80 



SOIL AND ITS RELATION TO ROOTS 



Conclusion. 1. By what means do plants get a fresh supply 

 of nitrogen ? 



2. Why do peas and beans contain so much protein food ? 



Problem 63 : What is crop rotation and what is its use? 



NOTE. A regular order of crops in, which some nitrogen-fixing crops are fol- 

 lowed by plants which take nitrogen from the soil is known as crop rotation. 



Method. Suppose on four farms crops are planted each year 

 as follows : 



Conclusion. 1. Which of the above crops are nitrogen pro- 

 ducing? Nitrogen taking? 



2. Which of the four farms gets the most out of the soil ? Why ? 



3. Explain what is meant by crop rotation. Why is it of great 

 importance ? 



Problem 64 : What roots are useful as food ? 



Method. Test as many different roots as possible for the 

 presence of nutrients. 



Make a list of some roots used by man as food and some used 

 by animals other than man. 



Conclusion. 1. What roots are most useful to man as food? 



2. What roots are used by animals other than man ? 



