346 



ANNUAL REPORT OF THE 



Off. Doc. 



It will be seen from tliese figures that even in July and August 

 the soil temperature is but little above that which is found to give 

 best results. 



Aside from the direct effect which a higher temperature has on 

 the ability of seeds to germinate, it greatly influences other pro- 

 cesses in the soil. We know that warm water will dissolve more 

 sugar or salt than will cold water. Now, as the plant food taken 

 from the soil must be in solution, and since much of this material 

 is not easily soluble at best, the advange of a higher temperature 

 is obvious. 



Again, bacteriology teaches us that there is an optimum, as well 

 as a maximum and minimum, temperature at which germ life will 

 thrive. The higher the soil temperature, therefore, and the earlier 

 it can be increased, the sooner nitrification and other changes will 

 go forward, or in other words, the sooner plant food will become 

 available. 



There are yet other actions which will be intensified by an in- 

 creased temperature. Plants absorb their dissolved food through 

 the rootlets by osmosis. As tlie temperature is increased this goes 

 on more readily, the dissolved material is removed more quickly, 

 and, as a result, the process of working over plant food is facilitated. 

 The circulation of the air in the soil is also increased as the tempera- 

 ture rises. When a good fire is desired the draught is turned on, 

 in order that there may be a continual supply of oxygen to unite 

 with the wood or coal. It is just as necessary to have good draught 

 in the soil in order that there may alw\ays be oxygen present to take 

 the place of that used up by the plant in the soil. 



Now, as to the manner in which this question of temperature and 

 moisture are related to each other. Evaporation is a cooling pro- 

 cess. Upon this fact is based a physiological process which is 

 made use of by our bodies continuously. When our temperature 

 tends to become too high, perspiration comes to our rescue. Evap- 

 oration begins to take place and the cooling effect of this evapora- 



