EXPERIMENT STATION BULLETINS. 801 



ADDITIONAL EXPERIMENTAL DATA ON THE TEMPERATURE 

 OF CULTIVATED, UNCULTIVATED AND SOD SOIL. 



PLAN OP THE EXPERIMEOMT. 



A correct knowledge of the effect of cultural methods, such as cultiva- 

 tion, uncultivation and sod, upon the soil temperature is of great interest 

 and impo:i:ance both from the scientific as well as from the practical 

 standpoint. The current information concerning the effect of these cul- 

 tural methods upon soil temperature is limited and unsatisfactory. 

 Consequently, in November, 1911, at the time that the foregoing series 

 of experiments were started, a systematic and thorough investigation of 

 this problem was also instituted. The research consisted of measuring 

 the temperature of soil under the above conditions by means of thermo- 

 graphs^. It was thought and hoped that by the use of such instruments, 

 which make continuous pecords, very definite and extremely important 

 information would be procured upon the subject. Unfortunately, how- 

 ever, these instruments proved to be a failure, as the bulbs containing 

 the liquid medium would always leak in spite of many precautionary 

 measures taken and the numerous repairs made. It seems that the 

 joints between the tube and the hollow wire would corrode in the soil 

 and allow the liquid to escape. After employing these instruments, 

 seven in number, three double and two single, for two years they were 

 abandoned because the data obtained by them could not be relied upon. 

 They were replaced, however, by soil mercury thermometers graduated 

 to 0.5°F. Only two years' data have been secured by the latter instru- 

 ments. During the year 1913 the temperature was measured at 7-inch 

 depth, three times a day as usual. During 1915, however, it was recorded 

 at 3 and 6-inch depths. In Table 87 are presented the monthly maximum, 

 minimum, amplitude and average temperature of the soil under the 

 various cultural conditions dui*ing the two years. 



It should be stated that the uncultivated plot was kept undistributed 

 but free of weeds; the cultivated plot was stirred almost always after 

 a rain ; the vegetation of the sod land consisted of alfalfa and grass and 

 was never cut throughout the four years. 



^Obtained from Frietz, Baltimore, Md. 

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