The present practice of deep tillage, coupled with abundant organic fertilizer application, had so improved the soil that it became a healthy breeding ground for microorganisms such as nematodes. Nematode population in the 25-50cm region had dramatically increased as compared with soils that were tilled using the conventional shallow tillage. Consequently, the effective control of these parasites became even more necessary.The purpose of this study is to determine a suitable method for controlling nematodes that live in the deep layers of the soil. To this end, a conventional single injection type fumigator and a double injection type deep fumigator were tested on the field. The results are as follows:1) On the seventh day after nematicide application, DD gas concentration was more than 10ppm at all points up to 50cm depth. This was true for both the single injection and double injection types of fumigation. However, it was noted that DD gas concentration in the 25-50cm layer was higher for the double injection type as compared to the single injection type. This gives a higher potential for the use of the double injection method. Moreover, rapid gas diffusion in the upper half of the soil layer was implied by the low DD gas concentration values. This could have been aided by the 25-30 degrees Centigrade ambient temperature.2) On the seventh day after nematicide application, percent mortality ranged from 98% to 100% for both the single injection and double injection types of fumigation. However, nematode population gradually increased to the range of 30-88% on the 30th day after fumigation. This could be attributed to the survival of nematode eggs during nematicide application.3) The double injection type of fumigator is more efficient because although it used less chemicals, it effected the same degree of mortality on the nematodes as compared to the single injection type. Furthermore, injecting the nematicide to soils with high moisture content and covering the field with vinyl sheet for 30 days both helped in maintaining a low nematode population for a longer period.Further studies should be concentrated on effecting uniform gas distribution, keeping the gas in the soil for longer periods of time, and finding ways how to eliminate the nematode eggs.