Because a torch plasma has many useful characteristics such as high temperature, high brightness, high energy and high controllability, it can be applied for various fields such as large scale lighting, metal cutting, welding and also waste treatment. Moreover it works well in the field of soil reforming. However, research reports on the acid soil reforming are few. Acid rain influences on forest declining, dying aquatic animals, and dissolving cultural properties. Especially, the acid soil causes stopping growth of plants, dropping amount of crops and declining resistance to dis eases [1][2]. Therefore it is tried to explore a new application of the torch plasma for a quick neutralizing treatment of the acid soil. In this paper, a quick forced variation of pH of the acid soil is examined by irradiating thermal torch plasma of 200A in current for a few minutes by using a DC plasma torch with Ar gas as a plasma gas. As a result, pH of the acid soil is so quickly in a minute or so varied into about neutral pH of 7.7 from the original one of 4.4 in the acid region. So the neutralizing goal in the acid soil or a quick reforming could be almost achieved. This system uses no water, but a dry type. By controlling the irradiation time of the torch plasma a pH value of the acid soil can be changed into an any demanded value to be adequate for each plant.
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