Investigation of the Effect of Soil Moisture in the Sub-root Zone Layer on Water Uptake Amount in Three Different Soil Textures

Changing in precipitation pattern and incidence drought stress shows the necessity of optimal use of water resources and saving in consumption is emerged more than before. The soil moisture content under the root zone can provide part of the plant's water requirement. Currently, the zone under the root of plant is not considered in the calculation of the water balance and the plant water requirement so water entering to this zone is considered as a part of deep percolation losses. In this research, HYDRUS 2D/3D software was used to simulate water flow in the soil in the area under the roots of the sugar beet plant. The investigated scenarios included 4 buffer treatments with different depths under the root zone and three different soil textures including loam, silty clay loam and sandy loam. The results showed that in all three soil textures, increasing the depth of the buffer caused more water to be uptaken by the roots, the best result was obtained for the loam texture, with the buffer depth of 50 cm below the root zone, so that the amount of water uptake compared to the condition without buffer depth, was increased by 7.9%. This value was obtained for the texture of silty clay loam and sandy loam at the buffer depth of 75 cm, with an increase of 8.8% and 4.3%, respectively. Deep percolation in loam, silty clay loam and sandy loam texture decreased by 81, 56 and 90% respectively with increasing buffer depth.