Root uptake compensation factor for non-uniform soil moisture conditions

In this study, with measuring water uptake in different soil layers, the role of different parts of root system in crop water supply during water stress conditions is characterized. Four cylindrical lysimeters with 25 cm diameter and 100 cm height were filled with clay loam soil. Soil columns were separated to 4 layers with 3 cm sand layers. Subsurface irrigation was applied with water stress patterns (decreasing number of layers which were irrigated from subsurface). Sand layers in each column which were preventing soil moisture exchange, could characterize the real role of each sub-layer root in water uptake when surface layers were under water stress. In this study root water uptake equation is corrected for water stress condition with presenting a compensation factor. With this corrected equation root water uptake in soil layers under water stress condition is investigated. The results showed that corrected equation determined root water uptake better than other equations in some conditions. Compensation factor is dependent on a plant factor (), that was determined with inverse optimization technique from root water uptake data in each lysimeter (it is calculated as 1.1, 1.87, 2.23 and 2.38 for lysimeters 1, 2, 3 and 4, respectively). This factor increased with increasing water stress severity.