INFLUENCE OF CULTIVATION 4 1 



37. Drainage. — Good drainage is very essential in 

 order to properly regulate the water supply. If the 

 water which falls on the land is allowed to flow over 

 the surface and is not retained in the soil, there is not 

 sufficient reserve water for crop growth. The object 

 of good drainage is to store up as much water as pos- 

 sible in the subsoil and to prevent surface accumula- 

 tion and losses. Good drainage is accomplished by 

 thorough cultivation, and in regions of heavy rainfall 

 bv tile drainage. Well-drained land is warmer in the 

 spring, has a larger reserve store of water, and is in 

 better condition for crop growth. 



38. Influence of Forest Regions. — The deforesting 

 of large areas near the source of rivers has an injurious 

 influence upon the moisture content of adjoining farm 

 lands. By cutting over and leaving barren large tracts, 

 less water is retained in the soil. Near forest regions 

 the air has a higher moisture content, due to the 

 water given off by evaporation. Farm lands adjacent 

 to deforested districts lose water more rapidly by 

 evaporation, because the air is so much drier. In 

 Section 24 it was stated that losses of water by trans- 

 piration could be indirectly influenced. This can be 

 accomplished by retaining our forest lands. 



Good drainage in agriculture means not onlv good 

 drainage for individual farms, but also good storage 

 capacity in the form of forest lands, for the surplus 

 water which accumulates near the sources of large 

 rivers. 



