Abstract
The characteristics of water uptake depth by root system was studied for both the each growth stage and the influence of planting density of maize (Zea maize L.), which has relatively large transpiration rate change during its growth. Electrical resistivity tomography method was used for monitoring the soil water content distribution along the two-dimensional vertical cross-section and also the stable isotope in the water of stem and soil was measured to estimate the water uptake depth by root system without soil water content.
The estimated water uptake depth showed a close relationship with the transpiration activity. In blooming stage, when the transpiration activity is most active, the transition of water uptake depth to deeper depth with soil drying has developed faster. The maize transpiration rate is higher than soil evaporation rate in a dense and sparse planting area. However, the reduced soil water content has been shown faster in the dense planting area than that in the sparse planting area because of the difference of total transpiration rate. This situation influences the maize root growth distribution and the root grows deeper in the dense planting area than that in the sparse planting area to get soil water from the deeper depth during its blooming stage.
In fully matured stage, when the transpiration activity decreased with leaves dying, the transition of water uptake depth to deeper depth with soil drying has been slower than that in blooming stage. Also the maize transpiration rate is approximately equal to soil evaporation rate in the sparse planting area, thus difference of available soil water amount at the shallow layer was smaller than that of blooming stage between the dense and sparse planting area. Hence, there was no clear difference on transition of water uptake depth to deeper depth with soil drying between the dense and sparse planting area.
