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 ? 



