Soil Water Movement Resulting from Transpiration : The Influence of Soil Characteristics and Lower Boundary Conditions

An experiment and a numerical simulation on soil column consisting of a root zone underlain by lower layers containing no roots were conducted under the same crop growth stage, root distribution and environmental conditions to evaluate the influence of soil characteristics (Mass and Kuroboku soils) and hydraulic conditions of lower boundary (water table and impervious layer) on soil moisture depletion distribution and upward capillary movement resulting from transpiration. For the water table and impervious layer condition soil moisture distribution during the experiment was small for Kuroboku soil. Soil moisture distribution for Masa soil, especially for the impervious condition, was large. Response of upward flux from the water table after start and upward flux deterioration after end of radiation were larger and quicker for Kuroboku soil compared with that of Masa soil. The simulation results were in good agreement with that of the experiment. The difference in the characteristics of soil moisture distribution and upward capillary movement between the soils could be explained by the difference in their water retentivity and hydraulic conductivity