THE TEMPERATURE OF THE SOIL 35 



other organisms in the soil, which break down the dead 

 plants, work much more rapidly at the higher tempera- 

 tures. The soil is a storehouse of plant food. A certain 

 amount of this must be unlocked each year to supply the 

 plants. Plant food becomes available in a shorter time 

 if the soil is warm. 



QUESTIONS 



1. Why are plants dormant in the winter? 



2. At what temperature will corn germinate best? 



3. At what temperature will wheat germinate best? 



4. Upon what three things does the temperature of the soil 

 depend ? 



5. Compare the temperatures of a sandy and a clay soil and 

 give reasons for the difference. 



6. Why will adding lime to a clay soil raise the temper- 

 ature ? 



7. Compare the temperature of an undrained field which is 

 wet with that of a drained field and give reasons for the differ- 

 ence. 



8. Why is a dark colored soil warmer than a light colored 

 one? 



9. How may a person change the color of his soil? 

 10. What benefits are derived from a warm soil ? 



