IRRIGATION AND UNDERDRAINAGE 211 



drainage not only improves land when it is too wet, but in the 

 dry time the crops grow better; for they have run their roots 

 down farther to seek the dampness, which has been lowered 

 by the drainage. Thus the plants have more soil from which 

 to draw. Also, since the land is left porous, the water-holding 

 capacity is increased. 



Drainage may take place on the surface, as well as from 

 underneath. If the land is very cheap, it may not be worth 

 while to go to the expense of putting in a system of under- 

 drainage. If, however, the land is valuable, underdrainage 

 should by all means be made use of, not only to save the 

 surface area, but also to make the tilling and planting more 

 convenient. 



References : 



1. 1601:253-264. Farm Drainage. 



2. 1601 : 269-275. Irrigation in Humid Climates ; Cost and 



Results. 



3. 1605:88-90. Irrigation. 



4. 1605 : 91-94. Drainage. 



5. Farmers' Bulletin No. 138. Irrigation in Field and Garden. 



6. Farmers' Bulletin No. 158. How to Build Small Irrigation 



Ditches. 



7. Farmers' Bulletin No. 187. Drainage of Farm Lands. 



8. Farmers' Bulletin No. 263. Practical Information for Begin- 



ners in Irrigation. 



9. Farmers' Bulletin No. 371. Drainage of Irrigated Lands. 



a. 1308 : 167-171. The Distribution of Water. 



b. 1309 : 319-321. History of Irrigation. 



c. 1310 : 134-137. The Effects of Irrigation. 



d. 1404 : 130-133. The Amount of Water for the Best 



Effects. 



e. 1602:34-35. Drainage Necessary. 

 /. 1603 : 15-17. Draining the Soil. 



g. 1606 : 53-54. Beneficial Effects of Underdrainage. 



