Measurement and Dynamic Simulation of Soil Water Flow with Emphasis on Root Water Uptake

Mechanisms of crop root water uptake play an important role in agricultural water management. The aim of this study was to investigate soil water dynamics and root water uptake for an apple tree. Surface irrigation was performed around of tree. Tube-time domain reflectometry (TDR) –Profile Probe type- was used to measure soil volumetric water content. Therefore Specific tubes of 1 meter length and distance of 30 cm from each other were installed in both side of tree trunk. Moisture simulations were carried out with HYDRUS- D model. Results showed that most changes in soil water occurred until the depth of 40 cm. These changes in surface layers are greater than above layers. Also root water uptake mostly is limited in the depth of 0-40 cm and radial distance of 0-60 cm from tree trunk. Root water uptake rate was reduced with increasing distance from the tree. HYDRUS- 2D model successfully simulated the variability of soil water dynamics in until depth of 40 cm¡ but predict of soil water dynamics from depth of 60 to 100 cm is not good. This Difference is due to soil of this layer is very compact. So with attention to these results¡ a more detailed schedule will be designed in relation to irrigation water management.