Soil structure consists of a lot of soil parti-cles, aggregates and their arrangements. Soft X-ray Digital Radiography （SXDR）was developed. SXDR is a methodology for evaluation of soil structure from a view point that a soft X-ray image of soil has informa-tion of soil structure. In this paper, overview of new methodology SXDR, and some examples of information of soil structure by using this methodology were indi-cated. In the SXDR, an analog image taken by using soft X-ray radiography was converted to a digitalone, and the digital image was analyzed with image pro-cessing such as statisticalanalysis, Semivariogram and Fourier Transform. Some results by using the SXDR were examined on information of soil structure. Some results appeared to be related to soil structure. The SXDR provided to evolution of the studies on soil struc-ture by using soft X-ray.
Particle size is one of the most important factors to determine soil structure. In this paper, mea-suring of particle size of soil by using Soft X-ray Digi-tal Radiography （SXDR） was examined. Soft X-ray im-age of glass beads and sand of some kinds of particle size were taken, and analyzed by statistical methods. Arithmetic mean, median,standard deviation and coef-ficient of variation of gray levels of pixels in the im-agewere calculated. As a result, it was observed that d, particle size of samples, affectedσgl, standard deviation of gray levels of pixels in the image. Theσgl increased with increasing the d. In addition, correlation between the d and theσgl was aff ected by the number of pixels which was used to calculateσgl. This fact provides us measuring of particle size of soil by using SXDR. To measure of particle size by using the method, sufficient size of image was demanded.
This research aimed at clarifying the infl-ence of the oxidation-reduction state in soil by ground-water level control on the growth and the yields of soybeans and the uptake of cadmium in soybean seeds. We cultivated soybeans in three devices which could control groundwater levels. In the first and second de-vices, the groundwater levels were fixed at 10 cm and 40 cm, respectively. In the third device the groundwa-ter level could be altered between 10 cm and 40 cm by using a flexible overflow relief well. All three devices were filled with the same 80 % pulverizability soil and the experiment was conducted for three years from 2007 to 2009. 1）In all the three devices, the soil above the ground-water was in an oxidation state （>300 mV） through-out the cultivation period, and soil under the ground-water level was in a reduction state（<300 mV）. In the third device, redox potential in the soil changed quickly when the groundwater level was altered. 2）The volumes of roots in the three devices were the largest between the surface and the 10 cm depth. At a depth lower than 10 cm, the volumes of roots de-creased. Many rootlets were found spread laterally at the 0－10 cm depth in the first and the third devices. In the second device, thick roots existed at as low as the 40 cm depth. In the third device, the volume of roots at a depth lower than 10 cm was less than that in the second device, but they extended down to the 40 cm depth. 3）The yield of the first device was less than those of the others. In the second and third devices, the growth of the soybean plants was similar up to the beginning of the blooming phase. But the yield of the third device was lower than that of the second one. 4）The concentration of cadmium in soybean seeds in the first and third devices was lower than in those in the second device. 5）Our experiment suggested that the groundwater level control after blooming was effective on the con-trol of cadmium uptake.
Developments in acoustic theory of soil have allowed acoustic methods to be used to investi-gate soil physical properties. There have been few studies on the measurement of air conductivity. In ad-dition, some research has suggested that the charac-teristic scale of the air phase structure of soil could be evaluated using acoustic methods; however, there is little understanding of its value and the relationship to the soil water condition. Therefore, our study objec-tives were to develop an acoustic method for measur-ing air conductivity and provide the characteristic scale of the air phase structure using acoustic mea-surements. Combining acoustic theory with the rela-tionship between volumetric air content and tortuosity, we determined the formulae to calculate volumetric air content and air conductivity from acoustic impedance. The Tottori dune sand was used as sample. The re-sults showed that the estimate of the volumetric air content obtained by the acoustic method was less than 15% of that obtained by the traditional gravimetric method over the range of 14‒34%. The estimates of conductivity were within 3-fold that obtained by tradi-tional air conductivity measurement. The results also showed that, in some cases, a sand sample can be re-garded as an assembled mass of air, which has a char-acteristic scale of about 0.6‒3.7cm and roughly propor-tional to the volumetric air content.