments L1, L2, L3, L4 and L5 was 100, 82.9, 75.4, 69.8 and 64.1 % of the water requirement, respectively. The highest values of fresh and dry biomass and grain yield, harvest index, 1000 kernel weight and plant height were recorded as 67.265, 27.196 and 13.858 tons/ha, 50.77 %, 367.89 g and 258.2 cm in L1 treatment, respectively, and the lowest values were recorded as 34.272, 17.150 and 7.511 tons/ha, 43.40 %, 252.67 g and 177.9 cm in L5 treatment. Deficit irrigation caused a significant decrease in all six traits. Irrigation water productivity based on fresh and dry biomass and grain yield did not show significant differences in different treatments, but in all three cases, the lowest values were related to L5 treatment.