EXERCISE 9 

 THE PERCOLATION OF WATER IN SOILS 



Object. To compare the rate of percolation of water 

 through soils of different texture. 



Explanation. The capacity of soils to absorb water that 

 falls as rain depends upon its texture, or the size of the soil 

 particles. A coarse-textured soil absorbs moisture rapidly, 

 but in such a soil the water percolates through it quickly, 

 and thus a large part of the rain that is absorbed is lost 

 from the soil as percolating water. A fine-grained soil 

 absorbs rain water slowly, but holds hi the soil a larger 

 portion of the water that is absorbed. An ideal soil is one 

 that is coarse enough to absorb moisture with fair rapidity, 

 yet fine enough to retain a large portion of the moisture 

 absorbed. 



The condition of the surface of the soil also affects the 

 capacity of a soil to absorb moisture. A soil that is hard 

 and compact at the surface will absorb moisture much more 

 slowly than one that is loose and open. Thus, plowing the 

 ground when it is compact or cultivating it when it is crusted, 

 favors the absorption and percolation of moisture into the soil. 



Equipment. 1 . Six percolation cylinders with rack and 

 supply tank. 



2. Six beakers 400 or 500 c.c. 



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