46 FARM AND SCHOOL PROBLEMS. 



Suggestions for Plat Work. 



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Similar plot work may be used to demonstrate the effects of 

 lime in the seeding to clover, alfalfa or other legumes. (See 

 chapter on School Gardens). 



Questions. 



1. How many different chemical elements are absolutely essential 

 to plant growth? Name them. 



2. What are the two general sources of plant food? 



3. What elements of plant food are derived from the soil and 

 what from th air? 



4. What elements of plant food are most likely to be deficient in 

 soils ? 



5. How does the plant get its food from the air? How from the 

 soil? 



6. Name at least three reasons why wet land should be drained. 



7. What do we mean when we say a soil is "heavy"? 



8. What do you understand by acid or sour soil? 



9. How may acid in the soil be overcome? 



10. Name some of the more important fertilizing materials, giving 

 their source and composition. 



11. What is the difference between nitrogen and ammonia? 



12. What are the principal reasons for decrease in soil fertility? 



13. Distinguish between acid phosphate and phosphoric acid. 



14. Name the three principal forms of lime and distinguish between 

 them. 



15. How would you determine whether or not a soil needs lime? 



16. What is meant by crop rotation? 



17. Indicate what you consider a good rotation for your community. 

 Give reasons. 



