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ELEMENTS OF AGRICULTURE 



This simple diagram serves to illustrate a common 

 rotation which is usually called the four-shift system: 



Questions 



1. What is meant by a rotation of crops? 2. Give an ex- 

 ample of rotation. 3. In what kind of farming is rotation 

 of crops much practiced? 4. Clean cultivation exposes the 

 soil to what danger? 5. How does rotation lessen the 

 danger arising from clean cultivation? 6. Why is it best 

 to grew a crop with deep-growing roots after a crop with 

 shallow roots? 7. When one crop is grown continuously, 

 is the drain upon the soil's supply of plant food uniform? 

 8. How is this irregularity corrected by rotation? 9. How 

 does rotation check the spread of weeds? 10. How does 

 rotation check the spread of injurious insects? How does 

 rotation check plant diseases? 11. Is rotation of crops prac- 

 ticed in your neighborhood? 12. Give a few examples of 



rotation. 



PROBLEM 



Make a diagram showing a five-shift rotation consisting 

 of corn, oats, wheat,* and two years clover. 



