DRAINAGE 255 



Drainage and warmth. A wet soil becomes warm 

 more slowly than a dry soil, for the water in the soil 

 takes up so much of the sun's heat. Drainage, by 

 removing the surplus water, hastens the warming of 

 the soil in the spring. 



Swamp lands. In many soils that are irrigated, 

 drainage is necessary. An application of water may 

 so saturate the soil that unless there is good drainage, 

 it becomes unproductive. In the United States there 

 are still extensive areas of swamp lands that may be 

 converted into fertile farms by draining away the 

 water. 



QUESTIONS 



1. What are the advantages of having the soil well drained? 



2. In your locality how much of the land is unproductive 

 because of poor drainage ? 



3. How does underdrainage help crops to survive a drought? 



4. Why does a drained soil become warm earlier in the spring 

 than a wet soil? 



5. What things determine the depth at which a tile ditch 

 should be placed ? 



PRACTICAL EXERCISES 



1. Draw a map of the farm on which you live, showing the 

 location of the ditches. 



2. Visit a tile factory and study the operations in the manu- 

 facture of tiles. 



REFERENCES 



Farmers' Bulletins: 187, Drainage of farm lands; 371, 

 Drainage of irrigated lands. 



