Measurement and simulation of the water flow and root uptake in soil under subsurface drip irrigation of apple tree

This study was conducted to measure water flow and root uptake under the soil in a 2 m × 2 m plot around an apple tree 15 years old under subsurface drip irrigation in Miandoab region and simulated by different scenarios in HYDRUS-2D software. The emitters were installed at a depth of 30 cm and a distance of 1 m from the trunk of tree. The soil water content was measured daily using a TDR device for 4 months. In order to calibrate of root water uptake equations, samples from root and soil were collected from different parts of root development zone. The results showed that the highest and lowest amount of root water uptake were 0.129 and 0.024 cm3.cm-3, respectively, that occurred in the coordinates (radial, deep), (60 cm, 50 cm) and (150 cm, 75 cm) from the tree trunk, respectively. Approximately 81% of root water uptake was at a depth of 0-50 cm. The amounts of RMSE (0.0141- 0.0193), showed that, the HYDRUS-2D software can have an appropriate estimate from soil water content in subsurface drip irrigation. Comparison of different scenarios simulated in HYDRUS-2D with the results of field measurements showed that by reducing the emitter discharge by 2 lit/h and increasing the irrigation duration (in the constant amount of water used), the root water uptake increased by 5.08% and deep penetration decreased by 2.18% compared to actual condition.