Determination of saxual (Haloxylon aphyllum) water requirements by lysimeter experiments

Saxual (Haloxylon aphyllum) as one of the main species used in the sand fixation and desertification projects can be grown in a wide range of desert soils in Iran. Considering the ecological needs of plants, including water requirements for establishment and long-term stability, is essential. In this research, biomass (shoot and root), shoot to root ratio (S/R) and canopy size were determined under different soil moisture regimes. One year old plants grown in drainage and weighting lysimeters in natural condition were subjected to three soil moisture regimes, viz. well- watered (100%), low- watered (30%) and less- watered (15%) of total field capacity. For determining the evaporation rate and its role in crop evapotranspiration, a lysimeter was used without vegetation. Water requirement content to reach the soil moisture to optimum level, provided by weighting of lysimeters and use of TDR, weekly. Biomass rate and ratio of shoot to root decrease significantly (P<0.001) with a reduction in soil water content. The effects of different treatments on canopy size were not significantly different. Calculating of the amount of the plant production per unit of water consumpted showed that black saxual (Haloxylon aphyllum) trees, need to 2.4 m3 water for optimal annual growth.