霜柱氷層による作物の断根並にその防除に関する研究 : 第2報 数種作物の被害について

抄録

The results of investigation about the broken roots of red clover, alfalfa, yellow sweet clover hairy vetch, orchadgrass, timothy, rye, and rape in frozen soil are as follows. Red clover (Fig. 1. a.) : The root system is divided into two parts, upper and lower, by the pulling action of the icicle layer. Alfalfa (Fig. 1. b.), yellow sweet clover : These are similar as the case of red clover, but in early spring some heaved plants fall down and die. Hairy vetch (Fig. 1. c.) : Main roots are seldom cut, while branch roots are cut. Orchardgrass, timothy (Fig. 1. d.) : The greater part of the root system freezes to become a frozen block and the icicle layer is formed as if avoiding this block. Rye (Fig. 1.e.) : It is similar in the case of orchardgrass. But the injury of rye plant is greater than that of orchardgrass because of its shallowness of the root system. Rape (Fig. 1. f.) : Damaged plants are hardly found and in some cases holes around the main roots are found. From these observations we obtain knowledges as follows: (a) The injured manifestation of broken roots varies according to the kinds of plants or of types of their root systems. (b) The intensity of injury varies according to the development of root system of the plant. And therefore it concerns to the planting time, the manuring, the fertilizing, the planting rote etc. (C) The mechanism of the breaking of the roots consists of following two stages: 1 st stage; The several inches of the soil from surface freezes to from the concrete layer, and at the same time it fastens the roots in this layer. 2nd stage ; When the frozen concrete layer is heaved by the action of the icicle layer, the root systems in the unfrozen soil layer is pulled up from the fastened part of the root system in the icicle layer. (d) Main factors which concerns the breaking of the roots caused by the formation of the icicle layer seem as follows: (1) Heaving strength at the time of forming the icicle layer. (2) The resistant power of the plants. (3) The friction between plant and frozen soil. (4) Effects of the development of the root system upon the formation of the icicle layer.