اثر تنش آبي بر فرآيند جذب آب توسط بخش هاي مختلف ريشه

The role of water stress on water uptake in different root depths

Root water uptake is very important in hydrological models. The main subject of this study was characterization the role of different part of root system in crop water requirement during water stress conditions. 11 cylindrical lysimeters with 25 em diameter and 100 em height were filled with clayloam soil. In the first group, soil columns were separated to 4 layers with 3 em sand layers. In the second and third groups, there were 4 and 3 lysimeters, respectively. The first and second group, lysimeters were irrigated with subsurface method. Water stress was applied with decreasing the number of under subsurface irrigation layers. In the third group gravitational irrigation was applied on lysimeter 9 and 20 and 40 percent deficit irrigation on lysimeters 10 and II respectively. Sand layers in the first group (which were preventing soil moisture exchange) were used to characterize the real role of each layerʹs root in water uptake when surface layers been under water stress. Although the Root Length Density (RLD) in deep layers was lower than RLD in upper layers, Crop could increase its root activity in wet layers to uptake water and compensated water stress in dried parts of soil. Root water uptake in third group also showed that with increasing water stress because of deficit irrigation, the percentage of root water uptake from top layers was increased.