EXPERIMENT STATION BULLETINS. 



493 



has been the followiug: First, to investigate individually or in com- 

 bination, many of the chief soil factors affecting the soil temperature; 

 second to study the effects of these various factors on the temijeratuiii 

 of the soil under field conditions; and third, to ascertain the lelation- 

 sliip between soil temperatur<' and the different meteorological elements. 



By attacking the problem from this broad standpoint, and by using 

 the same kinds of soils for the study of many of the soil factors, it 

 was thought that the work would yield more definite and conclusive 

 knowledge, and it would also enable us to form a better and more defi- 

 nite idea as to the magnitude of these respective temperature factors, 

 also which ones are most predominant and play the greatest role in 

 determining or controlling the warmth of the soil. 



In the present bulletin are reported the results of the completed 

 laboratory experiments and the results of only one year of the field 

 experiments. It is hoped that the latter experiments will be conducted 

 through a number of years and that the data will be reported from time 

 to time. 



SPECIFIC HEAT OF SOILS. 



OBJECT AND METHOD OF EXPERIMENTATION. 



Specific heat is defined as the number of calories needed to raise one 

 gram of a substance 1° C. The specific heat of soils has received at- 

 tention from various investigators at different times, notably from 

 Pfaundler,^ von Schumacher,^ v. Liebenberg,^ Lang,* Ulrich,^ and Patten." 

 The results obtained by these investigators for the chief soil types are 

 given in the following table: 



TABLE 1.— SPECIFIC HEAT OF SOILS. 



It is evident that the specific heat of any one type of soil, as found 

 by the different experimenters, is significantly different. The reason 

 for such disagreement is undoubtedly due (1) to the difference in com- 

 position of the material, even tho it is designated by the same name; 

 (2) to the different methods employed; and (3) to the difference in 

 technic in the manipulation. 



Since it was necessary to know the exact specific heat of the particular 

 types of soil which were to be used for the various phases of soil tem- 

 perature study, and since such knowledge could not be obtained from 

 the above data, it was deemed essential to ascertain it directly. 



(1) Ann. d. Physik u. Chemie 5. Reihe, 9 Bd. (1866): 102-135. 



(2) Die Physik Des Bodens, Berlin (1864): 245. 



(3) Habilitationschrift Halle 1875. 



(4) Forsch. a. d. Geb. d. Agrikulturphysik Bd. 1,: 109. 



(5) Forsch. a. d. Geb. d. Agrikulturphysik Bd. 17: 1. 



(6) Bui. 69, U. S. Dept. of Agri., Bureau of Soils. 1909. 



