450 THE PRINCIPLES OF SOIL MANAGEMENT 



Table LXVII 



The figures in the above two tables indicate that the 

 temperature of the soil has a large influence on germi- 

 nation and growth of different plants. Those indivi- 

 duals which require a high temperature should not be 

 planted until the soil attains the desired degree of heat. 

 If planted before this point is reached, the seed will be 

 slow to germinate and may be destroyed by disease. 

 If it succeeds in germinating, the growth will be slow 

 and unsatisfactory; and, even if the proper soil tempera- 

 ture is attained, the vigor of the plant will have been so 

 reduced that the maximum yield can not be produced. 

 The soil temperature also makes it impossible to grow 

 certain crops where others thrive. This is a large factor 

 in the distribution of crops and wild species of plants. 



318. Activity of the soil organisms. The activity of 

 all soil organisms is reduced by low temperatures. 

 Consequently those biological changes which increase 

 soil fertility are less pronounced during periods of low 

 than during periods of high temperature. One of the 

 most important of these relations is the formation of 



