REVIEW QUESTIONS 



i. From what are soils derived ? 2. What are the physical prop- 

 erties of soils ? 3. Why do soils differ in weight? Arrange clay, 

 sand, loam, and peat in order of weight per cubic foot. 4. When 

 wet, what would be the order ? 5. What is the absolute and what the 

 apparent specific gravity of soils ? 6. Define the terms : Skeleton, fine 

 earth, fine sand, silt, and clay. 7. What are the physical properties 

 of clay ? 8. What are the forms of the soil particles? 9. How do 

 different types of soil vary as to the number of soil particles per 

 gram of soil ? 10. How is a mechanical analysis of a soil made ? 



1 1 . Why do certain crops thrive best on definite types of soil ? 



12. What factors must be taken into consideration in determining 

 the type to which a soil belongs? 13. Explain the mechanical 

 structure of a good potato soil. 14. How does a wheat soil differ in 

 mechanical structure from a truck soil? 15. A good corn soil is 

 also a good type for what other crops? 16. How much water is re- 

 quired to produce an average grain crop, and how do the rainfall 

 and the water removed in crops during the growing season compare ? 

 17. In what forms may water be present in soils ? 18. What is bot- 

 tom water and when may it be utilized by crops ? 19. What is capil- 

 lary water? 20. Explain the capillary movement of water. 21. Ex- 

 plain how the capillar}- and non-capillary spaces in the soil ma)* be 

 influenced by cultivation. 22. W T hat is hydroscopic water and of 

 what value is it to crops ? 23. What is percolation ? 24. To what 

 extent may losses occur by percolation ? 25. What are the factors 

 which influence evaporation ? 26. What is transpiration ? 27. In 

 what three ways may water be lost from the soil ? 28. Why does 

 shallow surface cultivation prevent evaporation ? 29. Why is it 

 necessary to cultivate the soil after a rain ? 30. Explain the move- 

 ment of the soil water after a light shower. 31. What influence 

 has rolling the land upon the moisture content of the soil ? 32. 

 What is subsoiling and how does it influence the moisture content 

 of soils ? 33. What influence does early spring plowing exert upon 

 the soil moisture? 34. What is the action of a mulch upon the soil? 

 35. Why should different soils be plowed to different depths? 36. What 

 is meant by the permeability of a soil ? 37. How ma}- cultivation 

 influence permeability? 38. How may commercial fertilizers influ- 

 ence the water content of soils ? 39. Explain the physical action 

 of well-prepared farm manures upon the soil and their influence 

 upon the soil water. 40. What is the object of good drainage ? 

 41. Why does deforesting a region unfavorably influence the agri- 

 cultural value of a country ? 42. What are the sources of heat in 

 soils ? 43. To what extent does the color of soils influence the tern- 



