So far as the natural soil and cultivated soil formed under conditions of shallow plowing are concerned, we can distinguish their profile horizons morphologically to a certain extent. But in case the soil is subject to a proper deep plowing, its surface soil, sub-soil and sometimes substratum are generally overturned and mixed up, and there will be little possibility for one to distinguish morphologically the profile horizons. This induces us to think whether it would be possible to distinguish the horizons chiefly on the basis of dynamic variations of soil fertility. We are convinced to believe that the influences of bioclimate to the upper and lower layers axe certainly diverse, and the transformation progression and rate of nutrient materials in these layers are also widely different, and hence these various layers have their different specific functions for plant growth. Owing to these, the dynamic variations of fertility may be considered to be the prime criterion for the horizon division of the cultivated soils.