Agricultural crop plants, vegetable and flower and ornamental plants, have an optimum growth temperature range that concentrates within 15-25 °C. A seasonal temperature change has strong influence on growing of agricultural products. The soil warming for plant husbandry is one of the effective growth promotion methods for agricultural crop plant. Generally, the ridge warming is performed by warm water circulation of underground. Moreover, there is another research which observed the growth process of the Welsh onion using an electrically heated wire for soil warming. These studies showed that the soil warming brings growth promotion of agricultural products. But all passed studies are carried out by using the heavy oil or electric power for soil warming as fuel. The experimental result of this study is shown that the relationship between heat amount of soil warming for plant husbandry by ground heat and the growth promoting effect. The underground 2-4m ground heat as a heat source keeps temperature range 15-25 °C through a year. However, the heat amount of this study is very smaller than other researches, so that the growth promoting effect is necessary to examine. The growth promoting effect is proved by the Japanese-mustard-spinach cultivation experiment by using the ground heat at an actual ridge. The growth promoting effect, weight, height and number of leaves, is evaluated in 10 times actual experiment for three years. This paper describes the relationship between growth promoting effect and the amount of ground heat transport for soil warming by heat pipe on the cold season.