Vector locus of an equivalent radius of the root in growing plants

Tree planting on arid land is taken up as one of the measures against global warming prevention. It is important for the tree planting to grasp growth state of the root after planting. To monitor the root advancement, a method measuring electric ground impedance of the root has been presented. By this method, we can know the growth state without digging the soil. To estimate the value of impedance, we introduce a concept of an equivalent radius. In this method, the value of ground impedance is converted to a radius of the disk electrode that has the same value as the object. Moreover, ground impedance of the root is indicated as complex number, which consists of resistance and capacity components of the root. The equivalent radius is also expressed by complex number. We propose the method indicating the change of equivalent radius as growing of the root by means of vector locus. It is demonstrated by the experiments on sunflower and kenaf during one summer that the present method is useful for estimating the growth state of the plant root.