The draft and power requirement of the tillage implement are generally concerned with the physical properties of soil, chiefly with the ATTERBERG'slimits. A theoretical discussion about the ATTERBERG's limits for the purpose ofdesigning the tillage implement is done in the present article. The shear value of all plastic soils is found to be in inverse proportion to the flow index under the same plastic index,and also to be the same one under the same value of plastic index and flow index. Table 1 and Fig. 1 show the ATTERBERG's limits established by the laboratory experiments of the writer for several soils from paddy fields.・・・