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FARM AND SCHOOL PROBLEMS. 



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Fig. 1. Drainage apparatus used to show the action of tile in a 

 drained soil. The drawing at the right shows the apparatus in use. The 

 height of the water table is indicated by the level of the liquid in the glass 

 tube. The figure to the left is a cross-section showing the slitted tubes 

 in place. This shows that when the water table rises after a rainfall the 

 deeper drain will be the first to carry water from the field. 



When rain falls upon the soil, its tendency is to sink 

 vertically downward until it reaches the water table, which is 

 the point at which the pores in the rock or soil are completely 

 filled with water. 



Ground-water does not often have a horizontal surface. It 

 usually rises or falls as the surface of the ground above it. 



Beneficial Effects of Drainage. 



The benefits derived from drainage are many and important 

 in their effects, among which may be mentioned some of the 

 following : 



It improves the physical condition of the soil. 



It increases aeration and improves sanitary conditions. 



It raises the average temperature, and lands warm up earlier 



in the spring. 



It improves granulation, increases available moisture capacity. 



It firms the soil and reduces heaving and erosion. 



It removes injurious salts from alkali soils and makes sour 



lands sweet. 



It enlarges the root zone and increases the available food supply. 



It promotes the growth of desirable organisms. 



It makes early plowing possible, and helps cultivation in killing 



weeds. 



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2. 



a. 



