102 RELATIONS OF SOIL TO WATER 



The experience at Wisconsin shows 3 however, that with 

 the same sand and loam in their natural condition in the 

 field no such large rise of the subsoil water occurs. The 

 experimental ground of the station is near Lake Mendota, 

 and the water level in the subsoil is, at different seasons of 

 the year, between four and seven feet below the surface. In 

 seasons of drought crops often suffer considerably on this 

 land from deficiency of water, although at the time the 

 water level in the subsoil may be only five feet below the 

 surface. 



The much smaller results from capillary action in natural 

 soils are doubtless due to their more irregular texture as 

 compared with the artificially prepared columns employed 

 in laboratory experiments. In the natural soil the capillary 

 passages are less uniform in size, and are always more or 

 less filled with air. The percentages of water found by 

 Loughridge in the alluvial soil (p. 100) wetted by a rise 

 of water from below, show that the soil was less than 

 two- thirds saturated at a height of 2 ft., and one-third 

 saturated at a height of 3 ft. above the water level, more 

 than 125 days after the commencement of the experiment. 

 It is in a saturated soil that water moves with the greatest 

 freedom, the largest passages forming the most effective 

 channels when the quantity of water moved is regarded. 

 In a well drained soil only the finest passages remain full 

 of water, and these will be often interrupted by wider 

 spaces full of air. The movement of water is thus limited 



in many places to the depth of two inches, the rate of evaporation rose from 

 0-95 Ib. per square foot to 1-76 Ib. When, on\he other hand, the uppermost 

 two inches of the sand were removed, and then replaced in a loose condition, 

 the rate of evaporation fell to 0-63 Ib. per square foot. For a further discussion 

 of this point see p. 113. 



