CHAPTER XXIV 

 SOIL WATER, DRAINAGE, AND IRRIGATION 



296. Questions for Discussion. 1. What kinds of soils are most 

 likely to remain sticky for some time following a rain? Can you de- 

 termine why this is true ? 2. If a piece of clay, a similar piece of black 

 loam, and a pile of pure sand are placed upon a heavy wet blotter, will 

 all the soils become moist and with equal rapidity ? Will they become 

 equally moist? 3. Is a wet soil colder or warmer than a dry soil? 

 Why? 4. How much water is used in making a ton of ordinary clover 

 hay? How much would be used in making the hay of a twenty-acre 

 field at the average rate of acre yield in your locality? 5. To save the 

 water supply in time of drought, is it best not to cultivate the soil? 

 Why ? 6. Why should artificial drainage be used in most soils ? 7. To 

 what extent is artificial drainage used in your locality ? Is there a notice- 

 able difference in yield in artificially drained regions as compared with 

 those not drained? 8. Where are the chief irrigation projects of the 

 United States ? 9. If there were enough water available, do you think 

 the solution of the world's food problems might be helped materially 

 by irrigating the arid lands of the United States? 10. Does dry farming 

 promise large returns in production? Why? 11. Where are the chief 

 swamp lands of your state ? What is being done toward reclaiming them ? 

 12. What advantages would there be to the United States from the 

 possession of a kind of wheat which would not be injured by drought? 



297. Amount of water in the soil. It is commonly observed 

 that coarse, gravelly soils do not hold water for a long time 

 and that fine soils do. If a series of glass tubes are filled 

 with soils of different degrees of coarseness, and the same 

 amount of water is poured into each, it will be noted that 

 less flows out from the finer soil. Why is this ? Water may 

 be held in the soil in either of two ways: it may adhere 

 closely to the surfaces of the soil particles, in which case it 

 is known as water of adhesion, or it may be free between 



