88 CROP PRODUCTION AND SOIL FERTILITY 



4. Project in seed improvement for various farm and garden crops may be 

 conducted at homes of students. 



Field Studies. 1. Compare growth where the tillage is thorough with the 

 same crops under poor tillage. 



2. Find examples where weeds have been smothered by heavy seeding of 

 crops as grains, cowpeas, millet, buckwheat, etc. 



3. Make field studies to attempt to diagnose the fertility or infertility of 

 field at home or on other farms. See the suggestions in this and other chapters. 



QUESTIONS 



1. Name the factors upon which successful crop production depends. 



2. What is meant by a fertile soil? 



3. What makes a fertile soil? 



4. What is a good combination to have in order to raise good crops? 



5. What is good seed? 



6. What advantage is there in planting large seeds rather than small ones of 



the same variety? In planting disease-resistant varieties? In planting 

 improved varieties? 



7. How may weather conditions affect crop growth? 



8. What relation has the weather to the farmer's activities? 



9. Discuss the relation of light to crop production. 



10. What are the best conditions under which to grow sugar beets? 



11. What are "smothering crops"? Explain how clover and alfalfa may serve 



in this capacity. What about weeds? 



12. What precaution should be observed in sowing nurse crops? 



13. How may a farmer protect his crops from injury? 



14. What is the meaning of soil fertility? 



15. Give meaning of "to maintain fertility." "To increase fertility." 



16. When is a soil said to have lost its fertility? What is infertility? 



17. Fertility of a soil in your locality has meaning only in relation to 



what crops? 



18. What indicates soil fertility? 



19. Name the factors determining fertility. 



20. When is it possible to obtain maximum yields? 



21. How may a soil lose its fertility or be limited hi its productive power? 



22. Explain why peats are frequently unproductive. Give remedy. 



23. What are common causes for failure of legumes? 



24. What is the meaning of "soil exhaustion"? What is a common cause of 



soil depletion? 



25. What is the effect of exhaustive cropping on the phosphorus supply of 



soils? Illustrate. 



26. Explain why it is not easy to restore the original fertility of a badly ex- 



hausted soil. 



27. Illustrate how the cause of infertility or low yields may be reasoned out. 



28. What is the secret in growing a good crop of corn? 



29. Suppose corn is planted in hills 3 feet 8 inches apart each way, 3 stalks 



in the hill, and each stalk produces an ear weighing three-quarters of a 

 pound when cured. What would the yield be? What would you do to 

 grow such a crop? 



30. For an outline summary of this chapter see table of contents. 



