Effect of tree roots on water infiltration rate into the soil

To study the effect of tree roots on increasing water infiltration in soil and also to determine and assess the coefficients of different infiltration models, some infiltration tests were performed in three tree plantation areas in Badjgah, Fars province with different soil textures (clay loam for pear plantation, sandy loam for grape plantation, loamy sand for pine trees). In each plantation, four double rings were installed, whereas two double rings were placed under the tree in two sides of the tree truck with 50 cm distance and the other two double rings were placed on open space between the trees. Vertical infiltration of water into the soil was measured and the coefficients of five models of infiltration (i.e. Kostiakov, Kostiakov-Lewis, Philip, Soil Conservation Service (SCS) and Horton) were assessed. Furthermore, soil texture and initial soil water content were determined in these points. Results showed that all models accurately fitted to the measured values. The infiltration rate under the trees was higher than those between the trees due to the occurrence of roots and root channels that improved the rate of infiltration of water into the soil. The 180-minute infiltration under the trees increased 69% and 354% in loamy sand and clay loam, respectively compared with those on open space between the trees.