PROBLEM TO BE SOLVED: To solve a problem in a soil disinfection machine in which conventionally the chemical is injected into a field by a chemical grouting nail while being mounted in a traveling vehicle and then covering it by a multi-film, and a sensor ring for velocity detection to control the chemical grouting is disposed on the multi-film, however the sensor ring wound by a sponge is used for preventing breakage of the multi-film and the detection accuracy is reduced.SOLUTION: A sensor ring 55 is disposed between an adjacent chemical grouting nail 41 and itself, and is directly grounded to the surface of a field. Also, a leveling plate 83 for leveling irregularities of the field surface is interposed between the most rear end of the sensor ring 55 of the chemical grouting nail 41 and the lower end of a film roll 3 of a multi-film 3a, and bottom edges 85b, 86b lowered and inclined toward both right and left sides are formed at the lower end of the leveling plate 83.
