Abstract
In the present paper, as a part of studies on forage roots and physical properties of grassland soil, I deal with the root-system distribution of forage grasses and mechanical strength of individual adventitious root. It was used in this examination that Italian ryegrass (Lolium multiflorum LAM.), timothy (phleum pratense L.), Kentucky 31 fescue (Festuca arundinacea SCHR.) and orchardgrass (Dactylis glomerata L.). The results are summarized as follows ; (1) Root-system of grown-up forage grasses formed a tendency to concentrated distribution for the range of certain length. And then, the author named their roots main-roots group. (2) According to the growth stages or species, there was little difference in length and diameter of individual adventitious root which formed main-roots group, ranging 15-25cm in length and 400-600μm in diameter, respectively. (3) Each root which formed the main-roots group showed the maximum tensile strength in one individual. (4) Tensile strength of individual root increases with advance of growth. In case of Italian ryegrass, the adventitious roots of a 20-week growth after sowing had three times as strong as a 4-week stage. (5) According to investigation of a few grass species with a 28-week growth, tensile strength ranking was timothy>Kentucky 31 fescue>orchardgrass. (6) From the results that the roots in the main-roots group were stronger than others in tensile strength, it is suggested that the growth of them was the one of terms advantageous to soil conservation.
