214 



Physics of the Soil. 



Table showing the mean monthly soil temperatures, at State 

 College, Pa. , by Dr. Frear, and at Munich, Germany, by 

 Ebermayer. 



AT STATE COLLEGE, PENNSYLVANIA. 



AT MUNICH, GERMANY. 



It may appear that the temperatures recorded in these 

 tables are too low to be in harmony with the comparatively 

 high temperatures given as the best for germination. It 

 must be understood, however, that the average must bo 

 lower than would be found in the soil during the warmest 

 portion of the day. In regard to the minimum tempera- 

 ture at which germination takes place it will be clear 

 enough that the April records for soil temperature are quite 

 in harmony with those given for germination. 



257. Influence of Soil Temperature on the Hate of Germi- 

 nation. The more quickly seeds are permitted to germi- 

 nate after they are placed in the soil the higher will be 

 the per cent, of seeds growing and, as a rule, the more vig- 

 orous will the plants be. Indeed, seeds of low vitality 

 placed in too cold a soil often fail to germinate at all. 



ITaberlandt found that, when corn would germinate in 

 3 days at a temperature of 65. 3 F., it required 11 days 

 when the soil was as low as 51 F., and Hellriegel showed 

 that when corn was planted under a mean temperature of 

 48 only 2 out of 10 kernels sprouted in 42 days; that 

 under the same temperature rye germinated in 9 days, 



