174 



Physics of the Soil. 



per two feet of soil contained, in spite of the larger crop, 

 much more moisture, but at the expense of that deeper in 

 the ground, as shown by the fact that in every case these 

 soils were dryest in the 3d and 4th feet 



202. Finning the Soil May Strengthen the Capillary Rise 

 of Soil Moisture. When soils have been rendered open and 

 loose by plowing or other deep stirring the first effect is 

 to permit the loose and open soil to become dry, because 

 this soil is less perfectly in contact with that below. If, 

 after such soil has become dry, it is firmed again the moist- 

 ure films will then increase in thickness over the surface 

 of the soil grains and, as a result of this, moisture will 

 be raised from depths as great as four feet to saturate the 

 firmed dryer soil. In the table below are shown the 

 changes which occurred in the deeper and superficial soil 

 layers as the result of rolling. 



Table showing how rolling may strengthen the capillary rise 

 of soil moisture. 



Erom this table it is seen that the first effect of rolling 

 is to increase the amount of moisture in the upper 18 

 inches of soil, but that when samples are taken deeper than 

 18 inches the total amount in the soil is decreased. la 

 other words, the first effect is to concentrate 'the deeper 

 soil moisture toward the surface. 



If, however, the soil is left firmed very long then the 

 whole column, to the surface, becomes dryer, until it has 

 lost so much moisture that it begins to act as a mulch. 



