Importance of Soil Warmth 427 



does, the plants are so much enfeebled that only a 

 slow growth results afterward. 



In the early part of the season, when ground is 

 being fitted for seeding, it should ever be kept in 

 mind that one of the chief objects of the early and 

 thorough tillage is to develop an abundance of 

 nitrates in the soil for the use of the crop. But 

 this is done by making the soil warmer, and by 

 introducing an abundance of air into it when there 

 is a good supply of moisture associated with the 

 humus upon which the niter germs feed. These 

 germs cease to develop niter from humus when the 

 soil temperature drops to 41 F. ; the action is only 

 barely appreciable at 54 F., and it reaches its maxi- 

 mum rate only at a temperature of 98 F. 



Now, the early, deep stirring of the soil in the 

 spring prevents the moisture from coming up from 

 below, and so lessens the rate of evaporation ; this 

 allows the soil to become warmer. Besides the heat is 

 not conducted as rapidly downward when the soil is 

 loose ; this makes the stirred, well ventilated portion 

 warmer also, so that for the germination of the seed 

 and for the development of plant-food, deep early 

 tillage is very important. It is plain, also, that the 

 well -drained field not only can be tilled earlier and 

 deeper, but will also have the soil warmer and richer, 

 for the reasons just stated. 



For the same reason that sugar dissolves faster in 

 warm than in cold water, so the ash ingredients of 

 plant-food are dissolved faster, and stronger solutions 

 of them are formed in the warm than in the cold 



