Study on degradation of rice straw buried in paddy fields using ¹³C as a tracer

C-14 released in the form of carbon dioxide into the atmosphere from a spent nuclear fuel reprocessing plant is taken up by rice plants through the photosynthesis process. Rice is one of the most important crops in Japan. The weight of its edible part is only less than a half of the total weight, and a large amount of plant residue is left after harvest in paddy fields as stubble and rice straw. In Aomori prefecture, it is recommended by the prefectural government that plant residue be buried into paddy fields after harvest for the purpose of soil improvement and/or for prevention of air pollution by combustion. Then, ¹⁴C absorbed and fixed in rice plant is, as a result, artificially added into agricultural fields. The purpose of this study is to model the migration of carbon among the atmosphere, plants and soil, and to clarify possible long-term accumulation of ¹⁴C in agricultural fields. (author)