SOIL RELATIONS 253 



On the other hand, the cooler temperature of the 

 soil than that of the air, without question, has great influ- 

 ence in counteracting the injurious effects of high tem- 

 peratures of the latter, during periods of excessive mid- 

 summer heat. A large part of the benefits of cultivation 

 of intertilled crops may be due to this cooling influence 

 of the turned-up soil. 



