CULTIVATION OP SOILS 127 



S. What is the most common form of plow? 4. Explain 

 one serious disadvantage of this form of plow. 5. How 

 may this trouble be remedied? 6. Why will not a plant 

 grow well in a coarse, rough soil? 7. Why do plants as a 

 rule develop best in well cultivated soils? 8. What effect 

 has good cultivation on the film moisture in soils? 9. How 

 does cultivation affect the oxygen supply of soils? 10. How 

 does cultivation destroy weeds and insects? 11. How may 

 fall plowing benefit heavy clay soils? 12. Under what con- 

 dition is it advisable to plow in the fall soils that are to 

 be planted in spring? 13. Why are young crops culti- 

 vated? 14. How does surface cultivation prevent surface 

 evaporation? 15. What is meant by terracing? 16. How 

 does terracing protect soils? 



