68 PRODUCTIVE FARMING 



covered drains, which may be composed either of tile (Fig. 

 38) or of broken stone, gravel, boulders, etc. Surface or 

 open ditches are cheaper to start with, but are not so good 

 as others. They do not give as good results, and are in 

 the way. 



Effect on Roots. Deep drainage increases the room for 

 plant-roots. The roots of most farm crops will not grow 

 down into any free water which may be standing in the sub- 

 soil. If drains carry away such water the roots may go into 

 the deeper soil to get plant-food (Fig. 39, D). 



FIG. 38. Ready to lay the six-inch drain tiles. 



This reduces suffering at time of drought, because the 

 roots are then so deep in the soil that the drying of the 

 surface does not harm them. They get their moisture from 

 lower depths and from a larger volume of soil. 



On the other hand, if the free water is allowed to remain 

 near the surface during the spring of the year (Fig. 39, F), 

 very shallow root systems are formed. Later, in July, when 

 a drought comes, the free water settles to a great depth too 

 quickly for the roots to follow. The shallow roots are then 

 surrounded by the dry soil near the surface and growth is 

 Stopped (Fig. 39, W). 



