<;P>;PROBLEM TO BE SOLVED: To solve problems that old tatami mats necessarily occurring in demolition of house, etc., are bulky, hardly burnable, are difficult to treat as waste, under the present situation, have to be put in charge of specialized waste disposer at cost of disposal, mainly burnt in a treatment method as waste, however, there is problems of air pollution by smoke/pollution by global warming, production of fertilizer by grinding, fermenting and aging old tatami mats is proposed as an effective utilization method, there is a problem with respect to cost versus effect due to requirement of specific process, on the other hand, rooftop vegetation is carried out as a means for solving environmental problems such as air pollution, a heat island phenomenon at an urban district, etc., many proposals of artificial soil are found, however, they are structurally complicated and there is a problem with respect to cost versus effect. <;P>;SOLUTION: Old tatami mats abandoned as architectural waste are utilized as a material for artificial soil. Namely, the artificial soil is obtained by boring holes through the surface of tatami padding in the direction of thickness of tatami padding, laying the tatami padding on a foundation of rooftop vegetation and filling culture soil to the holes. <;P>;COPYRIGHT: (C)2007,JPO&INPIT