646 STATE BOARD OF AGRICULTURE. 



• IJefore entering into the discussion of the foregoing results, the reader 

 should be reminded again that all these different types of soil were cov- 

 ered with a thin layer of a sandy soil in order to eliminate the factor of 

 color as this factor was investigated in a separate experiment, the results 

 of which will be presented subsequently. 



The thin layer of the sandy soil, besides giving the different soils 

 about the same shade of color, tended also to equalize the rate of evapo- 

 ration of their moisture. Both color and evaporation have a very marked 

 influence upon the soil temperature. If these different soils, therefore, 

 had not been covered with the thin layer of the sandy soil, probably 

 somewhat different results might have been obtained as indicated by the 

 data of the exjjeriment on the effect of different amounts of organic 

 matter on soil temi>erature — later to be presented. The temperature of 

 these different soil types, however, uncovered, is now being investigated 

 and the data will be reported later. 



With these facts in mind a detailed discussion of the foregoing results 

 is now in order. 



Beginning with the middle of November it is found that the daily 

 average temperature of the different types of soil runs somewhat in 

 this manner: The temperature at all three depths of all the different 

 soils decreased gradually until December 1 when the upper 6 inches 

 of every soil froze. They all stayed frozen for a few days, then thawed 

 and froze again the latter part of December. About this time the 

 lower depths also began to freeze. The 12-inch depth of the gravel froze 

 December 29, of the sand December 30, of the loam January 1, of the 

 clay January 2, of the peat January 2. The 18-inch depth of the 

 gravel and sand froze January 3, of the clay January 9, of the loam 

 January 12, and of the peat January 20. None of the temperatures of 

 any of the depths of any of the soils remained at the freezing ])oint 

 but continued to fall rapidly until a minimum was reached and then 

 began to rise again. At the depth of 6 inches the average minimum 

 was reached for gravel January 6 with 19.96° F., for sand January 

 6 with 14.73°, for loam January S with 21.86°, for clay January 8 

 with 21.7°, and for peat January 8 with 19.63°. At the depth of 12 

 inches the lowest average temperature was reached for gravel January 

 8 with 23.96°. for sand January 8 Avith 23.00°, for loam January 1.5 

 with 28.6°, for clay January 17 with 27.13°, and for peat January 13 

 with 27.8°. At the depth of 18 inches, the average minimum was at- 

 tained 'for gravel Januarv 13 with 29.7°, for sand January 17 with 30.1°. 

 for loam January 20 with. 30.5°, for clay January 22 with 29.83°, and 

 for peat January 30 with 30.76°. The rising in everv case was gradual. 

 \arying slightly from day to day and tending to attain the freezing 

 l)oint, but was below this throughout the cold period. Up to February 

 19 the temperature of the upjiPr 6 inches fluctuated near 28.0°, then 

 rose to about 30.0° and remained near that point till thawing com- 

 menced. The temperature of the 12-inch depth rose shortly after the 

 minimum was attained to about 29.0° and stayed near that tempera- 

 ture until about the middle of February, then rose to about 30.0° F. and 

 remained at about that point also till thawing took place. The tem- 

 perature of the 18-iiK'h depth of all the soils ranged near 30.0° to 31.0° 

 F. fnnn ilic time the lowest tem])crature look ^ik-ico till the thawing 



