FACTORS AFFECTING SOIL TEMPERATURE 453 



III. TEMPERATURE OF THE SOIL 



The temperature which the soil in any given position 

 will attain depends upon a number of factors. The more 

 important of these are as follows: (1) Heat supply. 

 (2) Specific gravity of the soil. (3) Specific heat of the 

 soil. (4) Color of the soil. (5) Attitude of the surface. 

 (6) Conductivity of the soil. (7) Circulation of air above 

 the soil. (8) Water-content of the soil. 



324. Heat supply. The heat supply is obviously 

 the most direct factor contributing to the soil tempera- 

 ture. This is reflected in the seasonal, daily and hourly 

 variations in the temperature. The hourly variations 

 in temperature at a depth of one foot below the surface 

 are shown by the following table and curves: 



Table LXVIII 



