Cultivation and Drainage 



59 



food be added to the 

 soil, the fertility of the 

 field is greatly increased, 

 and soil that would 

 otherwise be too wet for 

 farming is made produc- 

 tive. 



Drainage also protects 

 crops in time of drought, 

 a well-drained field being 

 drier in wet weather and 

 having more moisture 

 available in dry weather 

 than one that is not 

 drained. The reason for 

 this is that in an un- 

 drained field the roots 

 develop in the thin upper 

 layer of drier and venti- 

 lated soil. Later in the 

 season the plants may 

 even suffer from drought, 

 for as drier . weather 

 comes on the water table 

 is lowered and not enough 

 moisture may be left in 

 the surface soil to sup- 

 port the crop. But where there are drains the surplus 

 water is carried away in the rainy season, while in dry 

 weather the plants, being deeply rooted, do not 

 suffer. 



Protec- 

 tion against 

 drought 



W. T. Stilling 



FIG. 41. This flowerpot was filled with' 

 earth to which a small quantity of salt 

 had been added. Water that was allowed 

 to drain through carried with it much of 

 the salt. Note that a crust of salt was 

 left on the flowerpot when water seeped 

 through the sides of the pot and evapo- 

 rated. An alkali crust on the ground is 

 formed in a similar manner. 



