496 



STATE BOARD OF AGRICULTURE. 



TABLE 3.— SPECIFIC HEAT OF SOILS BY EQUAL VOLUMES. 



It will be seen that the difference in the heat capacity considered 

 from the equal volume standpoint is also small in magnitude between 

 the different soils, but that the order is verj different from that of 

 the specific heat by equal weights. In the latter case peat has the 

 highest specific heat and is followed in order by loam, clay, gravel, and 

 finally by sand; while in the case of equal volumes peat has the lowest 

 specific heat with, sand, loam, gravel, and clay coming next in respec- 

 tive order. 



INFLUENCE OF MOISTURE OX SPECIFIC HEAT OF SOILS. 



In field conditions the specific heat of soils by equal volume is also 

 unimportant because the different soils in their natural condition pos- 

 sess different amounts of water on account of their different water 

 holding capacity, and water as will be shown, is one of the predominant 

 controlling agents of soil temperature. With the exception of hydro- 

 gen gas, water possesses the highest heat capacity of any other sub- 

 stance. In comparison with that of the dry soils, it is five times greater. 

 This is very significant because it means that it requires five times as 

 much heat to raise the temperature of a unit quantity of water to one 

 degree as is uecessain' for a unit weight of soil. The different types 

 of soil possessing markedly different water contents, will have entirely 

 different specific heats than tliose shown above. 



To correctly value the tremendous influence tliat soil moisture has 

 upon soil temperature, this moisture must be determined by volume. 

 Such determination, then, gives a true comparison of the amount of 

 water the different soils may hold under natural condition, which con- 

 dition from the agricultural or practical standpoint is the most import- 

 ant and satisfactory. 



TABLE 4.— EFFECT OF MOISTURE ON THE SOIL TEMPERATURE. 



Name of soil. 



April 3, 1912: 



Gravel 



Sand 



Loam 



Clay •. 



Peat 



November 4, 1912: 



Gravel 



Sand 



Loam 



Clay 



Peat 



Wt. of a 

 cu. ft. lbs. 



109.2 

 102.7 

 72.93 

 70.35 

 30.76 



109.2 

 102.7 

 72.93 

 70.35 

 36.76 



Percent 

 moisture. 



10.45 

 16.96 

 40.7 

 29.16 

 250.5 



6.91 



3.78 



38.12 



26.81 



135.5 



Specific heat 

 of soils. 



.2045 

 .1915 

 .2154 

 .2059 

 .2525 



.2045 

 .1950 

 .2154 

 .2059 

 .2526 



Rise of temp. 



of dry soils 



by 100 heat 



units. 



.0008.=)4°C 



.011170 



.014010 



.013990 



.023740 



.009854 

 .011170 

 .014010 

 .013990 

 .023740 



Rise of temp. 



of moist 

 soils by 100 

 heat linits. 



.006520= 

 .005876 

 .004848 

 . 005790 

 .002127 



.007365 

 . 009208 

 .005056 

 . 000079 

 .003725 



