SOIL AS WATER RESERVOIR 



27 



tends to distribute itself inversely with the distance of a 

 soil particle from the wettest particle which is the source 

 of supply; that is, after an irrigation, the soil-moisture 

 film will be thickest in the top foot, and will become 

 steadily thinner in the lower soil layers. (Fig. 7.) 



If the soil is very dry, say near the wilting coefficient, 

 when an irrigation occurs, the downward movement 

 of water is slow. Under such a condition the upper soil 

 sections remain saturated until the moisture in the lower 



Percenr of water /rt 30 /'/ 



FIQ. 7. Distribution of water in soil immediately after an irrigation. 



