168 



PRACTICAL DRAINAGE 



not high enough entirely to prevent crop growth, there is 

 sufficient to reduce the yield to a point that is unprofit- 

 able. The expenses are practically the same in raising 

 half a crop as a full one. In the one case farming is carried 

 on at a loss, and in the other a good profit may be realized. 

 Thus, removing alkali by drainage may make highly pro- 

 ductive millions of acres of land that is only moderately 





Fig. 20. Field Ready for Laying Tile. 



successful. There are also millions of acres at present 

 wholly unproductive that may be made to yield bounte- 

 ously by removing the alkali. 



Drainage removes the excessive water from the soil. 

 By lowering the water-table the plant is given a larger root 

 zone from which to draw both food and water. If only 

 the surface foot or two can be drawn on for food the plant 

 cannot be expected to be so well supplied with nourish- 

 ment as it would with a feeding area of five or six feet. 



