Abstract
In the present paper, as a part of studies on forage roots and physical properties of grassland soil, we deal with the growth of root-system in fixed pore model which was made of steel nets or glass beads. Four crops as Italian ryegrass, dent corn, oats and ladino clover were used in this experiment. When the roots of these crops penetrated into the pores in model culture box, their numbers, length, thickness and root-system were investigated by using a projector. The results are summarized as follows ; (1) Each root of Italian ryegrass was able to penetrate into the pores of net with 300μm meshes only. From the result of investigation on the thickness of these penetrating roots, their roots were able to penetrate into the pores of which diameter is narrower than root-diameter. (2) In the case of Italian ryegrass, as compared with the roots in culture box with small pore size (300μm and below), the roots in culture box with large pore size (300〜775μm) showed maximum value in root number and root length. However they showed minimum value in root diameter. In case of other crops, the relation among the root number, root length and root diameter could not be observed. (3) If the pore size became narrower, root-system of Italian ryegrass was effected more sensitively than in other crops. That is, root number increased and individual root became fine and crooked (see Fig.3). (4) It is considered that grass roots such as Italian ryegrass grow up transforming themselves in the culture media with fixed and narrow pores.
