Water table contribution to plant water use is a significant element in improving water use efficiency (WUE) for agricultural water management. In this study, lysimeter experiments were conducted in a controlled greenhouse environment to investigate the response of soybean water uptake and growth parameters under four different water table depths (WTD) (30, 50, 70, and 90 cm). Soybean crop water use, WUE, and root distribution under the different WTD were examined. For 30, 50, 70, and 90 cm of WTD treatments, the average water table contributions were 89, 83, 79, and 72%; the grain yields were 15.1, 10.5, 14.1, and 17.2 g/lys.; and the WUEs were 0.22, 0.18, 0.25, and 0.31 g/lys./cm, respectively. Further analysis of the root mass and proportional distribution among the different soil layers illustrated that the lysimeters with 70 and 90 cm WTD had greater root mass with higher root distribution at 40-75 cm of the soil layer. The results indicated that 70 and 90 cm of constant WTD can yield higher grain yield and biomasses with greater WUE and better root distribution than the irrigated or shallow WTD treatments.Water 2019, 11, 931 2 of 12 contribution to plant water use can be a significant element in crop production by reducing drainage and surface irrigation water volumes, and by enhancing crop water uptake from water table [6]. Thus, water table contributions to crop growth have gained attention recently, with research in controlled environments (i.e., laboratories and greenhouses) using weighed lysimeters and in the field using controlled drainage practices [5,[7][8][9].When an optimal water table depth is maintained for a crop, the water table can be considered as accessible water source to support the crop water requirement. Hence, the higher performance of the crop can be obtained with a lower amount and frequency of surface irrigation. Besides, the optimum water table depth can supply the necessary respiration and aeration for plant roots [10]. Most of the irrigation scheduling programs assume that the water table is too deep and only surface irrigation water is required to meet the plant water demand [11]. However, shallow water table can be a water source that helps to decrease the need for irrigation water [12,13]. Several researches showed that the water table can contribute to crop production through capillary rise and provide sufficient moisture for the crop root zone [6,14,15]. Meyer et al. [16] investigated the effect of soil type on soybean water use from shallow water table, and they found that 24% and 6.5% of the contribution to soybean water use in loam and clay loam soils was supplied from the water table, respectively. They found the soybean root length to be two times denser in the loam soil compared to the clay loam soil. Luo et al. [17] reported that 75% of the wheat water requirements could be met from a water table depths (WTD) of 100 cm, but that contributions from water table decreased with increasing WTD from 30 to 90 cm. This showed an inverse relationship between WTD and water tab...