PROBLEM TO BE SOLVED: To provide a ground surface thermal core heating system that directly radiates a large quantity of low-temperature far-infrared ray onto foliages of crop plants without warming up air in an agricultural greenhouse, and allows the crop plants to grow even if temperature drops below lower limit growth temperature.SOLUTION: A high radiation tube has high-absorption radiation in which graphene composite is blended into pulverized plastic raw material resin in a dispersed manner, and a three-dimensional structure group of a mat-shaped nano unit is formed on a cylinder external surface to increase a surface area. The tube is constituted such that hot water is circulated through each circulation circuit which is densely installed on each plow layer, a large quantity of low-temperature far-infrared ray is emitted from the tube, and at the same time, a shallow layer part of each plow layer is heated via a metal thermal core which is arranged in an embedded manner at an appropriate gap on a lower surface of the tube.SELECTED DRAWING: Figure 8
