Preliminary Column Experiment on Dynamics of Water and Ion Transport in Soil Affected by Root Absorption

Water deficit and salt accumulation in soil are serious problems in crop fields in semi-arid regions, and these problems are likely to depend on active transpiration and selective ion absorption by crop roots. In this study, a large sized soil column system was newly developed, and a preliminary experiment with the system was conducted to examine the system performance for analyses of dynamics of water and ion trans- port and salt accumulation in soil with special reference to effects of the active and selective absorption of roots of different crops (i.e., corn plants, sunflower plants and no plants). The column system was equipped with on-line systems for the control of groundwater level and the TDR measurement, which ena- bled time course evaluations of upward flux of the groundwater, volumetric water content of soils at the dif- ferent depths and electrical conductivity of the extract from the saturated soil. Furthermore, distribution and accumulation of ions in soil layers, plant organs and xylem sap were analyzed using an ion chromato- graph. In this column experiment, diurnal and long term daily changes in water movement and ions accu- mulation in soil affected by characteristics of root absorption were evaluated. This can suggest that this column system is applicable for quantitative analyses of effects of root absorption of different crops on water deficit and salinization in soils, aiming at proposing a scientific method of the crop rotation for the environmentally conscious agriculture in semi-arid regions.