552 STATE BOARD OF AGRICULTURE. 



air and the soil went down far below what it was before the rain began. 

 This niio;ht have been an exceptional sprinj;, but even then it does not 

 appear that the rainfall could be verv effective in raisinji; the tenii>era 

 ture of soil when it is considered (1) that it could be warmed up much 

 faster on a rainless warm day. and (2) that the evaporation after the 

 rainfall would tend to offset A\hatever Avarming effect the precipitation 

 might have had. 



From the theoretical standpoint snow ought to ])rot8ct the soil from 

 very severe freezing and thus keep its temperature higher and steadier. 

 Its effect would seem to be analogous to that of a cover crop, cover of 

 straw, etc. It ought to act as a blanket and reduce the ra]>id loss, of 

 heat, first by preventing the convection and wind current from coming 

 in contact with soil, and second, because it is such a poor heat con- 

 ductor. Where the thickness of the layer is considerable, snow is a 

 very efficient agent in ])rotecting the soil from very low temperature. 

 An ex])eriment that was conducted in the winter of 191 2-191 :^> by plac- 

 ing two electrical resistance thermometers 6 inches into the ground, 

 the area over one being kept free from snow and that over the other 

 being kej)t covered with snow, shows a marked difference in tempera- 

 ture between the two cases. For instance, on March 5, when the mini- 

 mum air temperature was — 1° F., the temperature of the soil covered 

 with about 5 inches of snow w^as 29.6° F., while that being free of 

 snow was 23.6° F. On INIarch 7, when the minimum air temperature 

 registered — 10° F., the temperature of the snow covered soil was 2S.9° 

 F., while that of the bare soil was 22.7° F. Before the snow^ had fallen, 

 however, the temperature of both plots was the same and fluctuated 

 to the same degree and with the same rapidity in both cases as the 

 air temperature varied. The temperatui-e records taken on the different 

 types of soil and also on the soil with different amounts of organic 

 matter throughout two winters show also very abundantly that w^hen- 

 ever these soils were covered with a thick layer of snow their tempera- 

 ture remained much higher and steadier than when they were entirely 

 unprotected, for the same or greater fall of air temperature. A typical 

 example of this fact will be found in the months of February and 

 March, 1913. During the first part of February, the soils were free of 

 snow, and their temperature fell very low whenever the air temperature 

 dropped down very low. On the 6th of that month, for instance, the 

 minimum air temperature registered was 3° F., and the temperatures of 

 some of the light soils went down as low as 12° F. On the 7th of 

 March, however, the soils were covered with about 5 inches of snow. 

 The minimum air temperature registered for this day was — 10^ F.. while 

 the temi)erature of all the soils remained along the freezing point. 32° 

 F,, showing very conclusively that snow tends to protect the soil from 

 very rapid changes and low temperature, and it is therefore of great 

 advantage in the winter time. This advantage, however, becomes a 

 teniy)orary disadvantage in the spring because a layer of snow will re 

 tard thawing on account of the large latent heat of fusion of snow. 



This protecting effect of snow is undoubtedly greater on soils covered 

 with straw or with growing vegetation which was planted in the fall 

 than on bare soils, because the vegetation being very porous and com 



