The Tonomine site for grassland study is located a little west of the centre of Hyogo Prefecture. The site is covered with the seminatural grassland dominated by M. sinensis which is maintained for a long time by the farmers' burning. The annual mean temperature is 10.79℃ and the mean annual rainfall is 2,313mm. Investigation of the vegetation and soil was made in 1968 in the plots which were located linearly on the south facing slope, 13 degrees in average dip and 143m in sloping length. The largest standing crop (above-and underground) appeared in Plot 3 situated on the base of the slope. The aboveground standing crop in August at Tonomine (450g/m^2) is higher than that of Hachibuse (378g/m^2), Hyogo Prefecture and Kawatabi (236-375g/m^2,north-eastern JAPAN). The underground standing crop of Plots 1,2 and 3 is in the order of Plot 3>Plot 1>Plot 2. The seasonal variation of the root weight is remarkable in the layer 0-10cm in depth from the surface. In the plot having a good soil condition, the root weight varies considerably, even in the layer 20-30cm in depth from the surface. The underground/aboveground ratio in dry weight in the M. sinonsis type grassland varies with the sampling site and the season. In general, the ratio in the high yield plot is smaller than that in the low yield plot. Concerning the distribution of the volume percentage of soil, the air phase in June, July and August was considerably great. It seemed to be closely related to the aeration in the growing season. The aeration in the growing season, as well as the production of inorganic nitrogen from organic nitrogenous compounds and the increase of the availability of potassium are important as to the grass production. In the present paper, we report the result of some measurements made on the ionic exchange capacity of the root as the first step of the ion absorption to plant. The samples were collected from the layers 0-15,15-35 and 35-50 cm in depth from the surface and the diameter of the roots was classified into two classes (0.02-0.06 and 0.16-0.68mm). The ionic exchange capacity of the root of M. sinensis is almost in the range of 5-9 me. In general, the ionic exchange capacity of coarse roots is smaller than that of finer roots. The absorption of ion is related not only to the ionic exchange capacity of the roots, but also to the vigour and the respiration of the roots.