1974 年 35 巻 4 号 p. 360-367
1 With the chizel type standard, the distribution of the temperature in soil was uneven, because the majiority of steam leaked out through the slit made by the standard-pass.
2 The standard of the wing type was fitted with the wing at the pointed end, and the steam-spouting pipe was put on the two points, above and below. As the results, the distribution of the temperature became even.
3 With the wing type, it was possible to make uniform the horizontal and vertical distribution of the temperature, by increasing the quantity of the steam. Considering the disinfection effect, the soil temperature must be above 55°C and this temperature must continue more than 30 minutes, the quantity of the steam needed was more than 100kg/m3 degree. But with the chizel type, the disinfection effect was not uniform.
4 After the application of the ateam, the temperature continued high in the depths of 10-20 centimeters but dropped a little at the depth of 5 centimeters. When the thermometer was placed on the surface, the temperature dropped rapidly as soon as the temperature-keeping canvas was taken off.
5 The highest inside temperature was 60°C in the clods of 50×55×50mm and 35×35×40mm. In order to complete the sterilization effect, the soil must be crushed into pieces.
6 The needed traction power of the plow at 20cm working-depth was 1.57 tons with chizel type and 1.75 tons with wing type.
7 In the growth-investigation on the sterilized soil, the beet-growth was obtained in the block which was mixed with barkmanure.
8 In the investigasion of damping-off, the steam-sterilization had remarkable effect and mixing organic matter had some good effect. Barkmanure was considered appropriate to supply organic material.
9 As regards the ability of nitrofication of soil, the amount of nitroficatic Bacteria* in the soil was kept by mixing organic matter after steam sterilization.
* Nitroficatic bacteria are composed of nitro bacter and nitrotrozomonas
10 The ability of the nitrofication of soil was reduced by the sterilization without regard to the quantity of mixed organic matter. And yet the ability of the block mixed with barkmanure was some what higher than other blocks.