CHAPTER VII 

 SOIL TEMPERATURE 



WE learned that roots need heat for their growth 

 and development. Now what is the relation of the 

 different kinds of soil toward heat or what are their 

 relative powers to absorb and hold heat ? 



Experiment. Some days before this experiment, 

 spread on a dry floor about a half bushel each of 

 sand, clay and decayed leaf mould or black woods 

 soil. Stir them occasionally till they are thoroughly 

 dry. When they are dry place them separately in 

 three boxes or large flower pots and keep dry. In 

 three similar boxes or pots place wet sand, wet clay, 

 and wet humus. Place a thermometer in each of 

 the soils, placing the bulb between one and two 

 inches below the surface (Fig. 31). Then place 

 the soils out of doors where the sun can shine on 

 them and leave them several days. If a rain should 

 come up protect the dry soils. Observe and make 

 a record of the temperatures of each soil several 

 times a day. Chart the average of several days ob- 

 servations. Fig. 32 shows the averages of several 

 days observations on a certain set of soils. 



It will be noticed that the temperature of the 

 soils increased until the early part of the afternoon 

 and after that time they lost heat. 



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