.548 STATE BOARD OF AGRICULTURE. 



Thus far the daily niarrh of averajje temperature for the five diifer- 

 ent kinds of soils has been jriven without any coninient or explanation 

 of tlio results. Tt will not be well to discuss the foreijoinp: data in a 

 brief manner and enqiliasi/.e Ihe most imj^ortant and essential facts. 

 After this tJie consideration of the meteorolopcal elements and their 

 influence upon the forefjoinj; results will be in order. 



One of the most important farts that needs emphasis is the rate at 

 which all the dilferent lypes of soil cooled and froze at the upper O-inch 

 depth. It is a common belief, and a logical one, that the lifjhtest soils 

 cool the fastest and the heaviest soils the slowest, and warm up in the 

 some order. The precedins: data, however, show very conclusively that 

 the jiravel and sand at the up])er G-inch depth cooled and froze about 

 the same time as the clay, loam and peat. 



In the sprinij the two li<iht soils thawed at the upper depth first and 

 both at the same time, followed by clay, one day later, loam two days 

 later, and ])eat ten days later, and that the temperature of the liiilit soils 

 rose and remained far above that of the heavy soils, for some time. 



The question now is why should there be this anomaly or disajjree- 

 ment. The explanation may be found, as will be subsequently j^iven, 

 in the difference in the moisture content of the various soils and in the 

 fluctuitino' downward and upward ti*end of the air temperature in the 

 fall and sprini? respectively. 



As previously stated, the moisture content of these soils was deter- 

 mined at various times of the year. In table 4 are ,2;i\'en the determina- 

 tions of April .J just before thawing commenced and in November 4 

 when the rapid cooling began. It is seen that the percentagT^ of the 

 water content varies tremendously among the various soils which in 

 turn affects their specific heat very greatly. As shown in that table 

 (4) 100 heat units or caloi-ies will raise the temperature of the soils in 

 the dry condition as follows: gravel, .0080.")° C. sand .01117°, loam 

 .01401°, clay .01399°, peat .02374°. When the moisture content is also 

 considered then the i-aise is as follows: gravel .000520° C, sand .005876°, 

 loam .004848°, clay .00.5090°. ])eat .002127". These latter figures show 

 that the temperature of the sand or gravel rises two or three times higher 

 than that of the peat with the same number of heat units. From this 

 we should expect that in the spring the light soils should warm much 

 cai-lier than the peat soils, and in the fall tliey should cool in the same 

 order. The foregoing data show that in the spring they do warm up 

 in the order given or in the order of their specific Jieats, but in the 

 fall they cool almost nt the same rate and freeze about the same time. 



The difference in the moisture content together with the upward and 

 downward trend of temperature in the s]>ring and fall resjiectively, 

 account for this disagreement. In the s])ring the daily march of the 

 air temperature has a continually upward trend. The lighter soils hav- 

 ing the lowest specific heat v.arm up early and their temperature lluctu- 

 ates as the weather elements vary, but the trend is ui)ward. The heavier 

 soils and (S]K'cijiIly the ]ieat having the greatest heat capacity warm up 

 slowly but gradually and finally reach the same temperature as the 

 lighter soils. In the fall the trend of the air temperature is downward 

 as is also that of the soils. On certain days the air temperature falls 

 very low, whereupon all the soils are cooled, the light soils the most 



